android/android-9.0.0_r35 : android/view/ViewGroup.java

ViewGroup
https://source.android.com/
/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.view;

import static android.os.Build.VERSION_CODES.JELLY_BEAN_MR1;

import android.animation.LayoutTransition;
import android.annotation.CallSuper;
import android.annotation.IdRes;
import android.annotation.NonNull;
import android.annotation.TestApi;
import android.annotation.UiThread;
import android.content.ClipData;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.res.Configuration;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Insets;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PointF;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.Region;
import android.os.Build;
import android.os.Bundle;
import android.os.Parcelable;
import android.os.SystemClock;
import android.util.AttributeSet;
import android.util.Log;
import android.util.Pools;
import android.util.Pools.SynchronizedPool;
import android.util.SparseArray;
import android.util.SparseBooleanArray;
import android.view.accessibility.AccessibilityEvent;
import android.view.accessibility.AccessibilityManager;
import android.view.accessibility.AccessibilityNodeInfo;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.view.animation.LayoutAnimationController;
import android.view.animation.Transformation;
import android.view.autofill.Helper;

import com.android.internal.R;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.function.Predicate;


A ViewGroup is a special view that can contain other views (called children.) The view group is the base class for layouts and views containers. This class also defines the LayoutParams class which serves as the base class for layouts parameters. 
 Also see LayoutParams for layout attributes. 

Developer Guides
For more information about creating user interface layouts, read the
XML Layouts developer
guide.
Here is a complete implementation of a custom ViewGroup that implements a simple FrameLayout along with the ability to stack children in left and right gutters.
{@sample development/samples/ApiDemos/src/com/example/android/apis/view/CustomLayout.java
     Complete}
If you are implementing XML layout attributes as shown in the example, this is the
corresponding definition for them that would go in res/values/attrs.xml:
{@sample development/samples/ApiDemos/res/values/attrs.xml CustomLayout}
Finally the layout manager can be used in an XML layout like so:
{@sample development/samples/ApiDemos/res/layout/custom_layout.xml Complete}
@attr ref android.R.styleable#ViewGroup_clipChildren
@attr ref android.R.styleable#ViewGroup_clipToPadding
@attr ref android.R.styleable#ViewGroup_layoutAnimation
@attr ref android.R.styleable#ViewGroup_animationCache
@attr ref android.R.styleable#ViewGroup_persistentDrawingCache
@attr ref android.R.styleable#ViewGroup_alwaysDrawnWithCache
@attr ref android.R.styleable#ViewGroup_addStatesFromChildren
@attr ref android.R.styleable#ViewGroup_descendantFocusability
@attr ref android.R.styleable#ViewGroup_animateLayoutChanges
@attr ref android.R.styleable#ViewGroup_splitMotionEvents
@attr ref android.R.styleable#ViewGroup_layoutMode/**
 * <p>
 * A <code>ViewGroup</code> is a special view that can contain other views
 * (called children.) The view group is the base class for layouts and views
 * containers. This class also defines the
 * {@link android.view.ViewGroup.LayoutParams} class which serves as the base
 * class for layouts parameters.
 * </p>
 *
 * <p>
 * Also see {@link LayoutParams} for layout attributes.
 * </p>
 *
 * <div class="special reference">
 * <h3>Developer Guides</h3>
 * <p>For more information about creating user interface layouts, read the
 * <a href="{@docRoot}guide/topics/ui/declaring-layout.html">XML Layouts</a> developer
 * guide.</p></div>
 *
 * <p>Here is a complete implementation of a custom ViewGroup that implements
 * a simple {@link android.widget.FrameLayout} along with the ability to stack
 * children in left and right gutters.</p>
 *
 * {@sample development/samples/ApiDemos/src/com/example/android/apis/view/CustomLayout.java
 *      Complete}
 *
 * <p>If you are implementing XML layout attributes as shown in the example, this is the
 * corresponding definition for them that would go in <code>res/values/attrs.xml</code>:</p>
 *
 * {@sample development/samples/ApiDemos/res/values/attrs.xml CustomLayout}
 *
 * <p>Finally the layout manager can be used in an XML layout like so:</p>
 *
 * {@sample development/samples/ApiDemos/res/layout/custom_layout.xml Complete}
 *
 * @attr ref android.R.styleable#ViewGroup_clipChildren
 * @attr ref android.R.styleable#ViewGroup_clipToPadding
 * @attr ref android.R.styleable#ViewGroup_layoutAnimation
 * @attr ref android.R.styleable#ViewGroup_animationCache
 * @attr ref android.R.styleable#ViewGroup_persistentDrawingCache
 * @attr ref android.R.styleable#ViewGroup_alwaysDrawnWithCache
 * @attr ref android.R.styleable#ViewGroup_addStatesFromChildren
 * @attr ref android.R.styleable#ViewGroup_descendantFocusability
 * @attr ref android.R.styleable#ViewGroup_animateLayoutChanges
 * @attr ref android.R.styleable#ViewGroup_splitMotionEvents
 * @attr ref android.R.styleable#ViewGroup_layoutMode
 */
@UiThread
public abstract class ViewGroup extends View implements ViewParent, ViewManager {
    private static final String TAG = "ViewGroup";

    private static final boolean DBG = false;

    Views which have been hidden or removed which need to be animated on
their way out.
This field should be made private, so it is hidden from the SDK.
{@hide}
/**
     * Views which have been hidden or removed which need to be animated on
     * their way out.
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected ArrayList<View> mDisappearingChildren;

    Listener used to propagate events indicating when children are added
and/or removed from a view group.
This field should be made private, so it is hidden from the SDK.
{@hide}
/**
     * Listener used to propagate events indicating when children are added
     * and/or removed from a view group.
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected OnHierarchyChangeListener mOnHierarchyChangeListener;

    // The view contained within this ViewGroup that has or contains focus.
    private View mFocused;
    // The view contained within this ViewGroup (excluding nested keyboard navigation clusters)
    // that is or contains a default-focus view.
    private View mDefaultFocus;
    // The last child of this ViewGroup which held focus within the current cluster
    View mFocusedInCluster;

    A Transformation used when drawing children, to
apply on the child being drawn.
/**
     * A Transformation used when drawing children, to
     * apply on the child being drawn.
     */
    private Transformation mChildTransformation;

    Used to track the current invalidation region.
/**
     * Used to track the current invalidation region.
     */
    RectF mInvalidateRegion;

    A Transformation used to calculate a correct
invalidation area when the application is autoscaled.
/**
     * A Transformation used to calculate a correct
     * invalidation area when the application is autoscaled.
     */
    Transformation mInvalidationTransformation;

    // Current frontmost child that can accept drag and lies under the drag location.
    // Used only to generate ENTER/EXIT events for pre-Nougat aps.
    private View mCurrentDragChild;

    // Metadata about the ongoing drag
    private DragEvent mCurrentDragStartEvent;
    private boolean mIsInterestedInDrag;
    private HashSet<View> mChildrenInterestedInDrag;

    // Used during drag dispatch
    private PointF mLocalPoint;

    // Lazily-created holder for point computations.
    private float[] mTempPoint;

    // Layout animation
    private LayoutAnimationController mLayoutAnimationController;
    private Animation.AnimationListener mAnimationListener;

    // First touch target in the linked list of touch targets.
    private TouchTarget mFirstTouchTarget;

    // For debugging only.  You can see these in hierarchyviewer.
    @SuppressWarnings({"FieldCanBeLocal", "UnusedDeclaration"})
    @ViewDebug.ExportedProperty(category = "events")
    private long mLastTouchDownTime;
    @ViewDebug.ExportedProperty(category = "events")
    private int mLastTouchDownIndex = -1;
    @SuppressWarnings({"FieldCanBeLocal", "UnusedDeclaration"})
    @ViewDebug.ExportedProperty(category = "events")
    private float mLastTouchDownX;
    @SuppressWarnings({"FieldCanBeLocal", "UnusedDeclaration"})
    @ViewDebug.ExportedProperty(category = "events")
    private float mLastTouchDownY;

    // First hover target in the linked list of hover targets.
    // The hover targets are children which have received ACTION_HOVER_ENTER.
    // They might not have actually handled the hover event, but we will
    // continue sending hover events to them as long as the pointer remains over
    // their bounds and the view group does not intercept hover.
    private HoverTarget mFirstHoverTarget;

    // True if the view group itself received a hover event.
    // It might not have actually handled the hover event.
    private boolean mHoveredSelf;

    // The child capable of showing a tooltip and currently under the pointer.
    private View mTooltipHoverTarget;

    // True if the view group is capable of showing a tooltip and the pointer is directly
    // over the view group but not one of its child views.
    private boolean mTooltipHoveredSelf;

    Internal flags.
This field should be made private, so it is hidden from the SDK.
{@hide}
/**
     * Internal flags.
     *
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    @ViewDebug.ExportedProperty(flagMapping = {
            @ViewDebug.FlagToString(mask = FLAG_CLIP_CHILDREN, equals = FLAG_CLIP_CHILDREN,
                    name = "CLIP_CHILDREN"),
            @ViewDebug.FlagToString(mask = FLAG_CLIP_TO_PADDING, equals = FLAG_CLIP_TO_PADDING,
                    name = "CLIP_TO_PADDING"),
            @ViewDebug.FlagToString(mask = FLAG_PADDING_NOT_NULL, equals = FLAG_PADDING_NOT_NULL,
                    name = "PADDING_NOT_NULL")
    }, formatToHexString = true)
    protected int mGroupFlags;

    Either LAYOUT_MODE_CLIP_BOUNDS or LAYOUT_MODE_OPTICAL_BOUNDS. /**
     * Either {@link #LAYOUT_MODE_CLIP_BOUNDS} or {@link #LAYOUT_MODE_OPTICAL_BOUNDS}.
     */
    private int mLayoutMode = LAYOUT_MODE_UNDEFINED;

    NOTE: If you change the flags below make sure to reflect the changes
      the DisplayList class
/**
     * NOTE: If you change the flags below make sure to reflect the changes
     *       the DisplayList class
     */

    // When set, ViewGroup invalidates only the child's rectangle
    // Set by default
    static final int FLAG_CLIP_CHILDREN = 0x1;

    // When set, ViewGroup excludes the padding area from the invalidate rectangle
    // Set by default
    private static final int FLAG_CLIP_TO_PADDING = 0x2;

    // When set, dispatchDraw() will invoke invalidate(); this is set by drawChild() when
    // a child needs to be invalidated and FLAG_OPTIMIZE_INVALIDATE is set
    static final int FLAG_INVALIDATE_REQUIRED  = 0x4;

    // When set, dispatchDraw() will run the layout animation and unset the flag
    private static final int FLAG_RUN_ANIMATION = 0x8;

    // When set, there is either no layout animation on the ViewGroup or the layout
    // animation is over
    // Set by default
    static final int FLAG_ANIMATION_DONE = 0x10;

    // If set, this ViewGroup has padding; if unset there is no padding and we don't need
    // to clip it, even if FLAG_CLIP_TO_PADDING is set
    private static final int FLAG_PADDING_NOT_NULL = 0x20;

    Deprecated: - functionality removed/** @deprecated - functionality removed */
    @Deprecated
    private static final int FLAG_ANIMATION_CACHE = 0x40;

    // When set, this ViewGroup converts calls to invalidate(Rect) to invalidate() during a
    // layout animation; this avoid clobbering the hierarchy
    // Automatically set when the layout animation starts, depending on the animation's
    // characteristics
    static final int FLAG_OPTIMIZE_INVALIDATE = 0x80;

    // When set, the next call to drawChild() will clear mChildTransformation's matrix
    static final int FLAG_CLEAR_TRANSFORMATION = 0x100;

    // When set, this ViewGroup invokes mAnimationListener.onAnimationEnd() and removes
    // the children's Bitmap caches if necessary
    // This flag is set when the layout animation is over (after FLAG_ANIMATION_DONE is set)
    private static final int FLAG_NOTIFY_ANIMATION_LISTENER = 0x200;

    When set, the drawing method will call getChildDrawingOrder(int, int) to get the index of the child to draw for that iteration. 
@hide /**
     * When set, the drawing method will call {@link #getChildDrawingOrder(int, int)}
     * to get the index of the child to draw for that iteration.
     *
     * @hide
     */
    protected static final int FLAG_USE_CHILD_DRAWING_ORDER = 0x400;

    When set, this ViewGroup supports static transformations on children; this causes getChildStaticTransformation(View, Transformation) to be invoked when a child is drawn. Any subclass overriding getChildStaticTransformation(View, Transformation) should set this flags in mGroupFlags. {@hide} /**
     * When set, this ViewGroup supports static transformations on children; this causes
     * {@link #getChildStaticTransformation(View, android.view.animation.Transformation)} to be
     * invoked when a child is drawn.
     *
     * Any subclass overriding
     * {@link #getChildStaticTransformation(View, android.view.animation.Transformation)} should
     * set this flags in {@link #mGroupFlags}.
     *
     * {@hide}
     */
    protected static final int FLAG_SUPPORT_STATIC_TRANSFORMATIONS = 0x800;

    // UNUSED FLAG VALUE: 0x1000;

    When set, this ViewGroup's drawable states also include those
of its children.
/**
     * When set, this ViewGroup's drawable states also include those
     * of its children.
     */
    private static final int FLAG_ADD_STATES_FROM_CHILDREN = 0x2000;

    Deprecated: functionality removed/** @deprecated functionality removed */
    @Deprecated
    private static final int FLAG_ALWAYS_DRAWN_WITH_CACHE = 0x4000;

    Deprecated: functionality removed/** @deprecated functionality removed */
    @Deprecated
    private static final int FLAG_CHILDREN_DRAWN_WITH_CACHE = 0x8000;

    When set, this group will go through its list of children to notify them of
any drawable state change.
/**
     * When set, this group will go through its list of children to notify them of
     * any drawable state change.
     */
    private static final int FLAG_NOTIFY_CHILDREN_ON_DRAWABLE_STATE_CHANGE = 0x10000;

    private static final int FLAG_MASK_FOCUSABILITY = 0x60000;

    This view will get focus before any of its descendants.
/**
     * This view will get focus before any of its descendants.
     */
    public static final int FOCUS_BEFORE_DESCENDANTS = 0x20000;

    This view will get focus only if none of its descendants want it.
/**
     * This view will get focus only if none of its descendants want it.
     */
    public static final int FOCUS_AFTER_DESCENDANTS = 0x40000;

    This view will block any of its descendants from getting focus, even
if they are focusable.
/**
     * This view will block any of its descendants from getting focus, even
     * if they are focusable.
     */
    public static final int FOCUS_BLOCK_DESCENDANTS = 0x60000;

    Used to map between enum in attrubutes and flag values.
/**
     * Used to map between enum in attrubutes and flag values.
     */
    private static final int[] DESCENDANT_FOCUSABILITY_FLAGS =
            {FOCUS_BEFORE_DESCENDANTS, FOCUS_AFTER_DESCENDANTS,
                    FOCUS_BLOCK_DESCENDANTS};

    When set, this ViewGroup should not intercept touch events.
{@hide}
/**
     * When set, this ViewGroup should not intercept touch events.
     * {@hide}
     */
    protected static final int FLAG_DISALLOW_INTERCEPT = 0x80000;

    When set, this ViewGroup will split MotionEvents to multiple child Views when appropriate.
/**
     * When set, this ViewGroup will split MotionEvents to multiple child Views when appropriate.
     */
    private static final int FLAG_SPLIT_MOTION_EVENTS = 0x200000;

    When set, this ViewGroup will not dispatch onAttachedToWindow calls
to children when adding new views. This is used to prevent multiple
onAttached calls when a ViewGroup adds children in its own onAttached method.
/**
     * When set, this ViewGroup will not dispatch onAttachedToWindow calls
     * to children when adding new views. This is used to prevent multiple
     * onAttached calls when a ViewGroup adds children in its own onAttached method.
     */
    private static final int FLAG_PREVENT_DISPATCH_ATTACHED_TO_WINDOW = 0x400000;

    When true, indicates that a layoutMode has been explicitly set, either with an explicit call to setLayoutMode(int) in code or from an XML resource. This distinguishes the situation in which a layout mode was inherited from one of the ViewGroup's ancestors and cached locally. /**
     * When true, indicates that a layoutMode has been explicitly set, either with
     * an explicit call to {@link #setLayoutMode(int)} in code or from an XML resource.
     * This distinguishes the situation in which a layout mode was inherited from
     * one of the ViewGroup's ancestors and cached locally.
     */
    private static final int FLAG_LAYOUT_MODE_WAS_EXPLICITLY_SET = 0x800000;

    static final int FLAG_IS_TRANSITION_GROUP = 0x1000000;

    static final int FLAG_IS_TRANSITION_GROUP_SET = 0x2000000;

    When set, focus will not be permitted to enter this group if a touchscreen is present.
/**
     * When set, focus will not be permitted to enter this group if a touchscreen is present.
     */
    static final int FLAG_TOUCHSCREEN_BLOCKS_FOCUS = 0x4000000;

    When true, indicates that a call to startActionModeForChild was made with the type parameter
and should not be ignored. This helps in backwards compatibility with the existing method
without a type.
See Also: startActionModeForChild(View, Callback)
startActionModeForChild(View, Callback, int)/**
     * When true, indicates that a call to startActionModeForChild was made with the type parameter
     * and should not be ignored. This helps in backwards compatibility with the existing method
     * without a type.
     *
     * @see #startActionModeForChild(View, android.view.ActionMode.Callback)
     * @see #startActionModeForChild(View, android.view.ActionMode.Callback, int)
     */
    private static final int FLAG_START_ACTION_MODE_FOR_CHILD_IS_TYPED = 0x8000000;

    When true, indicates that a call to startActionModeForChild was made without the type
parameter. This helps in backwards compatibility with the existing method
without a type.
See Also: startActionModeForChild(View, Callback)
startActionModeForChild(View, Callback, int)/**
     * When true, indicates that a call to startActionModeForChild was made without the type
     * parameter. This helps in backwards compatibility with the existing method
     * without a type.
     *
     * @see #startActionModeForChild(View, android.view.ActionMode.Callback)
     * @see #startActionModeForChild(View, android.view.ActionMode.Callback, int)
     */
    private static final int FLAG_START_ACTION_MODE_FOR_CHILD_IS_NOT_TYPED = 0x10000000;

    When set, indicates that a call to showContextMenuForChild was made with explicit
coordinates within the initiating child view.
/**
     * When set, indicates that a call to showContextMenuForChild was made with explicit
     * coordinates within the initiating child view.
     */
    private static final int FLAG_SHOW_CONTEXT_MENU_WITH_COORDS = 0x20000000;

    Indicates which types of drawing caches are to be kept in memory.
This field should be made private, so it is hidden from the SDK.
{@hide}
/**
     * Indicates which types of drawing caches are to be kept in memory.
     * This field should be made private, so it is hidden from the SDK.
     * {@hide}
     */
    protected int mPersistentDrawingCache;

    Used to indicate that no drawing cache should be kept in memory.
Deprecated: The view drawing cache was largely made obsolete with the introduction of hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache layers are largely unnecessary and can easily result in a net loss in performance due to the cost of creating and updating the layer. In the rare cases where caching layers are useful, such as for alpha animations, View.setLayerType(int, Paint) handles this with hardware rendering. For software-rendered snapshots of a small part of the View hierarchy or individual Views it is recommended to create a Canvas from either a Bitmap or Picture and call View.draw(Canvas) on the View. However these software-rendered usages are discouraged and have compatibility issues with hardware-only rendering features such as Config.HARDWARE bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback reports or unit testing the PixelCopy API is recommended./**
     * Used to indicate that no drawing cache should be kept in memory.
     *
     * @deprecated The view drawing cache was largely made obsolete with the introduction of
     * hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache
     * layers are largely unnecessary and can easily result in a net loss in performance due to the
     * cost of creating and updating the layer. In the rare cases where caching layers are useful,
     * such as for alpha animations, {@link #setLayerType(int, Paint)} handles this with hardware
     * rendering. For software-rendered snapshots of a small part of the View hierarchy or
     * individual Views it is recommended to create a {@link Canvas} from either a {@link Bitmap} or
     * {@link android.graphics.Picture} and call {@link #draw(Canvas)} on the View. However these
     * software-rendered usages are discouraged and have compatibility issues with hardware-only
     * rendering features such as {@link android.graphics.Bitmap.Config#HARDWARE Config.HARDWARE}
     * bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback
     * reports or unit testing the {@link PixelCopy} API is recommended.
     */
    @Deprecated
    public static final int PERSISTENT_NO_CACHE = 0x0;

    Used to indicate that the animation drawing cache should be kept in memory.
Deprecated: The view drawing cache was largely made obsolete with the introduction of hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache layers are largely unnecessary and can easily result in a net loss in performance due to the cost of creating and updating the layer. In the rare cases where caching layers are useful, such as for alpha animations, View.setLayerType(int, Paint) handles this with hardware rendering. For software-rendered snapshots of a small part of the View hierarchy or individual Views it is recommended to create a Canvas from either a Bitmap or Picture and call View.draw(Canvas) on the View. However these software-rendered usages are discouraged and have compatibility issues with hardware-only rendering features such as Config.HARDWARE bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback reports or unit testing the PixelCopy API is recommended./**
     * Used to indicate that the animation drawing cache should be kept in memory.
     *
     * @deprecated The view drawing cache was largely made obsolete with the introduction of
     * hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache
     * layers are largely unnecessary and can easily result in a net loss in performance due to the
     * cost of creating and updating the layer. In the rare cases where caching layers are useful,
     * such as for alpha animations, {@link #setLayerType(int, Paint)} handles this with hardware
     * rendering. For software-rendered snapshots of a small part of the View hierarchy or
     * individual Views it is recommended to create a {@link Canvas} from either a {@link Bitmap} or
     * {@link android.graphics.Picture} and call {@link #draw(Canvas)} on the View. However these
     * software-rendered usages are discouraged and have compatibility issues with hardware-only
     * rendering features such as {@link android.graphics.Bitmap.Config#HARDWARE Config.HARDWARE}
     * bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback
     * reports or unit testing the {@link PixelCopy} API is recommended.
     */
    @Deprecated
    public static final int PERSISTENT_ANIMATION_CACHE = 0x1;

    Used to indicate that the scrolling drawing cache should be kept in memory.
Deprecated: The view drawing cache was largely made obsolete with the introduction of hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache layers are largely unnecessary and can easily result in a net loss in performance due to the cost of creating and updating the layer. In the rare cases where caching layers are useful, such as for alpha animations, View.setLayerType(int, Paint) handles this with hardware rendering. For software-rendered snapshots of a small part of the View hierarchy or individual Views it is recommended to create a Canvas from either a Bitmap or Picture and call View.draw(Canvas) on the View. However these software-rendered usages are discouraged and have compatibility issues with hardware-only rendering features such as Config.HARDWARE bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback reports or unit testing the PixelCopy API is recommended./**
     * Used to indicate that the scrolling drawing cache should be kept in memory.
     *
     * @deprecated The view drawing cache was largely made obsolete with the introduction of
     * hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache
     * layers are largely unnecessary and can easily result in a net loss in performance due to the
     * cost of creating and updating the layer. In the rare cases where caching layers are useful,
     * such as for alpha animations, {@link #setLayerType(int, Paint)} handles this with hardware
     * rendering. For software-rendered snapshots of a small part of the View hierarchy or
     * individual Views it is recommended to create a {@link Canvas} from either a {@link Bitmap} or
     * {@link android.graphics.Picture} and call {@link #draw(Canvas)} on the View. However these
     * software-rendered usages are discouraged and have compatibility issues with hardware-only
     * rendering features such as {@link android.graphics.Bitmap.Config#HARDWARE Config.HARDWARE}
     * bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback
     * reports or unit testing the {@link PixelCopy} API is recommended.
     */
    @Deprecated
    public static final int PERSISTENT_SCROLLING_CACHE = 0x2;

    Used to indicate that all drawing caches should be kept in memory.
Deprecated: The view drawing cache was largely made obsolete with the introduction of hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache layers are largely unnecessary and can easily result in a net loss in performance due to the cost of creating and updating the layer. In the rare cases where caching layers are useful, such as for alpha animations, View.setLayerType(int, Paint) handles this with hardware rendering. For software-rendered snapshots of a small part of the View hierarchy or individual Views it is recommended to create a Canvas from either a Bitmap or Picture and call View.draw(Canvas) on the View. However these software-rendered usages are discouraged and have compatibility issues with hardware-only rendering features such as Config.HARDWARE bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback reports or unit testing the PixelCopy API is recommended./**
     * Used to indicate that all drawing caches should be kept in memory.
     *
     * @deprecated The view drawing cache was largely made obsolete with the introduction of
     * hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache
     * layers are largely unnecessary and can easily result in a net loss in performance due to the
     * cost of creating and updating the layer. In the rare cases where caching layers are useful,
     * such as for alpha animations, {@link #setLayerType(int, Paint)} handles this with hardware
     * rendering. For software-rendered snapshots of a small part of the View hierarchy or
     * individual Views it is recommended to create a {@link Canvas} from either a {@link Bitmap} or
     * {@link android.graphics.Picture} and call {@link #draw(Canvas)} on the View. However these
     * software-rendered usages are discouraged and have compatibility issues with hardware-only
     * rendering features such as {@link android.graphics.Bitmap.Config#HARDWARE Config.HARDWARE}
     * bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback
     * reports or unit testing the {@link PixelCopy} API is recommended.
     */
    @Deprecated
    public static final int PERSISTENT_ALL_CACHES = 0x3;

    // Layout Modes

    private static final int LAYOUT_MODE_UNDEFINED = -1;

    This constant is a layoutMode. Clip bounds are the raw values of left, top, right and bottom. /**
     * This constant is a {@link #setLayoutMode(int) layoutMode}.
     * Clip bounds are the raw values of {@link #getLeft() left}, {@link #getTop() top},
     * {@link #getRight() right} and {@link #getBottom() bottom}.
     */
    public static final int LAYOUT_MODE_CLIP_BOUNDS = 0;

    This constant is a layoutMode. Optical bounds describe where a widget appears to be. They sit inside the clip bounds which need to cover a larger area to allow other effects, such as shadows and glows, to be drawn. /**
     * This constant is a {@link #setLayoutMode(int) layoutMode}.
     * Optical bounds describe where a widget appears to be. They sit inside the clip
     * bounds which need to cover a larger area to allow other effects,
     * such as shadows and glows, to be drawn.
     */
    public static final int LAYOUT_MODE_OPTICAL_BOUNDS = 1;

    @hide /** @hide */
    public static int LAYOUT_MODE_DEFAULT = LAYOUT_MODE_CLIP_BOUNDS;

    We clip to padding when FLAG_CLIP_TO_PADDING and FLAG_PADDING_NOT_NULL
are set at the same time.
/**
     * We clip to padding when FLAG_CLIP_TO_PADDING and FLAG_PADDING_NOT_NULL
     * are set at the same time.
     */
    protected static final int CLIP_TO_PADDING_MASK = FLAG_CLIP_TO_PADDING | FLAG_PADDING_NOT_NULL;

    // Index of the child's left position in the mLocation array
    private static final int CHILD_LEFT_INDEX = 0;
    // Index of the child's top position in the mLocation array
    private static final int CHILD_TOP_INDEX = 1;

    // Child views of this ViewGroup
    private View[] mChildren;
    // Number of valid children in the mChildren array, the rest should be null or not
    // considered as children
    private int mChildrenCount;

    // Whether layout calls are currently being suppressed, controlled by calls to
    // suppressLayout()
    boolean mSuppressLayout = false;

    // Whether any layout calls have actually been suppressed while mSuppressLayout
    // has been true. This tracks whether we need to issue a requestLayout() when
    // layout is later re-enabled.
    private boolean mLayoutCalledWhileSuppressed = false;

    private static final int ARRAY_INITIAL_CAPACITY = 12;
    private static final int ARRAY_CAPACITY_INCREMENT = 12;

    private static float[] sDebugLines;

    // Used to draw cached views
    Paint mCachePaint;

    // Used to animate add/remove changes in layout
    private LayoutTransition mTransition;

    // The set of views that are currently being transitioned. This list is used to track views
    // being removed that should not actually be removed from the parent yet because they are
    // being animated.
    private ArrayList<View> mTransitioningViews;

    // List of children changing visibility. This is used to potentially keep rendering
    // views during a transition when they otherwise would have become gone/invisible
    private ArrayList<View> mVisibilityChangingChildren;

    // Temporary holder of presorted children, only used for
    // input/software draw dispatch for correctly Z ordering.
    private ArrayList<View> mPreSortedChildren;

    // Indicates how many of this container's child subtrees contain transient state
    @ViewDebug.ExportedProperty(category = "layout")
    private int mChildCountWithTransientState = 0;

    Currently registered axes for nested scrolling. Flag set consisting of View.SCROLL_AXIS_HORIZONTAL View.SCROLL_AXIS_VERTICAL or View.SCROLL_AXIS_NONE for null. /**
     * Currently registered axes for nested scrolling. Flag set consisting of
     * {@link #SCROLL_AXIS_HORIZONTAL} {@link #SCROLL_AXIS_VERTICAL} or {@link #SCROLL_AXIS_NONE}
     * for null.
     */
    private int mNestedScrollAxes;

    // Used to manage the list of transient views, added by addTransientView()
    private List<Integer> mTransientIndices = null;
    private List<View> mTransientViews = null;

    Keeps track of how many child views have UnhandledKeyEventListeners. This should only be
updated on the UI thread so shouldn't require explicit synchronization.
/**
     * Keeps track of how many child views have UnhandledKeyEventListeners. This should only be
     * updated on the UI thread so shouldn't require explicit synchronization.
     */
    int mChildUnhandledKeyListeners = 0;

    Empty ActionMode used as a sentinel in recursive entries to startActionModeForChild.
See Also: startActionModeForChild(View, Callback)
startActionModeForChild(View, Callback, int)/**
     * Empty ActionMode used as a sentinel in recursive entries to startActionModeForChild.
     *
     * @see #startActionModeForChild(View, android.view.ActionMode.Callback)
     * @see #startActionModeForChild(View, android.view.ActionMode.Callback, int)
     */
    private static final ActionMode SENTINEL_ACTION_MODE = new ActionMode() {
        @Override
        public void setTitle(CharSequence title) {}

        @Override
        public void setTitle(int resId) {}

        @Override
        public void setSubtitle(CharSequence subtitle) {}

        @Override
        public void setSubtitle(int resId) {}

        @Override
        public void setCustomView(View view) {}

        @Override
        public void invalidate() {}

        @Override
        public void finish() {}

        @Override
        public Menu getMenu() {
            return null;
        }

        @Override
        public CharSequence getTitle() {
            return null;
        }

        @Override
        public CharSequence getSubtitle() {
            return null;
        }

        @Override
        public View getCustomView() {
            return null;
        }

        @Override
        public MenuInflater getMenuInflater() {
            return null;
        }
    };

    public ViewGroup(Context context) {
        this(context, null);
    }

    public ViewGroup(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public ViewGroup(Context context, AttributeSet attrs, int defStyleAttr) {
        this(context, attrs, defStyleAttr, 0);
    }

    public ViewGroup(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);

        initViewGroup();
        initFromAttributes(context, attrs, defStyleAttr, defStyleRes);
    }

    private void initViewGroup() {
        // ViewGroup doesn't draw by default
        if (!debugDraw()) {
            setFlags(WILL_NOT_DRAW, DRAW_MASK);
        }
        mGroupFlags |= FLAG_CLIP_CHILDREN;
        mGroupFlags |= FLAG_CLIP_TO_PADDING;
        mGroupFlags |= FLAG_ANIMATION_DONE;
        mGroupFlags |= FLAG_ANIMATION_CACHE;
        mGroupFlags |= FLAG_ALWAYS_DRAWN_WITH_CACHE;

        if (mContext.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.HONEYCOMB) {
            mGroupFlags |= FLAG_SPLIT_MOTION_EVENTS;
        }

        setDescendantFocusability(FOCUS_BEFORE_DESCENDANTS);

        mChildren = new View[ARRAY_INITIAL_CAPACITY];
        mChildrenCount = 0;

        mPersistentDrawingCache = PERSISTENT_SCROLLING_CACHE;
    }

    private void initFromAttributes(
            Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ViewGroup, defStyleAttr,
                defStyleRes);

        final int N = a.getIndexCount();
        for (int i = 0; i < N; i++) {
            int attr = a.getIndex(i);
            switch (attr) {
                case R.styleable.ViewGroup_clipChildren:
                    setClipChildren(a.getBoolean(attr, true));
                    break;
                case R.styleable.ViewGroup_clipToPadding:
                    setClipToPadding(a.getBoolean(attr, true));
                    break;
                case R.styleable.ViewGroup_animationCache:
                    setAnimationCacheEnabled(a.getBoolean(attr, true));
                    break;
                case R.styleable.ViewGroup_persistentDrawingCache:
                    setPersistentDrawingCache(a.getInt(attr, PERSISTENT_SCROLLING_CACHE));
                    break;
                case R.styleable.ViewGroup_addStatesFromChildren:
                    setAddStatesFromChildren(a.getBoolean(attr, false));
                    break;
                case R.styleable.ViewGroup_alwaysDrawnWithCache:
                    setAlwaysDrawnWithCacheEnabled(a.getBoolean(attr, true));
                    break;
                case R.styleable.ViewGroup_layoutAnimation:
                    int id = a.getResourceId(attr, -1);
                    if (id > 0) {
                        setLayoutAnimation(AnimationUtils.loadLayoutAnimation(mContext, id));
                    }
                    break;
                case R.styleable.ViewGroup_descendantFocusability:
                    setDescendantFocusability(DESCENDANT_FOCUSABILITY_FLAGS[a.getInt(attr, 0)]);
                    break;
                case R.styleable.ViewGroup_splitMotionEvents:
                    setMotionEventSplittingEnabled(a.getBoolean(attr, false));
                    break;
                case R.styleable.ViewGroup_animateLayoutChanges:
                    boolean animateLayoutChanges = a.getBoolean(attr, false);
                    if (animateLayoutChanges) {
                        setLayoutTransition(new LayoutTransition());
                    }
                    break;
                case R.styleable.ViewGroup_layoutMode:
                    setLayoutMode(a.getInt(attr, LAYOUT_MODE_UNDEFINED));
                    break;
                case R.styleable.ViewGroup_transitionGroup:
                    setTransitionGroup(a.getBoolean(attr, false));
                    break;
                case R.styleable.ViewGroup_touchscreenBlocksFocus:
                    setTouchscreenBlocksFocus(a.getBoolean(attr, false));
                    break;
            }
        }

        a.recycle();
    }

    Gets the descendant focusability of this view group. The descendant focusability defines the relationship between this view group and its descendants when looking for a view to take focus in requestFocus(int, Rect). 
Returns: one of FOCUS_BEFORE_DESCENDANTS, FOCUS_AFTER_DESCENDANTS, FOCUS_BLOCK_DESCENDANTS./**
     * Gets the descendant focusability of this view group.  The descendant
     * focusability defines the relationship between this view group and its
     * descendants when looking for a view to take focus in
     * {@link #requestFocus(int, android.graphics.Rect)}.
     *
     * @return one of {@link #FOCUS_BEFORE_DESCENDANTS}, {@link #FOCUS_AFTER_DESCENDANTS},
     *   {@link #FOCUS_BLOCK_DESCENDANTS}.
     */
    @ViewDebug.ExportedProperty(category = "focus", mapping = {
        @ViewDebug.IntToString(from = FOCUS_BEFORE_DESCENDANTS, to = "FOCUS_BEFORE_DESCENDANTS"),
        @ViewDebug.IntToString(from = FOCUS_AFTER_DESCENDANTS, to = "FOCUS_AFTER_DESCENDANTS"),
        @ViewDebug.IntToString(from = FOCUS_BLOCK_DESCENDANTS, to = "FOCUS_BLOCK_DESCENDANTS")
    })
    public int getDescendantFocusability() {
        return mGroupFlags & FLAG_MASK_FOCUSABILITY;
    }

    Set the descendant focusability of this view group. This defines the relationship between this view group and its descendants when looking for a view to take focus in requestFocus(int, Rect). 
Params: focusability – one of FOCUS_BEFORE_DESCENDANTS, FOCUS_AFTER_DESCENDANTS, FOCUS_BLOCK_DESCENDANTS./**
     * Set the descendant focusability of this view group. This defines the relationship
     * between this view group and its descendants when looking for a view to
     * take focus in {@link #requestFocus(int, android.graphics.Rect)}.
     *
     * @param focusability one of {@link #FOCUS_BEFORE_DESCENDANTS}, {@link #FOCUS_AFTER_DESCENDANTS},
     *   {@link #FOCUS_BLOCK_DESCENDANTS}.
     */
    public void setDescendantFocusability(int focusability) {
        switch (focusability) {
            case FOCUS_BEFORE_DESCENDANTS:
            case FOCUS_AFTER_DESCENDANTS:
            case FOCUS_BLOCK_DESCENDANTS:
                break;
            default:
                throw new IllegalArgumentException("must be one of FOCUS_BEFORE_DESCENDANTS, "
                        + "FOCUS_AFTER_DESCENDANTS, FOCUS_BLOCK_DESCENDANTS");
        }
        mGroupFlags &= ~FLAG_MASK_FOCUSABILITY;
        mGroupFlags |= (focusability & FLAG_MASK_FOCUSABILITY);
    }

    @Override
    void handleFocusGainInternal(int direction, Rect previouslyFocusedRect) {
        if (mFocused != null) {
            mFocused.unFocus(this);
            mFocused = null;
            mFocusedInCluster = null;
        }
        super.handleFocusGainInternal(direction, previouslyFocusedRect);
    }

    @Override
    public void requestChildFocus(View child, View focused) {
        if (DBG) {
            System.out.println(this + " requestChildFocus()");
        }
        if (getDescendantFocusability() == FOCUS_BLOCK_DESCENDANTS) {
            return;
        }

        // Unfocus us, if necessary
        super.unFocus(focused);

        // We had a previous notion of who had focus. Clear it.
        if (mFocused != child) {
            if (mFocused != null) {
                mFocused.unFocus(focused);
            }

            mFocused = child;
        }
        if (mParent != null) {
            mParent.requestChildFocus(this, focused);
        }
    }

    void setDefaultFocus(View child) {
        // Stop at any higher view which is explicitly focused-by-default
        if (mDefaultFocus != null && mDefaultFocus.isFocusedByDefault()) {
            return;
        }

        mDefaultFocus = child;

        if (mParent instanceof ViewGroup) {
            ((ViewGroup) mParent).setDefaultFocus(this);
        }
    }

    Clears the default-focus chain from {@param child} up to the first parent which has another
default-focusable branch below it or until there is no default-focus chain.
Params: child – /**
     * Clears the default-focus chain from {@param child} up to the first parent which has another
     * default-focusable branch below it or until there is no default-focus chain.
     *
     * @param child
     */
    void clearDefaultFocus(View child) {
        // Stop at any higher view which is explicitly focused-by-default
        if (mDefaultFocus != child && mDefaultFocus != null
                && mDefaultFocus.isFocusedByDefault()) {
            return;
        }

        mDefaultFocus = null;

        // Search child siblings for default focusables.
        for (int i = 0; i < mChildrenCount; ++i) {
            View sibling = mChildren[i];
            if (sibling.isFocusedByDefault()) {
                mDefaultFocus = sibling;
                return;
            } else if (mDefaultFocus == null && sibling.hasDefaultFocus()) {
                mDefaultFocus = sibling;
            }
        }

        if (mParent instanceof ViewGroup) {
            ((ViewGroup) mParent).clearDefaultFocus(this);
        }
    }

    @Override
    boolean hasDefaultFocus() {
        return mDefaultFocus != null || super.hasDefaultFocus();
    }

    Removes child (and associated focusedInCluster chain) from the cluster containing it. 
 This is intended to be run on child's immediate parent. This is necessary because the chain is sometimes cleared after child has been detached. /**
     * Removes {@code child} (and associated focusedInCluster chain) from the cluster containing
     * it.
     * <br>
     * This is intended to be run on {@code child}'s immediate parent. This is necessary because
     * the chain is sometimes cleared after {@code child} has been detached.
     */
    void clearFocusedInCluster(View child) {
        if (mFocusedInCluster != child) {
            return;
        }
        clearFocusedInCluster();
    }

    Removes the focusedInCluster chain from this up to the cluster containing it.
/**
     * Removes the focusedInCluster chain from this up to the cluster containing it.
     */
    void clearFocusedInCluster() {
        View top = findKeyboardNavigationCluster();
        ViewParent parent = this;
        do {
            ((ViewGroup) parent).mFocusedInCluster = null;
            if (parent == top) {
                break;
            }
            parent = parent.getParent();
        } while (parent instanceof ViewGroup);
    }

    @Override
    public void focusableViewAvailable(View v) {
        if (mParent != null
                // shortcut: don't report a new focusable view if we block our descendants from
                // getting focus or if we're not visible
                && (getDescendantFocusability() != FOCUS_BLOCK_DESCENDANTS)
                && ((mViewFlags & VISIBILITY_MASK) == VISIBLE)
                && (isFocusableInTouchMode() || !shouldBlockFocusForTouchscreen())
                // shortcut: don't report a new focusable view if we already are focused
                // (and we don't prefer our descendants)
                //
                // note: knowing that mFocused is non-null is not a good enough reason
                // to break the traversal since in that case we'd actually have to find
                // the focused view and make sure it wasn't FOCUS_AFTER_DESCENDANTS and
                // an ancestor of v; this will get checked for at ViewAncestor
                && !(isFocused() && getDescendantFocusability() != FOCUS_AFTER_DESCENDANTS)) {
            mParent.focusableViewAvailable(v);
        }
    }

    @Override
    public boolean showContextMenuForChild(View originalView) {
        if (isShowingContextMenuWithCoords()) {
            // We're being called for compatibility. Return false and let the version
            // with coordinates recurse up.
            return false;
        }
        return mParent != null && mParent.showContextMenuForChild(originalView);
    }

    @hide used internally for compatibility with existing app code only/**
     * @hide used internally for compatibility with existing app code only
     */
    public final boolean isShowingContextMenuWithCoords() {
        return (mGroupFlags & FLAG_SHOW_CONTEXT_MENU_WITH_COORDS) != 0;
    }

    @Override
    public boolean showContextMenuForChild(View originalView, float x, float y) {
        try {
            mGroupFlags |= FLAG_SHOW_CONTEXT_MENU_WITH_COORDS;
            if (showContextMenuForChild(originalView)) {
                return true;
            }
        } finally {
            mGroupFlags &= ~FLAG_SHOW_CONTEXT_MENU_WITH_COORDS;
        }
        return mParent != null && mParent.showContextMenuForChild(originalView, x, y);
    }

    @Override
    public ActionMode startActionModeForChild(View originalView, ActionMode.Callback callback) {
        if ((mGroupFlags & FLAG_START_ACTION_MODE_FOR_CHILD_IS_TYPED) == 0) {
            // This is the original call.
            try {
                mGroupFlags |= FLAG_START_ACTION_MODE_FOR_CHILD_IS_NOT_TYPED;
                return startActionModeForChild(originalView, callback, ActionMode.TYPE_PRIMARY);
            } finally {
                mGroupFlags &= ~FLAG_START_ACTION_MODE_FOR_CHILD_IS_NOT_TYPED;
            }
        } else {
            // We are being called from the new method with type.
            return SENTINEL_ACTION_MODE;
        }
    }

    @Override
    public ActionMode startActionModeForChild(
            View originalView, ActionMode.Callback callback, int type) {
        if ((mGroupFlags & FLAG_START_ACTION_MODE_FOR_CHILD_IS_NOT_TYPED) == 0
                && type == ActionMode.TYPE_PRIMARY) {
            ActionMode mode;
            try {
                mGroupFlags |= FLAG_START_ACTION_MODE_FOR_CHILD_IS_TYPED;
                mode = startActionModeForChild(originalView, callback);
            } finally {
                mGroupFlags &= ~FLAG_START_ACTION_MODE_FOR_CHILD_IS_TYPED;
            }
            if (mode != SENTINEL_ACTION_MODE) {
                return mode;
            }
        }
        if (mParent != null) {
            try {
                return mParent.startActionModeForChild(originalView, callback, type);
            } catch (AbstractMethodError ame) {
                // Custom view parents might not implement this method.
                return mParent.startActionModeForChild(originalView, callback);
            }
        }
        return null;
    }

    @hide /**
     * @hide
     */
    @Override
    public boolean dispatchActivityResult(
            String who, int requestCode, int resultCode, Intent data) {
        if (super.dispatchActivityResult(who, requestCode, resultCode, data)) {
            return true;
        }
        int childCount = getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = getChildAt(i);
            if (child.dispatchActivityResult(who, requestCode, resultCode, data)) {
                return true;
            }
        }
        return false;
    }

    Find the nearest view in the specified direction that wants to take
focus.
Params: focused – The view that currently has focus
direction – One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and
       FOCUS_RIGHT, or 0 for not applicable./**
     * Find the nearest view in the specified direction that wants to take
     * focus.
     *
     * @param focused The view that currently has focus
     * @param direction One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and
     *        FOCUS_RIGHT, or 0 for not applicable.
     */
    @Override
    public View focusSearch(View focused, int direction) {
        if (isRootNamespace()) {
            // root namespace means we should consider ourselves the top of the
            // tree for focus searching; otherwise we could be focus searching
            // into other tabs.  see LocalActivityManager and TabHost for more info.
            return FocusFinder.getInstance().findNextFocus(this, focused, direction);
        } else if (mParent != null) {
            return mParent.focusSearch(focused, direction);
        }
        return null;
    }

    @Override
    public boolean requestChildRectangleOnScreen(View child, Rect rectangle, boolean immediate) {
        return false;
    }

    @Override
    public boolean requestSendAccessibilityEvent(View child, AccessibilityEvent event) {
        ViewParent parent = mParent;
        if (parent == null) {
            return false;
        }
        final boolean propagate = onRequestSendAccessibilityEvent(child, event);
        if (!propagate) {
            return false;
        }
        return parent.requestSendAccessibilityEvent(this, event);
    }

    Called when a child has requested sending an AccessibilityEvent and gives an opportunity to its parent to augment the event.  If an AccessibilityDelegate has been specified via calling View.setAccessibilityDelegate(AccessibilityDelegate) its AccessibilityDelegate.onRequestSendAccessibilityEvent(ViewGroup, View, AccessibilityEvent) is responsible for handling this call. 
Params: child – The child which requests sending the event.
event – The event to be sent.
See Also: requestSendAccessibilityEvent(View, AccessibilityEvent)
Returns: True if the event should be sent./**
     * Called when a child has requested sending an {@link AccessibilityEvent} and
     * gives an opportunity to its parent to augment the event.
     * <p>
     * If an {@link android.view.View.AccessibilityDelegate} has been specified via calling
     * {@link android.view.View#setAccessibilityDelegate(android.view.View.AccessibilityDelegate)} its
     * {@link android.view.View.AccessibilityDelegate#onRequestSendAccessibilityEvent(ViewGroup, View, AccessibilityEvent)}
     * is responsible for handling this call.
     * </p>
     *
     * @param child The child which requests sending the event.
     * @param event The event to be sent.
     * @return True if the event should be sent.
     *
     * @see #requestSendAccessibilityEvent(View, AccessibilityEvent)
     */
    public boolean onRequestSendAccessibilityEvent(View child, AccessibilityEvent event) {
        if (mAccessibilityDelegate != null) {
            return mAccessibilityDelegate.onRequestSendAccessibilityEvent(this, child, event);
        } else {
            return onRequestSendAccessibilityEventInternal(child, event);
        }
    }

    See Also:  Note: Called from the default AccessibilityDelegate.
@hide /**
     * @see #onRequestSendAccessibilityEvent(View, AccessibilityEvent)
     *
     * Note: Called from the default {@link View.AccessibilityDelegate}.
     *
     * @hide
     */
    public boolean onRequestSendAccessibilityEventInternal(View child, AccessibilityEvent event) {
        return true;
    }

    Called when a child view has changed whether or not it is tracking transient state.
/**
     * Called when a child view has changed whether or not it is tracking transient state.
     */
    @Override
    public void childHasTransientStateChanged(View child, boolean childHasTransientState) {
        final boolean oldHasTransientState = hasTransientState();
        if (childHasTransientState) {
            mChildCountWithTransientState++;
        } else {
            mChildCountWithTransientState--;
        }

        final boolean newHasTransientState = hasTransientState();
        if (mParent != null && oldHasTransientState != newHasTransientState) {
            try {
                mParent.childHasTransientStateChanged(this, newHasTransientState);
            } catch (AbstractMethodError e) {
                Log.e(TAG, mParent.getClass().getSimpleName() +
                        " does not fully implement ViewParent", e);
            }
        }
    }

    @Override
    public boolean hasTransientState() {
        return mChildCountWithTransientState > 0 || super.hasTransientState();
    }

    @Override
    public boolean dispatchUnhandledMove(View focused, int direction) {
        return mFocused != null &&
                mFocused.dispatchUnhandledMove(focused, direction);
    }

    @Override
    public void clearChildFocus(View child) {
        if (DBG) {
            System.out.println(this + " clearChildFocus()");
        }

        mFocused = null;
        if (mParent != null) {
            mParent.clearChildFocus(this);
        }
    }

    @Override
    public void clearFocus() {
        if (DBG) {
            System.out.println(this + " clearFocus()");
        }
        if (mFocused == null) {
            super.clearFocus();
        } else {
            View focused = mFocused;
            mFocused = null;
            focused.clearFocus();
        }
    }

    @Override
    void unFocus(View focused) {
        if (DBG) {
            System.out.println(this + " unFocus()");
        }
        if (mFocused == null) {
            super.unFocus(focused);
        } else {
            mFocused.unFocus(focused);
            mFocused = null;
        }
    }

    Returns the focused child of this view, if any. The child may have focus
or contain focus.
Returns: the focused child or null./**
     * Returns the focused child of this view, if any. The child may have focus
     * or contain focus.
     *
     * @return the focused child or null.
     */
    public View getFocusedChild() {
        return mFocused;
    }

    View getDeepestFocusedChild() {
        View v = this;
        while (v != null) {
            if (v.isFocused()) {
                return v;
            }
            v = v instanceof ViewGroup ? ((ViewGroup) v).getFocusedChild() : null;
        }
        return null;
    }

    Returns true if this view has or contains focus
Returns: true if this view has or contains focus/**
     * Returns true if this view has or contains focus
     *
     * @return true if this view has or contains focus
     */
    @Override
    public boolean hasFocus() {
        return (mPrivateFlags & PFLAG_FOCUSED) != 0 || mFocused != null;
    }

    /*
     * (non-Javadoc)
     *
     * @see android.view.View#findFocus()
     */
    @Override
    public View findFocus() {
        if (DBG) {
            System.out.println("Find focus in " + this + ": flags="
                    + isFocused() + ", child=" + mFocused);
        }

        if (isFocused()) {
            return this;
        }

        if (mFocused != null) {
            return mFocused.findFocus();
        }
        return null;
    }

    @Override
    boolean hasFocusable(boolean allowAutoFocus, boolean dispatchExplicit) {
        // This should probably be super.hasFocusable, but that would change
        // behavior. Historically, we have not checked the ancestor views for
        // shouldBlockFocusForTouchscreen() in ViewGroup.hasFocusable.

        // Invisible and gone views are never focusable.
        if ((mViewFlags & VISIBILITY_MASK) != VISIBLE) {
            return false;
        }

        // Only use effective focusable value when allowed.
        if ((allowAutoFocus || getFocusable() != FOCUSABLE_AUTO) && isFocusable()) {
            return true;
        }

        // Determine whether we have a focused descendant.
        final int descendantFocusability = getDescendantFocusability();
        if (descendantFocusability != FOCUS_BLOCK_DESCENDANTS) {
            return hasFocusableChild(dispatchExplicit);
        }

        return false;
    }

    boolean hasFocusableChild(boolean dispatchExplicit) {
        // Determine whether we have a focusable descendant.
        final int count = mChildrenCount;
        final View[] children = mChildren;

        for (int i = 0; i < count; i++) {
            final View child = children[i];

            // In case the subclass has overridden has[Explicit]Focusable, dispatch
            // to the expected one for each child even though we share logic here.
            if ((dispatchExplicit && child.hasExplicitFocusable())
                    || (!dispatchExplicit && child.hasFocusable())) {
                return true;
            }
        }

        return false;
    }

    @Override
    public void addFocusables(ArrayList<View> views, int direction, int focusableMode) {
        final int focusableCount = views.size();

        final int descendantFocusability = getDescendantFocusability();
        final boolean blockFocusForTouchscreen = shouldBlockFocusForTouchscreen();
        final boolean focusSelf = (isFocusableInTouchMode() || !blockFocusForTouchscreen);

        if (descendantFocusability == FOCUS_BLOCK_DESCENDANTS) {
            if (focusSelf) {
                super.addFocusables(views, direction, focusableMode);
            }
            return;
        }

        if (blockFocusForTouchscreen) {
            focusableMode |= FOCUSABLES_TOUCH_MODE;
        }

        if ((descendantFocusability == FOCUS_BEFORE_DESCENDANTS) && focusSelf) {
            super.addFocusables(views, direction, focusableMode);
        }

        int count = 0;
        final View[] children = new View[mChildrenCount];
        for (int i = 0; i < mChildrenCount; ++i) {
            View child = mChildren[i];
            if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE) {
                children[count++] = child;
            }
        }
        FocusFinder.sort(children, 0, count, this, isLayoutRtl());
        for (int i = 0; i < count; ++i) {
            children[i].addFocusables(views, direction, focusableMode);
        }

        // When set to FOCUS_AFTER_DESCENDANTS, we only add ourselves if
        // there aren't any focusable descendants.  this is
        // to avoid the focus search finding layouts when a more precise search
        // among the focusable children would be more interesting.
        if ((descendantFocusability == FOCUS_AFTER_DESCENDANTS) && focusSelf
                && focusableCount == views.size()) {
            super.addFocusables(views, direction, focusableMode);
        }
    }

    @Override
    public void addKeyboardNavigationClusters(Collection<View> views, int direction) {
        final int focusableCount = views.size();

        if (isKeyboardNavigationCluster()) {
            // Cluster-navigation can enter a touchscreenBlocksFocus cluster, so temporarily
            // disable touchscreenBlocksFocus to evaluate whether it contains focusables.
            final boolean blockedFocus = getTouchscreenBlocksFocus();
            try {
                setTouchscreenBlocksFocusNoRefocus(false);
                super.addKeyboardNavigationClusters(views, direction);
            } finally {
                setTouchscreenBlocksFocusNoRefocus(blockedFocus);
            }
        } else {
            super.addKeyboardNavigationClusters(views, direction);
        }

        if (focusableCount != views.size()) {
            // No need to look for groups inside a group.
            return;
        }

        if (getDescendantFocusability() == FOCUS_BLOCK_DESCENDANTS) {
            return;
        }

        int count = 0;
        final View[] visibleChildren = new View[mChildrenCount];
        for (int i = 0; i < mChildrenCount; ++i) {
            final View child = mChildren[i];
            if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE) {
                visibleChildren[count++] = child;
            }
        }
        FocusFinder.sort(visibleChildren, 0, count, this, isLayoutRtl());
        for (int i = 0; i < count; ++i) {
            visibleChildren[i].addKeyboardNavigationClusters(views, direction);
        }
    }

    Set whether this ViewGroup should ignore focus requests for itself and its children.
If this option is enabled and the ViewGroup or a descendant currently has focus, focus
will proceed forward.
Params: touchscreenBlocksFocus – true to enable blocking focus in the presence of a touchscreen/**
     * Set whether this ViewGroup should ignore focus requests for itself and its children.
     * If this option is enabled and the ViewGroup or a descendant currently has focus, focus
     * will proceed forward.
     *
     * @param touchscreenBlocksFocus true to enable blocking focus in the presence of a touchscreen
     */
    public void setTouchscreenBlocksFocus(boolean touchscreenBlocksFocus) {
        if (touchscreenBlocksFocus) {
            mGroupFlags |= FLAG_TOUCHSCREEN_BLOCKS_FOCUS;
            if (hasFocus() && !isKeyboardNavigationCluster()) {
                final View focusedChild = getDeepestFocusedChild();
                if (!focusedChild.isFocusableInTouchMode()) {
                    final View newFocus = focusSearch(FOCUS_FORWARD);
                    if (newFocus != null) {
                        newFocus.requestFocus();
                    }
                }
            }
        } else {
            mGroupFlags &= ~FLAG_TOUCHSCREEN_BLOCKS_FOCUS;
        }
    }

    private void setTouchscreenBlocksFocusNoRefocus(boolean touchscreenBlocksFocus) {
        if (touchscreenBlocksFocus) {
            mGroupFlags |= FLAG_TOUCHSCREEN_BLOCKS_FOCUS;
        } else {
            mGroupFlags &= ~FLAG_TOUCHSCREEN_BLOCKS_FOCUS;
        }
    }

    Check whether this ViewGroup should ignore focus requests for itself and its children.
/**
     * Check whether this ViewGroup should ignore focus requests for itself and its children.
     */
    @ViewDebug.ExportedProperty(category = "focus")
    public boolean getTouchscreenBlocksFocus() {
        return (mGroupFlags & FLAG_TOUCHSCREEN_BLOCKS_FOCUS) != 0;
    }

    boolean shouldBlockFocusForTouchscreen() {
        // There is a special case for keyboard-navigation clusters. We allow cluster navigation
        // to jump into blockFocusForTouchscreen ViewGroups which are clusters. Once in the
        // cluster, focus is free to move around within it.
        return getTouchscreenBlocksFocus() &&
                mContext.getPackageManager().hasSystemFeature(PackageManager.FEATURE_TOUCHSCREEN)
                && !(isKeyboardNavigationCluster()
                        && (hasFocus() || (findKeyboardNavigationCluster() != this)));
    }

    @Override
    public void findViewsWithText(ArrayList<View> outViews, CharSequence text, int flags) {
        super.findViewsWithText(outViews, text, flags);
        final int childrenCount = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < childrenCount; i++) {
            View child = children[i];
            if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE
                    && (child.mPrivateFlags & PFLAG_IS_ROOT_NAMESPACE) == 0) {
                child.findViewsWithText(outViews, text, flags);
            }
        }
    }

    @hide /** @hide */
    @Override
    public View findViewByAccessibilityIdTraversal(int accessibilityId) {
        View foundView = super.findViewByAccessibilityIdTraversal(accessibilityId);
        if (foundView != null) {
            return foundView;
        }

        if (getAccessibilityNodeProvider() != null) {
            return null;
        }

        final int childrenCount = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < childrenCount; i++) {
            View child = children[i];
            foundView = child.findViewByAccessibilityIdTraversal(accessibilityId);
            if (foundView != null) {
                return foundView;
            }
        }

        return null;
    }

    @hide /** @hide */
    @Override
    public View findViewByAutofillIdTraversal(int autofillId) {
        View foundView = super.findViewByAutofillIdTraversal(autofillId);
        if (foundView != null) {
            return foundView;
        }

        final int childrenCount = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < childrenCount; i++) {
            View child = children[i];
            foundView = child.findViewByAutofillIdTraversal(autofillId);
            if (foundView != null) {
                return foundView;
            }
        }

        return null;
    }

    @Override
    public void dispatchWindowFocusChanged(boolean hasFocus) {
        super.dispatchWindowFocusChanged(hasFocus);
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].dispatchWindowFocusChanged(hasFocus);
        }
    }

    @Override
    public void addTouchables(ArrayList<View> views) {
        super.addTouchables(views);

        final int count = mChildrenCount;
        final View[] children = mChildren;

        for (int i = 0; i < count; i++) {
            final View child = children[i];
            if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE) {
                child.addTouchables(views);
            }
        }
    }

    @hide /**
     * @hide
     */
    @Override
    public void makeOptionalFitsSystemWindows() {
        super.makeOptionalFitsSystemWindows();
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].makeOptionalFitsSystemWindows();
        }
    }

    @Override
    public void dispatchDisplayHint(int hint) {
        super.dispatchDisplayHint(hint);
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].dispatchDisplayHint(hint);
        }
    }

    Called when a view's visibility has changed. Notify the parent to take any appropriate
action.
Params: child – The view whose visibility has changed
oldVisibility – The previous visibility value (GONE, INVISIBLE, or VISIBLE).
newVisibility – The new visibility value (GONE, INVISIBLE, or VISIBLE).
@hide /**
     * Called when a view's visibility has changed. Notify the parent to take any appropriate
     * action.
     *
     * @param child The view whose visibility has changed
     * @param oldVisibility The previous visibility value (GONE, INVISIBLE, or VISIBLE).
     * @param newVisibility The new visibility value (GONE, INVISIBLE, or VISIBLE).
     * @hide
     */
    protected void onChildVisibilityChanged(View child, int oldVisibility, int newVisibility) {
        if (mTransition != null) {
            if (newVisibility == VISIBLE) {
                mTransition.showChild(this, child, oldVisibility);
            } else {
                mTransition.hideChild(this, child, newVisibility);
                if (mTransitioningViews != null && mTransitioningViews.contains(child)) {
                    // Only track this on disappearing views - appearing views are already visible
                    // and don't need special handling during drawChild()
                    if (mVisibilityChangingChildren == null) {
                        mVisibilityChangingChildren = new ArrayList<View>();
                    }
                    mVisibilityChangingChildren.add(child);
                    addDisappearingView(child);
                }
            }
        }

        // in all cases, for drags
        if (newVisibility == VISIBLE && mCurrentDragStartEvent != null) {
            if (!mChildrenInterestedInDrag.contains(child)) {
                notifyChildOfDragStart(child);
            }
        }
    }

    @Override
    protected void dispatchVisibilityChanged(View changedView, int visibility) {
        super.dispatchVisibilityChanged(changedView, visibility);
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].dispatchVisibilityChanged(changedView, visibility);
        }
    }

    @Override
    public void dispatchWindowVisibilityChanged(int visibility) {
        super.dispatchWindowVisibilityChanged(visibility);
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].dispatchWindowVisibilityChanged(visibility);
        }
    }

    @Override
    boolean dispatchVisibilityAggregated(boolean isVisible) {
        isVisible = super.dispatchVisibilityAggregated(isVisible);
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            // Only dispatch to visible children. Not visible children and their subtrees already
            // know that they aren't visible and that's not going to change as a result of
            // whatever triggered this dispatch.
            if (children[i].getVisibility() == VISIBLE) {
                children[i].dispatchVisibilityAggregated(isVisible);
            }
        }
        return isVisible;
    }

    @Override
    public void dispatchConfigurationChanged(Configuration newConfig) {
        super.dispatchConfigurationChanged(newConfig);
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].dispatchConfigurationChanged(newConfig);
        }
    }

    @Override
    public void recomputeViewAttributes(View child) {
        if (mAttachInfo != null && !mAttachInfo.mRecomputeGlobalAttributes) {
            ViewParent parent = mParent;
            if (parent != null) parent.recomputeViewAttributes(this);
        }
    }

    @Override
    void dispatchCollectViewAttributes(AttachInfo attachInfo, int visibility) {
        if ((visibility & VISIBILITY_MASK) == VISIBLE) {
            super.dispatchCollectViewAttributes(attachInfo, visibility);
            final int count = mChildrenCount;
            final View[] children = mChildren;
            for (int i = 0; i < count; i++) {
                final View child = children[i];
                child.dispatchCollectViewAttributes(attachInfo,
                        visibility | (child.mViewFlags&VISIBILITY_MASK));
            }
        }
    }

    @Override
    public void bringChildToFront(View child) {
        final int index = indexOfChild(child);
        if (index >= 0) {
            removeFromArray(index);
            addInArray(child, mChildrenCount);
            child.mParent = this;
            requestLayout();
            invalidate();
        }
    }

    private PointF getLocalPoint() {
        if (mLocalPoint == null) mLocalPoint = new PointF();
        return mLocalPoint;
    }

    @Override
    boolean dispatchDragEnterExitInPreN(DragEvent event) {
        if (event.mAction == DragEvent.ACTION_DRAG_EXITED && mCurrentDragChild != null) {
            // The drag exited a sub-tree of views; notify of the exit all descendants that are in
            // entered state.
            // We don't need this recursive delivery for ENTERED events because they get generated
            // from the recursive delivery of LOCATION/DROP events, and hence, don't need their own
            // recursion.
            mCurrentDragChild.dispatchDragEnterExitInPreN(event);
            mCurrentDragChild = null;
        }
        return mIsInterestedInDrag && super.dispatchDragEnterExitInPreN(event);
    }

    // TODO: Write real docs
    @Override
    public boolean dispatchDragEvent(DragEvent event) {
        boolean retval = false;
        final float tx = event.mX;
        final float ty = event.mY;
        final ClipData td = event.mClipData;

        // Dispatch down the view hierarchy
        final PointF localPoint = getLocalPoint();

        switch (event.mAction) {
        case DragEvent.ACTION_DRAG_STARTED: {
            // Clear the state to recalculate which views we drag over.
            mCurrentDragChild = null;

            // Set up our tracking of drag-started notifications
            mCurrentDragStartEvent = DragEvent.obtain(event);
            if (mChildrenInterestedInDrag == null) {
                mChildrenInterestedInDrag = new HashSet<View>();
            } else {
                mChildrenInterestedInDrag.clear();
            }

            // Now dispatch down to our children, caching the responses
            final int count = mChildrenCount;
            final View[] children = mChildren;
            for (int i = 0; i < count; i++) {
                final View child = children[i];
                child.mPrivateFlags2 &= ~View.DRAG_MASK;
                if (child.getVisibility() == VISIBLE) {
                    if (notifyChildOfDragStart(children[i])) {
                        retval = true;
                    }
                }
            }

            // Notify itself of the drag start.
            mIsInterestedInDrag = super.dispatchDragEvent(event);
            if (mIsInterestedInDrag) {
                retval = true;
            }

            if (!retval) {
                // Neither us nor any of our children are interested in this drag, so stop tracking
                // the current drag event.
                mCurrentDragStartEvent.recycle();
                mCurrentDragStartEvent = null;
            }
        } break;

        case DragEvent.ACTION_DRAG_ENDED: {
            // Release the bookkeeping now that the drag lifecycle has ended
            final HashSet<View> childrenInterestedInDrag = mChildrenInterestedInDrag;
            if (childrenInterestedInDrag != null) {
                for (View child : childrenInterestedInDrag) {
                    // If a child was interested in the ongoing drag, it's told that it's over
                    if (child.dispatchDragEvent(event)) {
                        retval = true;
                    }
                }
                childrenInterestedInDrag.clear();
            }
            if (mCurrentDragStartEvent != null) {
                mCurrentDragStartEvent.recycle();
                mCurrentDragStartEvent = null;
            }

            if (mIsInterestedInDrag) {
                if (super.dispatchDragEvent(event)) {
                    retval = true;
                }
                mIsInterestedInDrag = false;
            }
        } break;

        case DragEvent.ACTION_DRAG_LOCATION:
        case DragEvent.ACTION_DROP: {
            // Find the [possibly new] drag target
            View target = findFrontmostDroppableChildAt(event.mX, event.mY, localPoint);

            if (target != mCurrentDragChild) {
                if (sCascadedDragDrop) {
                    // For pre-Nougat apps, make sure that the whole hierarchy of views that contain
                    // the drag location is kept in the state between ENTERED and EXITED events.
                    // (Starting with N, only the innermost view will be in that state).

                    final int action = event.mAction;
                    // Position should not be available for ACTION_DRAG_ENTERED and
                    // ACTION_DRAG_EXITED.
                    event.mX = 0;
                    event.mY = 0;
                    event.mClipData = null;

                    if (mCurrentDragChild != null) {
                        event.mAction = DragEvent.ACTION_DRAG_EXITED;
                        mCurrentDragChild.dispatchDragEnterExitInPreN(event);
                    }

                    if (target != null) {
                        event.mAction = DragEvent.ACTION_DRAG_ENTERED;
                        target.dispatchDragEnterExitInPreN(event);
                    }

                    event.mAction = action;
                    event.mX = tx;
                    event.mY = ty;
                    event.mClipData = td;
                }
                mCurrentDragChild = target;
            }

            if (target == null && mIsInterestedInDrag) {
                target = this;
            }

            // Dispatch the actual drag notice, localized into the target coordinates.
            if (target != null) {
                if (target != this) {
                    event.mX = localPoint.x;
                    event.mY = localPoint.y;

                    retval = target.dispatchDragEvent(event);

                    event.mX = tx;
                    event.mY = ty;

                    if (mIsInterestedInDrag) {
                        final boolean eventWasConsumed;
                        if (sCascadedDragDrop) {
                            eventWasConsumed = retval;
                        } else {
                            eventWasConsumed = event.mEventHandlerWasCalled;
                        }

                        if (!eventWasConsumed) {
                            retval = super.dispatchDragEvent(event);
                        }
                    }
                } else {
                    retval = super.dispatchDragEvent(event);
                }
            }
        } break;
        }

        return retval;
    }

    // Find the frontmost child view that lies under the given point, and calculate
    // the position within its own local coordinate system.
    View findFrontmostDroppableChildAt(float x, float y, PointF outLocalPoint) {
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = count - 1; i >= 0; i--) {
            final View child = children[i];
            if (!child.canAcceptDrag()) {
                continue;
            }

            if (isTransformedTouchPointInView(x, y, child, outLocalPoint)) {
                return child;
            }
        }
        return null;
    }

    boolean notifyChildOfDragStart(View child) {
        // The caller guarantees that the child is not in mChildrenInterestedInDrag yet.

        if (ViewDebug.DEBUG_DRAG) {
            Log.d(View.VIEW_LOG_TAG, "Sending drag-started to view: " + child);
        }

        final float tx = mCurrentDragStartEvent.mX;
        final float ty = mCurrentDragStartEvent.mY;

        final float[] point = getTempPoint();
        point[0] = tx;
        point[1] = ty;
        transformPointToViewLocal(point, child);

        mCurrentDragStartEvent.mX = point[0];
        mCurrentDragStartEvent.mY = point[1];
        final boolean canAccept = child.dispatchDragEvent(mCurrentDragStartEvent);
        mCurrentDragStartEvent.mX = tx;
        mCurrentDragStartEvent.mY = ty;
        mCurrentDragStartEvent.mEventHandlerWasCalled = false;
        if (canAccept) {
            mChildrenInterestedInDrag.add(child);
            if (!child.canAcceptDrag()) {
                child.mPrivateFlags2 |= View.PFLAG2_DRAG_CAN_ACCEPT;
                child.refreshDrawableState();
            }
        }
        return canAccept;
    }

    @Override
    public void dispatchWindowSystemUiVisiblityChanged(int visible) {
        super.dispatchWindowSystemUiVisiblityChanged(visible);

        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i=0; i <count; i++) {
            final View child = children[i];
            child.dispatchWindowSystemUiVisiblityChanged(visible);
        }
    }

    @Override
    public void dispatchSystemUiVisibilityChanged(int visible) {
        super.dispatchSystemUiVisibilityChanged(visible);

        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i=0; i <count; i++) {
            final View child = children[i];
            child.dispatchSystemUiVisibilityChanged(visible);
        }
    }

    @Override
    boolean updateLocalSystemUiVisibility(int localValue, int localChanges) {
        boolean changed = super.updateLocalSystemUiVisibility(localValue, localChanges);

        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i=0; i <count; i++) {
            final View child = children[i];
            changed |= child.updateLocalSystemUiVisibility(localValue, localChanges);
        }
        return changed;
    }

    @Override
    public boolean dispatchKeyEventPreIme(KeyEvent event) {
        if ((mPrivateFlags & (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS))
                == (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS)) {
            return super.dispatchKeyEventPreIme(event);
        } else if (mFocused != null && (mFocused.mPrivateFlags & PFLAG_HAS_BOUNDS)
                == PFLAG_HAS_BOUNDS) {
            return mFocused.dispatchKeyEventPreIme(event);
        }
        return false;
    }

    @Override
    public boolean dispatchKeyEvent(KeyEvent event) {
        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onKeyEvent(event, 1);
        }

        if ((mPrivateFlags & (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS))
                == (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS)) {
            if (super.dispatchKeyEvent(event)) {
                return true;
            }
        } else if (mFocused != null && (mFocused.mPrivateFlags & PFLAG_HAS_BOUNDS)
                == PFLAG_HAS_BOUNDS) {
            if (mFocused.dispatchKeyEvent(event)) {
                return true;
            }
        }

        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onUnhandledEvent(event, 1);
        }
        return false;
    }

    @Override
    public boolean dispatchKeyShortcutEvent(KeyEvent event) {
        if ((mPrivateFlags & (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS))
                == (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS)) {
            return super.dispatchKeyShortcutEvent(event);
        } else if (mFocused != null && (mFocused.mPrivateFlags & PFLAG_HAS_BOUNDS)
                == PFLAG_HAS_BOUNDS) {
            return mFocused.dispatchKeyShortcutEvent(event);
        }
        return false;
    }

    @Override
    public boolean dispatchTrackballEvent(MotionEvent event) {
        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onTrackballEvent(event, 1);
        }

        if ((mPrivateFlags & (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS))
                == (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS)) {
            if (super.dispatchTrackballEvent(event)) {
                return true;
            }
        } else if (mFocused != null && (mFocused.mPrivateFlags & PFLAG_HAS_BOUNDS)
                == PFLAG_HAS_BOUNDS) {
            if (mFocused.dispatchTrackballEvent(event)) {
                return true;
            }
        }

        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onUnhandledEvent(event, 1);
        }
        return false;
    }

    @Override
    public boolean dispatchCapturedPointerEvent(MotionEvent event) {
        if ((mPrivateFlags & (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS))
                == (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS)) {
            if (super.dispatchCapturedPointerEvent(event)) {
                return true;
            }
        } else if (mFocused != null && (mFocused.mPrivateFlags & PFLAG_HAS_BOUNDS)
                == PFLAG_HAS_BOUNDS) {
            if (mFocused.dispatchCapturedPointerEvent(event)) {
                return true;
            }
        }
        return false;
    }

    @Override
    public void dispatchPointerCaptureChanged(boolean hasCapture) {
        exitHoverTargets();

        super.dispatchPointerCaptureChanged(hasCapture);
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].dispatchPointerCaptureChanged(hasCapture);
        }
    }

    @Override
    public PointerIcon onResolvePointerIcon(MotionEvent event, int pointerIndex) {
        final float x = event.getX(pointerIndex);
        final float y = event.getY(pointerIndex);
        if (isOnScrollbarThumb(x, y) || isDraggingScrollBar()) {
            return PointerIcon.getSystemIcon(mContext, PointerIcon.TYPE_ARROW);
        }
        // Check what the child under the pointer says about the pointer.
        final int childrenCount = mChildrenCount;
        if (childrenCount != 0) {
            final ArrayList<View> preorderedList = buildOrderedChildList();
            final boolean customOrder = preorderedList == null
                    && isChildrenDrawingOrderEnabled();
            final View[] children = mChildren;
            for (int i = childrenCount - 1; i >= 0; i--) {
                final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);
                final View child = getAndVerifyPreorderedView(preorderedList, children, childIndex);
                if (!canViewReceivePointerEvents(child)
                        || !isTransformedTouchPointInView(x, y, child, null)) {
                    continue;
                }
                final PointerIcon pointerIcon =
                        dispatchResolvePointerIcon(event, pointerIndex, child);
                if (pointerIcon != null) {
                    if (preorderedList != null) preorderedList.clear();
                    return pointerIcon;
                }
            }
            if (preorderedList != null) preorderedList.clear();
        }

        // The pointer is not a child or the child has no preferences, returning the default
        // implementation.
        return super.onResolvePointerIcon(event, pointerIndex);
    }

    private PointerIcon dispatchResolvePointerIcon(MotionEvent event, int pointerIndex,
            View child) {
        final PointerIcon pointerIcon;
        if (!child.hasIdentityMatrix()) {
            MotionEvent transformedEvent = getTransformedMotionEvent(event, child);
            pointerIcon = child.onResolvePointerIcon(transformedEvent, pointerIndex);
            transformedEvent.recycle();
        } else {
            final float offsetX = mScrollX - child.mLeft;
            final float offsetY = mScrollY - child.mTop;
            event.offsetLocation(offsetX, offsetY);
            pointerIcon = child.onResolvePointerIcon(event, pointerIndex);
            event.offsetLocation(-offsetX, -offsetY);
        }
        return pointerIcon;
    }

    private int getAndVerifyPreorderedIndex(int childrenCount, int i, boolean customOrder) {
        final int childIndex;
        if (customOrder) {
            final int childIndex1 = getChildDrawingOrder(childrenCount, i);
            if (childIndex1 >= childrenCount) {
                throw new IndexOutOfBoundsException("getChildDrawingOrder() "
                        + "returned invalid index " + childIndex1
                        + " (child count is " + childrenCount + ")");
            }
            childIndex = childIndex1;
        } else {
            childIndex = i;
        }
        return childIndex;
    }

    @SuppressWarnings({"ConstantConditions"})
    @Override
    protected boolean dispatchHoverEvent(MotionEvent event) {
        final int action = event.getAction();

        // First check whether the view group wants to intercept the hover event.
        final boolean interceptHover = onInterceptHoverEvent(event);
        event.setAction(action); // restore action in case it was changed

        MotionEvent eventNoHistory = event;
        boolean handled = false;

        // Send events to the hovered children and build a new list of hover targets until
        // one is found that handles the event.
        HoverTarget firstOldHoverTarget = mFirstHoverTarget;
        mFirstHoverTarget = null;
        if (!interceptHover && action != MotionEvent.ACTION_HOVER_EXIT) {
            final float x = event.getX();
            final float y = event.getY();
            final int childrenCount = mChildrenCount;
            if (childrenCount != 0) {
                final ArrayList<View> preorderedList = buildOrderedChildList();
                final boolean customOrder = preorderedList == null
                        && isChildrenDrawingOrderEnabled();
                final View[] children = mChildren;
                HoverTarget lastHoverTarget = null;
                for (int i = childrenCount - 1; i >= 0; i--) {
                    final int childIndex = getAndVerifyPreorderedIndex(
                            childrenCount, i, customOrder);
                    final View child = getAndVerifyPreorderedView(
                            preorderedList, children, childIndex);
                    if (!canViewReceivePointerEvents(child)
                            || !isTransformedTouchPointInView(x, y, child, null)) {
                        continue;
                    }

                    // Obtain a hover target for this child.  Dequeue it from the
                    // old hover target list if the child was previously hovered.
                    HoverTarget hoverTarget = firstOldHoverTarget;
                    final boolean wasHovered;
                    for (HoverTarget predecessor = null; ;) {
                        if (hoverTarget == null) {
                            hoverTarget = HoverTarget.obtain(child);
                            wasHovered = false;
                            break;
                        }

                        if (hoverTarget.child == child) {
                            if (predecessor != null) {
                                predecessor.next = hoverTarget.next;
                            } else {
                                firstOldHoverTarget = hoverTarget.next;
                            }
                            hoverTarget.next = null;
                            wasHovered = true;
                            break;
                        }

                        predecessor = hoverTarget;
                        hoverTarget = hoverTarget.next;
                    }

                    // Enqueue the hover target onto the new hover target list.
                    if (lastHoverTarget != null) {
                        lastHoverTarget.next = hoverTarget;
                    } else {
                        mFirstHoverTarget = hoverTarget;
                    }
                    lastHoverTarget = hoverTarget;

                    // Dispatch the event to the child.
                    if (action == MotionEvent.ACTION_HOVER_ENTER) {
                        if (!wasHovered) {
                            // Send the enter as is.
                            handled |= dispatchTransformedGenericPointerEvent(
                                    event, child); // enter
                        }
                    } else if (action == MotionEvent.ACTION_HOVER_MOVE) {
                        if (!wasHovered) {
                            // Synthesize an enter from a move.
                            eventNoHistory = obtainMotionEventNoHistoryOrSelf(eventNoHistory);
                            eventNoHistory.setAction(MotionEvent.ACTION_HOVER_ENTER);
                            handled |= dispatchTransformedGenericPointerEvent(
                                    eventNoHistory, child); // enter
                            eventNoHistory.setAction(action);

                            handled |= dispatchTransformedGenericPointerEvent(
                                    eventNoHistory, child); // move
                        } else {
                            // Send the move as is.
                            handled |= dispatchTransformedGenericPointerEvent(event, child);
                        }
                    }
                    if (handled) {
                        break;
                    }
                }
                if (preorderedList != null) preorderedList.clear();
            }
        }

        // Send exit events to all previously hovered children that are no longer hovered.
        while (firstOldHoverTarget != null) {
            final View child = firstOldHoverTarget.child;

            // Exit the old hovered child.
            if (action == MotionEvent.ACTION_HOVER_EXIT) {
                // Send the exit as is.
                handled |= dispatchTransformedGenericPointerEvent(
                        event, child); // exit
            } else {
                // Synthesize an exit from a move or enter.
                // Ignore the result because hover focus has moved to a different view.
                if (action == MotionEvent.ACTION_HOVER_MOVE) {
                    final boolean hoverExitPending = event.isHoverExitPending();
                    event.setHoverExitPending(true);
                    dispatchTransformedGenericPointerEvent(
                            event, child); // move
                    event.setHoverExitPending(hoverExitPending);
                }
                eventNoHistory = obtainMotionEventNoHistoryOrSelf(eventNoHistory);
                eventNoHistory.setAction(MotionEvent.ACTION_HOVER_EXIT);
                dispatchTransformedGenericPointerEvent(
                        eventNoHistory, child); // exit
                eventNoHistory.setAction(action);
            }

            final HoverTarget nextOldHoverTarget = firstOldHoverTarget.next;
            firstOldHoverTarget.recycle();
            firstOldHoverTarget = nextOldHoverTarget;
        }

        // Send events to the view group itself if no children have handled it and the view group
        // itself is not currently being hover-exited.
        boolean newHoveredSelf = !handled &&
                (action != MotionEvent.ACTION_HOVER_EXIT) && !event.isHoverExitPending();
        if (newHoveredSelf == mHoveredSelf) {
            if (newHoveredSelf) {
                // Send event to the view group as before.
                handled |= super.dispatchHoverEvent(event);
            }
        } else {
            if (mHoveredSelf) {
                // Exit the view group.
                if (action == MotionEvent.ACTION_HOVER_EXIT) {
                    // Send the exit as is.
                    handled |= super.dispatchHoverEvent(event); // exit
                } else {
                    // Synthesize an exit from a move or enter.
                    // Ignore the result because hover focus is moving to a different view.
                    if (action == MotionEvent.ACTION_HOVER_MOVE) {
                        super.dispatchHoverEvent(event); // move
                    }
                    eventNoHistory = obtainMotionEventNoHistoryOrSelf(eventNoHistory);
                    eventNoHistory.setAction(MotionEvent.ACTION_HOVER_EXIT);
                    super.dispatchHoverEvent(eventNoHistory); // exit
                    eventNoHistory.setAction(action);
                }
                mHoveredSelf = false;
            }

            if (newHoveredSelf) {
                // Enter the view group.
                if (action == MotionEvent.ACTION_HOVER_ENTER) {
                    // Send the enter as is.
                    handled |= super.dispatchHoverEvent(event); // enter
                    mHoveredSelf = true;
                } else if (action == MotionEvent.ACTION_HOVER_MOVE) {
                    // Synthesize an enter from a move.
                    eventNoHistory = obtainMotionEventNoHistoryOrSelf(eventNoHistory);
                    eventNoHistory.setAction(MotionEvent.ACTION_HOVER_ENTER);
                    handled |= super.dispatchHoverEvent(eventNoHistory); // enter
                    eventNoHistory.setAction(action);

                    handled |= super.dispatchHoverEvent(eventNoHistory); // move
                    mHoveredSelf = true;
                }
            }
        }

        // Recycle the copy of the event that we made.
        if (eventNoHistory != event) {
            eventNoHistory.recycle();
        }

        // Done.
        return handled;
    }

    private void exitHoverTargets() {
        if (mHoveredSelf || mFirstHoverTarget != null) {
            final long now = SystemClock.uptimeMillis();
            MotionEvent event = MotionEvent.obtain(now, now,
                    MotionEvent.ACTION_HOVER_EXIT, 0.0f, 0.0f, 0);
            event.setSource(InputDevice.SOURCE_TOUCHSCREEN);
            dispatchHoverEvent(event);
            event.recycle();
        }
    }

    private void cancelHoverTarget(View view) {
        HoverTarget predecessor = null;
        HoverTarget target = mFirstHoverTarget;
        while (target != null) {
            final HoverTarget next = target.next;
            if (target.child == view) {
                if (predecessor == null) {
                    mFirstHoverTarget = next;
                } else {
                    predecessor.next = next;
                }
                target.recycle();

                final long now = SystemClock.uptimeMillis();
                MotionEvent event = MotionEvent.obtain(now, now,
                        MotionEvent.ACTION_HOVER_EXIT, 0.0f, 0.0f, 0);
                event.setSource(InputDevice.SOURCE_TOUCHSCREEN);
                view.dispatchHoverEvent(event);
                event.recycle();
                return;
            }
            predecessor = target;
            target = next;
        }
    }

    @Override
    boolean dispatchTooltipHoverEvent(MotionEvent event) {
        final int action = event.getAction();
        switch (action) {
            case MotionEvent.ACTION_HOVER_ENTER:
                break;

            case MotionEvent.ACTION_HOVER_MOVE:
                View newTarget = null;

                // Check what the child under the pointer says about the tooltip.
                final int childrenCount = mChildrenCount;
                if (childrenCount != 0) {
                    final float x = event.getX();
                    final float y = event.getY();

                    final ArrayList<View> preorderedList = buildOrderedChildList();
                    final boolean customOrder = preorderedList == null
                            && isChildrenDrawingOrderEnabled();
                    final View[] children = mChildren;
                    for (int i = childrenCount - 1; i >= 0; i--) {
                        final int childIndex =
                                getAndVerifyPreorderedIndex(childrenCount, i, customOrder);
                        final View child =
                                getAndVerifyPreorderedView(preorderedList, children, childIndex);
                        if (!canViewReceivePointerEvents(child)
                                || !isTransformedTouchPointInView(x, y, child, null)) {
                            continue;
                        }
                        if (dispatchTooltipHoverEvent(event, child)) {
                            newTarget = child;
                            break;
                        }
                    }
                    if (preorderedList != null) preorderedList.clear();
                }

                if (mTooltipHoverTarget != newTarget) {
                    if (mTooltipHoverTarget != null) {
                        event.setAction(MotionEvent.ACTION_HOVER_EXIT);
                        mTooltipHoverTarget.dispatchTooltipHoverEvent(event);
                        event.setAction(action);
                    }
                    mTooltipHoverTarget = newTarget;
                }

                if (mTooltipHoverTarget != null) {
                    if (mTooltipHoveredSelf) {
                        mTooltipHoveredSelf = false;
                        event.setAction(MotionEvent.ACTION_HOVER_EXIT);
                        super.dispatchTooltipHoverEvent(event);
                        event.setAction(action);
                    }
                    return true;
                }

                mTooltipHoveredSelf = super.dispatchTooltipHoverEvent(event);
                return mTooltipHoveredSelf;

            case MotionEvent.ACTION_HOVER_EXIT:
                if (mTooltipHoverTarget != null) {
                    mTooltipHoverTarget.dispatchTooltipHoverEvent(event);
                    mTooltipHoverTarget = null;
                } else if (mTooltipHoveredSelf) {
                    super.dispatchTooltipHoverEvent(event);
                    mTooltipHoveredSelf = false;
                }
                break;
        }
        return false;
    }

    private boolean dispatchTooltipHoverEvent(MotionEvent event, View child) {
        final boolean result;
        if (!child.hasIdentityMatrix()) {
            MotionEvent transformedEvent = getTransformedMotionEvent(event, child);
            result = child.dispatchTooltipHoverEvent(transformedEvent);
            transformedEvent.recycle();
        } else {
            final float offsetX = mScrollX - child.mLeft;
            final float offsetY = mScrollY - child.mTop;
            event.offsetLocation(offsetX, offsetY);
            result = child.dispatchTooltipHoverEvent(event);
            event.offsetLocation(-offsetX, -offsetY);
        }
        return result;
    }

    private void exitTooltipHoverTargets() {
        if (mTooltipHoveredSelf || mTooltipHoverTarget != null) {
            final long now = SystemClock.uptimeMillis();
            MotionEvent event = MotionEvent.obtain(now, now,
                    MotionEvent.ACTION_HOVER_EXIT, 0.0f, 0.0f, 0);
            event.setSource(InputDevice.SOURCE_TOUCHSCREEN);
            dispatchTooltipHoverEvent(event);
            event.recycle();
        }
    }

    @hide /** @hide */
    @Override
    protected boolean hasHoveredChild() {
        return mFirstHoverTarget != null;
    }

    @Override
    public void addChildrenForAccessibility(ArrayList<View> outChildren) {
        if (getAccessibilityNodeProvider() != null) {
            return;
        }
        ChildListForAccessibility children = ChildListForAccessibility.obtain(this, true);
        try {
            final int childrenCount = children.getChildCount();
            for (int i = 0; i < childrenCount; i++) {
                View child = children.getChildAt(i);
                if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE) {
                    if (child.includeForAccessibility()) {
                        outChildren.add(child);
                    } else {
                        child.addChildrenForAccessibility(outChildren);
                    }
                }
            }
        } finally {
            children.recycle();
        }
    }

    Implement this method to intercept hover events before they are handled
by child views.
 This method is called before dispatching a hover event to a child of the view group or to the view group's own View.onHoverEvent to allow the view group a chance to intercept the hover event. This method can also be used to watch all pointer motions that occur within the bounds of the view group even when the pointer is hovering over a child of the view group rather than over the view group itself. 

The view group can prevent its children from receiving hover events by
implementing this method and returning true to indicate
that it would like to intercept hover events.  The view group must
continuously return true from onInterceptHoverEvent for as long as it wishes to continue intercepting hover events from its children. 

Interception preserves the invariant that at most one view can be
hovered at a time by transferring hover focus from the currently hovered
child to the view group or vice-versa as needed.

If this method returns true and a child is already hovered, then the child view will first receive a hover exit event and then the view group itself will receive a hover enter event in View.onHoverEvent. Likewise, if this method had previously returned true to intercept hover
events and instead returns false while the pointer is hovering within the bounds of one of a child, then the view group will first receive a hover exit event in View.onHoverEvent and then the hovered child will receive a hover enter event. 

The default implementation handles mouse hover on the scroll bars.

Params: event – The motion event that describes the hover.
Returns: True if the view group would like to intercept the hover event
and prevent its children from receiving it./**
     * Implement this method to intercept hover events before they are handled
     * by child views.
     * <p>
     * This method is called before dispatching a hover event to a child of
     * the view group or to the view group's own {@link #onHoverEvent} to allow
     * the view group a chance to intercept the hover event.
     * This method can also be used to watch all pointer motions that occur within
     * the bounds of the view group even when the pointer is hovering over
     * a child of the view group rather than over the view group itself.
     * </p><p>
     * The view group can prevent its children from receiving hover events by
     * implementing this method and returning <code>true</code> to indicate
     * that it would like to intercept hover events.  The view group must
     * continuously return <code>true</code> from {@link #onInterceptHoverEvent}
     * for as long as it wishes to continue intercepting hover events from
     * its children.
     * </p><p>
     * Interception preserves the invariant that at most one view can be
     * hovered at a time by transferring hover focus from the currently hovered
     * child to the view group or vice-versa as needed.
     * </p><p>
     * If this method returns <code>true</code> and a child is already hovered, then the
     * child view will first receive a hover exit event and then the view group
     * itself will receive a hover enter event in {@link #onHoverEvent}.
     * Likewise, if this method had previously returned <code>true</code> to intercept hover
     * events and instead returns <code>false</code> while the pointer is hovering
     * within the bounds of one of a child, then the view group will first receive a
     * hover exit event in {@link #onHoverEvent} and then the hovered child will
     * receive a hover enter event.
     * </p><p>
     * The default implementation handles mouse hover on the scroll bars.
     * </p>
     *
     * @param event The motion event that describes the hover.
     * @return True if the view group would like to intercept the hover event
     * and prevent its children from receiving it.
     */
    public boolean onInterceptHoverEvent(MotionEvent event) {
        if (event.isFromSource(InputDevice.SOURCE_MOUSE)) {
            final int action = event.getAction();
            final float x = event.getX();
            final float y = event.getY();
            if ((action == MotionEvent.ACTION_HOVER_MOVE
                    || action == MotionEvent.ACTION_HOVER_ENTER) && isOnScrollbar(x, y)) {
                return true;
            }
        }
        return false;
    }

    private static MotionEvent obtainMotionEventNoHistoryOrSelf(MotionEvent event) {
        if (event.getHistorySize() == 0) {
            return event;
        }
        return MotionEvent.obtainNoHistory(event);
    }

    @Override
    protected boolean dispatchGenericPointerEvent(MotionEvent event) {
        // Send the event to the child under the pointer.
        final int childrenCount = mChildrenCount;
        if (childrenCount != 0) {
            final float x = event.getX();
            final float y = event.getY();

            final ArrayList<View> preorderedList = buildOrderedChildList();
            final boolean customOrder = preorderedList == null
                    && isChildrenDrawingOrderEnabled();
            final View[] children = mChildren;
            for (int i = childrenCount - 1; i >= 0; i--) {
                final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);
                final View child = getAndVerifyPreorderedView(preorderedList, children, childIndex);
                if (!canViewReceivePointerEvents(child)
                        || !isTransformedTouchPointInView(x, y, child, null)) {
                    continue;
                }

                if (dispatchTransformedGenericPointerEvent(event, child)) {
                    if (preorderedList != null) preorderedList.clear();
                    return true;
                }
            }
            if (preorderedList != null) preorderedList.clear();
        }

        // No child handled the event.  Send it to this view group.
        return super.dispatchGenericPointerEvent(event);
    }

    @Override
    protected boolean dispatchGenericFocusedEvent(MotionEvent event) {
        // Send the event to the focused child or to this view group if it has focus.
        if ((mPrivateFlags & (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS))
                == (PFLAG_FOCUSED | PFLAG_HAS_BOUNDS)) {
            return super.dispatchGenericFocusedEvent(event);
        } else if (mFocused != null && (mFocused.mPrivateFlags & PFLAG_HAS_BOUNDS)
                == PFLAG_HAS_BOUNDS) {
            return mFocused.dispatchGenericMotionEvent(event);
        }
        return false;
    }

    Dispatches a generic pointer event to a child, taking into account
transformations that apply to the child.
Params: event – The event to send.
child – The view to send the event to.
Returns: true if the child handled the event./**
     * Dispatches a generic pointer event to a child, taking into account
     * transformations that apply to the child.
     *
     * @param event The event to send.
     * @param child The view to send the event to.
     * @return {@code true} if the child handled the event.
     */
    private boolean dispatchTransformedGenericPointerEvent(MotionEvent event, View child) {
        boolean handled;
        if (!child.hasIdentityMatrix()) {
            MotionEvent transformedEvent = getTransformedMotionEvent(event, child);
            handled = child.dispatchGenericMotionEvent(transformedEvent);
            transformedEvent.recycle();
        } else {
            final float offsetX = mScrollX - child.mLeft;
            final float offsetY = mScrollY - child.mTop;
            event.offsetLocation(offsetX, offsetY);
            handled = child.dispatchGenericMotionEvent(event);
            event.offsetLocation(-offsetX, -offsetY);
        }
        return handled;
    }

    Returns a MotionEvent that's been transformed into the child's local coordinates.
It's the responsibility of the caller to recycle it once they're finished with it.
Params: event – The event to transform.
child – The view whose coordinate space is to be used.
Returns: A copy of the the given MotionEvent, transformed into the given View's coordinate
        space./**
     * Returns a MotionEvent that's been transformed into the child's local coordinates.
     *
     * It's the responsibility of the caller to recycle it once they're finished with it.
     * @param event The event to transform.
     * @param child The view whose coordinate space is to be used.
     * @return A copy of the the given MotionEvent, transformed into the given View's coordinate
     *         space.
     */
    private MotionEvent getTransformedMotionEvent(MotionEvent event, View child) {
        final float offsetX = mScrollX - child.mLeft;
        final float offsetY = mScrollY - child.mTop;
        final MotionEvent transformedEvent = MotionEvent.obtain(event);
        transformedEvent.offsetLocation(offsetX, offsetY);
        if (!child.hasIdentityMatrix()) {
            transformedEvent.transform(child.getInverseMatrix());
        }
        return transformedEvent;
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onTouchEvent(ev, 1);
        }

        // If the event targets the accessibility focused view and this is it, start
        // normal event dispatch. Maybe a descendant is what will handle the click.
        if (ev.isTargetAccessibilityFocus() && isAccessibilityFocusedViewOrHost()) {
            ev.setTargetAccessibilityFocus(false);
        }

        boolean handled = false;
        if (onFilterTouchEventForSecurity(ev)) {
            final int action = ev.getAction();
            final int actionMasked = action & MotionEvent.ACTION_MASK;

            // Handle an initial down.
            if (actionMasked == MotionEvent.ACTION_DOWN) {
                // Throw away all previous state when starting a new touch gesture.
                // The framework may have dropped the up or cancel event for the previous gesture
                // due to an app switch, ANR, or some other state change.
                cancelAndClearTouchTargets(ev);
                resetTouchState();
            }

            // Check for interception.
            final boolean intercepted;
            if (actionMasked == MotionEvent.ACTION_DOWN
                    || mFirstTouchTarget != null) {
                final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;
                if (!disallowIntercept) {
                    intercepted = onInterceptTouchEvent(ev);
                    ev.setAction(action); // restore action in case it was changed
                } else {
                    intercepted = false;
                }
            } else {
                // There are no touch targets and this action is not an initial down
                // so this view group continues to intercept touches.
                intercepted = true;
            }

            // If intercepted, start normal event dispatch. Also if there is already
            // a view that is handling the gesture, do normal event dispatch.
            if (intercepted || mFirstTouchTarget != null) {
                ev.setTargetAccessibilityFocus(false);
            }

            // Check for cancelation.
            final boolean canceled = resetCancelNextUpFlag(this)
                    || actionMasked == MotionEvent.ACTION_CANCEL;

            // Update list of touch targets for pointer down, if needed.
            final boolean split = (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) != 0;
            TouchTarget newTouchTarget = null;
            boolean alreadyDispatchedToNewTouchTarget = false;
            if (!canceled && !intercepted) {

                // If the event is targeting accessibility focus we give it to the
                // view that has accessibility focus and if it does not handle it
                // we clear the flag and dispatch the event to all children as usual.
                // We are looking up the accessibility focused host to avoid keeping
                // state since these events are very rare.
                View childWithAccessibilityFocus = ev.isTargetAccessibilityFocus()
                        ? findChildWithAccessibilityFocus() : null;

                if (actionMasked == MotionEvent.ACTION_DOWN
                        || (split && actionMasked == MotionEvent.ACTION_POINTER_DOWN)
                        || actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
                    final int actionIndex = ev.getActionIndex(); // always 0 for down
                    final int idBitsToAssign = split ? 1 << ev.getPointerId(actionIndex)
                            : TouchTarget.ALL_POINTER_IDS;

                    // Clean up earlier touch targets for this pointer id in case they
                    // have become out of sync.
                    removePointersFromTouchTargets(idBitsToAssign);

                    final int childrenCount = mChildrenCount;
                    if (newTouchTarget == null && childrenCount != 0) {
                        final float x = ev.getX(actionIndex);
                        final float y = ev.getY(actionIndex);
                        // Find a child that can receive the event.
                        // Scan children from front to back.
                        final ArrayList<View> preorderedList = buildTouchDispatchChildList();
                        final boolean customOrder = preorderedList == null
                                && isChildrenDrawingOrderEnabled();
                        final View[] children = mChildren;
                        for (int i = childrenCount - 1; i >= 0; i--) {
                            final int childIndex = getAndVerifyPreorderedIndex(
                                    childrenCount, i, customOrder);
                            final View child = getAndVerifyPreorderedView(
                                    preorderedList, children, childIndex);

                            // If there is a view that has accessibility focus we want it
                            // to get the event first and if not handled we will perform a
                            // normal dispatch. We may do a double iteration but this is
                            // safer given the timeframe.
                            if (childWithAccessibilityFocus != null) {
                                if (childWithAccessibilityFocus != child) {
                                    continue;
                                }
                                childWithAccessibilityFocus = null;
                                i = childrenCount - 1;
                            }

                            if (!canViewReceivePointerEvents(child)
                                    || !isTransformedTouchPointInView(x, y, child, null)) {
                                ev.setTargetAccessibilityFocus(false);
                                continue;
                            }

                            newTouchTarget = getTouchTarget(child);
                            if (newTouchTarget != null) {
                                // Child is already receiving touch within its bounds.
                                // Give it the new pointer in addition to the ones it is handling.
                                newTouchTarget.pointerIdBits |= idBitsToAssign;
                                break;
                            }

                            resetCancelNextUpFlag(child);
                            if (dispatchTransformedTouchEvent(ev, false, child, idBitsToAssign)) {
                                // Child wants to receive touch within its bounds.
                                mLastTouchDownTime = ev.getDownTime();
                                if (preorderedList != null) {
                                    // childIndex points into presorted list, find original index
                                    for (int j = 0; j < childrenCount; j++) {
                                        if (children[childIndex] == mChildren[j]) {
                                            mLastTouchDownIndex = j;
                                            break;
                                        }
                                    }
                                } else {
                                    mLastTouchDownIndex = childIndex;
                                }
                                mLastTouchDownX = ev.getX();
                                mLastTouchDownY = ev.getY();
                                newTouchTarget = addTouchTarget(child, idBitsToAssign);
                                alreadyDispatchedToNewTouchTarget = true;
                                break;
                            }

                            // The accessibility focus didn't handle the event, so clear
                            // the flag and do a normal dispatch to all children.
                            ev.setTargetAccessibilityFocus(false);
                        }
                        if (preorderedList != null) preorderedList.clear();
                    }

                    if (newTouchTarget == null && mFirstTouchTarget != null) {
                        // Did not find a child to receive the event.
                        // Assign the pointer to the least recently added target.
                        newTouchTarget = mFirstTouchTarget;
                        while (newTouchTarget.next != null) {
                            newTouchTarget = newTouchTarget.next;
                        }
                        newTouchTarget.pointerIdBits |= idBitsToAssign;
                    }
                }
            }

            // Dispatch to touch targets.
            if (mFirstTouchTarget == null) {
                // No touch targets so treat this as an ordinary view.
                handled = dispatchTransformedTouchEvent(ev, canceled, null,
                        TouchTarget.ALL_POINTER_IDS);
            } else {
                // Dispatch to touch targets, excluding the new touch target if we already
                // dispatched to it.  Cancel touch targets if necessary.
                TouchTarget predecessor = null;
                TouchTarget target = mFirstTouchTarget;
                while (target != null) {
                    final TouchTarget next = target.next;
                    if (alreadyDispatchedToNewTouchTarget && target == newTouchTarget) {
                        handled = true;
                    } else {
                        final boolean cancelChild = resetCancelNextUpFlag(target.child)
                                || intercepted;
                        if (dispatchTransformedTouchEvent(ev, cancelChild,
                                target.child, target.pointerIdBits)) {
                            handled = true;
                        }
                        if (cancelChild) {
                            if (predecessor == null) {
                                mFirstTouchTarget = next;
                            } else {
                                predecessor.next = next;
                            }
                            target.recycle();
                            target = next;
                            continue;
                        }
                    }
                    predecessor = target;
                    target = next;
                }
            }

            // Update list of touch targets for pointer up or cancel, if needed.
            if (canceled
                    || actionMasked == MotionEvent.ACTION_UP
                    || actionMasked == MotionEvent.ACTION_HOVER_MOVE) {
                resetTouchState();
            } else if (split && actionMasked == MotionEvent.ACTION_POINTER_UP) {
                final int actionIndex = ev.getActionIndex();
                final int idBitsToRemove = 1 << ev.getPointerId(actionIndex);
                removePointersFromTouchTargets(idBitsToRemove);
            }
        }

        if (!handled && mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onUnhandledEvent(ev, 1);
        }
        return handled;
    }

    Provide custom ordering of views in which the touch will be dispatched.
This is called within a tight loop, so you are not allowed to allocate objects, including
the return array. Instead, you should return a pre-allocated list that will be cleared
after the dispatch is finished.
@hide /**
     * Provide custom ordering of views in which the touch will be dispatched.
     *
     * This is called within a tight loop, so you are not allowed to allocate objects, including
     * the return array. Instead, you should return a pre-allocated list that will be cleared
     * after the dispatch is finished.
     * @hide
     */
    public ArrayList<View> buildTouchDispatchChildList() {
        return buildOrderedChildList();
    }

    Finds the child which has accessibility focus.
Returns: The child that has focus./**
     * Finds the child which has accessibility focus.
     *
     * @return The child that has focus.
     */
    private View findChildWithAccessibilityFocus() {
        ViewRootImpl viewRoot = getViewRootImpl();
        if (viewRoot == null) {
            return null;
        }

        View current = viewRoot.getAccessibilityFocusedHost();
        if (current == null) {
            return null;
        }

        ViewParent parent = current.getParent();
        while (parent instanceof View) {
            if (parent == this) {
                return current;
            }
            current = (View) parent;
            parent = current.getParent();
        }

        return null;
    }

    Resets all touch state in preparation for a new cycle.
/**
     * Resets all touch state in preparation for a new cycle.
     */
    private void resetTouchState() {
        clearTouchTargets();
        resetCancelNextUpFlag(this);
        mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;
        mNestedScrollAxes = SCROLL_AXIS_NONE;
    }

    Resets the cancel next up flag.
Returns true if the flag was previously set.
/**
     * Resets the cancel next up flag.
     * Returns true if the flag was previously set.
     */
    private static boolean resetCancelNextUpFlag(@NonNull View view) {
        if ((view.mPrivateFlags & PFLAG_CANCEL_NEXT_UP_EVENT) != 0) {
            view.mPrivateFlags &= ~PFLAG_CANCEL_NEXT_UP_EVENT;
            return true;
        }
        return false;
    }

    Clears all touch targets.
/**
     * Clears all touch targets.
     */
    private void clearTouchTargets() {
        TouchTarget target = mFirstTouchTarget;
        if (target != null) {
            do {
                TouchTarget next = target.next;
                target.recycle();
                target = next;
            } while (target != null);
            mFirstTouchTarget = null;
        }
    }

    Cancels and clears all touch targets.
/**
     * Cancels and clears all touch targets.
     */
    private void cancelAndClearTouchTargets(MotionEvent event) {
        if (mFirstTouchTarget != null) {
            boolean syntheticEvent = false;
            if (event == null) {
                final long now = SystemClock.uptimeMillis();
                event = MotionEvent.obtain(now, now,
                        MotionEvent.ACTION_CANCEL, 0.0f, 0.0f, 0);
                event.setSource(InputDevice.SOURCE_TOUCHSCREEN);
                syntheticEvent = true;
            }

            for (TouchTarget target = mFirstTouchTarget; target != null; target = target.next) {
                resetCancelNextUpFlag(target.child);
                dispatchTransformedTouchEvent(event, true, target.child, target.pointerIdBits);
            }
            clearTouchTargets();

            if (syntheticEvent) {
                event.recycle();
            }
        }
    }

    Gets the touch target for specified child view.
Returns null if not found.
/**
     * Gets the touch target for specified child view.
     * Returns null if not found.
     */
    private TouchTarget getTouchTarget(@NonNull View child) {
        for (TouchTarget target = mFirstTouchTarget; target != null; target = target.next) {
            if (target.child == child) {
                return target;
            }
        }
        return null;
    }

    Adds a touch target for specified child to the beginning of the list.
Assumes the target child is not already present.
/**
     * Adds a touch target for specified child to the beginning of the list.
     * Assumes the target child is not already present.
     */
    private TouchTarget addTouchTarget(@NonNull View child, int pointerIdBits) {
        final TouchTarget target = TouchTarget.obtain(child, pointerIdBits);
        target.next = mFirstTouchTarget;
        mFirstTouchTarget = target;
        return target;
    }

    Removes the pointer ids from consideration.
/**
     * Removes the pointer ids from consideration.
     */
    private void removePointersFromTouchTargets(int pointerIdBits) {
        TouchTarget predecessor = null;
        TouchTarget target = mFirstTouchTarget;
        while (target != null) {
            final TouchTarget next = target.next;
            if ((target.pointerIdBits & pointerIdBits) != 0) {
                target.pointerIdBits &= ~pointerIdBits;
                if (target.pointerIdBits == 0) {
                    if (predecessor == null) {
                        mFirstTouchTarget = next;
                    } else {
                        predecessor.next = next;
                    }
                    target.recycle();
                    target = next;
                    continue;
                }
            }
            predecessor = target;
            target = next;
        }
    }

    private void cancelTouchTarget(View view) {
        TouchTarget predecessor = null;
        TouchTarget target = mFirstTouchTarget;
        while (target != null) {
            final TouchTarget next = target.next;
            if (target.child == view) {
                if (predecessor == null) {
                    mFirstTouchTarget = next;
                } else {
                    predecessor.next = next;
                }
                target.recycle();

                final long now = SystemClock.uptimeMillis();
                MotionEvent event = MotionEvent.obtain(now, now,
                        MotionEvent.ACTION_CANCEL, 0.0f, 0.0f, 0);
                event.setSource(InputDevice.SOURCE_TOUCHSCREEN);
                view.dispatchTouchEvent(event);
                event.recycle();
                return;
            }
            predecessor = target;
            target = next;
        }
    }

    Returns true if a child view can receive pointer events.
@hide /**
     * Returns true if a child view can receive pointer events.
     * @hide
     */
    private static boolean canViewReceivePointerEvents(@NonNull View child) {
        return (child.mViewFlags & VISIBILITY_MASK) == VISIBLE
                || child.getAnimation() != null;
    }

    private float[] getTempPoint() {
        if (mTempPoint == null) {
            mTempPoint = new float[2];
        }
        return mTempPoint;
    }

    Returns true if a child view contains the specified point when transformed
into its coordinate space.
Child must not be null.
@hide /**
     * Returns true if a child view contains the specified point when transformed
     * into its coordinate space.
     * Child must not be null.
     * @hide
     */
    protected boolean isTransformedTouchPointInView(float x, float y, View child,
            PointF outLocalPoint) {
        final float[] point = getTempPoint();
        point[0] = x;
        point[1] = y;
        transformPointToViewLocal(point, child);
        final boolean isInView = child.pointInView(point[0], point[1]);
        if (isInView && outLocalPoint != null) {
            outLocalPoint.set(point[0], point[1]);
        }
        return isInView;
    }

    @hide /**
     * @hide
     */
    public void transformPointToViewLocal(float[] point, View child) {
        point[0] += mScrollX - child.mLeft;
        point[1] += mScrollY - child.mTop;

        if (!child.hasIdentityMatrix()) {
            child.getInverseMatrix().mapPoints(point);
        }
    }

    Transforms a motion event into the coordinate space of a particular child view,
filters out irrelevant pointer ids, and overrides its action if necessary.
If child is null, assumes the MotionEvent will be sent to this ViewGroup instead.
/**
     * Transforms a motion event into the coordinate space of a particular child view,
     * filters out irrelevant pointer ids, and overrides its action if necessary.
     * If child is null, assumes the MotionEvent will be sent to this ViewGroup instead.
     */
    private boolean dispatchTransformedTouchEvent(MotionEvent event, boolean cancel,
            View child, int desiredPointerIdBits) {
        final boolean handled;

        // Canceling motions is a special case.  We don't need to perform any transformations
        // or filtering.  The important part is the action, not the contents.
        final int oldAction = event.getAction();
        if (cancel || oldAction == MotionEvent.ACTION_CANCEL) {
            event.setAction(MotionEvent.ACTION_CANCEL);
            if (child == null) {
                handled = super.dispatchTouchEvent(event);
            } else {
                handled = child.dispatchTouchEvent(event);
            }
            event.setAction(oldAction);
            return handled;
        }

        // Calculate the number of pointers to deliver.
        final int oldPointerIdBits = event.getPointerIdBits();
        final int newPointerIdBits = oldPointerIdBits & desiredPointerIdBits;

        // If for some reason we ended up in an inconsistent state where it looks like we
        // might produce a motion event with no pointers in it, then drop the event.
        if (newPointerIdBits == 0) {
            return false;
        }

        // If the number of pointers is the same and we don't need to perform any fancy
        // irreversible transformations, then we can reuse the motion event for this
        // dispatch as long as we are careful to revert any changes we make.
        // Otherwise we need to make a copy.
        final MotionEvent transformedEvent;
        if (newPointerIdBits == oldPointerIdBits) {
            if (child == null || child.hasIdentityMatrix()) {
                if (child == null) {
                    handled = super.dispatchTouchEvent(event);
                } else {
                    final float offsetX = mScrollX - child.mLeft;
                    final float offsetY = mScrollY - child.mTop;
                    event.offsetLocation(offsetX, offsetY);

                    handled = child.dispatchTouchEvent(event);

                    event.offsetLocation(-offsetX, -offsetY);
                }
                return handled;
            }
            transformedEvent = MotionEvent.obtain(event);
        } else {
            transformedEvent = event.split(newPointerIdBits);
        }

        // Perform any necessary transformations and dispatch.
        if (child == null) {
            handled = super.dispatchTouchEvent(transformedEvent);
        } else {
            final float offsetX = mScrollX - child.mLeft;
            final float offsetY = mScrollY - child.mTop;
            transformedEvent.offsetLocation(offsetX, offsetY);
            if (! child.hasIdentityMatrix()) {
                transformedEvent.transform(child.getInverseMatrix());
            }

            handled = child.dispatchTouchEvent(transformedEvent);
        }

        // Done.
        transformedEvent.recycle();
        return handled;
    }

    Enable or disable the splitting of MotionEvents to multiple children during touch event dispatch. This behavior is enabled by default for applications that target an SDK version of VERSION_CODES.HONEYCOMB or newer. When this option is enabled MotionEvents may be split and dispatched to different child
views depending on where each pointer initially went down. This allows for user interactions
such as scrolling two panes of content independently, chording of buttons, and performing
independent gestures on different pieces of content.
Params: split – true to allow MotionEvents to be split and dispatched to multiple
             child views. false to only allow one child view to be the target of
             any MotionEvent received by this ViewGroup.
@attr ref android.R.styleable#ViewGroup_splitMotionEvents/**
     * Enable or disable the splitting of MotionEvents to multiple children during touch event
     * dispatch. This behavior is enabled by default for applications that target an
     * SDK version of {@link Build.VERSION_CODES#HONEYCOMB} or newer.
     *
     * <p>When this option is enabled MotionEvents may be split and dispatched to different child
     * views depending on where each pointer initially went down. This allows for user interactions
     * such as scrolling two panes of content independently, chording of buttons, and performing
     * independent gestures on different pieces of content.
     *
     * @param split <code>true</code> to allow MotionEvents to be split and dispatched to multiple
     *              child views. <code>false</code> to only allow one child view to be the target of
     *              any MotionEvent received by this ViewGroup.
     * @attr ref android.R.styleable#ViewGroup_splitMotionEvents
     */
    public void setMotionEventSplittingEnabled(boolean split) {
        // TODO Applications really shouldn't change this setting mid-touch event,
        // but perhaps this should handle that case and send ACTION_CANCELs to any child views
        // with gestures in progress when this is changed.
        if (split) {
            mGroupFlags |= FLAG_SPLIT_MOTION_EVENTS;
        } else {
            mGroupFlags &= ~FLAG_SPLIT_MOTION_EVENTS;
        }
    }

    Returns true if MotionEvents dispatched to this ViewGroup can be split to multiple children.
Returns: true if MotionEvents dispatched to this ViewGroup can be split to multiple children./**
     * Returns true if MotionEvents dispatched to this ViewGroup can be split to multiple children.
     * @return true if MotionEvents dispatched to this ViewGroup can be split to multiple children.
     */
    public boolean isMotionEventSplittingEnabled() {
        return (mGroupFlags & FLAG_SPLIT_MOTION_EVENTS) == FLAG_SPLIT_MOTION_EVENTS;
    }

    Returns true if this ViewGroup should be considered as a single entity for removal
when executing an Activity transition. If this is false, child elements will move
individually during the transition.
Returns: True if the ViewGroup should be acted on together during an Activity transition. The default value is true when there is a non-null background or if View.getTransitionName() is not null or if a non-null ViewOutlineProvider other than ViewOutlineProvider.BACKGROUND was given to View.setOutlineProvider(ViewOutlineProvider) and false otherwise./**
     * Returns true if this ViewGroup should be considered as a single entity for removal
     * when executing an Activity transition. If this is false, child elements will move
     * individually during the transition.
     *
     * @return True if the ViewGroup should be acted on together during an Activity transition.
     * The default value is true when there is a non-null background or if
     * {@link #getTransitionName()} is not null or if a
     * non-null {@link android.view.ViewOutlineProvider} other than
     * {@link android.view.ViewOutlineProvider#BACKGROUND} was given to
     * {@link #setOutlineProvider(ViewOutlineProvider)} and false otherwise.
     */
    public boolean isTransitionGroup() {
        if ((mGroupFlags & FLAG_IS_TRANSITION_GROUP_SET) != 0) {
            return ((mGroupFlags & FLAG_IS_TRANSITION_GROUP) != 0);
        } else {
            final ViewOutlineProvider outlineProvider = getOutlineProvider();
            return getBackground() != null || getTransitionName() != null ||
                    (outlineProvider != null && outlineProvider != ViewOutlineProvider.BACKGROUND);
        }
    }

    Changes whether or not this ViewGroup should be treated as a single entity during
Activity Transitions.
Params: isTransitionGroup – Whether or not the ViewGroup should be treated as a unit
                         in Activity transitions. If false, the ViewGroup won't transition,
                         only its children. If true, the entire ViewGroup will transition
                         together.
See Also: ActivityOptions.makeSceneTransitionAnimation(Activity, Pair<View,String>[])/**
     * Changes whether or not this ViewGroup should be treated as a single entity during
     * Activity Transitions.
     * @param isTransitionGroup Whether or not the ViewGroup should be treated as a unit
     *                          in Activity transitions. If false, the ViewGroup won't transition,
     *                          only its children. If true, the entire ViewGroup will transition
     *                          together.
     * @see android.app.ActivityOptions#makeSceneTransitionAnimation(android.app.Activity,
     * android.util.Pair[])
     */
    public void setTransitionGroup(boolean isTransitionGroup) {
        mGroupFlags |= FLAG_IS_TRANSITION_GROUP_SET;
        if (isTransitionGroup) {
            mGroupFlags |= FLAG_IS_TRANSITION_GROUP;
        } else {
            mGroupFlags &= ~FLAG_IS_TRANSITION_GROUP;
        }
    }

    @Override
    public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) {

        if (disallowIntercept == ((mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0)) {
            // We're already in this state, assume our ancestors are too
            return;
        }

        if (disallowIntercept) {
            mGroupFlags |= FLAG_DISALLOW_INTERCEPT;
        } else {
            mGroupFlags &= ~FLAG_DISALLOW_INTERCEPT;
        }

        // Pass it up to our parent
        if (mParent != null) {
            mParent.requestDisallowInterceptTouchEvent(disallowIntercept);
        }
    }

    Implement this method to intercept all touch screen motion events.  This
allows you to watch events as they are dispatched to your children, and
take ownership of the current gesture at any point.
Using this function takes some care, as it has a fairly complicated interaction with 
View.onTouchEvent(MotionEvent), and using it requires implementing that method as well as this one in the correct way. Events will be received in the following order: 

 You will receive the down event here.
 The down event will be handled either by a child of this view
group, or given to your own onTouchEvent() method to handle; this means
you should implement onTouchEvent() to return true, so you will
continue to see the rest of the gesture (instead of looking for
a parent view to handle it).  Also, by returning true from
onTouchEvent(), you will not receive any following
events in onInterceptTouchEvent() and all touch processing must
happen in onTouchEvent() like normal.
 For as long as you return false from this function, each following
event (up to and including the final up) will be delivered first here
and then to the target's onTouchEvent().
 If you return true from here, you will not receive any following events: the target view will receive the same event but with the action MotionEvent.ACTION_CANCEL, and all further events will be delivered to your onTouchEvent() method and no longer appear here. 
Params: ev – The motion event being dispatched down the hierarchy.
Returns: Return true to steal motion events from the children and have
them dispatched to this ViewGroup through onTouchEvent().
The current target will receive an ACTION_CANCEL event, and no further
messages will be delivered here./**
     * Implement this method to intercept all touch screen motion events.  This
     * allows you to watch events as they are dispatched to your children, and
     * take ownership of the current gesture at any point.
     *
     * <p>Using this function takes some care, as it has a fairly complicated
     * interaction with {@link View#onTouchEvent(MotionEvent)
     * View.onTouchEvent(MotionEvent)}, and using it requires implementing
     * that method as well as this one in the correct way.  Events will be
     * received in the following order:
     *
     * <ol>
     * <li> You will receive the down event here.
     * <li> The down event will be handled either by a child of this view
     * group, or given to your own onTouchEvent() method to handle; this means
     * you should implement onTouchEvent() to return true, so you will
     * continue to see the rest of the gesture (instead of looking for
     * a parent view to handle it).  Also, by returning true from
     * onTouchEvent(), you will not receive any following
     * events in onInterceptTouchEvent() and all touch processing must
     * happen in onTouchEvent() like normal.
     * <li> For as long as you return false from this function, each following
     * event (up to and including the final up) will be delivered first here
     * and then to the target's onTouchEvent().
     * <li> If you return true from here, you will not receive any
     * following events: the target view will receive the same event but
     * with the action {@link MotionEvent#ACTION_CANCEL}, and all further
     * events will be delivered to your onTouchEvent() method and no longer
     * appear here.
     * </ol>
     *
     * @param ev The motion event being dispatched down the hierarchy.
     * @return Return true to steal motion events from the children and have
     * them dispatched to this ViewGroup through onTouchEvent().
     * The current target will receive an ACTION_CANCEL event, and no further
     * messages will be delivered here.
     */
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        if (ev.isFromSource(InputDevice.SOURCE_MOUSE)
                && ev.getAction() == MotionEvent.ACTION_DOWN
                && ev.isButtonPressed(MotionEvent.BUTTON_PRIMARY)
                && isOnScrollbarThumb(ev.getX(), ev.getY())) {
            return true;
        }
        return false;
    }

    {@inheritDoc} Looks for a view to give focus to respecting the setting specified by getDescendantFocusability(). Uses onRequestFocusInDescendants(int, Rect) to find focus within the children of this group when appropriate. 
See Also: FOCUS_BEFORE_DESCENDANTS
FOCUS_AFTER_DESCENDANTS
FOCUS_BLOCK_DESCENDANTS
onRequestFocusInDescendants(int, Rect)/**
     * {@inheritDoc}
     *
     * Looks for a view to give focus to respecting the setting specified by
     * {@link #getDescendantFocusability()}.
     *
     * Uses {@link #onRequestFocusInDescendants(int, android.graphics.Rect)} to
     * find focus within the children of this group when appropriate.
     *
     * @see #FOCUS_BEFORE_DESCENDANTS
     * @see #FOCUS_AFTER_DESCENDANTS
     * @see #FOCUS_BLOCK_DESCENDANTS
     * @see #onRequestFocusInDescendants(int, android.graphics.Rect)
     */
    @Override
    public boolean requestFocus(int direction, Rect previouslyFocusedRect) {
        if (DBG) {
            System.out.println(this + " ViewGroup.requestFocus direction="
                    + direction);
        }
        int descendantFocusability = getDescendantFocusability();

        boolean result;
        switch (descendantFocusability) {
            case FOCUS_BLOCK_DESCENDANTS:
                result = super.requestFocus(direction, previouslyFocusedRect);
                break;
            case FOCUS_BEFORE_DESCENDANTS: {
                final boolean took = super.requestFocus(direction, previouslyFocusedRect);
                result = took ? took : onRequestFocusInDescendants(direction,
                        previouslyFocusedRect);
                break;
            }
            case FOCUS_AFTER_DESCENDANTS: {
                final boolean took = onRequestFocusInDescendants(direction, previouslyFocusedRect);
                result = took ? took : super.requestFocus(direction, previouslyFocusedRect);
                break;
            }
            default:
                throw new IllegalStateException("descendant focusability must be "
                        + "one of FOCUS_BEFORE_DESCENDANTS, FOCUS_AFTER_DESCENDANTS, FOCUS_BLOCK_DESCENDANTS "
                        + "but is " + descendantFocusability);
        }
        if (result && !isLayoutValid() && ((mPrivateFlags & PFLAG_WANTS_FOCUS) == 0)) {
            mPrivateFlags |= PFLAG_WANTS_FOCUS;
        }
        return result;
    }

    Look for a descendant to call View.requestFocus on. Called by requestFocus(int, Rect) when it wants to request focus within its children. Override this to customize how your ViewGroup requests focus within its children. 
Params: direction – One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and FOCUS_RIGHT
previouslyFocusedRect – The rectangle (in this View's coordinate system)
       to give a finer grained hint about where focus is coming from.  May be null
       if there is no hint.
Returns: Whether focus was taken./**
     * Look for a descendant to call {@link View#requestFocus} on.
     * Called by {@link ViewGroup#requestFocus(int, android.graphics.Rect)}
     * when it wants to request focus within its children.  Override this to
     * customize how your {@link ViewGroup} requests focus within its children.
     * @param direction One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and FOCUS_RIGHT
     * @param previouslyFocusedRect The rectangle (in this View's coordinate system)
     *        to give a finer grained hint about where focus is coming from.  May be null
     *        if there is no hint.
     * @return Whether focus was taken.
     */
    @SuppressWarnings({"ConstantConditions"})
    protected boolean onRequestFocusInDescendants(int direction,
            Rect previouslyFocusedRect) {
        int index;
        int increment;
        int end;
        int count = mChildrenCount;
        if ((direction & FOCUS_FORWARD) != 0) {
            index = 0;
            increment = 1;
            end = count;
        } else {
            index = count - 1;
            increment = -1;
            end = -1;
        }
        final View[] children = mChildren;
        for (int i = index; i != end; i += increment) {
            View child = children[i];
            if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE) {
                if (child.requestFocus(direction, previouslyFocusedRect)) {
                    return true;
                }
            }
        }
        return false;
    }

    @Override
    public boolean restoreDefaultFocus() {
        if (mDefaultFocus != null
                && getDescendantFocusability() != FOCUS_BLOCK_DESCENDANTS
                && (mDefaultFocus.mViewFlags & VISIBILITY_MASK) == VISIBLE
                && mDefaultFocus.restoreDefaultFocus()) {
            return true;
        }
        return super.restoreDefaultFocus();
    }

    @hide /**
     * @hide
     */
    @TestApi
    @Override
    public boolean restoreFocusInCluster(@FocusRealDirection int direction) {
        // Allow cluster-navigation to enter touchscreenBlocksFocus ViewGroups.
        if (isKeyboardNavigationCluster()) {
            final boolean blockedFocus = getTouchscreenBlocksFocus();
            try {
                setTouchscreenBlocksFocusNoRefocus(false);
                return restoreFocusInClusterInternal(direction);
            } finally {
                setTouchscreenBlocksFocusNoRefocus(blockedFocus);
            }
        } else {
            return restoreFocusInClusterInternal(direction);
        }
    }

    private boolean restoreFocusInClusterInternal(@FocusRealDirection int direction) {
        if (mFocusedInCluster != null && getDescendantFocusability() != FOCUS_BLOCK_DESCENDANTS
                && (mFocusedInCluster.mViewFlags & VISIBILITY_MASK) == VISIBLE
                && mFocusedInCluster.restoreFocusInCluster(direction)) {
            return true;
        }
        return super.restoreFocusInCluster(direction);
    }

    @hide /**
     * @hide
     */
    @Override
    public boolean restoreFocusNotInCluster() {
        if (mFocusedInCluster != null) {
            // since clusters don't nest; we can assume that a non-null mFocusedInCluster
            // will refer to a view not-in a cluster.
            return restoreFocusInCluster(View.FOCUS_DOWN);
        }
        if (isKeyboardNavigationCluster() || (mViewFlags & VISIBILITY_MASK) != VISIBLE) {
            return false;
        }
        int descendentFocusability = getDescendantFocusability();
        if (descendentFocusability == FOCUS_BLOCK_DESCENDANTS) {
            return super.requestFocus(FOCUS_DOWN, null);
        }
        if (descendentFocusability == FOCUS_BEFORE_DESCENDANTS
                && super.requestFocus(FOCUS_DOWN, null)) {
            return true;
        }
        for (int i = 0; i < mChildrenCount; ++i) {
            View child = mChildren[i];
            if (!child.isKeyboardNavigationCluster()
                    && child.restoreFocusNotInCluster()) {
                return true;
            }
        }
        if (descendentFocusability == FOCUS_AFTER_DESCENDANTS && !hasFocusableChild(false)) {
            return super.requestFocus(FOCUS_DOWN, null);
        }
        return false;
    }

    {@inheritDoc}
@hide /**
     * {@inheritDoc}
     *
     * @hide
     */
    @Override
    public void dispatchStartTemporaryDetach() {
        super.dispatchStartTemporaryDetach();
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].dispatchStartTemporaryDetach();
        }
    }

    {@inheritDoc}
@hide /**
     * {@inheritDoc}
     *
     * @hide
     */
    @Override
    public void dispatchFinishTemporaryDetach() {
        super.dispatchFinishTemporaryDetach();
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].dispatchFinishTemporaryDetach();
        }
    }

    @Override
    void dispatchAttachedToWindow(AttachInfo info, int visibility) {
        mGroupFlags |= FLAG_PREVENT_DISPATCH_ATTACHED_TO_WINDOW;
        super.dispatchAttachedToWindow(info, visibility);
        mGroupFlags &= ~FLAG_PREVENT_DISPATCH_ATTACHED_TO_WINDOW;

        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            final View child = children[i];
            child.dispatchAttachedToWindow(info,
                    combineVisibility(visibility, child.getVisibility()));
        }
        final int transientCount = mTransientIndices == null ? 0 : mTransientIndices.size();
        for (int i = 0; i < transientCount; ++i) {
            View view = mTransientViews.get(i);
            view.dispatchAttachedToWindow(info,
                    combineVisibility(visibility, view.getVisibility()));
        }
    }

    @Override
    void dispatchScreenStateChanged(int screenState) {
        super.dispatchScreenStateChanged(screenState);

        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].dispatchScreenStateChanged(screenState);
        }
    }

    @Override
    void dispatchMovedToDisplay(Display display, Configuration config) {
        super.dispatchMovedToDisplay(display, config);

        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].dispatchMovedToDisplay(display, config);
        }
    }

    @hide /** @hide */
    @Override
    public boolean dispatchPopulateAccessibilityEventInternal(AccessibilityEvent event) {
        boolean handled = false;
        if (includeForAccessibility()) {
            handled = super.dispatchPopulateAccessibilityEventInternal(event);
            if (handled) {
                return handled;
            }
        }
        // Let our children have a shot in populating the event.
        ChildListForAccessibility children = ChildListForAccessibility.obtain(this, true);
        try {
            final int childCount = children.getChildCount();
            for (int i = 0; i < childCount; i++) {
                View child = children.getChildAt(i);
                if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE) {
                    handled = child.dispatchPopulateAccessibilityEvent(event);
                    if (handled) {
                        return handled;
                    }
                }
            }
        } finally {
            children.recycle();
        }
        return false;
    }

    Dispatch creation of ViewStructure down the hierarchy. This implementation adds in all child views of the view group, in addition to calling the default View implementation. /**
     * Dispatch creation of {@link ViewStructure} down the hierarchy.  This implementation
     * adds in all child views of the view group, in addition to calling the default View
     * implementation.
     */
    @Override
    public void dispatchProvideStructure(ViewStructure structure) {
        super.dispatchProvideStructure(structure);
        if (isAssistBlocked() || structure.getChildCount() != 0) {
            return;
        }
        final int childrenCount = mChildrenCount;
        if (childrenCount <= 0) {
            return;
        }

        if (!isLaidOut()) {
            if (Helper.sVerbose) {
                Log.v(VIEW_LOG_TAG, "dispatchProvideStructure(): not laid out, ignoring "
                        + childrenCount + " children of " + getAccessibilityViewId());
            }
            return;
        }

        structure.setChildCount(childrenCount);
        ArrayList<View> preorderedList = buildOrderedChildList();
        boolean customOrder = preorderedList == null
                && isChildrenDrawingOrderEnabled();
        for (int i = 0; i < childrenCount; i++) {
            int childIndex;
            try {
                childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);
            } catch (IndexOutOfBoundsException e) {
                childIndex = i;
                if (mContext.getApplicationInfo().targetSdkVersion < Build.VERSION_CODES.M) {
                    Log.w(TAG, "Bad getChildDrawingOrder while collecting assist @ "
                            + i + " of " + childrenCount, e);
                    // At least one app is failing when we call getChildDrawingOrder
                    // at this point, so deal semi-gracefully with it by falling back
                    // on the basic order.
                    customOrder = false;
                    if (i > 0) {
                        // If we failed at the first index, there really isn't
                        // anything to do -- we will just proceed with the simple
                        // sequence order.
                        // Otherwise, we failed in the middle, so need to come up
                        // with an order for the remaining indices and use that.
                        // Failed at the first one, easy peasy.
                        int[] permutation = new int[childrenCount];
                        SparseBooleanArray usedIndices = new SparseBooleanArray();
                        // Go back and collected the indices we have done so far.
                        for (int j = 0; j < i; j++) {
                            permutation[j] = getChildDrawingOrder(childrenCount, j);
                            usedIndices.put(permutation[j], true);
                        }
                        // Fill in the remaining indices with indices that have not
                        // yet been used.
                        int nextIndex = 0;
                        for (int j = i; j < childrenCount; j++) {
                            while (usedIndices.get(nextIndex, false)) {
                                nextIndex++;
                            }
                            permutation[j] = nextIndex;
                            nextIndex++;
                        }
                        // Build the final view list.
                        preorderedList = new ArrayList<>(childrenCount);
                        for (int j = 0; j < childrenCount; j++) {
                            final int index = permutation[j];
                            final View child = mChildren[index];
                            preorderedList.add(child);
                        }
                    }
                } else {
                    throw e;
                }
            }
            final View child = getAndVerifyPreorderedView(preorderedList, mChildren,
                    childIndex);
            final ViewStructure cstructure = structure.newChild(i);
            child.dispatchProvideStructure(cstructure);
        }
        if (preorderedList != null) {
            preorderedList.clear();
        }
    }

    {@inheritDoc}
This implementation adds in all child views of the view group, in addition to calling the default View implementation. /**
     * {@inheritDoc}
     *
     * <p>This implementation adds in all child views of the view group, in addition to calling the
     * default {@link View} implementation.
     */
    @Override
    public void dispatchProvideAutofillStructure(ViewStructure structure,
            @AutofillFlags int flags) {
        super.dispatchProvideAutofillStructure(structure, flags);

        if (structure.getChildCount() != 0) {
            return;
        }

        if (!isLaidOut()) {
            if (Helper.sVerbose) {
                Log.v(VIEW_LOG_TAG, "dispatchProvideAutofillStructure(): not laid out, ignoring "
                        + mChildrenCount + " children of " + getAutofillId());
            }
            return;
        }

        final ChildListForAutoFill children = getChildrenForAutofill(flags);
        final int childrenCount = children.size();
        structure.setChildCount(childrenCount);
        for (int i = 0; i < childrenCount; i++) {
            final View child = children.get(i);
            final ViewStructure cstructure = structure.newChild(i);
            child.dispatchProvideAutofillStructure(cstructure, flags);
        }
        children.recycle();
    }

    Gets the children for autofill. Children for autofill are the first
level descendants that are important for autofill. The returned
child list object is pooled and the caller must recycle it once done.
@hide /**
     * Gets the children for autofill. Children for autofill are the first
     * level descendants that are important for autofill. The returned
     * child list object is pooled and the caller must recycle it once done.
     * @hide */
    private @NonNull ChildListForAutoFill getChildrenForAutofill(@AutofillFlags int flags) {
        final ChildListForAutoFill children = ChildListForAutoFill.obtain();
        populateChildrenForAutofill(children, flags);
        return children;
    }

    @hide /** @hide */
    private void populateChildrenForAutofill(ArrayList<View> list, @AutofillFlags int flags) {
        final int childrenCount = mChildrenCount;
        if (childrenCount <= 0) {
            return;
        }
        final ArrayList<View> preorderedList = buildOrderedChildList();
        final boolean customOrder = preorderedList == null
                && isChildrenDrawingOrderEnabled();
        for (int i = 0; i < childrenCount; i++) {
            final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);
            final View child = (preorderedList == null)
                    ? mChildren[childIndex] : preorderedList.get(childIndex);
            if ((flags & AUTOFILL_FLAG_INCLUDE_NOT_IMPORTANT_VIEWS) != 0
                    || child.isImportantForAutofill()) {
                list.add(child);
            } else if (child instanceof ViewGroup) {
                ((ViewGroup) child).populateChildrenForAutofill(list, flags);
            }
        }
    }

    private static View getAndVerifyPreorderedView(ArrayList<View> preorderedList, View[] children,
            int childIndex) {
        final View child;
        if (preorderedList != null) {
            child = preorderedList.get(childIndex);
            if (child == null) {
                throw new RuntimeException("Invalid preorderedList contained null child at index "
                        + childIndex);
            }
        } else {
            child = children[childIndex];
        }
        return child;
    }

    @hide /** @hide */
    @Override
    public void onInitializeAccessibilityNodeInfoInternal(AccessibilityNodeInfo info) {
        super.onInitializeAccessibilityNodeInfoInternal(info);
        if (getAccessibilityNodeProvider() != null) {
            return;
        }
        if (mAttachInfo != null) {
            final ArrayList<View> childrenForAccessibility = mAttachInfo.mTempArrayList;
            childrenForAccessibility.clear();
            addChildrenForAccessibility(childrenForAccessibility);
            final int childrenForAccessibilityCount = childrenForAccessibility.size();
            for (int i = 0; i < childrenForAccessibilityCount; i++) {
                final View child = childrenForAccessibility.get(i);
                info.addChildUnchecked(child);
            }
            childrenForAccessibility.clear();
        }
    }

    @Override
    public CharSequence getAccessibilityClassName() {
        return ViewGroup.class.getName();
    }

    @Override
    public void notifySubtreeAccessibilityStateChanged(View child, View source, int changeType) {
        // If this is a live region, we should send a subtree change event
        // from this view. Otherwise, we can let it propagate up.
        if (getAccessibilityLiveRegion() != ACCESSIBILITY_LIVE_REGION_NONE) {
            notifyViewAccessibilityStateChangedIfNeeded(
                    AccessibilityEvent.CONTENT_CHANGE_TYPE_SUBTREE);
        } else if (mParent != null) {
            try {
                mParent.notifySubtreeAccessibilityStateChanged(this, source, changeType);
            } catch (AbstractMethodError e) {
                Log.e(VIEW_LOG_TAG, mParent.getClass().getSimpleName() +
                        " does not fully implement ViewParent", e);
            }
        }
    }

    @hide /** @hide */
    @Override
    public void notifySubtreeAccessibilityStateChangedIfNeeded() {
        if (!AccessibilityManager.getInstance(mContext).isEnabled() || mAttachInfo == null) {
            return;
        }
        // If something important for a11y is happening in this subtree, make sure it's dispatched
        // from a view that is important for a11y so it doesn't get lost.
        if ((getImportantForAccessibility() != IMPORTANT_FOR_ACCESSIBILITY_NO_HIDE_DESCENDANTS)
                && !isImportantForAccessibility() && (getChildCount() > 0)) {
            ViewParent a11yParent = getParentForAccessibility();
            if (a11yParent instanceof View) {
                ((View) a11yParent).notifySubtreeAccessibilityStateChangedIfNeeded();
                return;
            }
        }
        super.notifySubtreeAccessibilityStateChangedIfNeeded();
    }

    @Override
    void resetSubtreeAccessibilityStateChanged() {
        super.resetSubtreeAccessibilityStateChanged();
        View[] children = mChildren;
        final int childCount = mChildrenCount;
        for (int i = 0; i < childCount; i++) {
            children[i].resetSubtreeAccessibilityStateChanged();
        }
    }

    Counts the number of children of this View that will be sent to an accessibility service.
Returns: The number of children an AccessibilityNodeInfo rooted at this View would have./**
     * Counts the number of children of this View that will be sent to an accessibility service.
     *
     * @return The number of children an {@code AccessibilityNodeInfo} rooted at this View
     * would have.
     */
    int getNumChildrenForAccessibility() {
        int numChildrenForAccessibility = 0;
        for (int i = 0; i < getChildCount(); i++) {
            View child = getChildAt(i);
            if (child.includeForAccessibility()) {
                numChildrenForAccessibility++;
            } else if (child instanceof ViewGroup) {
                numChildrenForAccessibility += ((ViewGroup) child)
                        .getNumChildrenForAccessibility();
            }
        }
        return numChildrenForAccessibility;
    }

    {@inheritDoc}
Subclasses should always call super.onNestedPrePerformAccessibilityAction
Params: target – The target view dispatching this action
action – Action being performed; see AccessibilityNodeInfo
args – Optional action arguments
Returns: false by default. Subclasses should return true if they handle the event./**
     * {@inheritDoc}
     *
     * <p>Subclasses should always call <code>super.onNestedPrePerformAccessibilityAction</code></p>
     *
     * @param target The target view dispatching this action
     * @param action Action being performed; see
     *               {@link android.view.accessibility.AccessibilityNodeInfo}
     * @param args Optional action arguments
     * @return false by default. Subclasses should return true if they handle the event.
     */
    @Override
    public boolean onNestedPrePerformAccessibilityAction(View target, int action, Bundle args) {
        return false;
    }

    @Override
    void dispatchDetachedFromWindow() {
        // If we still have a touch target, we are still in the process of
        // dispatching motion events to a child; we need to get rid of that
        // child to avoid dispatching events to it after the window is torn
        // down. To make sure we keep the child in a consistent state, we
        // first send it an ACTION_CANCEL motion event.
        cancelAndClearTouchTargets(null);

        // Similarly, set ACTION_EXIT to all hover targets and clear them.
        exitHoverTargets();
        exitTooltipHoverTargets();

        // In case view is detached while transition is running
        mLayoutCalledWhileSuppressed = false;

        // Tear down our drag tracking
        mChildrenInterestedInDrag = null;
        mIsInterestedInDrag = false;
        if (mCurrentDragStartEvent != null) {
            mCurrentDragStartEvent.recycle();
            mCurrentDragStartEvent = null;
        }

        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            children[i].dispatchDetachedFromWindow();
        }
        clearDisappearingChildren();
        final int transientCount = mTransientViews == null ? 0 : mTransientIndices.size();
        for (int i = 0; i < transientCount; ++i) {
            View view = mTransientViews.get(i);
            view.dispatchDetachedFromWindow();
        }
        super.dispatchDetachedFromWindow();
    }

    @hide /**
     * @hide
     */
    @Override
    protected void internalSetPadding(int left, int top, int right, int bottom) {
        super.internalSetPadding(left, top, right, bottom);

        if ((mPaddingLeft | mPaddingTop | mPaddingRight | mPaddingBottom) != 0) {
            mGroupFlags |= FLAG_PADDING_NOT_NULL;
        } else {
            mGroupFlags &= ~FLAG_PADDING_NOT_NULL;
        }
    }

    @Override
    protected void dispatchSaveInstanceState(SparseArray<Parcelable> container) {
        super.dispatchSaveInstanceState(container);
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            View c = children[i];
            if ((c.mViewFlags & PARENT_SAVE_DISABLED_MASK) != PARENT_SAVE_DISABLED) {
                c.dispatchSaveInstanceState(container);
            }
        }
    }

    Perform dispatching of a View.saveHierarchyState(SparseArray<Parcelable>) freeze()} to only this view, not to its children. For use when overriding dispatchSaveInstanceState(SparseArray<Parcelable>) dispatchFreeze()} to allow subclasses to freeze their own state but not the state of their children. 
Params: container – the container/**
     * Perform dispatching of a {@link #saveHierarchyState(android.util.SparseArray)}  freeze()}
     * to only this view, not to its children.  For use when overriding
     * {@link #dispatchSaveInstanceState(android.util.SparseArray)}  dispatchFreeze()} to allow
     * subclasses to freeze their own state but not the state of their children.
     *
     * @param container the container
     */
    protected void dispatchFreezeSelfOnly(SparseArray<Parcelable> container) {
        super.dispatchSaveInstanceState(container);
    }

    @Override
    protected void dispatchRestoreInstanceState(SparseArray<Parcelable> container) {
        super.dispatchRestoreInstanceState(container);
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            View c = children[i];
            if ((c.mViewFlags & PARENT_SAVE_DISABLED_MASK) != PARENT_SAVE_DISABLED) {
                c.dispatchRestoreInstanceState(container);
            }
        }
    }

    Perform dispatching of a View.restoreHierarchyState(SparseArray<Parcelable>) to only this view, not to its children. For use when overriding dispatchRestoreInstanceState(SparseArray<Parcelable>) to allow subclasses to thaw their own state but not the state of their children. 
Params: container – the container/**
     * Perform dispatching of a {@link #restoreHierarchyState(android.util.SparseArray)}
     * to only this view, not to its children.  For use when overriding
     * {@link #dispatchRestoreInstanceState(android.util.SparseArray)} to allow
     * subclasses to thaw their own state but not the state of their children.
     *
     * @param container the container
     */
    protected void dispatchThawSelfOnly(SparseArray<Parcelable> container) {
        super.dispatchRestoreInstanceState(container);
    }

    Enables or disables the drawing cache for each child of this view group.
Params: enabled – true to enable the cache, false to dispose of it
Deprecated: The view drawing cache was largely made obsolete with the introduction of hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache layers are largely unnecessary and can easily result in a net loss in performance due to the cost of creating and updating the layer. In the rare cases where caching layers are useful, such as for alpha animations, View.setLayerType(int, Paint) handles this with hardware rendering. For software-rendered snapshots of a small part of the View hierarchy or individual Views it is recommended to create a Canvas from either a Bitmap or Picture and call View.draw(Canvas) on the View. However these software-rendered usages are discouraged and have compatibility issues with hardware-only rendering features such as Config.HARDWARE bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback reports or unit testing the PixelCopy API is recommended./**
     * Enables or disables the drawing cache for each child of this view group.
     *
     * @param enabled true to enable the cache, false to dispose of it
     *
     * @deprecated The view drawing cache was largely made obsolete with the introduction of
     * hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache
     * layers are largely unnecessary and can easily result in a net loss in performance due to the
     * cost of creating and updating the layer. In the rare cases where caching layers are useful,
     * such as for alpha animations, {@link #setLayerType(int, Paint)} handles this with hardware
     * rendering. For software-rendered snapshots of a small part of the View hierarchy or
     * individual Views it is recommended to create a {@link Canvas} from either a {@link Bitmap} or
     * {@link android.graphics.Picture} and call {@link #draw(Canvas)} on the View. However these
     * software-rendered usages are discouraged and have compatibility issues with hardware-only
     * rendering features such as {@link android.graphics.Bitmap.Config#HARDWARE Config.HARDWARE}
     * bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback
     * reports or unit testing the {@link PixelCopy} API is recommended.
     */
    @Deprecated
    protected void setChildrenDrawingCacheEnabled(boolean enabled) {
        if (enabled || (mPersistentDrawingCache & PERSISTENT_ALL_CACHES) != PERSISTENT_ALL_CACHES) {
            final View[] children = mChildren;
            final int count = mChildrenCount;
            for (int i = 0; i < count; i++) {
                children[i].setDrawingCacheEnabled(enabled);
            }
        }
    }

    @hide /**
     * @hide
     */
    @Override
    public Bitmap createSnapshot(ViewDebug.CanvasProvider canvasProvider, boolean skipChildren) {
        int count = mChildrenCount;
        int[] visibilities = null;

        if (skipChildren) {
            visibilities = new int[count];
            for (int i = 0; i < count; i++) {
                View child = getChildAt(i);
                visibilities[i] = child.getVisibility();
                if (visibilities[i] == View.VISIBLE) {
                    child.mViewFlags = (child.mViewFlags & ~View.VISIBILITY_MASK)
                            | (View.INVISIBLE & View.VISIBILITY_MASK);
                }
            }
        }

        try {
            return super.createSnapshot(canvasProvider, skipChildren);
        } finally {
            if (skipChildren) {
                for (int i = 0; i < count; i++) {
                    View child = getChildAt(i);
                    child.mViewFlags = (child.mViewFlags & ~View.VISIBILITY_MASK)
                            | (visibilities[i] & View.VISIBILITY_MASK);
                }
            }
        }
    }

    Return true if this ViewGroup is laying out using optical bounds. /** Return true if this ViewGroup is laying out using optical bounds. */
    boolean isLayoutModeOptical() {
        return mLayoutMode == LAYOUT_MODE_OPTICAL_BOUNDS;
    }

    @Override
    Insets computeOpticalInsets() {
        if (isLayoutModeOptical()) {
            int left = 0;
            int top = 0;
            int right = 0;
            int bottom = 0;
            for (int i = 0; i < mChildrenCount; i++) {
                View child = getChildAt(i);
                if (child.getVisibility() == VISIBLE) {
                    Insets insets = child.getOpticalInsets();
                    left =   Math.max(left,   insets.left);
                    top =    Math.max(top,    insets.top);
                    right =  Math.max(right,  insets.right);
                    bottom = Math.max(bottom, insets.bottom);
                }
            }
            return Insets.of(left, top, right, bottom);
        } else {
            return Insets.NONE;
        }
    }

    private static void fillRect(Canvas canvas, Paint paint, int x1, int y1, int x2, int y2) {
        if (x1 != x2 && y1 != y2) {
            if (x1 > x2) {
                int tmp = x1; x1 = x2; x2 = tmp;
            }
            if (y1 > y2) {
                int tmp = y1; y1 = y2; y2 = tmp;
            }
            canvas.drawRect(x1, y1, x2, y2, paint);
        }
    }

    private static int sign(int x) {
        return (x >= 0) ? 1 : -1;
    }

    private static void drawCorner(Canvas c, Paint paint, int x1, int y1, int dx, int dy, int lw) {
        fillRect(c, paint, x1, y1, x1 + dx, y1 + lw * sign(dy));
        fillRect(c, paint, x1, y1, x1 + lw * sign(dx), y1 + dy);
    }

    private static void drawRectCorners(Canvas canvas, int x1, int y1, int x2, int y2, Paint paint,
            int lineLength, int lineWidth) {
        drawCorner(canvas, paint, x1, y1, lineLength, lineLength, lineWidth);
        drawCorner(canvas, paint, x1, y2, lineLength, -lineLength, lineWidth);
        drawCorner(canvas, paint, x2, y1, -lineLength, lineLength, lineWidth);
        drawCorner(canvas, paint, x2, y2, -lineLength, -lineLength, lineWidth);
    }

    private static void fillDifference(Canvas canvas,
            int x2, int y2, int x3, int y3,
            int dx1, int dy1, int dx2, int dy2, Paint paint) {
        int x1 = x2 - dx1;
        int y1 = y2 - dy1;

        int x4 = x3 + dx2;
        int y4 = y3 + dy2;

        fillRect(canvas, paint, x1, y1, x4, y2);
        fillRect(canvas, paint, x1, y2, x2, y3);
        fillRect(canvas, paint, x3, y2, x4, y3);
        fillRect(canvas, paint, x1, y3, x4, y4);
    }

    @hide /**
     * @hide
     */
    protected void onDebugDrawMargins(Canvas canvas, Paint paint) {
        for (int i = 0; i < getChildCount(); i++) {
            View c = getChildAt(i);
            c.getLayoutParams().onDebugDraw(c, canvas, paint);
        }
    }

    @hide /**
     * @hide
     */
    protected void onDebugDraw(Canvas canvas) {
        Paint paint = getDebugPaint();

        // Draw optical bounds
        {
            paint.setColor(Color.RED);
            paint.setStyle(Paint.Style.STROKE);

            for (int i = 0; i < getChildCount(); i++) {
                View c = getChildAt(i);
                if (c.getVisibility() != View.GONE) {
                    Insets insets = c.getOpticalInsets();

                    drawRect(canvas, paint,
                            c.getLeft() + insets.left,
                            c.getTop() + insets.top,
                            c.getRight() - insets.right - 1,
                            c.getBottom() - insets.bottom - 1);
                }
            }
        }

        // Draw margins
        {
            paint.setColor(Color.argb(63, 255, 0, 255));
            paint.setStyle(Paint.Style.FILL);

            onDebugDrawMargins(canvas, paint);
        }

        // Draw clip bounds
        {
            paint.setColor(DEBUG_CORNERS_COLOR);
            paint.setStyle(Paint.Style.FILL);

            int lineLength = dipsToPixels(DEBUG_CORNERS_SIZE_DIP);
            int lineWidth = dipsToPixels(1);
            for (int i = 0; i < getChildCount(); i++) {
                View c = getChildAt(i);
                if (c.getVisibility() != View.GONE) {
                    drawRectCorners(canvas, c.getLeft(), c.getTop(), c.getRight(), c.getBottom(),
                            paint, lineLength, lineWidth);
                }
            }
        }
    }

    @Override
    protected void dispatchDraw(Canvas canvas) {
        boolean usingRenderNodeProperties = canvas.isRecordingFor(mRenderNode);
        final int childrenCount = mChildrenCount;
        final View[] children = mChildren;
        int flags = mGroupFlags;

        if ((flags & FLAG_RUN_ANIMATION) != 0 && canAnimate()) {
            final boolean buildCache = !isHardwareAccelerated();
            for (int i = 0; i < childrenCount; i++) {
                final View child = children[i];
                if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE) {
                    final LayoutParams params = child.getLayoutParams();
                    attachLayoutAnimationParameters(child, params, i, childrenCount);
                    bindLayoutAnimation(child);
                }
            }

            final LayoutAnimationController controller = mLayoutAnimationController;
            if (controller.willOverlap()) {
                mGroupFlags |= FLAG_OPTIMIZE_INVALIDATE;
            }

            controller.start();

            mGroupFlags &= ~FLAG_RUN_ANIMATION;
            mGroupFlags &= ~FLAG_ANIMATION_DONE;

            if (mAnimationListener != null) {
                mAnimationListener.onAnimationStart(controller.getAnimation());
            }
        }

        int clipSaveCount = 0;
        final boolean clipToPadding = (flags & CLIP_TO_PADDING_MASK) == CLIP_TO_PADDING_MASK;
        if (clipToPadding) {
            clipSaveCount = canvas.save(Canvas.CLIP_SAVE_FLAG);
            canvas.clipRect(mScrollX + mPaddingLeft, mScrollY + mPaddingTop,
                    mScrollX + mRight - mLeft - mPaddingRight,
                    mScrollY + mBottom - mTop - mPaddingBottom);
        }

        // We will draw our child's animation, let's reset the flag
        mPrivateFlags &= ~PFLAG_DRAW_ANIMATION;
        mGroupFlags &= ~FLAG_INVALIDATE_REQUIRED;

        boolean more = false;
        final long drawingTime = getDrawingTime();

        if (usingRenderNodeProperties) canvas.insertReorderBarrier();
        final int transientCount = mTransientIndices == null ? 0 : mTransientIndices.size();
        int transientIndex = transientCount != 0 ? 0 : -1;
        // Only use the preordered list if not HW accelerated, since the HW pipeline will do the
        // draw reordering internally
        final ArrayList<View> preorderedList = usingRenderNodeProperties
                ? null : buildOrderedChildList();
        final boolean customOrder = preorderedList == null
                && isChildrenDrawingOrderEnabled();
        for (int i = 0; i < childrenCount; i++) {
            while (transientIndex >= 0 && mTransientIndices.get(transientIndex) == i) {
                final View transientChild = mTransientViews.get(transientIndex);
                if ((transientChild.mViewFlags & VISIBILITY_MASK) == VISIBLE ||
                        transientChild.getAnimation() != null) {
                    more |= drawChild(canvas, transientChild, drawingTime);
                }
                transientIndex++;
                if (transientIndex >= transientCount) {
                    transientIndex = -1;
                }
            }

            final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);
            final View child = getAndVerifyPreorderedView(preorderedList, children, childIndex);
            if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE || child.getAnimation() != null) {
                more |= drawChild(canvas, child, drawingTime);
            }
        }
        while (transientIndex >= 0) {
            // there may be additional transient views after the normal views
            final View transientChild = mTransientViews.get(transientIndex);
            if ((transientChild.mViewFlags & VISIBILITY_MASK) == VISIBLE ||
                    transientChild.getAnimation() != null) {
                more |= drawChild(canvas, transientChild, drawingTime);
            }
            transientIndex++;
            if (transientIndex >= transientCount) {
                break;
            }
        }
        if (preorderedList != null) preorderedList.clear();

        // Draw any disappearing views that have animations
        if (mDisappearingChildren != null) {
            final ArrayList<View> disappearingChildren = mDisappearingChildren;
            final int disappearingCount = disappearingChildren.size() - 1;
            // Go backwards -- we may delete as animations finish
            for (int i = disappearingCount; i >= 0; i--) {
                final View child = disappearingChildren.get(i);
                more |= drawChild(canvas, child, drawingTime);
            }
        }
        if (usingRenderNodeProperties) canvas.insertInorderBarrier();

        if (debugDraw()) {
            onDebugDraw(canvas);
        }

        if (clipToPadding) {
            canvas.restoreToCount(clipSaveCount);
        }

        // mGroupFlags might have been updated by drawChild()
        flags = mGroupFlags;

        if ((flags & FLAG_INVALIDATE_REQUIRED) == FLAG_INVALIDATE_REQUIRED) {
            invalidate(true);
        }

        if ((flags & FLAG_ANIMATION_DONE) == 0 && (flags & FLAG_NOTIFY_ANIMATION_LISTENER) == 0 &&
                mLayoutAnimationController.isDone() && !more) {
            // We want to erase the drawing cache and notify the listener after the
            // next frame is drawn because one extra invalidate() is caused by
            // drawChild() after the animation is over
            mGroupFlags |= FLAG_NOTIFY_ANIMATION_LISTENER;
            final Runnable end = new Runnable() {
               @Override
               public void run() {
                   notifyAnimationListener();
               }
            };
            post(end);
        }
    }

    Returns the ViewGroupOverlay for this view group, creating it if it does not yet exist. In addition to ViewOverlay's support for drawables, ViewGroupOverlay allows views to be added to the overlay. These views, like overlay drawables, are visual-only; they do not receive input events and should not be used as anything other than a temporary representation of a view in a parent container, such as might be used by an animation effect. Note: Overlays do not currently work correctly with SurfaceView or TextureView; contents in overlays for these types of views may not display correctly.
See Also: ViewGroupOverlay
Returns: The ViewGroupOverlay object for this view./**
     * Returns the ViewGroupOverlay for this view group, creating it if it does
     * not yet exist. In addition to {@link ViewOverlay}'s support for drawables,
     * {@link ViewGroupOverlay} allows views to be added to the overlay. These
     * views, like overlay drawables, are visual-only; they do not receive input
     * events and should not be used as anything other than a temporary
     * representation of a view in a parent container, such as might be used
     * by an animation effect.
     *
     * <p>Note: Overlays do not currently work correctly with {@link
     * SurfaceView} or {@link TextureView}; contents in overlays for these
     * types of views may not display correctly.</p>
     *
     * @return The ViewGroupOverlay object for this view.
     * @see ViewGroupOverlay
     */
    @Override
    public ViewGroupOverlay getOverlay() {
        if (mOverlay == null) {
            mOverlay = new ViewGroupOverlay(mContext, this);
        }
        return (ViewGroupOverlay) mOverlay;
    }

    Returns the index of the child to draw for this iteration. Override this
if you want to change the drawing order of children. By default, it
returns i.
 NOTE: In order for this method to be called, you must enable child ordering first by calling setChildrenDrawingOrderEnabled(boolean). 
Params: i – The current iteration.
See Also: setChildrenDrawingOrderEnabled(boolean)
isChildrenDrawingOrderEnabled()
Returns: The index of the child to draw this iteration./**
     * Returns the index of the child to draw for this iteration. Override this
     * if you want to change the drawing order of children. By default, it
     * returns i.
     * <p>
     * NOTE: In order for this method to be called, you must enable child ordering
     * first by calling {@link #setChildrenDrawingOrderEnabled(boolean)}.
     *
     * @param i The current iteration.
     * @return The index of the child to draw this iteration.
     *
     * @see #setChildrenDrawingOrderEnabled(boolean)
     * @see #isChildrenDrawingOrderEnabled()
     */
    protected int getChildDrawingOrder(int childCount, int i) {
        return i;
    }

    private boolean hasChildWithZ() {
        for (int i = 0; i < mChildrenCount; i++) {
            if (mChildren[i].getZ() != 0) return true;
        }
        return false;
    }

    Populates (and returns) mPreSortedChildren with a pre-ordered list of the View's children,
sorted first by Z, then by child drawing order (if applicable). This list must be cleared
after use to avoid leaking child Views.
Uses a stable, insertion sort which is commonly O(n) for ViewGroups with very few elevated
children.
/**
     * Populates (and returns) mPreSortedChildren with a pre-ordered list of the View's children,
     * sorted first by Z, then by child drawing order (if applicable). This list must be cleared
     * after use to avoid leaking child Views.
     *
     * Uses a stable, insertion sort which is commonly O(n) for ViewGroups with very few elevated
     * children.
     */
    ArrayList<View> buildOrderedChildList() {
        final int childrenCount = mChildrenCount;
        if (childrenCount <= 1 || !hasChildWithZ()) return null;

        if (mPreSortedChildren == null) {
            mPreSortedChildren = new ArrayList<>(childrenCount);
        } else {
            // callers should clear, so clear shouldn't be necessary, but for safety...
            mPreSortedChildren.clear();
            mPreSortedChildren.ensureCapacity(childrenCount);
        }

        final boolean customOrder = isChildrenDrawingOrderEnabled();
        for (int i = 0; i < childrenCount; i++) {
            // add next child (in child order) to end of list
            final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);
            final View nextChild = mChildren[childIndex];
            final float currentZ = nextChild.getZ();

            // insert ahead of any Views with greater Z
            int insertIndex = i;
            while (insertIndex > 0 && mPreSortedChildren.get(insertIndex - 1).getZ() > currentZ) {
                insertIndex--;
            }
            mPreSortedChildren.add(insertIndex, nextChild);
        }
        return mPreSortedChildren;
    }

    private void notifyAnimationListener() {
        mGroupFlags &= ~FLAG_NOTIFY_ANIMATION_LISTENER;
        mGroupFlags |= FLAG_ANIMATION_DONE;

        if (mAnimationListener != null) {
           final Runnable end = new Runnable() {
               @Override
               public void run() {
                   mAnimationListener.onAnimationEnd(mLayoutAnimationController.getAnimation());
               }
           };
           post(end);
        }

        invalidate(true);
    }

    This method is used to cause children of this ViewGroup to restore or recreate their
display lists. It is called by getDisplayList() when the parent ViewGroup does not need
to recreate its own display list, which would happen if it went through the normal
draw/dispatchDraw mechanisms.
@hide /**
     * This method is used to cause children of this ViewGroup to restore or recreate their
     * display lists. It is called by getDisplayList() when the parent ViewGroup does not need
     * to recreate its own display list, which would happen if it went through the normal
     * draw/dispatchDraw mechanisms.
     *
     * @hide
     */
    @Override
    protected void dispatchGetDisplayList() {
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            final View child = children[i];
            if (((child.mViewFlags & VISIBILITY_MASK) == VISIBLE || child.getAnimation() != null)) {
                recreateChildDisplayList(child);
            }
        }
        final int transientCount = mTransientViews == null ? 0 : mTransientIndices.size();
        for (int i = 0; i < transientCount; ++i) {
            View child = mTransientViews.get(i);
            if (((child.mViewFlags & VISIBILITY_MASK) == VISIBLE || child.getAnimation() != null)) {
                recreateChildDisplayList(child);
            }
        }
        if (mOverlay != null) {
            View overlayView = mOverlay.getOverlayView();
            recreateChildDisplayList(overlayView);
        }
        if (mDisappearingChildren != null) {
            final ArrayList<View> disappearingChildren = mDisappearingChildren;
            final int disappearingCount = disappearingChildren.size();
            for (int i = 0; i < disappearingCount; ++i) {
                final View child = disappearingChildren.get(i);
                recreateChildDisplayList(child);
            }
        }
    }

    private void recreateChildDisplayList(View child) {
        child.mRecreateDisplayList = (child.mPrivateFlags & PFLAG_INVALIDATED) != 0;
        child.mPrivateFlags &= ~PFLAG_INVALIDATED;
        child.updateDisplayListIfDirty();
        child.mRecreateDisplayList = false;
    }

    Draw one child of this View Group. This method is responsible for getting
the canvas in the right state. This includes clipping, translating so
that the child's scrolled origin is at 0, 0, and applying any animation
transformations.
Params: canvas – The canvas on which to draw the child
child – Who to draw
drawingTime – The time at which draw is occurring
Returns: True if an invalidate() was issued/**
     * Draw one child of this View Group. This method is responsible for getting
     * the canvas in the right state. This includes clipping, translating so
     * that the child's scrolled origin is at 0, 0, and applying any animation
     * transformations.
     *
     * @param canvas The canvas on which to draw the child
     * @param child Who to draw
     * @param drawingTime The time at which draw is occurring
     * @return True if an invalidate() was issued
     */
    protected boolean drawChild(Canvas canvas, View child, long drawingTime) {
        return child.draw(canvas, this, drawingTime);
    }

    @Override
    void getScrollIndicatorBounds(@NonNull Rect out) {
        super.getScrollIndicatorBounds(out);

        // If we have padding and we're supposed to clip children to that
        // padding, offset the scroll indicators to match our clip bounds.
        final boolean clipToPadding = (mGroupFlags & CLIP_TO_PADDING_MASK) == CLIP_TO_PADDING_MASK;
        if (clipToPadding) {
            out.left += mPaddingLeft;
            out.right -= mPaddingRight;
            out.top += mPaddingTop;
            out.bottom -= mPaddingBottom;
        }
    }

    Returns whether this group's children are clipped to their bounds before drawing.
The default value is true.
See Also: setClipChildren(boolean)
Returns: True if the group's children will be clipped to their bounds,
false otherwise./**
     * Returns whether this group's children are clipped to their bounds before drawing.
     * The default value is true.
     * @see #setClipChildren(boolean)
     *
     * @return True if the group's children will be clipped to their bounds,
     * false otherwise.
     */
    @ViewDebug.ExportedProperty(category = "drawing")
    public boolean getClipChildren() {
        return ((mGroupFlags & FLAG_CLIP_CHILDREN) != 0);
    }

    By default, children are clipped to their bounds before drawing. This
allows view groups to override this behavior for animations, etc.
Params: clipChildren – true to clip children to their bounds,
       false otherwise
@attr ref android.R.styleable#ViewGroup_clipChildren/**
     * By default, children are clipped to their bounds before drawing. This
     * allows view groups to override this behavior for animations, etc.
     *
     * @param clipChildren true to clip children to their bounds,
     *        false otherwise
     * @attr ref android.R.styleable#ViewGroup_clipChildren
     */
    public void setClipChildren(boolean clipChildren) {
        boolean previousValue = (mGroupFlags & FLAG_CLIP_CHILDREN) == FLAG_CLIP_CHILDREN;
        if (clipChildren != previousValue) {
            setBooleanFlag(FLAG_CLIP_CHILDREN, clipChildren);
            for (int i = 0; i < mChildrenCount; ++i) {
                View child = getChildAt(i);
                if (child.mRenderNode != null) {
                    child.mRenderNode.setClipToBounds(clipChildren);
                }
            }
            invalidate(true);
        }
    }

    Sets whether this ViewGroup will clip its children to its padding and resize (but not
clip) any EdgeEffect to the padded region, if padding is present.

By default, children are clipped to the padding of their parent
ViewGroup. This clipping behavior is only enabled if padding is non-zero.
Params: clipToPadding – true to clip children to the padding of the group, and resize (but
       not clip) any EdgeEffect to the padded region. False otherwise.
@attr ref android.R.styleable#ViewGroup_clipToPadding/**
     * Sets whether this ViewGroup will clip its children to its padding and resize (but not
     * clip) any EdgeEffect to the padded region, if padding is present.
     * <p>
     * By default, children are clipped to the padding of their parent
     * ViewGroup. This clipping behavior is only enabled if padding is non-zero.
     *
     * @param clipToPadding true to clip children to the padding of the group, and resize (but
     *        not clip) any EdgeEffect to the padded region. False otherwise.
     * @attr ref android.R.styleable#ViewGroup_clipToPadding
     */
    public void setClipToPadding(boolean clipToPadding) {
        if (hasBooleanFlag(FLAG_CLIP_TO_PADDING) != clipToPadding) {
            setBooleanFlag(FLAG_CLIP_TO_PADDING, clipToPadding);
            invalidate(true);
        }
    }

    Returns whether this ViewGroup will clip its children to its padding, and resize (but
not clip) any EdgeEffect to the padded region, if padding is present.

By default, children are clipped to the padding of their parent
Viewgroup. This clipping behavior is only enabled if padding is non-zero.
Returns: true if this ViewGroup clips children to its padding and resizes (but doesn't
        clip) any EdgeEffect to the padded region, false otherwise.
@attr ref android.R.styleable#ViewGroup_clipToPadding/**
     * Returns whether this ViewGroup will clip its children to its padding, and resize (but
     * not clip) any EdgeEffect to the padded region, if padding is present.
     * <p>
     * By default, children are clipped to the padding of their parent
     * Viewgroup. This clipping behavior is only enabled if padding is non-zero.
     *
     * @return true if this ViewGroup clips children to its padding and resizes (but doesn't
     *         clip) any EdgeEffect to the padded region, false otherwise.
     *
     * @attr ref android.R.styleable#ViewGroup_clipToPadding
     */
    @ViewDebug.ExportedProperty(category = "drawing")
    public boolean getClipToPadding() {
        return hasBooleanFlag(FLAG_CLIP_TO_PADDING);
    }

    @Override
    public void dispatchSetSelected(boolean selected) {
        final View[] children = mChildren;
        final int count = mChildrenCount;
        for (int i = 0; i < count; i++) {
            children[i].setSelected(selected);
        }
    }

    @Override
    public void dispatchSetActivated(boolean activated) {
        final View[] children = mChildren;
        final int count = mChildrenCount;
        for (int i = 0; i < count; i++) {
            children[i].setActivated(activated);
        }
    }

    @Override
    protected void dispatchSetPressed(boolean pressed) {
        final View[] children = mChildren;
        final int count = mChildrenCount;
        for (int i = 0; i < count; i++) {
            final View child = children[i];
            // Children that are clickable on their own should not
            // show a pressed state when their parent view does.
            // Clearing a pressed state always propagates.
            if (!pressed || (!child.isClickable() && !child.isLongClickable())) {
                child.setPressed(pressed);
            }
        }
    }

    Dispatches drawable hotspot changes to child views that meet at least
one of the following criteria:

    Returns false from both View.isClickable() and View.isLongClickable()
    Requests duplication of parent state via View.setDuplicateParentStateEnabled(boolean)

Params: x – hotspot x coordinate
y – hotspot y coordinate
See Also: View.drawableHotspotChanged(float, float)/**
     * Dispatches drawable hotspot changes to child views that meet at least
     * one of the following criteria:
     * <ul>
     *     <li>Returns {@code false} from both {@link View#isClickable()} and
     *     {@link View#isLongClickable()}</li>
     *     <li>Requests duplication of parent state via
     *     {@link View#setDuplicateParentStateEnabled(boolean)}</li>
     * </ul>
     *
     * @param x hotspot x coordinate
     * @param y hotspot y coordinate
     * @see #drawableHotspotChanged(float, float)
     */
    @Override
    public void dispatchDrawableHotspotChanged(float x, float y) {
        final int count = mChildrenCount;
        if (count == 0) {
            return;
        }

        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            final View child = children[i];
            // Children that are clickable on their own should not
            // receive hotspots when their parent view does.
            final boolean nonActionable = !child.isClickable() && !child.isLongClickable();
            final boolean duplicatesState = (child.mViewFlags & DUPLICATE_PARENT_STATE) != 0;
            if (nonActionable || duplicatesState) {
                final float[] point = getTempPoint();
                point[0] = x;
                point[1] = y;
                transformPointToViewLocal(point, child);
                child.drawableHotspotChanged(point[0], point[1]);
            }
        }
    }

    @Override
    void dispatchCancelPendingInputEvents() {
        super.dispatchCancelPendingInputEvents();

        final View[] children = mChildren;
        final int count = mChildrenCount;
        for (int i = 0; i < count; i++) {
            children[i].dispatchCancelPendingInputEvents();
        }
    }

    When this property is set to true, this ViewGroup supports static transformations on children; this causes getChildStaticTransformation(View, Transformation) to be invoked when a child is drawn. Any subclass overriding getChildStaticTransformation(View, Transformation) should set this property to true. 
Params: enabled – True to enable static transformations on children, false otherwise.
See Also: getChildStaticTransformation(View, Transformation)/**
     * When this property is set to true, this ViewGroup supports static transformations on
     * children; this causes
     * {@link #getChildStaticTransformation(View, android.view.animation.Transformation)} to be
     * invoked when a child is drawn.
     *
     * Any subclass overriding
     * {@link #getChildStaticTransformation(View, android.view.animation.Transformation)} should
     * set this property to true.
     *
     * @param enabled True to enable static transformations on children, false otherwise.
     *
     * @see #getChildStaticTransformation(View, android.view.animation.Transformation)
     */
    protected void setStaticTransformationsEnabled(boolean enabled) {
        setBooleanFlag(FLAG_SUPPORT_STATIC_TRANSFORMATIONS, enabled);
    }

    Sets  t to be the static transformation of the child, if set, returning a
boolean to indicate whether a static transform was set. The default implementation
simply returns false; subclasses may override this method for different behavior. setStaticTransformationsEnabled(boolean) must be set to true for this method to be called. 
Params: child – The child view whose static transform is being requested
t – The Transformation which will hold the result
See Also: setStaticTransformationsEnabled(boolean)
Returns: true if the transformation was set, false otherwise/**
     * Sets  <code>t</code> to be the static transformation of the child, if set, returning a
     * boolean to indicate whether a static transform was set. The default implementation
     * simply returns <code>false</code>; subclasses may override this method for different
     * behavior. {@link #setStaticTransformationsEnabled(boolean)} must be set to true
     * for this method to be called.
     *
     * @param child The child view whose static transform is being requested
     * @param t The Transformation which will hold the result
     * @return true if the transformation was set, false otherwise
     * @see #setStaticTransformationsEnabled(boolean)
     */
    protected boolean getChildStaticTransformation(View child, Transformation t) {
        return false;
    }

    Transformation getChildTransformation() {
        if (mChildTransformation == null) {
            mChildTransformation = new Transformation();
        }
        return mChildTransformation;
    }

    {@hide}
/**
     * {@hide}
     */
    @Override
    protected <T extends View> T findViewTraversal(@IdRes int id) {
        if (id == mID) {
            return (T) this;
        }

        final View[] where = mChildren;
        final int len = mChildrenCount;

        for (int i = 0; i < len; i++) {
            View v = where[i];

            if ((v.mPrivateFlags & PFLAG_IS_ROOT_NAMESPACE) == 0) {
                v = v.findViewById(id);

                if (v != null) {
                    return (T) v;
                }
            }
        }

        return null;
    }

    {@hide}
/**
     * {@hide}
     */
    @Override
    protected <T extends View> T findViewWithTagTraversal(Object tag) {
        if (tag != null && tag.equals(mTag)) {
            return (T) this;
        }

        final View[] where = mChildren;
        final int len = mChildrenCount;

        for (int i = 0; i < len; i++) {
            View v = where[i];

            if ((v.mPrivateFlags & PFLAG_IS_ROOT_NAMESPACE) == 0) {
                v = v.findViewWithTag(tag);

                if (v != null) {
                    return (T) v;
                }
            }
        }

        return null;
    }

    {@hide}
/**
     * {@hide}
     */
    @Override
    protected <T extends View> T findViewByPredicateTraversal(Predicate<View> predicate,
            View childToSkip) {
        if (predicate.test(this)) {
            return (T) this;
        }

        final View[] where = mChildren;
        final int len = mChildrenCount;

        for (int i = 0; i < len; i++) {
            View v = where[i];

            if (v != childToSkip && (v.mPrivateFlags & PFLAG_IS_ROOT_NAMESPACE) == 0) {
                v = v.findViewByPredicate(predicate);

                if (v != null) {
                    return (T) v;
                }
            }
        }

        return null;
    }

    This method adds a view to this container at the specified index purely for the
purposes of allowing that view to draw even though it is not a normal child of
the container. That is, the view does not participate in layout, focus, accessibility,
input, or other normal view operations; it is purely an item to be drawn during the normal
rendering operation of this container. The index that it is added at is the order
in which it will be drawn, with respect to the other views in the container.
For example, a transient view added at index 0 will be drawn before all other views
in the container because it will be drawn first (including before any real view
at index 0). There can be more than one transient view at any particular index;
these views will be drawn in the order in which they were added to the list of
transient views. The index of transient views can also be greater than the number
of normal views in the container; that just means that they will be drawn after all
other views are drawn.
Note that since transient views do not participate in layout, they must be sized
manually or, more typically, they should just use the size that they had before they
were removed from their container.
Transient views are useful for handling animations of views that have been removed
from the container, but which should be animated out after the removal. Adding these
views as transient views allows them to participate in drawing without side-effecting
the layout of the container.
Transient views must always be explicitly removed from the container when they are no longer needed. For example, a transient view which is added in order to fade it out in its old location should be removed once the animation is complete.
Params: view – The view to be added
index – The index at which this view should be drawn, must be >= 0. This value is relative to the index values in the normal child list of this container, where any transient view at a particular index will be drawn before any normal child at that same index.
@hide /**
     * This method adds a view to this container at the specified index purely for the
     * purposes of allowing that view to draw even though it is not a normal child of
     * the container. That is, the view does not participate in layout, focus, accessibility,
     * input, or other normal view operations; it is purely an item to be drawn during the normal
     * rendering operation of this container. The index that it is added at is the order
     * in which it will be drawn, with respect to the other views in the container.
     * For example, a transient view added at index 0 will be drawn before all other views
     * in the container because it will be drawn first (including before any real view
     * at index 0). There can be more than one transient view at any particular index;
     * these views will be drawn in the order in which they were added to the list of
     * transient views. The index of transient views can also be greater than the number
     * of normal views in the container; that just means that they will be drawn after all
     * other views are drawn.
     *
     * <p>Note that since transient views do not participate in layout, they must be sized
     * manually or, more typically, they should just use the size that they had before they
     * were removed from their container.</p>
     *
     * <p>Transient views are useful for handling animations of views that have been removed
     * from the container, but which should be animated out after the removal. Adding these
     * views as transient views allows them to participate in drawing without side-effecting
     * the layout of the container.</p>
     *
     * <p>Transient views must always be explicitly {@link #removeTransientView(View) removed}
     * from the container when they are no longer needed. For example, a transient view
     * which is added in order to fade it out in its old location should be removed
     * once the animation is complete.</p>
     *
     * @param view The view to be added
     * @param index The index at which this view should be drawn, must be >= 0.
     * This value is relative to the {@link #getChildAt(int) index} values in the normal
     * child list of this container, where any transient view at a particular index will
     * be drawn before any normal child at that same index.
     *
     * @hide
     */
    public void addTransientView(View view, int index) {
        if (index < 0) {
            return;
        }
        if (mTransientIndices == null) {
            mTransientIndices = new ArrayList<Integer>();
            mTransientViews = new ArrayList<View>();
        }
        final int oldSize = mTransientIndices.size();
        if (oldSize > 0) {
            int insertionIndex;
            for (insertionIndex = 0; insertionIndex < oldSize; ++insertionIndex) {
                if (index < mTransientIndices.get(insertionIndex)) {
                    break;
                }
            }
            mTransientIndices.add(insertionIndex, index);
            mTransientViews.add(insertionIndex, view);
        } else {
            mTransientIndices.add(index);
            mTransientViews.add(view);
        }
        view.mParent = this;
        view.dispatchAttachedToWindow(mAttachInfo, (mViewFlags&VISIBILITY_MASK));
        invalidate(true);
    }

    Removes a view from the list of transient views in this container. If there is no
such transient view, this method does nothing.
Params: view – The transient view to be removed
@hide /**
     * Removes a view from the list of transient views in this container. If there is no
     * such transient view, this method does nothing.
     *
     * @param view The transient view to be removed
     *
     * @hide
     */
    public void removeTransientView(View view) {
        if (mTransientViews == null) {
            return;
        }
        final int size = mTransientViews.size();
        for (int i = 0; i < size; ++i) {
            if (view == mTransientViews.get(i)) {
                mTransientViews.remove(i);
                mTransientIndices.remove(i);
                view.mParent = null;
                view.dispatchDetachedFromWindow();
                invalidate(true);
                return;
            }
        }
    }

    Returns the number of transient views in this container. Specific transient views and the index at which they were added can be retrieved via getTransientView(int) and getTransientViewIndex(int). 
See Also: addTransientView(View, int)
Returns: The number of transient views in this container
@hide /**
     * Returns the number of transient views in this container. Specific transient
     * views and the index at which they were added can be retrieved via
     * {@link #getTransientView(int)} and {@link #getTransientViewIndex(int)}.
     *
     * @see #addTransientView(View, int)
     * @return The number of transient views in this container
     *
     * @hide
     */
    public int getTransientViewCount() {
        return mTransientIndices == null ? 0 : mTransientIndices.size();
    }

    Given a valid position within the list of transient views, returns the index of
the transient view at that position.
Params: position – The position of the index being queried. Must be at least 0 and less than the value returned by getTransientViewCount().
Returns: The index of the transient view stored in the given position if the
position is valid, otherwise -1
@hide /**
     * Given a valid position within the list of transient views, returns the index of
     * the transient view at that position.
     *
     * @param position The position of the index being queried. Must be at least 0
     * and less than the value returned by {@link #getTransientViewCount()}.
     * @return The index of the transient view stored in the given position if the
     * position is valid, otherwise -1
     *
     * @hide
     */
    public int getTransientViewIndex(int position) {
        if (position < 0 || mTransientIndices == null || position >= mTransientIndices.size()) {
            return -1;
        }
        return mTransientIndices.get(position);
    }

    Given a valid position within the list of transient views, returns the
transient view at that position.
Params: position – The position of the view being queried. Must be at least 0 and less than the value returned by getTransientViewCount().
Returns: The transient view stored in the given position if the
position is valid, otherwise null
@hide /**
     * Given a valid position within the list of transient views, returns the
     * transient view at that position.
     *
     * @param position The position of the view being queried. Must be at least 0
     * and less than the value returned by {@link #getTransientViewCount()}.
     * @return The transient view stored in the given position if the
     * position is valid, otherwise null
     *
     * @hide
     */
    public View getTransientView(int position) {
        if (mTransientViews == null || position >= mTransientViews.size()) {
            return null;
        }
        return mTransientViews.get(position);
    }

    Adds a child view. If no layout parameters are already set on the child, the
default parameters for this ViewGroup are set on the child.
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
Params: child – the child view to add
See Also: generateDefaultLayoutParams()/**
     * <p>Adds a child view. If no layout parameters are already set on the child, the
     * default parameters for this ViewGroup are set on the child.</p>
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     *
     * @param child the child view to add
     *
     * @see #generateDefaultLayoutParams()
     */
    public void addView(View child) {
        addView(child, -1);
    }

    Adds a child view. If no layout parameters are already set on the child, the
default parameters for this ViewGroup are set on the child.
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
Params: child – the child view to add
index – the position at which to add the child
See Also: generateDefaultLayoutParams()/**
     * Adds a child view. If no layout parameters are already set on the child, the
     * default parameters for this ViewGroup are set on the child.
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     *
     * @param child the child view to add
     * @param index the position at which to add the child
     *
     * @see #generateDefaultLayoutParams()
     */
    public void addView(View child, int index) {
        if (child == null) {
            throw new IllegalArgumentException("Cannot add a null child view to a ViewGroup");
        }
        LayoutParams params = child.getLayoutParams();
        if (params == null) {
            params = generateDefaultLayoutParams();
            if (params == null) {
                throw new IllegalArgumentException("generateDefaultLayoutParams() cannot return null");
            }
        }
        addView(child, index, params);
    }

    Adds a child view with this ViewGroup's default layout parameters and the
specified width and height.
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
Params: child – the child view to add/**
     * Adds a child view with this ViewGroup's default layout parameters and the
     * specified width and height.
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     *
     * @param child the child view to add
     */
    public void addView(View child, int width, int height) {
        final LayoutParams params = generateDefaultLayoutParams();
        params.width = width;
        params.height = height;
        addView(child, -1, params);
    }

    Adds a child view with the specified layout parameters.
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
Params: child – the child view to add
params – the layout parameters to set on the child/**
     * Adds a child view with the specified layout parameters.
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     *
     * @param child the child view to add
     * @param params the layout parameters to set on the child
     */
    @Override
    public void addView(View child, LayoutParams params) {
        addView(child, -1, params);
    }

    Adds a child view with the specified layout parameters.
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
Params: child – the child view to add
index – the position at which to add the child or -1 to add last
params – the layout parameters to set on the child/**
     * Adds a child view with the specified layout parameters.
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     *
     * @param child the child view to add
     * @param index the position at which to add the child or -1 to add last
     * @param params the layout parameters to set on the child
     */
    public void addView(View child, int index, LayoutParams params) {
        if (DBG) {
            System.out.println(this + " addView");
        }

        if (child == null) {
            throw new IllegalArgumentException("Cannot add a null child view to a ViewGroup");
        }

        // addViewInner() will call child.requestLayout() when setting the new LayoutParams
        // therefore, we call requestLayout() on ourselves before, so that the child's request
        // will be blocked at our level
        requestLayout();
        invalidate(true);
        addViewInner(child, index, params, false);
    }

    @Override
    public void updateViewLayout(View view, ViewGroup.LayoutParams params) {
        if (!checkLayoutParams(params)) {
            throw new IllegalArgumentException("Invalid LayoutParams supplied to " + this);
        }
        if (view.mParent != this) {
            throw new IllegalArgumentException("Given view not a child of " + this);
        }
        view.setLayoutParams(params);
    }

    protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
        return  p != null;
    }

    Interface definition for a callback to be invoked when the hierarchy
within this view changed. The hierarchy changes whenever a child is added
to or removed from this view.
/**
     * Interface definition for a callback to be invoked when the hierarchy
     * within this view changed. The hierarchy changes whenever a child is added
     * to or removed from this view.
     */
    public interface OnHierarchyChangeListener {
        Called when a new child is added to a parent view.
Params: parent – the view in which a child was added
child – the new child view added in the hierarchy/**
         * Called when a new child is added to a parent view.
         *
         * @param parent the view in which a child was added
         * @param child the new child view added in the hierarchy
         */
        void onChildViewAdded(View parent, View child);

        Called when a child is removed from a parent view.
Params: parent – the view from which the child was removed
child – the child removed from the hierarchy/**
         * Called when a child is removed from a parent view.
         *
         * @param parent the view from which the child was removed
         * @param child the child removed from the hierarchy
         */
        void onChildViewRemoved(View parent, View child);
    }

    Register a callback to be invoked when a child is added to or removed
from this view.
Params: listener – the callback to invoke on hierarchy change/**
     * Register a callback to be invoked when a child is added to or removed
     * from this view.
     *
     * @param listener the callback to invoke on hierarchy change
     */
    public void setOnHierarchyChangeListener(OnHierarchyChangeListener listener) {
        mOnHierarchyChangeListener = listener;
    }

    void dispatchViewAdded(View child) {
        onViewAdded(child);
        if (mOnHierarchyChangeListener != null) {
            mOnHierarchyChangeListener.onChildViewAdded(this, child);
        }
    }

    Called when a new child is added to this ViewGroup. Overrides should always
call super.onViewAdded.
Params: child – the added child view/**
     * Called when a new child is added to this ViewGroup. Overrides should always
     * call super.onViewAdded.
     *
     * @param child the added child view
     */
    public void onViewAdded(View child) {
    }

    void dispatchViewRemoved(View child) {
        onViewRemoved(child);
        if (mOnHierarchyChangeListener != null) {
            mOnHierarchyChangeListener.onChildViewRemoved(this, child);
        }
    }

    Called when a child view is removed from this ViewGroup. Overrides should always
call super.onViewRemoved.
Params: child – the removed child view/**
     * Called when a child view is removed from this ViewGroup. Overrides should always
     * call super.onViewRemoved.
     *
     * @param child the removed child view
     */
    public void onViewRemoved(View child) {
    }

    private void clearCachedLayoutMode() {
        if (!hasBooleanFlag(FLAG_LAYOUT_MODE_WAS_EXPLICITLY_SET)) {
           mLayoutMode = LAYOUT_MODE_UNDEFINED;
        }
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        clearCachedLayoutMode();
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        clearCachedLayoutMode();
    }

    @hide /** @hide */
    @Override
    protected void destroyHardwareResources() {
        super.destroyHardwareResources();
        int count = getChildCount();
        for (int i = 0; i < count; i++) {
            getChildAt(i).destroyHardwareResources();
        }
    }

    Adds a view during layout. This is useful if in your onLayout() method,
you need to add more views (as does the list view for example).
If index is negative, it means put it at the end of the list.
Params: child – the view to add to the group
index – the index at which the child must be added or -1 to add last
params – the layout parameters to associate with the child
Returns: true if the child was added, false otherwise/**
     * Adds a view during layout. This is useful if in your onLayout() method,
     * you need to add more views (as does the list view for example).
     *
     * If index is negative, it means put it at the end of the list.
     *
     * @param child the view to add to the group
     * @param index the index at which the child must be added or -1 to add last
     * @param params the layout parameters to associate with the child
     * @return true if the child was added, false otherwise
     */
    protected boolean addViewInLayout(View child, int index, LayoutParams params) {
        return addViewInLayout(child, index, params, false);
    }

    Adds a view during layout. This is useful if in your onLayout() method,
you need to add more views (as does the list view for example).
If index is negative, it means put it at the end of the list.
Params: child – the view to add to the group
index – the index at which the child must be added or -1 to add last
params – the layout parameters to associate with the child
preventRequestLayout – if true, calling this method will not trigger a
       layout request on child
Returns: true if the child was added, false otherwise/**
     * Adds a view during layout. This is useful if in your onLayout() method,
     * you need to add more views (as does the list view for example).
     *
     * If index is negative, it means put it at the end of the list.
     *
     * @param child the view to add to the group
     * @param index the index at which the child must be added or -1 to add last
     * @param params the layout parameters to associate with the child
     * @param preventRequestLayout if true, calling this method will not trigger a
     *        layout request on child
     * @return true if the child was added, false otherwise
     */
    protected boolean addViewInLayout(View child, int index, LayoutParams params,
            boolean preventRequestLayout) {
        if (child == null) {
            throw new IllegalArgumentException("Cannot add a null child view to a ViewGroup");
        }
        child.mParent = null;
        addViewInner(child, index, params, preventRequestLayout);
        child.mPrivateFlags = (child.mPrivateFlags & ~PFLAG_DIRTY_MASK) | PFLAG_DRAWN;
        return true;
    }

    Prevents the specified child to be laid out during the next layout pass.
Params: child – the child on which to perform the cleanup/**
     * Prevents the specified child to be laid out during the next layout pass.
     *
     * @param child the child on which to perform the cleanup
     */
    protected void cleanupLayoutState(View child) {
        child.mPrivateFlags &= ~View.PFLAG_FORCE_LAYOUT;
    }

    private void addViewInner(View child, int index, LayoutParams params,
            boolean preventRequestLayout) {

        if (mTransition != null) {
            // Don't prevent other add transitions from completing, but cancel remove
            // transitions to let them complete the process before we add to the container
            mTransition.cancel(LayoutTransition.DISAPPEARING);
        }

        if (child.getParent() != null) {
            throw new IllegalStateException("The specified child already has a parent. " +
                    "You must call removeView() on the child's parent first.");
        }

        if (mTransition != null) {
            mTransition.addChild(this, child);
        }

        if (!checkLayoutParams(params)) {
            params = generateLayoutParams(params);
        }

        if (preventRequestLayout) {
            child.mLayoutParams = params;
        } else {
            child.setLayoutParams(params);
        }

        if (index < 0) {
            index = mChildrenCount;
        }

        addInArray(child, index);

        // tell our children
        if (preventRequestLayout) {
            child.assignParent(this);
        } else {
            child.mParent = this;
        }
        if (child.hasUnhandledKeyListener()) {
            incrementChildUnhandledKeyListeners();
        }

        final boolean childHasFocus = child.hasFocus();
        if (childHasFocus) {
            requestChildFocus(child, child.findFocus());
        }

        AttachInfo ai = mAttachInfo;
        if (ai != null && (mGroupFlags & FLAG_PREVENT_DISPATCH_ATTACHED_TO_WINDOW) == 0) {
            boolean lastKeepOn = ai.mKeepScreenOn;
            ai.mKeepScreenOn = false;
            child.dispatchAttachedToWindow(mAttachInfo, (mViewFlags&VISIBILITY_MASK));
            if (ai.mKeepScreenOn) {
                needGlobalAttributesUpdate(true);
            }
            ai.mKeepScreenOn = lastKeepOn;
        }

        if (child.isLayoutDirectionInherited()) {
            child.resetRtlProperties();
        }

        dispatchViewAdded(child);

        if ((child.mViewFlags & DUPLICATE_PARENT_STATE) == DUPLICATE_PARENT_STATE) {
            mGroupFlags |= FLAG_NOTIFY_CHILDREN_ON_DRAWABLE_STATE_CHANGE;
        }

        if (child.hasTransientState()) {
            childHasTransientStateChanged(child, true);
        }

        if (child.getVisibility() != View.GONE) {
            notifySubtreeAccessibilityStateChangedIfNeeded();
        }

        if (mTransientIndices != null) {
            final int transientCount = mTransientIndices.size();
            for (int i = 0; i < transientCount; ++i) {
                final int oldIndex = mTransientIndices.get(i);
                if (index <= oldIndex) {
                    mTransientIndices.set(i, oldIndex + 1);
                }
            }
        }

        if (mCurrentDragStartEvent != null && child.getVisibility() == VISIBLE) {
            notifyChildOfDragStart(child);
        }

        if (child.hasDefaultFocus()) {
            // When adding a child that contains default focus, either during inflation or while
            // manually assembling the hierarchy, update the ancestor default-focus chain.
            setDefaultFocus(child);
        }

        touchAccessibilityNodeProviderIfNeeded(child);
    }

    We may need to touch the provider to bring up the a11y layer. In a11y mode
clients inspect the screen or the user touches it which triggers bringing up
of the a11y infrastructure while in autofill mode we want the infra up and
running from the beginning since we watch for a11y events to drive autofill.
/**
     * We may need to touch the provider to bring up the a11y layer. In a11y mode
     * clients inspect the screen or the user touches it which triggers bringing up
     * of the a11y infrastructure while in autofill mode we want the infra up and
     * running from the beginning since we watch for a11y events to drive autofill.
     */
    private void touchAccessibilityNodeProviderIfNeeded(View child) {
        if (mContext.isAutofillCompatibilityEnabled()) {
            child.getAccessibilityNodeProvider();
        }
    }

    private void addInArray(View child, int index) {
        View[] children = mChildren;
        final int count = mChildrenCount;
        final int size = children.length;
        if (index == count) {
            if (size == count) {
                mChildren = new View[size + ARRAY_CAPACITY_INCREMENT];
                System.arraycopy(children, 0, mChildren, 0, size);
                children = mChildren;
            }
            children[mChildrenCount++] = child;
        } else if (index < count) {
            if (size == count) {
                mChildren = new View[size + ARRAY_CAPACITY_INCREMENT];
                System.arraycopy(children, 0, mChildren, 0, index);
                System.arraycopy(children, index, mChildren, index + 1, count - index);
                children = mChildren;
            } else {
                System.arraycopy(children, index, children, index + 1, count - index);
            }
            children[index] = child;
            mChildrenCount++;
            if (mLastTouchDownIndex >= index) {
                mLastTouchDownIndex++;
            }
        } else {
            throw new IndexOutOfBoundsException("index=" + index + " count=" + count);
        }
    }

    // This method also sets the child's mParent to null
    private void removeFromArray(int index) {
        final View[] children = mChildren;
        if (!(mTransitioningViews != null && mTransitioningViews.contains(children[index]))) {
            children[index].mParent = null;
        }
        final int count = mChildrenCount;
        if (index == count - 1) {
            children[--mChildrenCount] = null;
        } else if (index >= 0 && index < count) {
            System.arraycopy(children, index + 1, children, index, count - index - 1);
            children[--mChildrenCount] = null;
        } else {
            throw new IndexOutOfBoundsException();
        }
        if (mLastTouchDownIndex == index) {
            mLastTouchDownTime = 0;
            mLastTouchDownIndex = -1;
        } else if (mLastTouchDownIndex > index) {
            mLastTouchDownIndex--;
        }
    }

    // This method also sets the children's mParent to null
    private void removeFromArray(int start, int count) {
        final View[] children = mChildren;
        final int childrenCount = mChildrenCount;

        start = Math.max(0, start);
        final int end = Math.min(childrenCount, start + count);

        if (start == end) {
            return;
        }

        if (end == childrenCount) {
            for (int i = start; i < end; i++) {
                children[i].mParent = null;
                children[i] = null;
            }
        } else {
            for (int i = start; i < end; i++) {
                children[i].mParent = null;
            }

            // Since we're looping above, we might as well do the copy, but is arraycopy()
            // faster than the extra 2 bounds checks we would do in the loop?
            System.arraycopy(children, end, children, start, childrenCount - end);

            for (int i = childrenCount - (end - start); i < childrenCount; i++) {
                children[i] = null;
            }
        }

        mChildrenCount -= (end - start);
    }

    private void bindLayoutAnimation(View child) {
        Animation a = mLayoutAnimationController.getAnimationForView(child);
        child.setAnimation(a);
    }

    Subclasses should override this method to set layout animation
parameters on the supplied child.
Params: child – the child to associate with animation parameters
params – the child's layout parameters which hold the animation
       parameters
index – the index of the child in the view group
count – the number of children in the view group/**
     * Subclasses should override this method to set layout animation
     * parameters on the supplied child.
     *
     * @param child the child to associate with animation parameters
     * @param params the child's layout parameters which hold the animation
     *        parameters
     * @param index the index of the child in the view group
     * @param count the number of children in the view group
     */
    protected void attachLayoutAnimationParameters(View child,
            LayoutParams params, int index, int count) {
        LayoutAnimationController.AnimationParameters animationParams =
                    params.layoutAnimationParameters;
        if (animationParams == null) {
            animationParams = new LayoutAnimationController.AnimationParameters();
            params.layoutAnimationParameters = animationParams;
        }

        animationParams.count = count;
        animationParams.index = index;
    }

    {@inheritDoc}
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
/**
     * {@inheritDoc}
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     */
    @Override
    public void removeView(View view) {
        if (removeViewInternal(view)) {
            requestLayout();
            invalidate(true);
        }
    }

    Removes a view during layout. This is useful if in your onLayout() method,
you need to remove more views.
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
Params: view – the view to remove from the group/**
     * Removes a view during layout. This is useful if in your onLayout() method,
     * you need to remove more views.
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     *
     * @param view the view to remove from the group
     */
    public void removeViewInLayout(View view) {
        removeViewInternal(view);
    }

    Removes a range of views during layout. This is useful if in your onLayout() method,
you need to remove more views.
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
Params: start – the index of the first view to remove from the group
count – the number of views to remove from the group/**
     * Removes a range of views during layout. This is useful if in your onLayout() method,
     * you need to remove more views.
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     *
     * @param start the index of the first view to remove from the group
     * @param count the number of views to remove from the group
     */
    public void removeViewsInLayout(int start, int count) {
        removeViewsInternal(start, count);
    }

    Removes the view at the specified position in the group.
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
Params: index – the position in the group of the view to remove/**
     * Removes the view at the specified position in the group.
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     *
     * @param index the position in the group of the view to remove
     */
    public void removeViewAt(int index) {
        removeViewInternal(index, getChildAt(index));
        requestLayout();
        invalidate(true);
    }

    Removes the specified range of views from the group.
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
Params: start – the first position in the group of the range of views to remove
count – the number of views to remove/**
     * Removes the specified range of views from the group.
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     *
     * @param start the first position in the group of the range of views to remove
     * @param count the number of views to remove
     */
    public void removeViews(int start, int count) {
        removeViewsInternal(start, count);
        requestLayout();
        invalidate(true);
    }

    private boolean removeViewInternal(View view) {
        final int index = indexOfChild(view);
        if (index >= 0) {
            removeViewInternal(index, view);
            return true;
        }
        return false;
    }

    private void removeViewInternal(int index, View view) {
        if (mTransition != null) {
            mTransition.removeChild(this, view);
        }

        boolean clearChildFocus = false;
        if (view == mFocused) {
            view.unFocus(null);
            clearChildFocus = true;
        }
        if (view == mFocusedInCluster) {
            clearFocusedInCluster(view);
        }

        view.clearAccessibilityFocus();

        cancelTouchTarget(view);
        cancelHoverTarget(view);

        if (view.getAnimation() != null ||
                (mTransitioningViews != null && mTransitioningViews.contains(view))) {
            addDisappearingView(view);
        } else if (view.mAttachInfo != null) {
           view.dispatchDetachedFromWindow();
        }

        if (view.hasTransientState()) {
            childHasTransientStateChanged(view, false);
        }

        needGlobalAttributesUpdate(false);

        removeFromArray(index);

        if (view.hasUnhandledKeyListener()) {
            decrementChildUnhandledKeyListeners();
        }

        if (view == mDefaultFocus) {
            clearDefaultFocus(view);
        }
        if (clearChildFocus) {
            clearChildFocus(view);
            if (!rootViewRequestFocus()) {
                notifyGlobalFocusCleared(this);
            }
        }

        dispatchViewRemoved(view);

        if (view.getVisibility() != View.GONE) {
            notifySubtreeAccessibilityStateChangedIfNeeded();
        }

        int transientCount = mTransientIndices == null ? 0 : mTransientIndices.size();
        for (int i = 0; i < transientCount; ++i) {
            final int oldIndex = mTransientIndices.get(i);
            if (index < oldIndex) {
                mTransientIndices.set(i, oldIndex - 1);
            }
        }

        if (mCurrentDragStartEvent != null) {
            mChildrenInterestedInDrag.remove(view);
        }
    }

    Sets the LayoutTransition object for this ViewGroup. If the LayoutTransition object is
not null, changes in layout which occur because of children being added to or removed from
the ViewGroup will be animated according to the animations defined in that LayoutTransition
object. By default, the transition object is null (so layout changes are not animated).
Replacing a non-null transition will cause that previous transition to be
canceled, if it is currently running, to restore this container to
its correct post-transition state.
Params: transition – The LayoutTransition object that will animated changes in layout. A value
of null means no transition will run on layout changes.
@attr ref android.R.styleable#ViewGroup_animateLayoutChanges/**
     * Sets the LayoutTransition object for this ViewGroup. If the LayoutTransition object is
     * not null, changes in layout which occur because of children being added to or removed from
     * the ViewGroup will be animated according to the animations defined in that LayoutTransition
     * object. By default, the transition object is null (so layout changes are not animated).
     *
     * <p>Replacing a non-null transition will cause that previous transition to be
     * canceled, if it is currently running, to restore this container to
     * its correct post-transition state.</p>
     *
     * @param transition The LayoutTransition object that will animated changes in layout. A value
     * of <code>null</code> means no transition will run on layout changes.
     * @attr ref android.R.styleable#ViewGroup_animateLayoutChanges
     */
    public void setLayoutTransition(LayoutTransition transition) {
        if (mTransition != null) {
            LayoutTransition previousTransition = mTransition;
            previousTransition.cancel();
            previousTransition.removeTransitionListener(mLayoutTransitionListener);
        }
        mTransition = transition;
        if (mTransition != null) {
            mTransition.addTransitionListener(mLayoutTransitionListener);
        }
    }

    Gets the LayoutTransition object for this ViewGroup. If the LayoutTransition object is
not null, changes in layout which occur because of children being added to or removed from
the ViewGroup will be animated according to the animations defined in that LayoutTransition
object. By default, the transition object is null (so layout changes are not animated).
Returns: LayoutTranstion The LayoutTransition object that will animated changes in layout.
A value of null means no transition will run on layout changes./**
     * Gets the LayoutTransition object for this ViewGroup. If the LayoutTransition object is
     * not null, changes in layout which occur because of children being added to or removed from
     * the ViewGroup will be animated according to the animations defined in that LayoutTransition
     * object. By default, the transition object is null (so layout changes are not animated).
     *
     * @return LayoutTranstion The LayoutTransition object that will animated changes in layout.
     * A value of <code>null</code> means no transition will run on layout changes.
     */
    public LayoutTransition getLayoutTransition() {
        return mTransition;
    }

    private void removeViewsInternal(int start, int count) {
        final int end = start + count;

        if (start < 0 || count < 0 || end > mChildrenCount) {
            throw new IndexOutOfBoundsException();
        }

        final View focused = mFocused;
        final boolean detach = mAttachInfo != null;
        boolean clearChildFocus = false;
        View clearDefaultFocus = null;

        final View[] children = mChildren;

        for (int i = start; i < end; i++) {
            final View view = children[i];

            if (mTransition != null) {
                mTransition.removeChild(this, view);
            }

            if (view == focused) {
                view.unFocus(null);
                clearChildFocus = true;
            }
            if (view == mDefaultFocus) {
                clearDefaultFocus = view;
            }
            if (view == mFocusedInCluster) {
                clearFocusedInCluster(view);
            }

            view.clearAccessibilityFocus();

            cancelTouchTarget(view);
            cancelHoverTarget(view);

            if (view.getAnimation() != null ||
                (mTransitioningViews != null && mTransitioningViews.contains(view))) {
                addDisappearingView(view);
            } else if (detach) {
               view.dispatchDetachedFromWindow();
            }

            if (view.hasTransientState()) {
                childHasTransientStateChanged(view, false);
            }

            needGlobalAttributesUpdate(false);

            dispatchViewRemoved(view);
        }

        removeFromArray(start, count);

        if (clearDefaultFocus != null) {
            clearDefaultFocus(clearDefaultFocus);
        }
        if (clearChildFocus) {
            clearChildFocus(focused);
            if (!rootViewRequestFocus()) {
                notifyGlobalFocusCleared(focused);
            }
        }
    }

    Call this method to remove all child views from the
ViewGroup.
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
/**
     * Call this method to remove all child views from the
     * ViewGroup.
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     */
    public void removeAllViews() {
        removeAllViewsInLayout();
        requestLayout();
        invalidate(true);
    }

    Called by a ViewGroup subclass to remove child views from itself,
when it must first know its size on screen before it can calculate how many
child views it will render. An example is a Gallery or a ListView, which
may "have" 50 children, but actually only render the number of children
that can currently fit inside the object on screen. Do not call
this method unless you are extending ViewGroup and understand the
view measuring and layout pipeline.
Note: do not invoke this method from View.draw(Canvas), View.onDraw(Canvas), dispatchDraw(Canvas) or any related method.
/**
     * Called by a ViewGroup subclass to remove child views from itself,
     * when it must first know its size on screen before it can calculate how many
     * child views it will render. An example is a Gallery or a ListView, which
     * may "have" 50 children, but actually only render the number of children
     * that can currently fit inside the object on screen. Do not call
     * this method unless you are extending ViewGroup and understand the
     * view measuring and layout pipeline.
     *
     * <p><strong>Note:</strong> do not invoke this method from
     * {@link #draw(android.graphics.Canvas)}, {@link #onDraw(android.graphics.Canvas)},
     * {@link #dispatchDraw(android.graphics.Canvas)} or any related method.</p>
     */
    public void removeAllViewsInLayout() {
        final int count = mChildrenCount;
        if (count <= 0) {
            return;
        }

        final View[] children = mChildren;
        mChildrenCount = 0;

        final View focused = mFocused;
        final boolean detach = mAttachInfo != null;
        boolean clearChildFocus = false;

        needGlobalAttributesUpdate(false);

        for (int i = count - 1; i >= 0; i--) {
            final View view = children[i];

            if (mTransition != null) {
                mTransition.removeChild(this, view);
            }

            if (view == focused) {
                view.unFocus(null);
                clearChildFocus = true;
            }

            view.clearAccessibilityFocus();

            cancelTouchTarget(view);
            cancelHoverTarget(view);

            if (view.getAnimation() != null ||
                    (mTransitioningViews != null && mTransitioningViews.contains(view))) {
                addDisappearingView(view);
            } else if (detach) {
               view.dispatchDetachedFromWindow();
            }

            if (view.hasTransientState()) {
                childHasTransientStateChanged(view, false);
            }

            dispatchViewRemoved(view);

            view.mParent = null;
            children[i] = null;
        }

        if (mDefaultFocus != null) {
            clearDefaultFocus(mDefaultFocus);
        }
        if (mFocusedInCluster != null) {
            clearFocusedInCluster(mFocusedInCluster);
        }
        if (clearChildFocus) {
            clearChildFocus(focused);
            if (!rootViewRequestFocus()) {
                notifyGlobalFocusCleared(focused);
            }
        }
    }

    Finishes the removal of a detached view. This method will dispatch the detached from
window event and notify the hierarchy change listener.
 This method is intended to be lightweight and makes no assumptions about whether the parent or child should be redrawn. Proper use of this method will include also making any appropriate View.requestLayout() or View.invalidate() calls. For example, callers can post a Runnable which performs a View.requestLayout() on the next frame, after all detach/remove calls are finished, causing layout to be run prior to redrawing the view hierarchy. 
Params: child – the child to be definitely removed from the view hierarchy
animate – if true and the view has an animation, the view is placed in the
               disappearing views list, otherwise, it is detached from the window
See Also: attachViewToParent(View, int, LayoutParams)
detachAllViewsFromParent()
detachViewFromParent(View)
detachViewFromParent(int)/**
     * Finishes the removal of a detached view. This method will dispatch the detached from
     * window event and notify the hierarchy change listener.
     * <p>
     * This method is intended to be lightweight and makes no assumptions about whether the
     * parent or child should be redrawn. Proper use of this method will include also making
     * any appropriate {@link #requestLayout()} or {@link #invalidate()} calls.
     * For example, callers can {@link #post(Runnable) post} a {@link Runnable}
     * which performs a {@link #requestLayout()} on the next frame, after all detach/remove
     * calls are finished, causing layout to be run prior to redrawing the view hierarchy.
     *
     * @param child the child to be definitely removed from the view hierarchy
     * @param animate if true and the view has an animation, the view is placed in the
     *                disappearing views list, otherwise, it is detached from the window
     *
     * @see #attachViewToParent(View, int, android.view.ViewGroup.LayoutParams)
     * @see #detachAllViewsFromParent()
     * @see #detachViewFromParent(View)
     * @see #detachViewFromParent(int)
     */
    protected void removeDetachedView(View child, boolean animate) {
        if (mTransition != null) {
            mTransition.removeChild(this, child);
        }

        if (child == mFocused) {
            child.clearFocus();
        }
        if (child == mDefaultFocus) {
            clearDefaultFocus(child);
        }
        if (child == mFocusedInCluster) {
            clearFocusedInCluster(child);
        }

        child.clearAccessibilityFocus();

        cancelTouchTarget(child);
        cancelHoverTarget(child);

        if ((animate && child.getAnimation() != null) ||
                (mTransitioningViews != null && mTransitioningViews.contains(child))) {
            addDisappearingView(child);
        } else if (child.mAttachInfo != null) {
            child.dispatchDetachedFromWindow();
        }

        if (child.hasTransientState()) {
            childHasTransientStateChanged(child, false);
        }

        dispatchViewRemoved(child);
    }

    Attaches a view to this view group. Attaching a view assigns this group as the parent, sets the layout parameters and puts the view in the list of children so that it can be retrieved by calling getChildAt(int).  This method is intended to be lightweight and makes no assumptions about whether the parent or child should be redrawn. Proper use of this method will include also making any appropriate View.requestLayout() or View.invalidate() calls. For example, callers can post a Runnable which performs a View.requestLayout() on the next frame, after all detach/attach calls are finished, causing layout to be run prior to redrawing the view hierarchy. 

This method should be called only for views which were detached from their parent.
Params: child – the child to attach
index – the index at which the child should be attached
params – the layout parameters of the child
See Also: removeDetachedView(View, boolean)
detachAllViewsFromParent()
detachViewFromParent(View)
detachViewFromParent(int)/**
     * Attaches a view to this view group. Attaching a view assigns this group as the parent,
     * sets the layout parameters and puts the view in the list of children so that
     * it can be retrieved by calling {@link #getChildAt(int)}.
     * <p>
     * This method is intended to be lightweight and makes no assumptions about whether the
     * parent or child should be redrawn. Proper use of this method will include also making
     * any appropriate {@link #requestLayout()} or {@link #invalidate()} calls.
     * For example, callers can {@link #post(Runnable) post} a {@link Runnable}
     * which performs a {@link #requestLayout()} on the next frame, after all detach/attach
     * calls are finished, causing layout to be run prior to redrawing the view hierarchy.
     * <p>
     * This method should be called only for views which were detached from their parent.
     *
     * @param child the child to attach
     * @param index the index at which the child should be attached
     * @param params the layout parameters of the child
     *
     * @see #removeDetachedView(View, boolean)
     * @see #detachAllViewsFromParent()
     * @see #detachViewFromParent(View)
     * @see #detachViewFromParent(int)
     */
    protected void attachViewToParent(View child, int index, LayoutParams params) {
        child.mLayoutParams = params;

        if (index < 0) {
            index = mChildrenCount;
        }

        addInArray(child, index);

        child.mParent = this;
        child.mPrivateFlags = (child.mPrivateFlags & ~PFLAG_DIRTY_MASK
                        & ~PFLAG_DRAWING_CACHE_VALID)
                | PFLAG_DRAWN | PFLAG_INVALIDATED;
        this.mPrivateFlags |= PFLAG_INVALIDATED;

        if (child.hasFocus()) {
            requestChildFocus(child, child.findFocus());
        }
        dispatchVisibilityAggregated(isAttachedToWindow() && getWindowVisibility() == VISIBLE
                && isShown());
        notifySubtreeAccessibilityStateChangedIfNeeded();
    }

    Detaches a view from its parent. Detaching a view should be followed either by a call to attachViewToParent(View, int, LayoutParams) or a call to removeDetachedView(View, boolean). Detachment should only be temporary; reattachment or removal should happen within the same drawing cycle as detachment. When a view is detached, its parent is null and cannot be retrieved by a call to getChildAt(int). 
Params: child – the child to detach
See Also: detachViewFromParent(int)
detachViewsFromParent(int, int)
detachAllViewsFromParent()
attachViewToParent(View, int, LayoutParams)
removeDetachedView(View, boolean)/**
     * Detaches a view from its parent. Detaching a view should be followed
     * either by a call to
     * {@link #attachViewToParent(View, int, android.view.ViewGroup.LayoutParams)}
     * or a call to {@link #removeDetachedView(View, boolean)}. Detachment should only be
     * temporary; reattachment or removal should happen within the same drawing cycle as
     * detachment. When a view is detached, its parent is null and cannot be retrieved by a
     * call to {@link #getChildAt(int)}.
     *
     * @param child the child to detach
     *
     * @see #detachViewFromParent(int)
     * @see #detachViewsFromParent(int, int)
     * @see #detachAllViewsFromParent()
     * @see #attachViewToParent(View, int, android.view.ViewGroup.LayoutParams)
     * @see #removeDetachedView(View, boolean)
     */
    protected void detachViewFromParent(View child) {
        removeFromArray(indexOfChild(child));
    }

    Detaches a view from its parent. Detaching a view should be followed either by a call to attachViewToParent(View, int, LayoutParams) or a call to removeDetachedView(View, boolean). Detachment should only be temporary; reattachment or removal should happen within the same drawing cycle as detachment. When a view is detached, its parent is null and cannot be retrieved by a call to getChildAt(int). 
Params: index – the index of the child to detach
See Also: detachViewFromParent(View)
detachAllViewsFromParent()
detachViewsFromParent(int, int)
attachViewToParent(View, int, LayoutParams)
removeDetachedView(View, boolean)/**
     * Detaches a view from its parent. Detaching a view should be followed
     * either by a call to
     * {@link #attachViewToParent(View, int, android.view.ViewGroup.LayoutParams)}
     * or a call to {@link #removeDetachedView(View, boolean)}. Detachment should only be
     * temporary; reattachment or removal should happen within the same drawing cycle as
     * detachment. When a view is detached, its parent is null and cannot be retrieved by a
     * call to {@link #getChildAt(int)}.
     *
     * @param index the index of the child to detach
     *
     * @see #detachViewFromParent(View)
     * @see #detachAllViewsFromParent()
     * @see #detachViewsFromParent(int, int)
     * @see #attachViewToParent(View, int, android.view.ViewGroup.LayoutParams)
     * @see #removeDetachedView(View, boolean)
     */
    protected void detachViewFromParent(int index) {
        removeFromArray(index);
    }

    Detaches a range of views from their parents. Detaching a view should be followed either by a call to attachViewToParent(View, int, LayoutParams) or a call to removeDetachedView(View, boolean). Detachment should only be temporary; reattachment or removal should happen within the same drawing cycle as detachment. When a view is detached, its parent is null and cannot be retrieved by a call to getChildAt(int). 
Params: start – the first index of the childrend range to detach
count – the number of children to detach
See Also: detachViewFromParent(View)
detachViewFromParent(int)
detachAllViewsFromParent()
attachViewToParent(View, int, LayoutParams)
removeDetachedView(View, boolean)/**
     * Detaches a range of views from their parents. Detaching a view should be followed
     * either by a call to
     * {@link #attachViewToParent(View, int, android.view.ViewGroup.LayoutParams)}
     * or a call to {@link #removeDetachedView(View, boolean)}. Detachment should only be
     * temporary; reattachment or removal should happen within the same drawing cycle as
     * detachment. When a view is detached, its parent is null and cannot be retrieved by a
     * call to {@link #getChildAt(int)}.
     *
     * @param start the first index of the childrend range to detach
     * @param count the number of children to detach
     *
     * @see #detachViewFromParent(View)
     * @see #detachViewFromParent(int)
     * @see #detachAllViewsFromParent()
     * @see #attachViewToParent(View, int, android.view.ViewGroup.LayoutParams)
     * @see #removeDetachedView(View, boolean)
     */
    protected void detachViewsFromParent(int start, int count) {
        removeFromArray(start, count);
    }

    Detaches all views from the parent. Detaching a view should be followed either by a call to attachViewToParent(View, int, LayoutParams) or a call to removeDetachedView(View, boolean). Detachment should only be temporary; reattachment or removal should happen within the same drawing cycle as detachment. When a view is detached, its parent is null and cannot be retrieved by a call to getChildAt(int). 
See Also: detachViewFromParent(View)
detachViewFromParent(int)
detachViewsFromParent(int, int)
attachViewToParent(View, int, LayoutParams)
removeDetachedView(View, boolean)/**
     * Detaches all views from the parent. Detaching a view should be followed
     * either by a call to
     * {@link #attachViewToParent(View, int, android.view.ViewGroup.LayoutParams)}
     * or a call to {@link #removeDetachedView(View, boolean)}. Detachment should only be
     * temporary; reattachment or removal should happen within the same drawing cycle as
     * detachment. When a view is detached, its parent is null and cannot be retrieved by a
     * call to {@link #getChildAt(int)}.
     *
     * @see #detachViewFromParent(View)
     * @see #detachViewFromParent(int)
     * @see #detachViewsFromParent(int, int)
     * @see #attachViewToParent(View, int, android.view.ViewGroup.LayoutParams)
     * @see #removeDetachedView(View, boolean)
     */
    protected void detachAllViewsFromParent() {
        final int count = mChildrenCount;
        if (count <= 0) {
            return;
        }

        final View[] children = mChildren;
        mChildrenCount = 0;

        for (int i = count - 1; i >= 0; i--) {
            children[i].mParent = null;
            children[i] = null;
        }
    }

    @Override
    @CallSuper
    public void onDescendantInvalidated(@NonNull View child, @NonNull View target) {
        /*
         * HW-only, Rect-ignoring damage codepath
         *
         * We don't deal with rectangles here, since RenderThread native code computes damage for
         * everything drawn by HWUI (and SW layer / drawing cache doesn't keep track of damage area)
         */

        // if set, combine the animation flag into the parent
        mPrivateFlags |= (target.mPrivateFlags & PFLAG_DRAW_ANIMATION);

        if ((target.mPrivateFlags & ~PFLAG_DIRTY_MASK) != 0) {
            // We lazily use PFLAG_DIRTY, since computing opaque isn't worth the potential
            // optimization in provides in a DisplayList world.
            mPrivateFlags = (mPrivateFlags & ~PFLAG_DIRTY_MASK) | PFLAG_DIRTY;

            // simplified invalidateChildInParent behavior: clear cache validity to be safe...
            mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
        }

        // ... and mark inval if in software layer that needs to repaint (hw handled in native)
        if (mLayerType == LAYER_TYPE_SOFTWARE) {
            // Layered parents should be invalidated. Escalate to a full invalidate (and note that
            // we do this after consuming any relevant flags from the originating descendant)
            mPrivateFlags |= PFLAG_INVALIDATED | PFLAG_DIRTY;
            target = this;
        }

        if (mParent != null) {
            mParent.onDescendantInvalidated(this, target);
        }
    }


    Don't call or override this method. It is used for the implementation of
the view hierarchy.
Deprecated: Use onDescendantInvalidated(View, View) instead to observe updates to draw state in descendants./**
     * Don't call or override this method. It is used for the implementation of
     * the view hierarchy.
     *
     * @deprecated Use {@link #onDescendantInvalidated(View, View)} instead to observe updates to
     * draw state in descendants.
     */
    @Deprecated
    @Override
    public final void invalidateChild(View child, final Rect dirty) {
        final AttachInfo attachInfo = mAttachInfo;
        if (attachInfo != null && attachInfo.mHardwareAccelerated) {
            // HW accelerated fast path
            onDescendantInvalidated(child, child);
            return;
        }

        ViewParent parent = this;
        if (attachInfo != null) {
            // If the child is drawing an animation, we want to copy this flag onto
            // ourselves and the parent to make sure the invalidate request goes
            // through
            final boolean drawAnimation = (child.mPrivateFlags & PFLAG_DRAW_ANIMATION) != 0;

            // Check whether the child that requests the invalidate is fully opaque
            // Views being animated or transformed are not considered opaque because we may
            // be invalidating their old position and need the parent to paint behind them.
            Matrix childMatrix = child.getMatrix();
            final boolean isOpaque = child.isOpaque() && !drawAnimation &&
                    child.getAnimation() == null && childMatrix.isIdentity();
            // Mark the child as dirty, using the appropriate flag
            // Make sure we do not set both flags at the same time
            int opaqueFlag = isOpaque ? PFLAG_DIRTY_OPAQUE : PFLAG_DIRTY;

            if (child.mLayerType != LAYER_TYPE_NONE) {
                mPrivateFlags |= PFLAG_INVALIDATED;
                mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
            }

            final int[] location = attachInfo.mInvalidateChildLocation;
            location[CHILD_LEFT_INDEX] = child.mLeft;
            location[CHILD_TOP_INDEX] = child.mTop;
            if (!childMatrix.isIdentity() ||
                    (mGroupFlags & ViewGroup.FLAG_SUPPORT_STATIC_TRANSFORMATIONS) != 0) {
                RectF boundingRect = attachInfo.mTmpTransformRect;
                boundingRect.set(dirty);
                Matrix transformMatrix;
                if ((mGroupFlags & ViewGroup.FLAG_SUPPORT_STATIC_TRANSFORMATIONS) != 0) {
                    Transformation t = attachInfo.mTmpTransformation;
                    boolean transformed = getChildStaticTransformation(child, t);
                    if (transformed) {
                        transformMatrix = attachInfo.mTmpMatrix;
                        transformMatrix.set(t.getMatrix());
                        if (!childMatrix.isIdentity()) {
                            transformMatrix.preConcat(childMatrix);
                        }
                    } else {
                        transformMatrix = childMatrix;
                    }
                } else {
                    transformMatrix = childMatrix;
                }
                transformMatrix.mapRect(boundingRect);
                dirty.set((int) Math.floor(boundingRect.left),
                        (int) Math.floor(boundingRect.top),
                        (int) Math.ceil(boundingRect.right),
                        (int) Math.ceil(boundingRect.bottom));
            }

            do {
                View view = null;
                if (parent instanceof View) {
                    view = (View) parent;
                }

                if (drawAnimation) {
                    if (view != null) {
                        view.mPrivateFlags |= PFLAG_DRAW_ANIMATION;
                    } else if (parent instanceof ViewRootImpl) {
                        ((ViewRootImpl) parent).mIsAnimating = true;
                    }
                }

                // If the parent is dirty opaque or not dirty, mark it dirty with the opaque
                // flag coming from the child that initiated the invalidate
                if (view != null) {
                    if ((view.mViewFlags & FADING_EDGE_MASK) != 0 &&
                            view.getSolidColor() == 0) {
                        opaqueFlag = PFLAG_DIRTY;
                    }
                    if ((view.mPrivateFlags & PFLAG_DIRTY_MASK) != PFLAG_DIRTY) {
                        view.mPrivateFlags = (view.mPrivateFlags & ~PFLAG_DIRTY_MASK) | opaqueFlag;
                    }
                }

                parent = parent.invalidateChildInParent(location, dirty);
                if (view != null) {
                    // Account for transform on current parent
                    Matrix m = view.getMatrix();
                    if (!m.isIdentity()) {
                        RectF boundingRect = attachInfo.mTmpTransformRect;
                        boundingRect.set(dirty);
                        m.mapRect(boundingRect);
                        dirty.set((int) Math.floor(boundingRect.left),
                                (int) Math.floor(boundingRect.top),
                                (int) Math.ceil(boundingRect.right),
                                (int) Math.ceil(boundingRect.bottom));
                    }
                }
            } while (parent != null);
        }
    }

    Don't call or override this method. It is used for the implementation of
the view hierarchy.
This implementation returns null if this ViewGroup does not have a parent,
if this ViewGroup is already fully invalidated or if the dirty rectangle
does not intersect with this ViewGroup's bounds.
Deprecated: Use onDescendantInvalidated(View, View) instead to observe updates to draw state in descendants./**
     * Don't call or override this method. It is used for the implementation of
     * the view hierarchy.
     *
     * This implementation returns null if this ViewGroup does not have a parent,
     * if this ViewGroup is already fully invalidated or if the dirty rectangle
     * does not intersect with this ViewGroup's bounds.
     *
     * @deprecated Use {@link #onDescendantInvalidated(View, View)} instead to observe updates to
     * draw state in descendants.
     */
    @Deprecated
    @Override
    public ViewParent invalidateChildInParent(final int[] location, final Rect dirty) {
        if ((mPrivateFlags & (PFLAG_DRAWN | PFLAG_DRAWING_CACHE_VALID)) != 0) {
            // either DRAWN, or DRAWING_CACHE_VALID
            if ((mGroupFlags & (FLAG_OPTIMIZE_INVALIDATE | FLAG_ANIMATION_DONE))
                    != FLAG_OPTIMIZE_INVALIDATE) {
                dirty.offset(location[CHILD_LEFT_INDEX] - mScrollX,
                        location[CHILD_TOP_INDEX] - mScrollY);
                if ((mGroupFlags & FLAG_CLIP_CHILDREN) == 0) {
                    dirty.union(0, 0, mRight - mLeft, mBottom - mTop);
                }

                final int left = mLeft;
                final int top = mTop;

                if ((mGroupFlags & FLAG_CLIP_CHILDREN) == FLAG_CLIP_CHILDREN) {
                    if (!dirty.intersect(0, 0, mRight - left, mBottom - top)) {
                        dirty.setEmpty();
                    }
                }

                location[CHILD_LEFT_INDEX] = left;
                location[CHILD_TOP_INDEX] = top;
            } else {

                if ((mGroupFlags & FLAG_CLIP_CHILDREN) == FLAG_CLIP_CHILDREN) {
                    dirty.set(0, 0, mRight - mLeft, mBottom - mTop);
                } else {
                    // in case the dirty rect extends outside the bounds of this container
                    dirty.union(0, 0, mRight - mLeft, mBottom - mTop);
                }
                location[CHILD_LEFT_INDEX] = mLeft;
                location[CHILD_TOP_INDEX] = mTop;

                mPrivateFlags &= ~PFLAG_DRAWN;
            }
            mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
            if (mLayerType != LAYER_TYPE_NONE) {
                mPrivateFlags |= PFLAG_INVALIDATED;
            }

            return mParent;
        }

        return null;
    }

    Offset a rectangle that is in a descendant's coordinate
space into our coordinate space.
Params: descendant – A descendant of this view
rect – A rectangle defined in descendant's coordinate space./**
     * Offset a rectangle that is in a descendant's coordinate
     * space into our coordinate space.
     * @param descendant A descendant of this view
     * @param rect A rectangle defined in descendant's coordinate space.
     */
    public final void offsetDescendantRectToMyCoords(View descendant, Rect rect) {
        offsetRectBetweenParentAndChild(descendant, rect, true, false);
    }

    Offset a rectangle that is in our coordinate space into an ancestor's
coordinate space.
Params: descendant – A descendant of this view
rect – A rectangle defined in descendant's coordinate space./**
     * Offset a rectangle that is in our coordinate space into an ancestor's
     * coordinate space.
     * @param descendant A descendant of this view
     * @param rect A rectangle defined in descendant's coordinate space.
     */
    public final void offsetRectIntoDescendantCoords(View descendant, Rect rect) {
        offsetRectBetweenParentAndChild(descendant, rect, false, false);
    }

    Helper method that offsets a rect either from parent to descendant or
descendant to parent.
/**
     * Helper method that offsets a rect either from parent to descendant or
     * descendant to parent.
     */
    void offsetRectBetweenParentAndChild(View descendant, Rect rect,
            boolean offsetFromChildToParent, boolean clipToBounds) {

        // already in the same coord system :)
        if (descendant == this) {
            return;
        }

        ViewParent theParent = descendant.mParent;

        // search and offset up to the parent
        while ((theParent != null)
                && (theParent instanceof View)
                && (theParent != this)) {

            if (offsetFromChildToParent) {
                rect.offset(descendant.mLeft - descendant.mScrollX,
                        descendant.mTop - descendant.mScrollY);
                if (clipToBounds) {
                    View p = (View) theParent;
                    boolean intersected = rect.intersect(0, 0, p.mRight - p.mLeft,
                            p.mBottom - p.mTop);
                    if (!intersected) {
                        rect.setEmpty();
                    }
                }
            } else {
                if (clipToBounds) {
                    View p = (View) theParent;
                    boolean intersected = rect.intersect(0, 0, p.mRight - p.mLeft,
                            p.mBottom - p.mTop);
                    if (!intersected) {
                        rect.setEmpty();
                    }
                }
                rect.offset(descendant.mScrollX - descendant.mLeft,
                        descendant.mScrollY - descendant.mTop);
            }

            descendant = (View) theParent;
            theParent = descendant.mParent;
        }

        // now that we are up to this view, need to offset one more time
        // to get into our coordinate space
        if (theParent == this) {
            if (offsetFromChildToParent) {
                rect.offset(descendant.mLeft - descendant.mScrollX,
                        descendant.mTop - descendant.mScrollY);
            } else {
                rect.offset(descendant.mScrollX - descendant.mLeft,
                        descendant.mScrollY - descendant.mTop);
            }
        } else {
            throw new IllegalArgumentException("parameter must be a descendant of this view");
        }
    }

    Offset the vertical location of all children of this view by the specified number of pixels.
Params: offset – the number of pixels to offset
@hide /**
     * Offset the vertical location of all children of this view by the specified number of pixels.
     *
     * @param offset the number of pixels to offset
     *
     * @hide
     */
    public void offsetChildrenTopAndBottom(int offset) {
        final int count = mChildrenCount;
        final View[] children = mChildren;
        boolean invalidate = false;

        for (int i = 0; i < count; i++) {
            final View v = children[i];
            v.mTop += offset;
            v.mBottom += offset;
            if (v.mRenderNode != null) {
                invalidate = true;
                v.mRenderNode.offsetTopAndBottom(offset);
            }
        }

        if (invalidate) {
            invalidateViewProperty(false, false);
        }
        notifySubtreeAccessibilityStateChangedIfNeeded();
    }

    @Override
    public boolean getChildVisibleRect(View child, Rect r, android.graphics.Point offset) {
        return getChildVisibleRect(child, r, offset, false);
    }

    Params: forceParentCheck – true to guarantee that this call will propagate to all ancestors,
     false otherwise
@hide /**
     * @param forceParentCheck true to guarantee that this call will propagate to all ancestors,
     *      false otherwise
     *
     * @hide
     */
    public boolean getChildVisibleRect(
            View child, Rect r, android.graphics.Point offset, boolean forceParentCheck) {
        // It doesn't make a whole lot of sense to call this on a view that isn't attached,
        // but for some simple tests it can be useful. If we don't have attach info this
        // will allocate memory.
        final RectF rect = mAttachInfo != null ? mAttachInfo.mTmpTransformRect : new RectF();
        rect.set(r);

        if (!child.hasIdentityMatrix()) {
            child.getMatrix().mapRect(rect);
        }

        final int dx = child.mLeft - mScrollX;
        final int dy = child.mTop - mScrollY;

        rect.offset(dx, dy);

        if (offset != null) {
            if (!child.hasIdentityMatrix()) {
                float[] position = mAttachInfo != null ? mAttachInfo.mTmpTransformLocation
                        : new float[2];
                position[0] = offset.x;
                position[1] = offset.y;
                child.getMatrix().mapPoints(position);
                offset.x = Math.round(position[0]);
                offset.y = Math.round(position[1]);
            }
            offset.x += dx;
            offset.y += dy;
        }

        final int width = mRight - mLeft;
        final int height = mBottom - mTop;

        boolean rectIsVisible = true;
        if (mParent == null ||
                (mParent instanceof ViewGroup && ((ViewGroup) mParent).getClipChildren())) {
            // Clip to bounds.
            rectIsVisible = rect.intersect(0, 0, width, height);
        }

        if ((forceParentCheck || rectIsVisible)
                && (mGroupFlags & CLIP_TO_PADDING_MASK) == CLIP_TO_PADDING_MASK) {
            // Clip to padding.
            rectIsVisible = rect.intersect(mPaddingLeft, mPaddingTop,
                    width - mPaddingRight, height - mPaddingBottom);
        }

        if ((forceParentCheck || rectIsVisible) && mClipBounds != null) {
            // Clip to clipBounds.
            rectIsVisible = rect.intersect(mClipBounds.left, mClipBounds.top, mClipBounds.right,
                    mClipBounds.bottom);
        }
        r.set((int) Math.floor(rect.left), (int) Math.floor(rect.top),
                (int) Math.ceil(rect.right), (int) Math.ceil(rect.bottom));

        if ((forceParentCheck || rectIsVisible) && mParent != null) {
            if (mParent instanceof ViewGroup) {
                rectIsVisible = ((ViewGroup) mParent)
                        .getChildVisibleRect(this, r, offset, forceParentCheck);
            } else {
                rectIsVisible = mParent.getChildVisibleRect(this, r, offset);
            }
        }
        return rectIsVisible;
    }

    @Override
    public final void layout(int l, int t, int r, int b) {
        if (!mSuppressLayout && (mTransition == null || !mTransition.isChangingLayout())) {
            if (mTransition != null) {
                mTransition.layoutChange(this);
            }
            super.layout(l, t, r, b);
        } else {
            // record the fact that we noop'd it; request layout when transition finishes
            mLayoutCalledWhileSuppressed = true;
        }
    }

    @Override
    protected abstract void onLayout(boolean changed,
            int l, int t, int r, int b);

    Indicates whether the view group has the ability to animate its children
after the first layout.
Returns: true if the children can be animated, false otherwise/**
     * Indicates whether the view group has the ability to animate its children
     * after the first layout.
     *
     * @return true if the children can be animated, false otherwise
     */
    protected boolean canAnimate() {
        return mLayoutAnimationController != null;
    }

    Runs the layout animation. Calling this method triggers a relayout of
this view group.
/**
     * Runs the layout animation. Calling this method triggers a relayout of
     * this view group.
     */
    public void startLayoutAnimation() {
        if (mLayoutAnimationController != null) {
            mGroupFlags |= FLAG_RUN_ANIMATION;
            requestLayout();
        }
    }

    Schedules the layout animation to be played after the next layout pass
of this view group. This can be used to restart the layout animation
when the content of the view group changes or when the activity is
paused and resumed.
/**
     * Schedules the layout animation to be played after the next layout pass
     * of this view group. This can be used to restart the layout animation
     * when the content of the view group changes or when the activity is
     * paused and resumed.
     */
    public void scheduleLayoutAnimation() {
        mGroupFlags |= FLAG_RUN_ANIMATION;
    }

    Sets the layout animation controller used to animate the group's
children after the first layout.
Params: controller – the animation controller/**
     * Sets the layout animation controller used to animate the group's
     * children after the first layout.
     *
     * @param controller the animation controller
     */
    public void setLayoutAnimation(LayoutAnimationController controller) {
        mLayoutAnimationController = controller;
        if (mLayoutAnimationController != null) {
            mGroupFlags |= FLAG_RUN_ANIMATION;
        }
    }

    Returns the layout animation controller used to animate the group's
children.
Returns: the current animation controller/**
     * Returns the layout animation controller used to animate the group's
     * children.
     *
     * @return the current animation controller
     */
    public LayoutAnimationController getLayoutAnimation() {
        return mLayoutAnimationController;
    }

    Indicates whether the children's drawing cache is used during a layout
animation. By default, the drawing cache is enabled but this will prevent
nested layout animations from working. To nest animations, you must disable
the cache.
See Also: setAnimationCacheEnabled(boolean)
View.setDrawingCacheEnabled(boolean)
Returns: true if the animation cache is enabled, false otherwise
Deprecated: As of VERSION_CODES.M, this property is ignored. Caching behavior of children may be controlled through View.setLayerType(int, Paint)./**
     * Indicates whether the children's drawing cache is used during a layout
     * animation. By default, the drawing cache is enabled but this will prevent
     * nested layout animations from working. To nest animations, you must disable
     * the cache.
     *
     * @return true if the animation cache is enabled, false otherwise
     *
     * @see #setAnimationCacheEnabled(boolean)
     * @see View#setDrawingCacheEnabled(boolean)
     *
     * @deprecated As of {@link android.os.Build.VERSION_CODES#M}, this property is ignored.
     * Caching behavior of children may be controlled through {@link View#setLayerType(int, Paint)}.
     */
    @Deprecated
    public boolean isAnimationCacheEnabled() {
        return (mGroupFlags & FLAG_ANIMATION_CACHE) == FLAG_ANIMATION_CACHE;
    }

    Enables or disables the children's drawing cache during a layout animation.
By default, the drawing cache is enabled but this will prevent nested
layout animations from working. To nest animations, you must disable the
cache.
Params: enabled – true to enable the animation cache, false otherwise
See Also: isAnimationCacheEnabled()
View.setDrawingCacheEnabled(boolean)
Deprecated: As of VERSION_CODES.M, this property is ignored. Caching behavior of children may be controlled through View.setLayerType(int, Paint)./**
     * Enables or disables the children's drawing cache during a layout animation.
     * By default, the drawing cache is enabled but this will prevent nested
     * layout animations from working. To nest animations, you must disable the
     * cache.
     *
     * @param enabled true to enable the animation cache, false otherwise
     *
     * @see #isAnimationCacheEnabled()
     * @see View#setDrawingCacheEnabled(boolean)
     *
     * @deprecated As of {@link android.os.Build.VERSION_CODES#M}, this property is ignored.
     * Caching behavior of children may be controlled through {@link View#setLayerType(int, Paint)}.
     */
    @Deprecated
    public void setAnimationCacheEnabled(boolean enabled) {
        setBooleanFlag(FLAG_ANIMATION_CACHE, enabled);
    }

    Indicates whether this ViewGroup will always try to draw its children using their
drawing cache. By default this property is enabled.
See Also: setAlwaysDrawnWithCacheEnabled(boolean)
setChildrenDrawnWithCacheEnabled(boolean)
View.setDrawingCacheEnabled(boolean)
Returns: true if the animation cache is enabled, false otherwise
Deprecated: As of VERSION_CODES.M, this property is ignored. Child views may no longer have their caching behavior disabled by parents./**
     * Indicates whether this ViewGroup will always try to draw its children using their
     * drawing cache. By default this property is enabled.
     *
     * @return true if the animation cache is enabled, false otherwise
     *
     * @see #setAlwaysDrawnWithCacheEnabled(boolean)
     * @see #setChildrenDrawnWithCacheEnabled(boolean)
     * @see View#setDrawingCacheEnabled(boolean)
     *
     * @deprecated As of {@link android.os.Build.VERSION_CODES#M}, this property is ignored.
     * Child views may no longer have their caching behavior disabled by parents.
     */
    @Deprecated
    public boolean isAlwaysDrawnWithCacheEnabled() {
        return (mGroupFlags & FLAG_ALWAYS_DRAWN_WITH_CACHE) == FLAG_ALWAYS_DRAWN_WITH_CACHE;
    }

    Indicates whether this ViewGroup will always try to draw its children using their
drawing cache. This property can be set to true when the cache rendering is
slightly different from the children's normal rendering. Renderings can be different,
for instance, when the cache's quality is set to low.
When this property is disabled, the ViewGroup will use the drawing cache of its
children only when asked to. It's usually the task of subclasses to tell ViewGroup
when to start using the drawing cache and when to stop using it.
Params: always – true to always draw with the drawing cache, false otherwise
See Also: isAlwaysDrawnWithCacheEnabled()
setChildrenDrawnWithCacheEnabled(boolean)
View.setDrawingCacheEnabled(boolean)
View.setDrawingCacheQuality(int)
Deprecated: As of VERSION_CODES.M, this property is ignored. Child views may no longer have their caching behavior disabled by parents./**
     * Indicates whether this ViewGroup will always try to draw its children using their
     * drawing cache. This property can be set to true when the cache rendering is
     * slightly different from the children's normal rendering. Renderings can be different,
     * for instance, when the cache's quality is set to low.
     *
     * When this property is disabled, the ViewGroup will use the drawing cache of its
     * children only when asked to. It's usually the task of subclasses to tell ViewGroup
     * when to start using the drawing cache and when to stop using it.
     *
     * @param always true to always draw with the drawing cache, false otherwise
     *
     * @see #isAlwaysDrawnWithCacheEnabled()
     * @see #setChildrenDrawnWithCacheEnabled(boolean)
     * @see View#setDrawingCacheEnabled(boolean)
     * @see View#setDrawingCacheQuality(int)
     *
     * @deprecated As of {@link android.os.Build.VERSION_CODES#M}, this property is ignored.
     * Child views may no longer have their caching behavior disabled by parents.
     */
    @Deprecated
    public void setAlwaysDrawnWithCacheEnabled(boolean always) {
        setBooleanFlag(FLAG_ALWAYS_DRAWN_WITH_CACHE, always);
    }

    Indicates whether the ViewGroup is currently drawing its children using
their drawing cache.
See Also: setAlwaysDrawnWithCacheEnabled(boolean)
setChildrenDrawnWithCacheEnabled(boolean)
Returns: true if children should be drawn with their cache, false otherwise
Deprecated: As of VERSION_CODES.M, this property is ignored. Child views may no longer be forced to cache their rendering state by their parents. Use View.setLayerType(int, Paint) on individual Views instead./**
     * Indicates whether the ViewGroup is currently drawing its children using
     * their drawing cache.
     *
     * @return true if children should be drawn with their cache, false otherwise
     *
     * @see #setAlwaysDrawnWithCacheEnabled(boolean)
     * @see #setChildrenDrawnWithCacheEnabled(boolean)
     *
     * @deprecated As of {@link android.os.Build.VERSION_CODES#M}, this property is ignored.
     * Child views may no longer be forced to cache their rendering state by their parents.
     * Use {@link View#setLayerType(int, Paint)} on individual Views instead.
     */
    @Deprecated
    protected boolean isChildrenDrawnWithCacheEnabled() {
        return (mGroupFlags & FLAG_CHILDREN_DRAWN_WITH_CACHE) == FLAG_CHILDREN_DRAWN_WITH_CACHE;
    }

    Tells the ViewGroup to draw its children using their drawing cache. This property is ignored when isAlwaysDrawnWithCacheEnabled() is true. A child's drawing cache will be used only if it has been enabled. Subclasses should call this method to start and stop using the drawing cache when they perform performance sensitive operations, like scrolling or animating. 
Params: enabled – true if children should be drawn with their cache, false otherwise
See Also: setAlwaysDrawnWithCacheEnabled(boolean)
isChildrenDrawnWithCacheEnabled()
Deprecated: As of VERSION_CODES.M, this property is ignored. Child views may no longer be forced to cache their rendering state by their parents. Use View.setLayerType(int, Paint) on individual Views instead./**
     * Tells the ViewGroup to draw its children using their drawing cache. This property
     * is ignored when {@link #isAlwaysDrawnWithCacheEnabled()} is true. A child's drawing cache
     * will be used only if it has been enabled.
     *
     * Subclasses should call this method to start and stop using the drawing cache when
     * they perform performance sensitive operations, like scrolling or animating.
     *
     * @param enabled true if children should be drawn with their cache, false otherwise
     *
     * @see #setAlwaysDrawnWithCacheEnabled(boolean)
     * @see #isChildrenDrawnWithCacheEnabled()
     *
     * @deprecated As of {@link android.os.Build.VERSION_CODES#M}, this property is ignored.
     * Child views may no longer be forced to cache their rendering state by their parents.
     * Use {@link View#setLayerType(int, Paint)} on individual Views instead.
     */
    @Deprecated
    protected void setChildrenDrawnWithCacheEnabled(boolean enabled) {
        setBooleanFlag(FLAG_CHILDREN_DRAWN_WITH_CACHE, enabled);
    }

    Indicates whether the ViewGroup is drawing its children in the order defined by getChildDrawingOrder(int, int). 
See Also: setChildrenDrawingOrderEnabled(boolean)
getChildDrawingOrder(int, int)
Returns: true if children drawing order is defined by getChildDrawingOrder(int, int), false otherwise/**
     * Indicates whether the ViewGroup is drawing its children in the order defined by
     * {@link #getChildDrawingOrder(int, int)}.
     *
     * @return true if children drawing order is defined by {@link #getChildDrawingOrder(int, int)},
     *         false otherwise
     *
     * @see #setChildrenDrawingOrderEnabled(boolean)
     * @see #getChildDrawingOrder(int, int)
     */
    @ViewDebug.ExportedProperty(category = "drawing")
    protected boolean isChildrenDrawingOrderEnabled() {
        return (mGroupFlags & FLAG_USE_CHILD_DRAWING_ORDER) == FLAG_USE_CHILD_DRAWING_ORDER;
    }

    Tells the ViewGroup whether to draw its children in the order defined by the method getChildDrawingOrder(int, int).  Note that Z reordering, done by dispatchDraw(Canvas), will override custom child ordering done via this method. 
Params: enabled – true if the order of the children when drawing is determined by getChildDrawingOrder(int, int), false otherwise
See Also: isChildrenDrawingOrderEnabled()
getChildDrawingOrder(int, int)/**
     * Tells the ViewGroup whether to draw its children in the order defined by the method
     * {@link #getChildDrawingOrder(int, int)}.
     * <p>
     * Note that {@link View#getZ() Z} reordering, done by {@link #dispatchDraw(Canvas)},
     * will override custom child ordering done via this method.
     *
     * @param enabled true if the order of the children when drawing is determined by
     *        {@link #getChildDrawingOrder(int, int)}, false otherwise
     *
     * @see #isChildrenDrawingOrderEnabled()
     * @see #getChildDrawingOrder(int, int)
     */
    protected void setChildrenDrawingOrderEnabled(boolean enabled) {
        setBooleanFlag(FLAG_USE_CHILD_DRAWING_ORDER, enabled);
    }

    private boolean hasBooleanFlag(int flag) {
        return (mGroupFlags & flag) == flag;
    }

    private void setBooleanFlag(int flag, boolean value) {
        if (value) {
            mGroupFlags |= flag;
        } else {
            mGroupFlags &= ~flag;
        }
    }

    Returns an integer indicating what types of drawing caches are kept in memory.
See Also: setPersistentDrawingCache(int)
setAnimationCacheEnabled(boolean)
Returns: one or a combination of PERSISTENT_NO_CACHE, PERSISTENT_ANIMATION_CACHE, PERSISTENT_SCROLLING_CACHE and PERSISTENT_ALL_CACHES
Deprecated: The view drawing cache was largely made obsolete with the introduction of hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache layers are largely unnecessary and can easily result in a net loss in performance due to the cost of creating and updating the layer. In the rare cases where caching layers are useful, such as for alpha animations, View.setLayerType(int, Paint) handles this with hardware rendering. For software-rendered snapshots of a small part of the View hierarchy or individual Views it is recommended to create a Canvas from either a Bitmap or Picture and call View.draw(Canvas) on the View. However these software-rendered usages are discouraged and have compatibility issues with hardware-only rendering features such as Config.HARDWARE bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback reports or unit testing the PixelCopy API is recommended./**
     * Returns an integer indicating what types of drawing caches are kept in memory.
     *
     * @see #setPersistentDrawingCache(int)
     * @see #setAnimationCacheEnabled(boolean)
     *
     * @return one or a combination of {@link #PERSISTENT_NO_CACHE},
     *         {@link #PERSISTENT_ANIMATION_CACHE}, {@link #PERSISTENT_SCROLLING_CACHE}
     *         and {@link #PERSISTENT_ALL_CACHES}
     *
     * @deprecated The view drawing cache was largely made obsolete with the introduction of
     * hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache
     * layers are largely unnecessary and can easily result in a net loss in performance due to the
     * cost of creating and updating the layer. In the rare cases where caching layers are useful,
     * such as for alpha animations, {@link #setLayerType(int, Paint)} handles this with hardware
     * rendering. For software-rendered snapshots of a small part of the View hierarchy or
     * individual Views it is recommended to create a {@link Canvas} from either a {@link Bitmap} or
     * {@link android.graphics.Picture} and call {@link #draw(Canvas)} on the View. However these
     * software-rendered usages are discouraged and have compatibility issues with hardware-only
     * rendering features such as {@link android.graphics.Bitmap.Config#HARDWARE Config.HARDWARE}
     * bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback
     * reports or unit testing the {@link PixelCopy} API is recommended.
     */
    @Deprecated
    @ViewDebug.ExportedProperty(category = "drawing", mapping = {
        @ViewDebug.IntToString(from = PERSISTENT_NO_CACHE,        to = "NONE"),
        @ViewDebug.IntToString(from = PERSISTENT_ANIMATION_CACHE, to = "ANIMATION"),
        @ViewDebug.IntToString(from = PERSISTENT_SCROLLING_CACHE, to = "SCROLLING"),
        @ViewDebug.IntToString(from = PERSISTENT_ALL_CACHES,      to = "ALL")
    })
    public int getPersistentDrawingCache() {
        return mPersistentDrawingCache;
    }

    Indicates what types of drawing caches should be kept in memory after
they have been created.
Params: drawingCacheToKeep – one or a combination of PERSISTENT_NO_CACHE, PERSISTENT_ANIMATION_CACHE, PERSISTENT_SCROLLING_CACHE and PERSISTENT_ALL_CACHES
See Also: getPersistentDrawingCache()
setAnimationCacheEnabled(boolean)
Deprecated: The view drawing cache was largely made obsolete with the introduction of hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache layers are largely unnecessary and can easily result in a net loss in performance due to the cost of creating and updating the layer. In the rare cases where caching layers are useful, such as for alpha animations, View.setLayerType(int, Paint) handles this with hardware rendering. For software-rendered snapshots of a small part of the View hierarchy or individual Views it is recommended to create a Canvas from either a Bitmap or Picture and call View.draw(Canvas) on the View. However these software-rendered usages are discouraged and have compatibility issues with hardware-only rendering features such as Config.HARDWARE bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback reports or unit testing the PixelCopy API is recommended./**
     * Indicates what types of drawing caches should be kept in memory after
     * they have been created.
     *
     * @see #getPersistentDrawingCache()
     * @see #setAnimationCacheEnabled(boolean)
     *
     * @param drawingCacheToKeep one or a combination of {@link #PERSISTENT_NO_CACHE},
     *        {@link #PERSISTENT_ANIMATION_CACHE}, {@link #PERSISTENT_SCROLLING_CACHE}
     *        and {@link #PERSISTENT_ALL_CACHES}
     *
     * @deprecated The view drawing cache was largely made obsolete with the introduction of
     * hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache
     * layers are largely unnecessary and can easily result in a net loss in performance due to the
     * cost of creating and updating the layer. In the rare cases where caching layers are useful,
     * such as for alpha animations, {@link #setLayerType(int, Paint)} handles this with hardware
     * rendering. For software-rendered snapshots of a small part of the View hierarchy or
     * individual Views it is recommended to create a {@link Canvas} from either a {@link Bitmap} or
     * {@link android.graphics.Picture} and call {@link #draw(Canvas)} on the View. However these
     * software-rendered usages are discouraged and have compatibility issues with hardware-only
     * rendering features such as {@link android.graphics.Bitmap.Config#HARDWARE Config.HARDWARE}
     * bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback
     * reports or unit testing the {@link PixelCopy} API is recommended.
     */
    @Deprecated
    public void setPersistentDrawingCache(int drawingCacheToKeep) {
        mPersistentDrawingCache = drawingCacheToKeep & PERSISTENT_ALL_CACHES;
    }

    private void setLayoutMode(int layoutMode, boolean explicitly) {
        mLayoutMode = layoutMode;
        setBooleanFlag(FLAG_LAYOUT_MODE_WAS_EXPLICITLY_SET, explicitly);
    }

    Recursively traverse the view hierarchy, resetting the layoutMode of any
descendants that had inherited a different layoutMode from a previous parent.
Recursion terminates when a descendant's mode is:

    Undefined
    The same as the root node's
    A mode that had been explicitly set

The first two clauses are optimizations.
Params: layoutModeOfRoot – /**
     * Recursively traverse the view hierarchy, resetting the layoutMode of any
     * descendants that had inherited a different layoutMode from a previous parent.
     * Recursion terminates when a descendant's mode is:
     * <ul>
     *     <li>Undefined</li>
     *     <li>The same as the root node's</li>
     *     <li>A mode that had been explicitly set</li>
     * <ul/>
     * The first two clauses are optimizations.
     * @param layoutModeOfRoot
     */
    @Override
    void invalidateInheritedLayoutMode(int layoutModeOfRoot) {
        if (mLayoutMode == LAYOUT_MODE_UNDEFINED ||
            mLayoutMode == layoutModeOfRoot ||
            hasBooleanFlag(FLAG_LAYOUT_MODE_WAS_EXPLICITLY_SET)) {
            return;
        }
        setLayoutMode(LAYOUT_MODE_UNDEFINED, false);

        // apply recursively
        for (int i = 0, N = getChildCount(); i < N; i++) {
            getChildAt(i).invalidateInheritedLayoutMode(layoutModeOfRoot);
        }
    }

    Returns the basis of alignment during layout operations on this ViewGroup: either LAYOUT_MODE_CLIP_BOUNDS or LAYOUT_MODE_OPTICAL_BOUNDS.  If no layoutMode was explicitly set, either programmatically or in an XML resource, the method returns the layoutMode of the view's parent ViewGroup if such a parent exists, otherwise the method returns a default value of LAYOUT_MODE_CLIP_BOUNDS. 
See Also: setLayoutMode(int)
Returns: the layout mode to use during layout operations/**
     * Returns the basis of alignment during layout operations on this ViewGroup:
     * either {@link #LAYOUT_MODE_CLIP_BOUNDS} or {@link #LAYOUT_MODE_OPTICAL_BOUNDS}.
     * <p>
     * If no layoutMode was explicitly set, either programmatically or in an XML resource,
     * the method returns the layoutMode of the view's parent ViewGroup if such a parent exists,
     * otherwise the method returns a default value of {@link #LAYOUT_MODE_CLIP_BOUNDS}.
     *
     * @return the layout mode to use during layout operations
     *
     * @see #setLayoutMode(int)
     */
    public int getLayoutMode() {
        if (mLayoutMode == LAYOUT_MODE_UNDEFINED) {
            int inheritedLayoutMode = (mParent instanceof ViewGroup) ?
                    ((ViewGroup) mParent).getLayoutMode() : LAYOUT_MODE_DEFAULT;
            setLayoutMode(inheritedLayoutMode, false);
        }
        return mLayoutMode;
    }

    Sets the basis of alignment during the layout of this ViewGroup. Valid values are either LAYOUT_MODE_CLIP_BOUNDS or LAYOUT_MODE_OPTICAL_BOUNDS. 
Params: layoutMode – the layout mode to use during layout operations
See Also: getLayoutMode()
@attr ref android.R.styleable#ViewGroup_layoutMode/**
     * Sets the basis of alignment during the layout of this ViewGroup.
     * Valid values are either {@link #LAYOUT_MODE_CLIP_BOUNDS} or
     * {@link #LAYOUT_MODE_OPTICAL_BOUNDS}.
     *
     * @param layoutMode the layout mode to use during layout operations
     *
     * @see #getLayoutMode()
     * @attr ref android.R.styleable#ViewGroup_layoutMode
     */
    public void setLayoutMode(int layoutMode) {
        if (mLayoutMode != layoutMode) {
            invalidateInheritedLayoutMode(layoutMode);
            setLayoutMode(layoutMode, layoutMode != LAYOUT_MODE_UNDEFINED);
            requestLayout();
        }
    }

    Returns a new set of layout parameters based on the supplied attributes set.
Params: attrs – the attributes to build the layout parameters from
Returns: an instance of LayoutParams or one of its descendants/**
     * Returns a new set of layout parameters based on the supplied attributes set.
     *
     * @param attrs the attributes to build the layout parameters from
     *
     * @return an instance of {@link android.view.ViewGroup.LayoutParams} or one
     *         of its descendants
     */
    public LayoutParams generateLayoutParams(AttributeSet attrs) {
        return new LayoutParams(getContext(), attrs);
    }

    Returns a safe set of layout parameters based on the supplied layout params. When a ViewGroup is passed a View whose layout params do not pass the test of checkLayoutParams(LayoutParams), this method is invoked. This method should return a new set of layout params suitable for this ViewGroup, possibly by copying the appropriate attributes from the specified set of layout params. 
Params: p – The layout parameters to convert into a suitable set of layout parameters
         for this ViewGroup.
Returns: an instance of LayoutParams or one of its descendants/**
     * Returns a safe set of layout parameters based on the supplied layout params.
     * When a ViewGroup is passed a View whose layout params do not pass the test of
     * {@link #checkLayoutParams(android.view.ViewGroup.LayoutParams)}, this method
     * is invoked. This method should return a new set of layout params suitable for
     * this ViewGroup, possibly by copying the appropriate attributes from the
     * specified set of layout params.
     *
     * @param p The layout parameters to convert into a suitable set of layout parameters
     *          for this ViewGroup.
     *
     * @return an instance of {@link android.view.ViewGroup.LayoutParams} or one
     *         of its descendants
     */
    protected LayoutParams generateLayoutParams(ViewGroup.LayoutParams p) {
        return p;
    }

    Returns a set of default layout parameters. These parameters are requested when the View passed to addView(View) has no layout parameters already set. If null is returned, an exception is thrown from addView. 
Returns: a set of default layout parameters or null/**
     * Returns a set of default layout parameters. These parameters are requested
     * when the View passed to {@link #addView(View)} has no layout parameters
     * already set. If null is returned, an exception is thrown from addView.
     *
     * @return a set of default layout parameters or null
     */
    protected LayoutParams generateDefaultLayoutParams() {
        return new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
    }

    @Override
    protected void debug(int depth) {
        super.debug(depth);
        String output;

        if (mFocused != null) {
            output = debugIndent(depth);
            output += "mFocused";
            Log.d(VIEW_LOG_TAG, output);
            mFocused.debug(depth + 1);
        }
        if (mDefaultFocus != null) {
            output = debugIndent(depth);
            output += "mDefaultFocus";
            Log.d(VIEW_LOG_TAG, output);
            mDefaultFocus.debug(depth + 1);
        }
        if (mFocusedInCluster != null) {
            output = debugIndent(depth);
            output += "mFocusedInCluster";
            Log.d(VIEW_LOG_TAG, output);
            mFocusedInCluster.debug(depth + 1);
        }
        if (mChildrenCount != 0) {
            output = debugIndent(depth);
            output += "{";
            Log.d(VIEW_LOG_TAG, output);
        }
        int count = mChildrenCount;
        for (int i = 0; i < count; i++) {
            View child = mChildren[i];
            child.debug(depth + 1);
        }

        if (mChildrenCount != 0) {
            output = debugIndent(depth);
            output += "}";
            Log.d(VIEW_LOG_TAG, output);
        }
    }

    Returns the position in the group of the specified child view.
Params: child – the view for which to get the position
Returns: a positive integer representing the position of the view in the
        group, or -1 if the view does not exist in the group/**
     * Returns the position in the group of the specified child view.
     *
     * @param child the view for which to get the position
     * @return a positive integer representing the position of the view in the
     *         group, or -1 if the view does not exist in the group
     */
    public int indexOfChild(View child) {
        final int count = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < count; i++) {
            if (children[i] == child) {
                return i;
            }
        }
        return -1;
    }

    Returns the number of children in the group.
Returns: a positive integer representing the number of children in
        the group/**
     * Returns the number of children in the group.
     *
     * @return a positive integer representing the number of children in
     *         the group
     */
    public int getChildCount() {
        return mChildrenCount;
    }

    Returns the view at the specified position in the group.
Params: index – the position at which to get the view from
Returns: the view at the specified position or null if the position
        does not exist within the group/**
     * Returns the view at the specified position in the group.
     *
     * @param index the position at which to get the view from
     * @return the view at the specified position or null if the position
     *         does not exist within the group
     */
    public View getChildAt(int index) {
        if (index < 0 || index >= mChildrenCount) {
            return null;
        }
        return mChildren[index];
    }

    Ask all of the children of this view to measure themselves, taking into
account both the MeasureSpec requirements for this view and its padding.
We skip children that are in the GONE state The heavy lifting is done in
getChildMeasureSpec.
Params: widthMeasureSpec – The width requirements for this view
heightMeasureSpec – The height requirements for this view/**
     * Ask all of the children of this view to measure themselves, taking into
     * account both the MeasureSpec requirements for this view and its padding.
     * We skip children that are in the GONE state The heavy lifting is done in
     * getChildMeasureSpec.
     *
     * @param widthMeasureSpec The width requirements for this view
     * @param heightMeasureSpec The height requirements for this view
     */
    protected void measureChildren(int widthMeasureSpec, int heightMeasureSpec) {
        final int size = mChildrenCount;
        final View[] children = mChildren;
        for (int i = 0; i < size; ++i) {
            final View child = children[i];
            if ((child.mViewFlags & VISIBILITY_MASK) != GONE) {
                measureChild(child, widthMeasureSpec, heightMeasureSpec);
            }
        }
    }

    Ask one of the children of this view to measure itself, taking into
account both the MeasureSpec requirements for this view and its padding.
The heavy lifting is done in getChildMeasureSpec.
Params: child – The child to measure
parentWidthMeasureSpec – The width requirements for this view
parentHeightMeasureSpec – The height requirements for this view/**
     * Ask one of the children of this view to measure itself, taking into
     * account both the MeasureSpec requirements for this view and its padding.
     * The heavy lifting is done in getChildMeasureSpec.
     *
     * @param child The child to measure
     * @param parentWidthMeasureSpec The width requirements for this view
     * @param parentHeightMeasureSpec The height requirements for this view
     */
    protected void measureChild(View child, int parentWidthMeasureSpec,
            int parentHeightMeasureSpec) {
        final LayoutParams lp = child.getLayoutParams();

        final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec,
                mPaddingLeft + mPaddingRight, lp.width);
        final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec,
                mPaddingTop + mPaddingBottom, lp.height);

        child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
    }

    Ask one of the children of this view to measure itself, taking into
account both the MeasureSpec requirements for this view and its padding
and margins. The child must have MarginLayoutParams The heavy lifting is
done in getChildMeasureSpec.
Params: child – The child to measure
parentWidthMeasureSpec – The width requirements for this view
widthUsed – Extra space that has been used up by the parent
       horizontally (possibly by other children of the parent)
parentHeightMeasureSpec – The height requirements for this view
heightUsed – Extra space that has been used up by the parent
       vertically (possibly by other children of the parent)/**
     * Ask one of the children of this view to measure itself, taking into
     * account both the MeasureSpec requirements for this view and its padding
     * and margins. The child must have MarginLayoutParams The heavy lifting is
     * done in getChildMeasureSpec.
     *
     * @param child The child to measure
     * @param parentWidthMeasureSpec The width requirements for this view
     * @param widthUsed Extra space that has been used up by the parent
     *        horizontally (possibly by other children of the parent)
     * @param parentHeightMeasureSpec The height requirements for this view
     * @param heightUsed Extra space that has been used up by the parent
     *        vertically (possibly by other children of the parent)
     */
    protected void measureChildWithMargins(View child,
            int parentWidthMeasureSpec, int widthUsed,
            int parentHeightMeasureSpec, int heightUsed) {
        final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();

        final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec,
                mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin
                        + widthUsed, lp.width);
        final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec,
                mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin
                        + heightUsed, lp.height);

        child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
    }

    Does the hard part of measureChildren: figuring out the MeasureSpec to
pass to a particular child. This method figures out the right MeasureSpec
for one dimension (height or width) of one child view.
The goal is to combine information from our MeasureSpec with the
LayoutParams of the child to get the best possible results. For example,
if the this view knows its size (because its MeasureSpec has a mode of
EXACTLY), and the child has indicated in its LayoutParams that it wants
to be the same size as the parent, the parent should ask the child to
layout given an exact size.
Params: spec – The requirements for this view
padding – The padding of this view for the current dimension and
       margins, if applicable
childDimension – How big the child wants to be in the current
       dimension
Returns: a MeasureSpec integer for the child/**
     * Does the hard part of measureChildren: figuring out the MeasureSpec to
     * pass to a particular child. This method figures out the right MeasureSpec
     * for one dimension (height or width) of one child view.
     *
     * The goal is to combine information from our MeasureSpec with the
     * LayoutParams of the child to get the best possible results. For example,
     * if the this view knows its size (because its MeasureSpec has a mode of
     * EXACTLY), and the child has indicated in its LayoutParams that it wants
     * to be the same size as the parent, the parent should ask the child to
     * layout given an exact size.
     *
     * @param spec The requirements for this view
     * @param padding The padding of this view for the current dimension and
     *        margins, if applicable
     * @param childDimension How big the child wants to be in the current
     *        dimension
     * @return a MeasureSpec integer for the child
     */
    public static int getChildMeasureSpec(int spec, int padding, int childDimension) {
        int specMode = MeasureSpec.getMode(spec);
        int specSize = MeasureSpec.getSize(spec);

        int size = Math.max(0, specSize - padding);

        int resultSize = 0;
        int resultMode = 0;

        switch (specMode) {
        // Parent has imposed an exact size on us
        case MeasureSpec.EXACTLY:
            if (childDimension >= 0) {
                resultSize = childDimension;
                resultMode = MeasureSpec.EXACTLY;
            } else if (childDimension == LayoutParams.MATCH_PARENT) {
                // Child wants to be our size. So be it.
                resultSize = size;
                resultMode = MeasureSpec.EXACTLY;
            } else if (childDimension == LayoutParams.WRAP_CONTENT) {
                // Child wants to determine its own size. It can't be
                // bigger than us.
                resultSize = size;
                resultMode = MeasureSpec.AT_MOST;
            }
            break;

        // Parent has imposed a maximum size on us
        case MeasureSpec.AT_MOST:
            if (childDimension >= 0) {
                // Child wants a specific size... so be it
                resultSize = childDimension;
                resultMode = MeasureSpec.EXACTLY;
            } else if (childDimension == LayoutParams.MATCH_PARENT) {
                // Child wants to be our size, but our size is not fixed.
                // Constrain child to not be bigger than us.
                resultSize = size;
                resultMode = MeasureSpec.AT_MOST;
            } else if (childDimension == LayoutParams.WRAP_CONTENT) {
                // Child wants to determine its own size. It can't be
                // bigger than us.
                resultSize = size;
                resultMode = MeasureSpec.AT_MOST;
            }
            break;

        // Parent asked to see how big we want to be
        case MeasureSpec.UNSPECIFIED:
            if (childDimension >= 0) {
                // Child wants a specific size... let him have it
                resultSize = childDimension;
                resultMode = MeasureSpec.EXACTLY;
            } else if (childDimension == LayoutParams.MATCH_PARENT) {
                // Child wants to be our size... find out how big it should
                // be
                resultSize = View.sUseZeroUnspecifiedMeasureSpec ? 0 : size;
                resultMode = MeasureSpec.UNSPECIFIED;
            } else if (childDimension == LayoutParams.WRAP_CONTENT) {
                // Child wants to determine its own size.... find out how
                // big it should be
                resultSize = View.sUseZeroUnspecifiedMeasureSpec ? 0 : size;
                resultMode = MeasureSpec.UNSPECIFIED;
            }
            break;
        }
        //noinspection ResourceType
        return MeasureSpec.makeMeasureSpec(resultSize, resultMode);
    }


    Removes any pending animations for views that have been removed. Call
this if you don't want animations for exiting views to stack up.
/**
     * Removes any pending animations for views that have been removed. Call
     * this if you don't want animations for exiting views to stack up.
     */
    public void clearDisappearingChildren() {
        final ArrayList<View> disappearingChildren = mDisappearingChildren;
        if (disappearingChildren != null) {
            final int count = disappearingChildren.size();
            for (int i = 0; i < count; i++) {
                final View view = disappearingChildren.get(i);
                if (view.mAttachInfo != null) {
                    view.dispatchDetachedFromWindow();
                }
                view.clearAnimation();
            }
            disappearingChildren.clear();
            invalidate();
        }
    }

    Add a view which is removed from mChildren but still needs animation
Params: v – View to add/**
     * Add a view which is removed from mChildren but still needs animation
     *
     * @param v View to add
     */
    private void addDisappearingView(View v) {
        ArrayList<View> disappearingChildren = mDisappearingChildren;

        if (disappearingChildren == null) {
            disappearingChildren = mDisappearingChildren = new ArrayList<View>();
        }

        disappearingChildren.add(v);
    }

    Cleanup a view when its animation is done. This may mean removing it from
the list of disappearing views.
Params: view – The view whose animation has finished
animation – The animation, cannot be null/**
     * Cleanup a view when its animation is done. This may mean removing it from
     * the list of disappearing views.
     *
     * @param view The view whose animation has finished
     * @param animation The animation, cannot be null
     */
    void finishAnimatingView(final View view, Animation animation) {
        final ArrayList<View> disappearingChildren = mDisappearingChildren;
        if (disappearingChildren != null) {
            if (disappearingChildren.contains(view)) {
                disappearingChildren.remove(view);

                if (view.mAttachInfo != null) {
                    view.dispatchDetachedFromWindow();
                }

                view.clearAnimation();
                mGroupFlags |= FLAG_INVALIDATE_REQUIRED;
            }
        }

        if (animation != null && !animation.getFillAfter()) {
            view.clearAnimation();
        }

        if ((view.mPrivateFlags & PFLAG_ANIMATION_STARTED) == PFLAG_ANIMATION_STARTED) {
            view.onAnimationEnd();
            // Should be performed by onAnimationEnd() but this avoid an infinite loop,
            // so we'd rather be safe than sorry
            view.mPrivateFlags &= ~PFLAG_ANIMATION_STARTED;
            // Draw one more frame after the animation is done
            mGroupFlags |= FLAG_INVALIDATE_REQUIRED;
        }
    }

    Utility function called by View during invalidation to determine whether a view that
is invisible or gone should still be invalidated because it is being transitioned (and
therefore still needs to be drawn).
/**
     * Utility function called by View during invalidation to determine whether a view that
     * is invisible or gone should still be invalidated because it is being transitioned (and
     * therefore still needs to be drawn).
     */
    boolean isViewTransitioning(View view) {
        return (mTransitioningViews != null && mTransitioningViews.contains(view));
    }

    This method tells the ViewGroup that the given View object, which should have this ViewGroup as its parent, should be kept around (re-displayed when the ViewGroup draws its children) even if it is removed from its parent. This allows animations, such as those used by Fragment and LayoutTransition to animate the removal of views. A call to this method should always be accompanied by a later call to endViewTransition(View), such as after an animation on the View has finished, so that the View finally gets removed. 
Params: view – The View object to be kept visible even if it gets removed from its parent./**
     * This method tells the ViewGroup that the given View object, which should have this
     * ViewGroup as its parent,
     * should be kept around  (re-displayed when the ViewGroup draws its children) even if it
     * is removed from its parent. This allows animations, such as those used by
     * {@link android.app.Fragment} and {@link android.animation.LayoutTransition} to animate
     * the removal of views. A call to this method should always be accompanied by a later call
     * to {@link #endViewTransition(View)}, such as after an animation on the View has finished,
     * so that the View finally gets removed.
     *
     * @param view The View object to be kept visible even if it gets removed from its parent.
     */
    public void startViewTransition(View view) {
        if (view.mParent == this) {
            if (mTransitioningViews == null) {
                mTransitioningViews = new ArrayList<View>();
            }
            mTransitioningViews.add(view);
        }
    }

    This method should always be called following an earlier call to startViewTransition(View). The given View is finally removed from its parent and will no longer be displayed. Note that this method does not perform the functionality of removing a view from its parent; it just discontinues the display of a View that has previously been removed. 
Returns: view The View object that has been removed but is being kept around in the visible hierarchy by an earlier call to startViewTransition(View)./**
     * This method should always be called following an earlier call to
     * {@link #startViewTransition(View)}. The given View is finally removed from its parent
     * and will no longer be displayed. Note that this method does not perform the functionality
     * of removing a view from its parent; it just discontinues the display of a View that
     * has previously been removed.
     *
     * @return view The View object that has been removed but is being kept around in the visible
     * hierarchy by an earlier call to {@link #startViewTransition(View)}.
     */
    public void endViewTransition(View view) {
        if (mTransitioningViews != null) {
            mTransitioningViews.remove(view);
            final ArrayList<View> disappearingChildren = mDisappearingChildren;
            if (disappearingChildren != null && disappearingChildren.contains(view)) {
                disappearingChildren.remove(view);
                if (mVisibilityChangingChildren != null &&
                        mVisibilityChangingChildren.contains(view)) {
                    mVisibilityChangingChildren.remove(view);
                } else {
                    if (view.mAttachInfo != null) {
                        view.dispatchDetachedFromWindow();
                    }
                    if (view.mParent != null) {
                        view.mParent = null;
                    }
                }
                invalidate();
            }
        }
    }

    private LayoutTransition.TransitionListener mLayoutTransitionListener =
            new LayoutTransition.TransitionListener() {
        @Override
        public void startTransition(LayoutTransition transition, ViewGroup container,
                View view, int transitionType) {
            // We only care about disappearing items, since we need special logic to keep
            // those items visible after they've been 'removed'
            if (transitionType == LayoutTransition.DISAPPEARING) {
                startViewTransition(view);
            }
        }

        @Override
        public void endTransition(LayoutTransition transition, ViewGroup container,
                View view, int transitionType) {
            if (mLayoutCalledWhileSuppressed && !transition.isChangingLayout()) {
                requestLayout();
                mLayoutCalledWhileSuppressed = false;
            }
            if (transitionType == LayoutTransition.DISAPPEARING && mTransitioningViews != null) {
                endViewTransition(view);
            }
        }
    };

    Tells this ViewGroup to suppress all layout() calls until layout
suppression is disabled with a later call to suppressLayout(false).
When layout suppression is disabled, a requestLayout() call is sent
if layout() was attempted while layout was being suppressed.
@hide /**
     * Tells this ViewGroup to suppress all layout() calls until layout
     * suppression is disabled with a later call to suppressLayout(false).
     * When layout suppression is disabled, a requestLayout() call is sent
     * if layout() was attempted while layout was being suppressed.
     *
     * @hide
     */
    public void suppressLayout(boolean suppress) {
        mSuppressLayout = suppress;
        if (!suppress) {
            if (mLayoutCalledWhileSuppressed) {
                requestLayout();
                mLayoutCalledWhileSuppressed = false;
            }
        }
    }

    Returns whether layout calls on this container are currently being suppressed, due to an earlier call to suppressLayout(boolean). 
Returns: true if layout calls are currently suppressed, false otherwise.
@hide /**
     * Returns whether layout calls on this container are currently being
     * suppressed, due to an earlier call to {@link #suppressLayout(boolean)}.
     *
     * @return true if layout calls are currently suppressed, false otherwise.
     *
     * @hide
     */
    public boolean isLayoutSuppressed() {
        return mSuppressLayout;
    }

    @Override
    public boolean gatherTransparentRegion(Region region) {
        // If no transparent regions requested, we are always opaque.
        final boolean meOpaque = (mPrivateFlags & View.PFLAG_REQUEST_TRANSPARENT_REGIONS) == 0;
        if (meOpaque && region == null) {
            // The caller doesn't care about the region, so stop now.
            return true;
        }
        super.gatherTransparentRegion(region);
        // Instead of naively traversing the view tree, we have to traverse according to the Z
        // order here. We need to go with the same order as dispatchDraw().
        // One example is that after surfaceView punch a hole, we will still allow other views drawn
        // on top of that hole. In this case, those other views should be able to cut the
        // transparent region into smaller area.
        final int childrenCount = mChildrenCount;
        boolean noneOfTheChildrenAreTransparent = true;
        if (childrenCount > 0) {
            final ArrayList<View> preorderedList = buildOrderedChildList();
            final boolean customOrder = preorderedList == null
                    && isChildrenDrawingOrderEnabled();
            final View[] children = mChildren;
            for (int i = 0; i < childrenCount; i++) {
                final int childIndex = getAndVerifyPreorderedIndex(childrenCount, i, customOrder);
                final View child = getAndVerifyPreorderedView(preorderedList, children, childIndex);
                if ((child.mViewFlags & VISIBILITY_MASK) == VISIBLE || child.getAnimation() != null) {
                    if (!child.gatherTransparentRegion(region)) {
                        noneOfTheChildrenAreTransparent = false;
                    }
                }
            }
            if (preorderedList != null) preorderedList.clear();
        }
        return meOpaque || noneOfTheChildrenAreTransparent;
    }

    @Override
    public void requestTransparentRegion(View child) {
        if (child != null) {
            child.mPrivateFlags |= View.PFLAG_REQUEST_TRANSPARENT_REGIONS;
            if (mParent != null) {
                mParent.requestTransparentRegion(this);
            }
        }
    }

    @Override
    public WindowInsets dispatchApplyWindowInsets(WindowInsets insets) {
        insets = super.dispatchApplyWindowInsets(insets);
        if (!insets.isConsumed()) {
            final int count = getChildCount();
            for (int i = 0; i < count; i++) {
                insets = getChildAt(i).dispatchApplyWindowInsets(insets);
                if (insets.isConsumed()) {
                    break;
                }
            }
        }
        return insets;
    }

    Returns the animation listener to which layout animation events are
sent.
Returns: an AnimationListener/**
     * Returns the animation listener to which layout animation events are
     * sent.
     *
     * @return an {@link android.view.animation.Animation.AnimationListener}
     */
    public Animation.AnimationListener getLayoutAnimationListener() {
        return mAnimationListener;
    }

    @Override
    protected void drawableStateChanged() {
        super.drawableStateChanged();

        if ((mGroupFlags & FLAG_NOTIFY_CHILDREN_ON_DRAWABLE_STATE_CHANGE) != 0) {
            if ((mGroupFlags & FLAG_ADD_STATES_FROM_CHILDREN) != 0) {
                throw new IllegalStateException("addStateFromChildren cannot be enabled if a"
                        + " child has duplicateParentState set to true");
            }

            final View[] children = mChildren;
            final int count = mChildrenCount;

            for (int i = 0; i < count; i++) {
                final View child = children[i];
                if ((child.mViewFlags & DUPLICATE_PARENT_STATE) != 0) {
                    child.refreshDrawableState();
                }
            }
        }
    }

    @Override
    public void jumpDrawablesToCurrentState() {
        super.jumpDrawablesToCurrentState();
        final View[] children = mChildren;
        final int count = mChildrenCount;
        for (int i = 0; i < count; i++) {
            children[i].jumpDrawablesToCurrentState();
        }
    }

    @Override
    protected int[] onCreateDrawableState(int extraSpace) {
        if ((mGroupFlags & FLAG_ADD_STATES_FROM_CHILDREN) == 0) {
            return super.onCreateDrawableState(extraSpace);
        }

        int need = 0;
        int n = getChildCount();
        for (int i = 0; i < n; i++) {
            int[] childState = getChildAt(i).getDrawableState();

            if (childState != null) {
                need += childState.length;
            }
        }

        int[] state = super.onCreateDrawableState(extraSpace + need);

        for (int i = 0; i < n; i++) {
            int[] childState = getChildAt(i).getDrawableState();

            if (childState != null) {
                state = mergeDrawableStates(state, childState);
            }
        }

        return state;
    }

    Sets whether this ViewGroup's drawable states also include
its children's drawable states.  This is used, for example, to
make a group appear to be focused when its child EditText or button
is focused.
/**
     * Sets whether this ViewGroup's drawable states also include
     * its children's drawable states.  This is used, for example, to
     * make a group appear to be focused when its child EditText or button
     * is focused.
     */
    public void setAddStatesFromChildren(boolean addsStates) {
        if (addsStates) {
            mGroupFlags |= FLAG_ADD_STATES_FROM_CHILDREN;
        } else {
            mGroupFlags &= ~FLAG_ADD_STATES_FROM_CHILDREN;
        }

        refreshDrawableState();
    }

    Returns whether this ViewGroup's drawable states also include
its children's drawable states.  This is used, for example, to
make a group appear to be focused when its child EditText or button
is focused.
/**
     * Returns whether this ViewGroup's drawable states also include
     * its children's drawable states.  This is used, for example, to
     * make a group appear to be focused when its child EditText or button
     * is focused.
     */
    public boolean addStatesFromChildren() {
        return (mGroupFlags & FLAG_ADD_STATES_FROM_CHILDREN) != 0;
    }

    If addStatesFromChildren is true, refreshes this group's drawable state (to include the states from its children). /**
     * If {@link #addStatesFromChildren} is true, refreshes this group's
     * drawable state (to include the states from its children).
     */
    @Override
    public void childDrawableStateChanged(View child) {
        if ((mGroupFlags & FLAG_ADD_STATES_FROM_CHILDREN) != 0) {
            refreshDrawableState();
        }
    }

    Specifies the animation listener to which layout animation events must be sent. Only AnimationListener.onAnimationStart(Animation) and AnimationListener.onAnimationEnd(Animation) are invoked. 
Params: animationListener – the layout animation listener/**
     * Specifies the animation listener to which layout animation events must
     * be sent. Only
     * {@link android.view.animation.Animation.AnimationListener#onAnimationStart(Animation)}
     * and
     * {@link android.view.animation.Animation.AnimationListener#onAnimationEnd(Animation)}
     * are invoked.
     *
     * @param animationListener the layout animation listener
     */
    public void setLayoutAnimationListener(Animation.AnimationListener animationListener) {
        mAnimationListener = animationListener;
    }

    This method is called by LayoutTransition when there are 'changing' animations that need
to start after the layout/setup phase. The request is forwarded to the ViewAncestor, who
starts all pending transitions prior to the drawing phase in the current traversal.
Params: transition – The LayoutTransition to be started on the next traversal.
@hide /**
     * This method is called by LayoutTransition when there are 'changing' animations that need
     * to start after the layout/setup phase. The request is forwarded to the ViewAncestor, who
     * starts all pending transitions prior to the drawing phase in the current traversal.
     *
     * @param transition The LayoutTransition to be started on the next traversal.
     *
     * @hide
     */
    public void requestTransitionStart(LayoutTransition transition) {
        ViewRootImpl viewAncestor = getViewRootImpl();
        if (viewAncestor != null) {
            viewAncestor.requestTransitionStart(transition);
        }
    }

    @hide /**
     * @hide
     */
    @Override
    public boolean resolveRtlPropertiesIfNeeded() {
        final boolean result = super.resolveRtlPropertiesIfNeeded();
        // We dont need to resolve the children RTL properties if nothing has changed for the parent
        if (result) {
            int count = getChildCount();
            for (int i = 0; i < count; i++) {
                final View child = getChildAt(i);
                if (child.isLayoutDirectionInherited()) {
                    child.resolveRtlPropertiesIfNeeded();
                }
            }
        }
        return result;
    }

    @hide /**
     * @hide
     */
    @Override
    public boolean resolveLayoutDirection() {
        final boolean result = super.resolveLayoutDirection();
        if (result) {
            int count = getChildCount();
            for (int i = 0; i < count; i++) {
                final View child = getChildAt(i);
                if (child.isLayoutDirectionInherited()) {
                    child.resolveLayoutDirection();
                }
            }
        }
        return result;
    }

    @hide /**
     * @hide
     */
    @Override
    public boolean resolveTextDirection() {
        final boolean result = super.resolveTextDirection();
        if (result) {
            int count = getChildCount();
            for (int i = 0; i < count; i++) {
                final View child = getChildAt(i);
                if (child.isTextDirectionInherited()) {
                    child.resolveTextDirection();
                }
            }
        }
        return result;
    }

    @hide /**
     * @hide
     */
    @Override
    public boolean resolveTextAlignment() {
        final boolean result = super.resolveTextAlignment();
        if (result) {
            int count = getChildCount();
            for (int i = 0; i < count; i++) {
                final View child = getChildAt(i);
                if (child.isTextAlignmentInherited()) {
                    child.resolveTextAlignment();
                }
            }
        }
        return result;
    }

    @hide /**
     * @hide
     */
    @Override
    public void resolvePadding() {
        super.resolvePadding();
        int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.isLayoutDirectionInherited() && !child.isPaddingResolved()) {
                child.resolvePadding();
            }
        }
    }

    @hide /**
     * @hide
     */
    @Override
    protected void resolveDrawables() {
        super.resolveDrawables();
        int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.isLayoutDirectionInherited() && !child.areDrawablesResolved()) {
                child.resolveDrawables();
            }
        }
    }

    @hide /**
     * @hide
     */
    @Override
    public void resolveLayoutParams() {
        super.resolveLayoutParams();
        int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            child.resolveLayoutParams();
        }
    }

    @hide /**
     * @hide
     */
    @Override
    public void resetResolvedLayoutDirection() {
        super.resetResolvedLayoutDirection();

        int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.isLayoutDirectionInherited()) {
                child.resetResolvedLayoutDirection();
            }
        }
    }

    @hide /**
     * @hide
     */
    @Override
    public void resetResolvedTextDirection() {
        super.resetResolvedTextDirection();

        int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.isTextDirectionInherited()) {
                child.resetResolvedTextDirection();
            }
        }
    }

    @hide /**
     * @hide
     */
    @Override
    public void resetResolvedTextAlignment() {
        super.resetResolvedTextAlignment();

        int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.isTextAlignmentInherited()) {
                child.resetResolvedTextAlignment();
            }
        }
    }

    @hide /**
     * @hide
     */
    @Override
    public void resetResolvedPadding() {
        super.resetResolvedPadding();

        int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.isLayoutDirectionInherited()) {
                child.resetResolvedPadding();
            }
        }
    }

    @hide /**
     * @hide
     */
    @Override
    protected void resetResolvedDrawables() {
        super.resetResolvedDrawables();

        int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.isLayoutDirectionInherited()) {
                child.resetResolvedDrawables();
            }
        }
    }

    Return true if the pressed state should be delayed for children or descendants of this
ViewGroup. Generally, this should be done for containers that can scroll, such as a List.
This prevents the pressed state from appearing when the user is actually trying to scroll
the content.
The default implementation returns true for compatibility reasons. Subclasses that do
not scroll should generally override this method and return false.
/**
     * Return true if the pressed state should be delayed for children or descendants of this
     * ViewGroup. Generally, this should be done for containers that can scroll, such as a List.
     * This prevents the pressed state from appearing when the user is actually trying to scroll
     * the content.
     *
     * The default implementation returns true for compatibility reasons. Subclasses that do
     * not scroll should generally override this method and return false.
     */
    public boolean shouldDelayChildPressedState() {
        return true;
    }

    @inheritDoc /**
     * @inheritDoc
     */
    @Override
    public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
        return false;
    }

    @inheritDoc /**
     * @inheritDoc
     */
    @Override
    public void onNestedScrollAccepted(View child, View target, int axes) {
        mNestedScrollAxes = axes;
    }

    @inheritDoc 
The default implementation of onStopNestedScroll calls View.stopNestedScroll() to halt any recursive nested scrolling in progress./**
     * @inheritDoc
     *
     * <p>The default implementation of onStopNestedScroll calls
     * {@link #stopNestedScroll()} to halt any recursive nested scrolling in progress.</p>
     */
    @Override
    public void onStopNestedScroll(View child) {
        // Stop any recursive nested scrolling.
        stopNestedScroll();
        mNestedScrollAxes = 0;
    }

    @inheritDoc /**
     * @inheritDoc
     */
    @Override
    public void onNestedScroll(View target, int dxConsumed, int dyConsumed,
            int dxUnconsumed, int dyUnconsumed) {
        // Re-dispatch up the tree by default
        dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, null);
    }

    @inheritDoc /**
     * @inheritDoc
     */
    @Override
    public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
        // Re-dispatch up the tree by default
        dispatchNestedPreScroll(dx, dy, consumed, null);
    }

    @inheritDoc /**
     * @inheritDoc
     */
    @Override
    public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
        // Re-dispatch up the tree by default
        return dispatchNestedFling(velocityX, velocityY, consumed);
    }

    @inheritDoc /**
     * @inheritDoc
     */
    @Override
    public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
        // Re-dispatch up the tree by default
        return dispatchNestedPreFling(velocityX, velocityY);
    }

    Return the current axes of nested scrolling for this ViewGroup.
A ViewGroup returning something other than View.SCROLL_AXIS_NONE is currently acting as a nested scrolling parent for one or more descendant views in the hierarchy.
See Also: View.SCROLL_AXIS_HORIZONTAL
View.SCROLL_AXIS_VERTICAL
View.SCROLL_AXIS_NONE
Returns: Flags indicating the current axes of nested scrolling/**
     * Return the current axes of nested scrolling for this ViewGroup.
     *
     * <p>A ViewGroup returning something other than {@link #SCROLL_AXIS_NONE} is currently
     * acting as a nested scrolling parent for one or more descendant views in the hierarchy.</p>
     *
     * @return Flags indicating the current axes of nested scrolling
     * @see #SCROLL_AXIS_HORIZONTAL
     * @see #SCROLL_AXIS_VERTICAL
     * @see #SCROLL_AXIS_NONE
     */
    public int getNestedScrollAxes() {
        return mNestedScrollAxes;
    }

    @hide /** @hide */
    protected void onSetLayoutParams(View child, LayoutParams layoutParams) {
        requestLayout();
    }

    @hide /** @hide */
    @Override
    public void captureTransitioningViews(List<View> transitioningViews) {
        if (getVisibility() != View.VISIBLE) {
            return;
        }
        if (isTransitionGroup()) {
            transitioningViews.add(this);
        } else {
            int count = getChildCount();
            for (int i = 0; i < count; i++) {
                View child = getChildAt(i);
                child.captureTransitioningViews(transitioningViews);
            }
        }
    }

    @hide /** @hide */
    @Override
    public void findNamedViews(Map<String, View> namedElements) {
        if (getVisibility() != VISIBLE && mGhostView == null) {
            return;
        }
        super.findNamedViews(namedElements);
        int count = getChildCount();
        for (int i = 0; i < count; i++) {
            View child = getChildAt(i);
            child.findNamedViews(namedElements);
        }
    }

    @Override
    boolean hasUnhandledKeyListener() {
        return (mChildUnhandledKeyListeners > 0) || super.hasUnhandledKeyListener();
    }

    void incrementChildUnhandledKeyListeners() {
        mChildUnhandledKeyListeners += 1;
        if (mChildUnhandledKeyListeners == 1) {
            if (mParent instanceof ViewGroup) {
                ((ViewGroup) mParent).incrementChildUnhandledKeyListeners();
            }
        }
    }

    void decrementChildUnhandledKeyListeners() {
        mChildUnhandledKeyListeners -= 1;
        if (mChildUnhandledKeyListeners == 0) {
            if (mParent instanceof ViewGroup) {
                ((ViewGroup) mParent).decrementChildUnhandledKeyListeners();
            }
        }
    }

    @Override
    View dispatchUnhandledKeyEvent(KeyEvent evt) {
        if (!hasUnhandledKeyListener()) {
            return null;
        }
        ArrayList<View> orderedViews = buildOrderedChildList();
        if (orderedViews != null) {
            try {
                for (int i = orderedViews.size() - 1; i >= 0; --i) {
                    View v = orderedViews.get(i);
                    View consumer = v.dispatchUnhandledKeyEvent(evt);
                    if (consumer != null) {
                        return consumer;
                    }
                }
            } finally {
                orderedViews.clear();
            }
        } else {
            for (int i = getChildCount() - 1; i >= 0; --i) {
                View v = getChildAt(i);
                View consumer = v.dispatchUnhandledKeyEvent(evt);
                if (consumer != null) {
                    return consumer;
                }
            }
        }
        if (onUnhandledKeyEvent(evt)) {
            return this;
        }
        return null;
    }

    LayoutParams are used by views to tell their parents how they want to be laid out. See ViewGroup Layout Attributes for a list of all child view attributes that this class supports. 
The base LayoutParams class just describes how big the view wants to be
for both width and height. For each dimension, it can specify one of:

FILL_PARENT (renamed MATCH_PARENT in API Level 8 and higher), which
means that the view wants to be as big as its parent (minus padding)
 WRAP_CONTENT, which means that the view wants to be just big enough
to enclose its content (plus padding)
 an exact number

There are subclasses of LayoutParams for different subclasses of
ViewGroup. For example, AbsoluteLayout has its own subclass of
LayoutParams which adds an X and Y value.

Developer Guides
For more information about creating user interface layouts, read the
XML Layouts developer
guide.
@attr ref android.R.styleable#ViewGroup_Layout_layout_height
@attr ref android.R.styleable#ViewGroup_Layout_layout_width/**
     * LayoutParams are used by views to tell their parents how they want to be
     * laid out. See
     * {@link android.R.styleable#ViewGroup_Layout ViewGroup Layout Attributes}
     * for a list of all child view attributes that this class supports.
     *
     * <p>
     * The base LayoutParams class just describes how big the view wants to be
     * for both width and height. For each dimension, it can specify one of:
     * <ul>
     * <li>FILL_PARENT (renamed MATCH_PARENT in API Level 8 and higher), which
     * means that the view wants to be as big as its parent (minus padding)
     * <li> WRAP_CONTENT, which means that the view wants to be just big enough
     * to enclose its content (plus padding)
     * <li> an exact number
     * </ul>
     * There are subclasses of LayoutParams for different subclasses of
     * ViewGroup. For example, AbsoluteLayout has its own subclass of
     * LayoutParams which adds an X and Y value.</p>
     *
     * <div class="special reference">
     * <h3>Developer Guides</h3>
     * <p>For more information about creating user interface layouts, read the
     * <a href="{@docRoot}guide/topics/ui/declaring-layout.html">XML Layouts</a> developer
     * guide.</p></div>
     *
     * @attr ref android.R.styleable#ViewGroup_Layout_layout_height
     * @attr ref android.R.styleable#ViewGroup_Layout_layout_width
     */
    public static class LayoutParams {
        Special value for the height or width requested by a View. FILL_PARENT means that the view wants to be as big as its parent, minus the parent's padding, if any. This value is deprecated starting in API Level 8 and replaced by MATCH_PARENT. /**
         * Special value for the height or width requested by a View.
         * FILL_PARENT means that the view wants to be as big as its parent,
         * minus the parent's padding, if any. This value is deprecated
         * starting in API Level 8 and replaced by {@link #MATCH_PARENT}.
         */
        @SuppressWarnings({"UnusedDeclaration"})
        @Deprecated
        public static final int FILL_PARENT = -1;

        Special value for the height or width requested by a View.
MATCH_PARENT means that the view wants to be as big as its parent,
minus the parent's padding, if any. Introduced in API Level 8.
/**
         * Special value for the height or width requested by a View.
         * MATCH_PARENT means that the view wants to be as big as its parent,
         * minus the parent's padding, if any. Introduced in API Level 8.
         */
        public static final int MATCH_PARENT = -1;

        Special value for the height or width requested by a View.
WRAP_CONTENT means that the view wants to be just large enough to fit
its own internal content, taking its own padding into account.
/**
         * Special value for the height or width requested by a View.
         * WRAP_CONTENT means that the view wants to be just large enough to fit
         * its own internal content, taking its own padding into account.
         */
        public static final int WRAP_CONTENT = -2;

        Information about how wide the view wants to be. Can be one of the
constants FILL_PARENT (replaced by MATCH_PARENT
in API Level 8) or WRAP_CONTENT, or an exact size.
/**
         * Information about how wide the view wants to be. Can be one of the
         * constants FILL_PARENT (replaced by MATCH_PARENT
         * in API Level 8) or WRAP_CONTENT, or an exact size.
         */
        @ViewDebug.ExportedProperty(category = "layout", mapping = {
            @ViewDebug.IntToString(from = MATCH_PARENT, to = "MATCH_PARENT"),
            @ViewDebug.IntToString(from = WRAP_CONTENT, to = "WRAP_CONTENT")
        })
        public int width;

        Information about how tall the view wants to be. Can be one of the
constants FILL_PARENT (replaced by MATCH_PARENT
in API Level 8) or WRAP_CONTENT, or an exact size.
/**
         * Information about how tall the view wants to be. Can be one of the
         * constants FILL_PARENT (replaced by MATCH_PARENT
         * in API Level 8) or WRAP_CONTENT, or an exact size.
         */
        @ViewDebug.ExportedProperty(category = "layout", mapping = {
            @ViewDebug.IntToString(from = MATCH_PARENT, to = "MATCH_PARENT"),
            @ViewDebug.IntToString(from = WRAP_CONTENT, to = "WRAP_CONTENT")
        })
        public int height;

        Used to animate layouts.
/**
         * Used to animate layouts.
         */
        public LayoutAnimationController.AnimationParameters layoutAnimationParameters;

        Creates a new set of layout parameters. The values are extracted from
the supplied attributes set and context. The XML attributes mapped
to this set of layout parameters are:

  layout_width: the width, either an exact value, WRAP_CONTENT, or FILL_PARENT (replaced by MATCH_PARENT in API Level 8)
  layout_height: the height, either an exact value, WRAP_CONTENT, or FILL_PARENT (replaced by MATCH_PARENT in API Level 8)

Params: c – the application environment
attrs – the set of attributes from which to extract the layout
             parameters' values/**
         * Creates a new set of layout parameters. The values are extracted from
         * the supplied attributes set and context. The XML attributes mapped
         * to this set of layout parameters are:
         *
         * <ul>
         *   <li><code>layout_width</code>: the width, either an exact value,
         *   {@link #WRAP_CONTENT}, or {@link #FILL_PARENT} (replaced by
         *   {@link #MATCH_PARENT} in API Level 8)</li>
         *   <li><code>layout_height</code>: the height, either an exact value,
         *   {@link #WRAP_CONTENT}, or {@link #FILL_PARENT} (replaced by
         *   {@link #MATCH_PARENT} in API Level 8)</li>
         * </ul>
         *
         * @param c the application environment
         * @param attrs the set of attributes from which to extract the layout
         *              parameters' values
         */
        public LayoutParams(Context c, AttributeSet attrs) {
            TypedArray a = c.obtainStyledAttributes(attrs, R.styleable.ViewGroup_Layout);
            setBaseAttributes(a,
                    R.styleable.ViewGroup_Layout_layout_width,
                    R.styleable.ViewGroup_Layout_layout_height);
            a.recycle();
        }

        Creates a new set of layout parameters with the specified width
and height.
Params: width – the width, either WRAP_CONTENT, FILL_PARENT (replaced by MATCH_PARENT in API Level 8), or a fixed size in pixels
height – the height, either WRAP_CONTENT, FILL_PARENT (replaced by MATCH_PARENT in API Level 8), or a fixed size in pixels/**
         * Creates a new set of layout parameters with the specified width
         * and height.
         *
         * @param width the width, either {@link #WRAP_CONTENT},
         *        {@link #FILL_PARENT} (replaced by {@link #MATCH_PARENT} in
         *        API Level 8), or a fixed size in pixels
         * @param height the height, either {@link #WRAP_CONTENT},
         *        {@link #FILL_PARENT} (replaced by {@link #MATCH_PARENT} in
         *        API Level 8), or a fixed size in pixels
         */
        public LayoutParams(int width, int height) {
            this.width = width;
            this.height = height;
        }

        Copy constructor. Clones the width and height values of the source.
Params: source – The layout params to copy from./**
         * Copy constructor. Clones the width and height values of the source.
         *
         * @param source The layout params to copy from.
         */
        public LayoutParams(LayoutParams source) {
            this.width = source.width;
            this.height = source.height;
        }

        Used internally by MarginLayoutParams.
@hide /**
         * Used internally by MarginLayoutParams.
         * @hide
         */
        LayoutParams() {
        }

        Extracts the layout parameters from the supplied attributes.
Params: a – the style attributes to extract the parameters from
widthAttr – the identifier of the width attribute
heightAttr – the identifier of the height attribute/**
         * Extracts the layout parameters from the supplied attributes.
         *
         * @param a the style attributes to extract the parameters from
         * @param widthAttr the identifier of the width attribute
         * @param heightAttr the identifier of the height attribute
         */
        protected void setBaseAttributes(TypedArray a, int widthAttr, int heightAttr) {
            width = a.getLayoutDimension(widthAttr, "layout_width");
            height = a.getLayoutDimension(heightAttr, "layout_height");
        }

        Resolve layout parameters depending on the layout direction. Subclasses that care about
layoutDirection changes should override this method. The default implementation does
nothing.
Params: layoutDirection – the direction of the layout View.LAYOUT_DIRECTION_LTR View.LAYOUT_DIRECTION_RTL/**
         * Resolve layout parameters depending on the layout direction. Subclasses that care about
         * layoutDirection changes should override this method. The default implementation does
         * nothing.
         *
         * @param layoutDirection the direction of the layout
         *
         * {@link View#LAYOUT_DIRECTION_LTR}
         * {@link View#LAYOUT_DIRECTION_RTL}
         */
        public void resolveLayoutDirection(int layoutDirection) {
        }

        Returns a String representation of this set of layout parameters.
Params: output – the String to prepend to the internal representation
Returns: a String with the following format: output +
        "ViewGroup.LayoutParams={ width=WIDTH, height=HEIGHT }"
@hide /**
         * Returns a String representation of this set of layout parameters.
         *
         * @param output the String to prepend to the internal representation
         * @return a String with the following format: output +
         *         "ViewGroup.LayoutParams={ width=WIDTH, height=HEIGHT }"
         *
         * @hide
         */
        public String debug(String output) {
            return output + "ViewGroup.LayoutParams={ width="
                    + sizeToString(width) + ", height=" + sizeToString(height) + " }";
        }

        Use canvas to draw suitable debugging annotations for these LayoutParameters. 
Params: view – the view that contains these layout parameters
canvas – the canvas on which to draw
@hide /**
         * Use {@code canvas} to draw suitable debugging annotations for these LayoutParameters.
         *
         * @param view the view that contains these layout parameters
         * @param canvas the canvas on which to draw
         *
         * @hide
         */
        public void onDebugDraw(View view, Canvas canvas, Paint paint) {
        }

        Converts the specified size to a readable String.
Params: size – the size to convert
Returns: a String instance representing the supplied size
@hide /**
         * Converts the specified size to a readable String.
         *
         * @param size the size to convert
         * @return a String instance representing the supplied size
         *
         * @hide
         */
        protected static String sizeToString(int size) {
            if (size == WRAP_CONTENT) {
                return "wrap-content";
            }
            if (size == MATCH_PARENT) {
                return "match-parent";
            }
            return String.valueOf(size);
        }

        @hide /** @hide */
        void encode(@NonNull ViewHierarchyEncoder encoder) {
            encoder.beginObject(this);
            encodeProperties(encoder);
            encoder.endObject();
        }

        @hide /** @hide */
        protected void encodeProperties(@NonNull ViewHierarchyEncoder encoder) {
            encoder.addProperty("width", width);
            encoder.addProperty("height", height);
        }
    }

    Per-child layout information for layouts that support margins. See ViewGroup Margin Layout Attributes for a list of all child view attributes that this class supports. 
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_margin
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginHorizontal
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginVertical
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginLeft
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginTop
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginRight
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginBottom
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginStart
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginEnd/**
     * Per-child layout information for layouts that support margins.
     * See
     * {@link android.R.styleable#ViewGroup_MarginLayout ViewGroup Margin Layout Attributes}
     * for a list of all child view attributes that this class supports.
     *
     * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_margin
     * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginHorizontal
     * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginVertical
     * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginLeft
     * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginTop
     * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginRight
     * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginBottom
     * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginStart
     * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginEnd
     */
    public static class MarginLayoutParams extends ViewGroup.LayoutParams {
        The left margin in pixels of the child. Margin values should be positive. Call View.setLayoutParams(LayoutParams) after reassigning a new value to this field. /**
         * The left margin in pixels of the child. Margin values should be positive.
         * Call {@link ViewGroup#setLayoutParams(LayoutParams)} after reassigning a new value
         * to this field.
         */
        @ViewDebug.ExportedProperty(category = "layout")
        public int leftMargin;

        The top margin in pixels of the child. Margin values should be positive. Call View.setLayoutParams(LayoutParams) after reassigning a new value to this field. /**
         * The top margin in pixels of the child. Margin values should be positive.
         * Call {@link ViewGroup#setLayoutParams(LayoutParams)} after reassigning a new value
         * to this field.
         */
        @ViewDebug.ExportedProperty(category = "layout")
        public int topMargin;

        The right margin in pixels of the child. Margin values should be positive. Call View.setLayoutParams(LayoutParams) after reassigning a new value to this field. /**
         * The right margin in pixels of the child. Margin values should be positive.
         * Call {@link ViewGroup#setLayoutParams(LayoutParams)} after reassigning a new value
         * to this field.
         */
        @ViewDebug.ExportedProperty(category = "layout")
        public int rightMargin;

        The bottom margin in pixels of the child. Margin values should be positive. Call View.setLayoutParams(LayoutParams) after reassigning a new value to this field. /**
         * The bottom margin in pixels of the child. Margin values should be positive.
         * Call {@link ViewGroup#setLayoutParams(LayoutParams)} after reassigning a new value
         * to this field.
         */
        @ViewDebug.ExportedProperty(category = "layout")
        public int bottomMargin;

        The start margin in pixels of the child. Margin values should be positive. Call View.setLayoutParams(LayoutParams) after reassigning a new value to this field. /**
         * The start margin in pixels of the child. Margin values should be positive.
         * Call {@link ViewGroup#setLayoutParams(LayoutParams)} after reassigning a new value
         * to this field.
         */
        @ViewDebug.ExportedProperty(category = "layout")
        private int startMargin = DEFAULT_MARGIN_RELATIVE;

        The end margin in pixels of the child. Margin values should be positive. Call View.setLayoutParams(LayoutParams) after reassigning a new value to this field. /**
         * The end margin in pixels of the child. Margin values should be positive.
         * Call {@link ViewGroup#setLayoutParams(LayoutParams)} after reassigning a new value
         * to this field.
         */
        @ViewDebug.ExportedProperty(category = "layout")
        private int endMargin = DEFAULT_MARGIN_RELATIVE;

        The default start and end margin.
@hide /**
         * The default start and end margin.
         * @hide
         */
        public static final int DEFAULT_MARGIN_RELATIVE = Integer.MIN_VALUE;

        Bit  0: layout direction
Bit  1: layout direction
Bit  2: left margin undefined
Bit  3: right margin undefined
Bit  4: is RTL compatibility mode
Bit  5: need resolution
Bit 6 to 7 not used
@hide /**
         * Bit  0: layout direction
         * Bit  1: layout direction
         * Bit  2: left margin undefined
         * Bit  3: right margin undefined
         * Bit  4: is RTL compatibility mode
         * Bit  5: need resolution
         *
         * Bit 6 to 7 not used
         *
         * @hide
         */
        @ViewDebug.ExportedProperty(category = "layout", flagMapping = {
                @ViewDebug.FlagToString(mask = LAYOUT_DIRECTION_MASK,
                        equals = LAYOUT_DIRECTION_MASK, name = "LAYOUT_DIRECTION"),
                @ViewDebug.FlagToString(mask = LEFT_MARGIN_UNDEFINED_MASK,
                        equals = LEFT_MARGIN_UNDEFINED_MASK, name = "LEFT_MARGIN_UNDEFINED_MASK"),
                @ViewDebug.FlagToString(mask = RIGHT_MARGIN_UNDEFINED_MASK,
                        equals = RIGHT_MARGIN_UNDEFINED_MASK, name = "RIGHT_MARGIN_UNDEFINED_MASK"),
                @ViewDebug.FlagToString(mask = RTL_COMPATIBILITY_MODE_MASK,
                        equals = RTL_COMPATIBILITY_MODE_MASK, name = "RTL_COMPATIBILITY_MODE_MASK"),
                @ViewDebug.FlagToString(mask = NEED_RESOLUTION_MASK,
                        equals = NEED_RESOLUTION_MASK, name = "NEED_RESOLUTION_MASK")
        }, formatToHexString = true)
        byte mMarginFlags;

        private static final int LAYOUT_DIRECTION_MASK = 0x00000003;
        private static final int LEFT_MARGIN_UNDEFINED_MASK = 0x00000004;
        private static final int RIGHT_MARGIN_UNDEFINED_MASK = 0x00000008;
        private static final int RTL_COMPATIBILITY_MODE_MASK = 0x00000010;
        private static final int NEED_RESOLUTION_MASK = 0x00000020;

        private static final int DEFAULT_MARGIN_RESOLVED = 0;
        private static final int UNDEFINED_MARGIN = DEFAULT_MARGIN_RELATIVE;

        Creates a new set of layout parameters. The values are extracted from
the supplied attributes set and context.
Params: c – the application environment
attrs – the set of attributes from which to extract the layout
             parameters' values/**
         * Creates a new set of layout parameters. The values are extracted from
         * the supplied attributes set and context.
         *
         * @param c the application environment
         * @param attrs the set of attributes from which to extract the layout
         *              parameters' values
         */
        public MarginLayoutParams(Context c, AttributeSet attrs) {
            super();

            TypedArray a = c.obtainStyledAttributes(attrs, R.styleable.ViewGroup_MarginLayout);
            setBaseAttributes(a,
                    R.styleable.ViewGroup_MarginLayout_layout_width,
                    R.styleable.ViewGroup_MarginLayout_layout_height);

            int margin = a.getDimensionPixelSize(
                    com.android.internal.R.styleable.ViewGroup_MarginLayout_layout_margin, -1);
            if (margin >= 0) {
                leftMargin = margin;
                topMargin = margin;
                rightMargin= margin;
                bottomMargin = margin;
            } else {
                int horizontalMargin = a.getDimensionPixelSize(
                        R.styleable.ViewGroup_MarginLayout_layout_marginHorizontal, -1);
                int verticalMargin = a.getDimensionPixelSize(
                        R.styleable.ViewGroup_MarginLayout_layout_marginVertical, -1);

                if (horizontalMargin >= 0) {
                    leftMargin = horizontalMargin;
                    rightMargin = horizontalMargin;
                } else {
                    leftMargin = a.getDimensionPixelSize(
                            R.styleable.ViewGroup_MarginLayout_layout_marginLeft,
                            UNDEFINED_MARGIN);
                    if (leftMargin == UNDEFINED_MARGIN) {
                        mMarginFlags |= LEFT_MARGIN_UNDEFINED_MASK;
                        leftMargin = DEFAULT_MARGIN_RESOLVED;
                    }
                    rightMargin = a.getDimensionPixelSize(
                            R.styleable.ViewGroup_MarginLayout_layout_marginRight,
                            UNDEFINED_MARGIN);
                    if (rightMargin == UNDEFINED_MARGIN) {
                        mMarginFlags |= RIGHT_MARGIN_UNDEFINED_MASK;
                        rightMargin = DEFAULT_MARGIN_RESOLVED;
                    }
                }

                startMargin = a.getDimensionPixelSize(
                        R.styleable.ViewGroup_MarginLayout_layout_marginStart,
                        DEFAULT_MARGIN_RELATIVE);
                endMargin = a.getDimensionPixelSize(
                        R.styleable.ViewGroup_MarginLayout_layout_marginEnd,
                        DEFAULT_MARGIN_RELATIVE);

                if (verticalMargin >= 0) {
                    topMargin = verticalMargin;
                    bottomMargin = verticalMargin;
                } else {
                    topMargin = a.getDimensionPixelSize(
                            R.styleable.ViewGroup_MarginLayout_layout_marginTop,
                            DEFAULT_MARGIN_RESOLVED);
                    bottomMargin = a.getDimensionPixelSize(
                            R.styleable.ViewGroup_MarginLayout_layout_marginBottom,
                            DEFAULT_MARGIN_RESOLVED);
                }

                if (isMarginRelative()) {
                   mMarginFlags |= NEED_RESOLUTION_MASK;
                }
            }

            final boolean hasRtlSupport = c.getApplicationInfo().hasRtlSupport();
            final int targetSdkVersion = c.getApplicationInfo().targetSdkVersion;
            if (targetSdkVersion < JELLY_BEAN_MR1 || !hasRtlSupport) {
                mMarginFlags |= RTL_COMPATIBILITY_MODE_MASK;
            }

            // Layout direction is LTR by default
            mMarginFlags |= LAYOUT_DIRECTION_LTR;

            a.recycle();
        }

        public MarginLayoutParams(int width, int height) {
            super(width, height);

            mMarginFlags |= LEFT_MARGIN_UNDEFINED_MASK;
            mMarginFlags |= RIGHT_MARGIN_UNDEFINED_MASK;

            mMarginFlags &= ~NEED_RESOLUTION_MASK;
            mMarginFlags &= ~RTL_COMPATIBILITY_MODE_MASK;
        }

        Copy constructor. Clones the width, height and margin values of the source.
Params: source – The layout params to copy from./**
         * Copy constructor. Clones the width, height and margin values of the source.
         *
         * @param source The layout params to copy from.
         */
        public MarginLayoutParams(MarginLayoutParams source) {
            this.width = source.width;
            this.height = source.height;

            this.leftMargin = source.leftMargin;
            this.topMargin = source.topMargin;
            this.rightMargin = source.rightMargin;
            this.bottomMargin = source.bottomMargin;
            this.startMargin = source.startMargin;
            this.endMargin = source.endMargin;

            this.mMarginFlags = source.mMarginFlags;
        }

        public MarginLayoutParams(LayoutParams source) {
            super(source);

            mMarginFlags |= LEFT_MARGIN_UNDEFINED_MASK;
            mMarginFlags |= RIGHT_MARGIN_UNDEFINED_MASK;

            mMarginFlags &= ~NEED_RESOLUTION_MASK;
            mMarginFlags &= ~RTL_COMPATIBILITY_MODE_MASK;
        }

        @hide Used internally./**
         * @hide Used internally.
         */
        public final void copyMarginsFrom(MarginLayoutParams source) {
            this.leftMargin = source.leftMargin;
            this.topMargin = source.topMargin;
            this.rightMargin = source.rightMargin;
            this.bottomMargin = source.bottomMargin;
            this.startMargin = source.startMargin;
            this.endMargin = source.endMargin;

            this.mMarginFlags = source.mMarginFlags;
        }

        Sets the margins, in pixels. A call to View.requestLayout() needs to be done so that the new margins are taken into account. Left and right margins may be overridden by View.requestLayout() depending on layout direction. Margin values should be positive. 
Params: left – the left margin size
top – the top margin size
right – the right margin size
bottom – the bottom margin size
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginLeft
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginTop
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginRight
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginBottom/**
         * Sets the margins, in pixels. A call to {@link android.view.View#requestLayout()} needs
         * to be done so that the new margins are taken into account. Left and right margins may be
         * overridden by {@link android.view.View#requestLayout()} depending on layout direction.
         * Margin values should be positive.
         *
         * @param left the left margin size
         * @param top the top margin size
         * @param right the right margin size
         * @param bottom the bottom margin size
         *
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginLeft
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginTop
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginRight
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginBottom
         */
        public void setMargins(int left, int top, int right, int bottom) {
            leftMargin = left;
            topMargin = top;
            rightMargin = right;
            bottomMargin = bottom;
            mMarginFlags &= ~LEFT_MARGIN_UNDEFINED_MASK;
            mMarginFlags &= ~RIGHT_MARGIN_UNDEFINED_MASK;
            if (isMarginRelative()) {
                mMarginFlags |= NEED_RESOLUTION_MASK;
            } else {
                mMarginFlags &= ~NEED_RESOLUTION_MASK;
            }
        }

        Sets the relative margins, in pixels. A call to View.requestLayout() needs to be done so that the new relative margins are taken into account. Left and right margins may be overridden by View.requestLayout() depending on layout direction. Margin values should be positive. 
Params: start – the start margin size
top – the top margin size
end – the right margin size
bottom – the bottom margin size
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginStart
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginTop
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginEnd
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginBottom
@hide /**
         * Sets the relative margins, in pixels. A call to {@link android.view.View#requestLayout()}
         * needs to be done so that the new relative margins are taken into account. Left and right
         * margins may be overridden by {@link android.view.View#requestLayout()} depending on
         * layout direction. Margin values should be positive.
         *
         * @param start the start margin size
         * @param top the top margin size
         * @param end the right margin size
         * @param bottom the bottom margin size
         *
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginStart
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginTop
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginEnd
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginBottom
         *
         * @hide
         */
        public void setMarginsRelative(int start, int top, int end, int bottom) {
            startMargin = start;
            topMargin = top;
            endMargin = end;
            bottomMargin = bottom;
            mMarginFlags |= NEED_RESOLUTION_MASK;
        }

        Sets the relative start margin. Margin values should be positive.
Params: start – the start margin size
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginStart/**
         * Sets the relative start margin. Margin values should be positive.
         *
         * @param start the start margin size
         *
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginStart
         */
        public void setMarginStart(int start) {
            startMargin = start;
            mMarginFlags |= NEED_RESOLUTION_MASK;
        }

        Returns the start margin in pixels.
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginStart
Returns: the start margin in pixels./**
         * Returns the start margin in pixels.
         *
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginStart
         *
         * @return the start margin in pixels.
         */
        public int getMarginStart() {
            if (startMargin != DEFAULT_MARGIN_RELATIVE) return startMargin;
            if ((mMarginFlags & NEED_RESOLUTION_MASK) == NEED_RESOLUTION_MASK) {
                doResolveMargins();
            }
            switch(mMarginFlags & LAYOUT_DIRECTION_MASK) {
                case View.LAYOUT_DIRECTION_RTL:
                    return rightMargin;
                case View.LAYOUT_DIRECTION_LTR:
                default:
                    return leftMargin;
            }
        }

        Sets the relative end margin. Margin values should be positive.
Params: end – the end margin size
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginEnd/**
         * Sets the relative end margin. Margin values should be positive.
         *
         * @param end the end margin size
         *
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginEnd
         */
        public void setMarginEnd(int end) {
            endMargin = end;
            mMarginFlags |= NEED_RESOLUTION_MASK;
        }

        Returns the end margin in pixels.
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginEnd
Returns: the end margin in pixels./**
         * Returns the end margin in pixels.
         *
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginEnd
         *
         * @return the end margin in pixels.
         */
        public int getMarginEnd() {
            if (endMargin != DEFAULT_MARGIN_RELATIVE) return endMargin;
            if ((mMarginFlags & NEED_RESOLUTION_MASK) == NEED_RESOLUTION_MASK) {
                doResolveMargins();
            }
            switch(mMarginFlags & LAYOUT_DIRECTION_MASK) {
                case View.LAYOUT_DIRECTION_RTL:
                    return leftMargin;
                case View.LAYOUT_DIRECTION_LTR:
                default:
                    return rightMargin;
            }
        }

        Check if margins are relative.
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginStart
@attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginEnd
Returns: true if either marginStart or marginEnd has been set./**
         * Check if margins are relative.
         *
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginStart
         * @attr ref android.R.styleable#ViewGroup_MarginLayout_layout_marginEnd
         *
         * @return true if either marginStart or marginEnd has been set.
         */
        public boolean isMarginRelative() {
            return (startMargin != DEFAULT_MARGIN_RELATIVE || endMargin != DEFAULT_MARGIN_RELATIVE);
        }

        Set the layout direction
Params: layoutDirection – the layout direction. Should be either View.LAYOUT_DIRECTION_LTR or View.LAYOUT_DIRECTION_RTL./**
         * Set the layout direction
         * @param layoutDirection the layout direction.
         *        Should be either {@link View#LAYOUT_DIRECTION_LTR}
         *                     or {@link View#LAYOUT_DIRECTION_RTL}.
         */
        public void setLayoutDirection(int layoutDirection) {
            if (layoutDirection != View.LAYOUT_DIRECTION_LTR &&
                    layoutDirection != View.LAYOUT_DIRECTION_RTL) return;
            if (layoutDirection != (mMarginFlags & LAYOUT_DIRECTION_MASK)) {
                mMarginFlags &= ~LAYOUT_DIRECTION_MASK;
                mMarginFlags |= (layoutDirection & LAYOUT_DIRECTION_MASK);
                if (isMarginRelative()) {
                    mMarginFlags |= NEED_RESOLUTION_MASK;
                } else {
                    mMarginFlags &= ~NEED_RESOLUTION_MASK;
                }
            }
        }

        Retuns the layout direction. Can be either View.LAYOUT_DIRECTION_LTR or View.LAYOUT_DIRECTION_RTL. 
Returns: the layout direction./**
         * Retuns the layout direction. Can be either {@link View#LAYOUT_DIRECTION_LTR} or
         * {@link View#LAYOUT_DIRECTION_RTL}.
         *
         * @return the layout direction.
         */
        public int getLayoutDirection() {
            return (mMarginFlags & LAYOUT_DIRECTION_MASK);
        }

        This will be called by View.requestLayout(). Left and Right margins may be overridden depending on layout direction. /**
         * This will be called by {@link android.view.View#requestLayout()}. Left and Right margins
         * may be overridden depending on layout direction.
         */
        @Override
        public void resolveLayoutDirection(int layoutDirection) {
            setLayoutDirection(layoutDirection);

            // No relative margin or pre JB-MR1 case or no need to resolve, just dont do anything
            // Will use the left and right margins if no relative margin is defined.
            if (!isMarginRelative() ||
                    (mMarginFlags & NEED_RESOLUTION_MASK) != NEED_RESOLUTION_MASK) return;

            // Proceed with resolution
            doResolveMargins();
        }

        private void doResolveMargins() {
            if ((mMarginFlags & RTL_COMPATIBILITY_MODE_MASK) == RTL_COMPATIBILITY_MODE_MASK) {
                // if left or right margins are not defined and if we have some start or end margin
                // defined then use those start and end margins.
                if ((mMarginFlags & LEFT_MARGIN_UNDEFINED_MASK) == LEFT_MARGIN_UNDEFINED_MASK
                        && startMargin > DEFAULT_MARGIN_RELATIVE) {
                    leftMargin = startMargin;
                }
                if ((mMarginFlags & RIGHT_MARGIN_UNDEFINED_MASK) == RIGHT_MARGIN_UNDEFINED_MASK
                        && endMargin > DEFAULT_MARGIN_RELATIVE) {
                    rightMargin = endMargin;
                }
            } else {
                // We have some relative margins (either the start one or the end one or both). So use
                // them and override what has been defined for left and right margins. If either start
                // or end margin is not defined, just set it to default "0".
                switch(mMarginFlags & LAYOUT_DIRECTION_MASK) {
                    case View.LAYOUT_DIRECTION_RTL:
                        leftMargin = (endMargin > DEFAULT_MARGIN_RELATIVE) ?
                                endMargin : DEFAULT_MARGIN_RESOLVED;
                        rightMargin = (startMargin > DEFAULT_MARGIN_RELATIVE) ?
                                startMargin : DEFAULT_MARGIN_RESOLVED;
                        break;
                    case View.LAYOUT_DIRECTION_LTR:
                    default:
                        leftMargin = (startMargin > DEFAULT_MARGIN_RELATIVE) ?
                                startMargin : DEFAULT_MARGIN_RESOLVED;
                        rightMargin = (endMargin > DEFAULT_MARGIN_RELATIVE) ?
                                endMargin : DEFAULT_MARGIN_RESOLVED;
                        break;
                }
            }
            mMarginFlags &= ~NEED_RESOLUTION_MASK;
        }

        @hide /**
         * @hide
         */
        public boolean isLayoutRtl() {
            return ((mMarginFlags & LAYOUT_DIRECTION_MASK) == View.LAYOUT_DIRECTION_RTL);
        }

        @hide /**
         * @hide
         */
        @Override
        public void onDebugDraw(View view, Canvas canvas, Paint paint) {
            Insets oi = isLayoutModeOptical(view.mParent) ? view.getOpticalInsets() : Insets.NONE;

            fillDifference(canvas,
                    view.getLeft()   + oi.left,
                    view.getTop()    + oi.top,
                    view.getRight()  - oi.right,
                    view.getBottom() - oi.bottom,
                    leftMargin,
                    topMargin,
                    rightMargin,
                    bottomMargin,
                    paint);
        }

        @hide /** @hide */
        @Override
        protected void encodeProperties(@NonNull ViewHierarchyEncoder encoder) {
            super.encodeProperties(encoder);
            encoder.addProperty("leftMargin", leftMargin);
            encoder.addProperty("topMargin", topMargin);
            encoder.addProperty("rightMargin", rightMargin);
            encoder.addProperty("bottomMargin", bottomMargin);
            encoder.addProperty("startMargin", startMargin);
            encoder.addProperty("endMargin", endMargin);
        }
    }

    /* Describes a touched view and the ids of the pointers that it has captured.
     *
     * This code assumes that pointer ids are always in the range 0..31 such that
     * it can use a bitfield to track which pointer ids are present.
     * As it happens, the lower layers of the input dispatch pipeline also use the
     * same trick so the assumption should be safe here...
     */
    private static final class TouchTarget {
        private static final int MAX_RECYCLED = 32;
        private static final Object sRecycleLock = new Object[0];
        private static TouchTarget sRecycleBin;
        private static int sRecycledCount;

        public static final int ALL_POINTER_IDS = -1; // all ones

        // The touched child view.
        public View child;

        // The combined bit mask of pointer ids for all pointers captured by the target.
        public int pointerIdBits;

        // The next target in the target list.
        public TouchTarget next;

        private TouchTarget() {
        }

        public static TouchTarget obtain(@NonNull View child, int pointerIdBits) {
            if (child == null) {
                throw new IllegalArgumentException("child must be non-null");
            }

            final TouchTarget target;
            synchronized (sRecycleLock) {
                if (sRecycleBin == null) {
                    target = new TouchTarget();
                } else {
                    target = sRecycleBin;
                    sRecycleBin = target.next;
                     sRecycledCount--;
                    target.next = null;
                }
            }
            target.child = child;
            target.pointerIdBits = pointerIdBits;
            return target;
        }

        public void recycle() {
            if (child == null) {
                throw new IllegalStateException("already recycled once");
            }

            synchronized (sRecycleLock) {
                if (sRecycledCount < MAX_RECYCLED) {
                    next = sRecycleBin;
                    sRecycleBin = this;
                    sRecycledCount += 1;
                } else {
                    next = null;
                }
                child = null;
            }
        }
    }

    /* Describes a hovered view. */
    private static final class HoverTarget {
        private static final int MAX_RECYCLED = 32;
        private static final Object sRecycleLock = new Object[0];
        private static HoverTarget sRecycleBin;
        private static int sRecycledCount;

        // The hovered child view.
        public View child;

        // The next target in the target list.
        public HoverTarget next;

        private HoverTarget() {
        }

        public static HoverTarget obtain(@NonNull View child) {
            if (child == null) {
                throw new IllegalArgumentException("child must be non-null");
            }

            final HoverTarget target;
            synchronized (sRecycleLock) {
                if (sRecycleBin == null) {
                    target = new HoverTarget();
                } else {
                    target = sRecycleBin;
                    sRecycleBin = target.next;
                    sRecycledCount--;
                    target.next = null;
                }
            }
            target.child = child;
            return target;
        }

        public void recycle() {
            if (child == null) {
                throw new IllegalStateException("already recycled once");
            }

            synchronized (sRecycleLock) {
                if (sRecycledCount < MAX_RECYCLED) {
                    next = sRecycleBin;
                    sRecycleBin = this;
                    sRecycledCount += 1;
                } else {
                    next = null;
                }
                child = null;
            }
        }
    }

    Pooled class that to hold the children for autifill.
/**
     * Pooled class that to hold the children for autifill.
     */
    static class ChildListForAutoFill extends ArrayList<View> {
        private static final int MAX_POOL_SIZE = 32;

        private static final Pools.SimplePool<ChildListForAutoFill> sPool =
                new Pools.SimplePool<>(MAX_POOL_SIZE);

        public static ChildListForAutoFill obtain() {
            ChildListForAutoFill list = sPool.acquire();
            if (list == null) {
                list = new ChildListForAutoFill();
            }
            return list;
        }

        public void recycle() {
            clear();
            sPool.release(this);
        }
    }

    Pooled class that orderes the children of a ViewGroup from start
to end based on how they are laid out and the layout direction.
/**
     * Pooled class that orderes the children of a ViewGroup from start
     * to end based on how they are laid out and the layout direction.
     */
    static class ChildListForAccessibility {

        private static final int MAX_POOL_SIZE = 32;

        private static final SynchronizedPool<ChildListForAccessibility> sPool =
                new SynchronizedPool<ChildListForAccessibility>(MAX_POOL_SIZE);

        private final ArrayList<View> mChildren = new ArrayList<View>();

        private final ArrayList<ViewLocationHolder> mHolders = new ArrayList<ViewLocationHolder>();

        public static ChildListForAccessibility obtain(ViewGroup parent, boolean sort) {
            ChildListForAccessibility list = sPool.acquire();
            if (list == null) {
                list = new ChildListForAccessibility();
            }
            list.init(parent, sort);
            return list;
        }

        public void recycle() {
            clear();
            sPool.release(this);
        }

        public int getChildCount() {
            return mChildren.size();
        }

        public View getChildAt(int index) {
            return mChildren.get(index);
        }

        private void init(ViewGroup parent, boolean sort) {
            ArrayList<View> children = mChildren;
            final int childCount = parent.getChildCount();
            for (int i = 0; i < childCount; i++) {
                View child = parent.getChildAt(i);
                children.add(child);
            }
            if (sort) {
                ArrayList<ViewLocationHolder> holders = mHolders;
                for (int i = 0; i < childCount; i++) {
                    View child = children.get(i);
                    ViewLocationHolder holder = ViewLocationHolder.obtain(parent, child);
                    holders.add(holder);
                }
                sort(holders);
                for (int i = 0; i < childCount; i++) {
                    ViewLocationHolder holder = holders.get(i);
                    children.set(i, holder.mView);
                    holder.recycle();
                }
                holders.clear();
            }
        }

        private void sort(ArrayList<ViewLocationHolder> holders) {
            // This is gross but the least risky solution. The current comparison
            // strategy breaks transitivity but produces very good results. Coming
            // up with a new strategy requires time which we do not have, so ...
            try {
                ViewLocationHolder.setComparisonStrategy(
                        ViewLocationHolder.COMPARISON_STRATEGY_STRIPE);
                Collections.sort(holders);
            } catch (IllegalArgumentException iae) {
                // Note that in practice this occurs extremely rarely in a couple
                // of pathological cases.
                ViewLocationHolder.setComparisonStrategy(
                        ViewLocationHolder.COMPARISON_STRATEGY_LOCATION);
                Collections.sort(holders);
            }
        }

        private void clear() {
            mChildren.clear();
        }
    }

    Pooled class that holds a View and its location with respect to
a specified root. This enables sorting of views based on their
coordinates without recomputing the position relative to the root
on every comparison.
/**
     * Pooled class that holds a View and its location with respect to
     * a specified root. This enables sorting of views based on their
     * coordinates without recomputing the position relative to the root
     * on every comparison.
     */
    static class ViewLocationHolder implements Comparable<ViewLocationHolder> {

        private static final int MAX_POOL_SIZE = 32;

        private static final SynchronizedPool<ViewLocationHolder> sPool =
                new SynchronizedPool<ViewLocationHolder>(MAX_POOL_SIZE);

        public static final int COMPARISON_STRATEGY_STRIPE = 1;

        public static final int COMPARISON_STRATEGY_LOCATION = 2;

        private static int sComparisonStrategy = COMPARISON_STRATEGY_STRIPE;

        private final Rect mLocation = new Rect();

        private ViewGroup mRoot;

        public View mView;

        private int mLayoutDirection;

        public static ViewLocationHolder obtain(ViewGroup root, View view) {
            ViewLocationHolder holder = sPool.acquire();
            if (holder == null) {
                holder = new ViewLocationHolder();
            }
            holder.init(root, view);
            return holder;
        }

        public static void setComparisonStrategy(int strategy) {
            sComparisonStrategy = strategy;
        }

        public void recycle() {
            clear();
            sPool.release(this);
        }

        @Override
        public int compareTo(ViewLocationHolder another) {
            // This instance is greater than an invalid argument.
            if (another == null) {
                return 1;
            }

            int boundsResult = compareBoundsOfTree(this, another);
            if (boundsResult != 0) {
                return boundsResult;
            }

            // Just break the tie somehow. The accessibility ids are unique
            // and stable, hence this is deterministic tie breaking.
            return mView.getAccessibilityViewId() - another.mView.getAccessibilityViewId();
        }

        Compare two views based on their bounds. Use the bounds of their children to break ties.
Params: holder1 – Holder of first view to compare
holder2 – Holder of second view to compare. Must have the same root at holder1.
Returns: The compare result, with equality if no good comparison was found./**
         * Compare two views based on their bounds. Use the bounds of their children to break ties.
         *
         * @param holder1 Holder of first view to compare
         * @param holder2 Holder of second view to compare. Must have the same root at holder1.
         * @return The compare result, with equality if no good comparison was found.
         */
        private static int compareBoundsOfTree(
                ViewLocationHolder holder1, ViewLocationHolder holder2) {
            if (sComparisonStrategy == COMPARISON_STRATEGY_STRIPE) {
                // First is above second.
                if (holder1.mLocation.bottom - holder2.mLocation.top <= 0) {
                    return -1;
                }
                // First is below second.
                if (holder1.mLocation.top - holder2.mLocation.bottom >= 0) {
                    return 1;
                }
            }

            // We are ordering left-to-right, top-to-bottom.
            if (holder1.mLayoutDirection == LAYOUT_DIRECTION_LTR) {
                final int leftDifference = holder1.mLocation.left - holder2.mLocation.left;
                if (leftDifference != 0) {
                    return leftDifference;
                }
            } else { // RTL
                final int rightDifference = holder1.mLocation.right - holder2.mLocation.right;
                if (rightDifference != 0) {
                    return -rightDifference;
                }
            }
            // We are ordering left-to-right, top-to-bottom.
            final int topDifference = holder1.mLocation.top - holder2.mLocation.top;
            if (topDifference != 0) {
                return topDifference;
            }
            // Break tie by height.
            final int heightDiference = holder1.mLocation.height() - holder2.mLocation.height();
            if (heightDiference != 0) {
                return -heightDiference;
            }
            // Break tie by width.
            final int widthDifference = holder1.mLocation.width() - holder2.mLocation.width();
            if (widthDifference != 0) {
                return -widthDifference;
            }

            // Find a child of each view with different screen bounds.
            final Rect view1Bounds = new Rect();
            final Rect view2Bounds = new Rect();
            final Rect tempRect = new Rect();
            holder1.mView.getBoundsOnScreen(view1Bounds, true);
            holder2.mView.getBoundsOnScreen(view2Bounds, true);
            final View child1 = holder1.mView.findViewByPredicateTraversal((view) -> {
                view.getBoundsOnScreen(tempRect, true);
                return !tempRect.equals(view1Bounds);
            }, null);
            final View child2 = holder2.mView.findViewByPredicateTraversal((view) -> {
                view.getBoundsOnScreen(tempRect, true);
                return !tempRect.equals(view2Bounds);
            }, null);


            // Compare the children recursively
            if ((child1 != null) && (child2 != null)) {
                final ViewLocationHolder childHolder1 =
                        ViewLocationHolder.obtain(holder1.mRoot, child1);
                final ViewLocationHolder childHolder2 =
                        ViewLocationHolder.obtain(holder1.mRoot, child2);
                return compareBoundsOfTree(childHolder1, childHolder2);
            }

            // If only one has a child, use that one
            if (child1 != null) {
                return 1;
            }

            if (child2 != null) {
                return -1;
            }

            // Give up
            return 0;
        }

        private void init(ViewGroup root, View view) {
            Rect viewLocation = mLocation;
            view.getDrawingRect(viewLocation);
            root.offsetDescendantRectToMyCoords(view, viewLocation);
            mView = view;
            mRoot = root;
            mLayoutDirection = root.getLayoutDirection();
        }

        private void clear() {
            mView = null;
            mLocation.set(0, 0, 0, 0);
        }
    }

    private static void drawRect(Canvas canvas, Paint paint, int x1, int y1, int x2, int y2) {
        if (sDebugLines== null) {
            // TODO: This won't work with multiple UI threads in a single process
            sDebugLines = new float[16];
        }

        sDebugLines[0] = x1;
        sDebugLines[1] = y1;
        sDebugLines[2] = x2;
        sDebugLines[3] = y1;

        sDebugLines[4] = x2;
        sDebugLines[5] = y1;
        sDebugLines[6] = x2;
        sDebugLines[7] = y2;

        sDebugLines[8] = x2;
        sDebugLines[9] = y2;
        sDebugLines[10] = x1;
        sDebugLines[11] = y2;

        sDebugLines[12] = x1;
        sDebugLines[13] = y2;
        sDebugLines[14] = x1;
        sDebugLines[15] = y1;

        canvas.drawLines(sDebugLines, paint);
    }

    @hide /** @hide */
    @Override
    protected void encodeProperties(@NonNull ViewHierarchyEncoder encoder) {
        super.encodeProperties(encoder);

        encoder.addProperty("focus:descendantFocusability", getDescendantFocusability());
        encoder.addProperty("drawing:clipChildren", getClipChildren());
        encoder.addProperty("drawing:clipToPadding", getClipToPadding());
        encoder.addProperty("drawing:childrenDrawingOrderEnabled", isChildrenDrawingOrderEnabled());
        encoder.addProperty("drawing:persistentDrawingCache", getPersistentDrawingCache());

        int n = getChildCount();
        encoder.addProperty("meta:__childCount__", (short)n);
        for (int i = 0; i < n; i++) {
            encoder.addPropertyKey("meta:__child__" + i);
            getChildAt(i).encode(encoder);
        }
    }
}
@attr	ref android.R.styleable#ViewGroup_clipChildren
@attr	ref android.R.styleable#ViewGroup_clipToPadding
@attr	ref android.R.styleable#ViewGroup_layoutAnimation
@attr	ref android.R.styleable#ViewGroup_animationCache
@attr	ref android.R.styleable#ViewGroup_persistentDrawingCache
@attr	ref android.R.styleable#ViewGroup_alwaysDrawnWithCache
@attr	ref android.R.styleable#ViewGroup_addStatesFromChildren
@attr	ref android.R.styleable#ViewGroup_descendantFocusability
@attr	ref android.R.styleable#ViewGroup_animateLayoutChanges
@attr	ref android.R.styleable#ViewGroup_splitMotionEvents
@attr	ref android.R.styleable#ViewGroup_layoutMode
Params:	child – The child which requests sending the event. event – The event to be sent.
See Also:	requestSendAccessibilityEvent(View, AccessibilityEvent)
Returns:	True if the event should be sent.
See Also:	Note: Called from the default `AccessibilityDelegate`.
@hide
Params:	child – The view whose visibility has changed oldVisibility – The previous visibility value (GONE, INVISIBLE, or VISIBLE). newVisibility – The new visibility value (GONE, INVISIBLE, or VISIBLE).
@hide
Params:	event – The motion event that describes the hover.
Returns:	True if the view group would like to intercept the hover event and prevent its children from receiving it.
Params:	event – The event to send. child – The view to send the event to.
Returns:	`true` if the child handled the event.
Params:	event – The event to transform. child – The view whose coordinate space is to be used.
Returns:	A copy of the the given MotionEvent, transformed into the given View's coordinate space.
Params:	split – `true` to allow MotionEvents to be split and dispatched to multiple child views. `false` to only allow one child view to be the target of any MotionEvent received by this ViewGroup.
@attr	ref android.R.styleable#ViewGroup_splitMotionEvents
Params:	isTransitionGroup – Whether or not the ViewGroup should be treated as a unit in Activity transitions. If false, the ViewGroup won't transition, only its children. If true, the entire ViewGroup will transition together.
See Also:	ActivityOptions.makeSceneTransitionAnimation(Activity, Pair<View,String>[])
Params:	ev – The motion event being dispatched down the hierarchy.
Returns:	Return true to steal motion events from the children and have them dispatched to this ViewGroup through onTouchEvent(). The current target will receive an ACTION_CANCEL event, and no further messages will be delivered here.
Params:	direction – One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and FOCUS_RIGHT previouslyFocusedRect – The rectangle (in this View's coordinate system) to give a finer grained hint about where focus is coming from. May be null if there is no hint.
Returns:	Whether focus was taken.
Params:	target – The target view dispatching this action action – Action being performed; see `AccessibilityNodeInfo` args – Optional action arguments
Returns:	false by default. Subclasses should return true if they handle the event.
See Also:	ViewGroupOverlay
Returns:	The ViewGroupOverlay object for this view.
Params:	i – The current iteration.
See Also:	setChildrenDrawingOrderEnabled(boolean) isChildrenDrawingOrderEnabled()
Returns:	The index of the child to draw this iteration.
Params:	canvas – The canvas on which to draw the child child – Who to draw drawingTime – The time at which draw is occurring
Returns:	True if an invalidate() was issued
See Also:	setClipChildren(boolean)
Returns:	True if the group's children will be clipped to their bounds, false otherwise.
Params:	clipChildren – true to clip children to their bounds, false otherwise
@attr	ref android.R.styleable#ViewGroup_clipChildren
Params:	clipToPadding – true to clip children to the padding of the group, and resize (but not clip) any EdgeEffect to the padded region. False otherwise.
@attr	ref android.R.styleable#ViewGroup_clipToPadding
Returns:	true if this ViewGroup clips children to its padding and resizes (but doesn't clip) any EdgeEffect to the padded region, false otherwise.
@attr	ref android.R.styleable#ViewGroup_clipToPadding
Params:	x – hotspot x coordinate y – hotspot y coordinate
See Also:	View.drawableHotspotChanged(float, float)
/

android/ android-9.0.0_r35/ android/view/ViewGroup.java

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