/*
 * Copyright (C) 2008 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 android.content.Context;
import android.graphics.Rect;
import android.graphics.Region;
import android.os.Build;
import android.util.Log;

import java.util.ArrayList;
import java.util.concurrent.CopyOnWriteArrayList;

A view tree observer is used to register listeners that can be notified of global changes in the view tree. Such global events include, but are not limited to, layout of the whole tree, beginning of the drawing pass, touch mode change.... A ViewTreeObserver should never be instantiated by applications as it is provided by the views hierarchy. Refer to View.getViewTreeObserver() for more information. /**
 * A view tree observer is used to register listeners that can be notified of global
 * changes in the view tree. Such global events include, but are not limited to,
 * layout of the whole tree, beginning of the drawing pass, touch mode change....
 *
 * A ViewTreeObserver should never be instantiated by applications as it is provided
 * by the views hierarchy. Refer to {@link android.view.View#getViewTreeObserver()}
 * for more information.
 */
public final class ViewTreeObserver {
    // Recursive listeners use CopyOnWriteArrayList
    private CopyOnWriteArrayList<OnWindowFocusChangeListener> mOnWindowFocusListeners;
    private CopyOnWriteArrayList<OnWindowAttachListener> mOnWindowAttachListeners;
    private CopyOnWriteArrayList<OnGlobalFocusChangeListener> mOnGlobalFocusListeners;
    private CopyOnWriteArrayList<OnTouchModeChangeListener> mOnTouchModeChangeListeners;
    private CopyOnWriteArrayList<OnEnterAnimationCompleteListener>
            mOnEnterAnimationCompleteListeners;

    // Non-recursive listeners use CopyOnWriteArray
    // Any listener invoked from ViewRootImpl.performTraversals() should not be recursive
    private CopyOnWriteArray<OnGlobalLayoutListener> mOnGlobalLayoutListeners;
    private CopyOnWriteArray<OnComputeInternalInsetsListener> mOnComputeInternalInsetsListeners;
    private CopyOnWriteArray<OnScrollChangedListener> mOnScrollChangedListeners;
    private CopyOnWriteArray<OnPreDrawListener> mOnPreDrawListeners;
    private CopyOnWriteArray<OnWindowShownListener> mOnWindowShownListeners;

    // These listeners cannot be mutated during dispatch
    private boolean mInDispatchOnDraw;
    private ArrayList<OnDrawListener> mOnDrawListeners;
    private static boolean sIllegalOnDrawModificationIsFatal;

    
Remains false until #dispatchOnWindowShown() is called. If a listener registers after
that the listener will be immediately called. /** Remains false until #dispatchOnWindowShown() is called. If a listener registers after
     * that the listener will be immediately called. */
    private boolean mWindowShown;

    private boolean mAlive = true;

    
Interface definition for a callback to be invoked when the view hierarchy is
attached to and detached from its window.
/**
     * Interface definition for a callback to be invoked when the view hierarchy is
     * attached to and detached from its window.
     */
    public interface OnWindowAttachListener {
        
Callback method to be invoked when the view hierarchy is attached to a window
/**
         * Callback method to be invoked when the view hierarchy is attached to a window
         */
        public void onWindowAttached();

        
Callback method to be invoked when the view hierarchy is detached from a window
/**
         * Callback method to be invoked when the view hierarchy is detached from a window
         */
        public void onWindowDetached();
    }

    
Interface definition for a callback to be invoked when the view hierarchy's window
focus state changes.
/**
     * Interface definition for a callback to be invoked when the view hierarchy's window
     * focus state changes.
     */
    public interface OnWindowFocusChangeListener {
        
Callback method to be invoked when the window focus changes in the view tree.
Params:
hasFocus – Set to true if the window is gaining focus, false if it is
losing focus./**
         * Callback method to be invoked when the window focus changes in the view tree.
         *
         * @param hasFocus Set to true if the window is gaining focus, false if it is
         * losing focus.
         */
        public void onWindowFocusChanged(boolean hasFocus);
    }

    
Interface definition for a callback to be invoked when the focus state within
the view tree changes.
/**
     * Interface definition for a callback to be invoked when the focus state within
     * the view tree changes.
     */
    public interface OnGlobalFocusChangeListener {
        
Callback method to be invoked when the focus changes in the view tree. When
the view tree transitions from touch mode to non-touch mode, oldFocus is null.
When the view tree transitions from non-touch mode to touch mode, newFocus is
null. When focus changes in non-touch mode (without transition from or to
touch mode) either oldFocus or newFocus can be null.
Params:
oldFocus – The previously focused view, if any.
newFocus – The newly focused View, if any./**
         * Callback method to be invoked when the focus changes in the view tree. When
         * the view tree transitions from touch mode to non-touch mode, oldFocus is null.
         * When the view tree transitions from non-touch mode to touch mode, newFocus is
         * null. When focus changes in non-touch mode (without transition from or to
         * touch mode) either oldFocus or newFocus can be null.
         *
         * @param oldFocus The previously focused view, if any.
         * @param newFocus The newly focused View, if any.
         */
        public void onGlobalFocusChanged(View oldFocus, View newFocus);
    }

    
Interface definition for a callback to be invoked when the global layout state
or the visibility of views within the view tree changes.
/**
     * Interface definition for a callback to be invoked when the global layout state
     * or the visibility of views within the view tree changes.
     */
    public interface OnGlobalLayoutListener {
        
Callback method to be invoked when the global layout state or the visibility of views
within the view tree changes
/**
         * Callback method to be invoked when the global layout state or the visibility of views
         * within the view tree changes
         */
        public void onGlobalLayout();
    }

    
Interface definition for a callback to be invoked when the view tree is about to be drawn.
/**
     * Interface definition for a callback to be invoked when the view tree is about to be drawn.
     */
    public interface OnPreDrawListener {
        
Callback method to be invoked when the view tree is about to be drawn. At this point, all
views in the tree have been measured and given a frame. Clients can use this to adjust
their scroll bounds or even to request a new layout before drawing occurs.
See Also:
View.onMeasure
View.onLayout
View.onDraw
Returns:
Return true to proceed with the current drawing pass, or false to cancel./**
         * Callback method to be invoked when the view tree is about to be drawn. At this point, all
         * views in the tree have been measured and given a frame. Clients can use this to adjust
         * their scroll bounds or even to request a new layout before drawing occurs.
         *
         * @return Return true to proceed with the current drawing pass, or false to cancel.
         *
         * @see android.view.View#onMeasure
         * @see android.view.View#onLayout
         * @see android.view.View#onDraw
         */
        public boolean onPreDraw();
    }

    
Interface definition for a callback to be invoked when the view tree is about to be drawn.
/**
     * Interface definition for a callback to be invoked when the view tree is about to be drawn.
     */
    public interface OnDrawListener {
        
Callback method to be invoked when the view tree is about to be drawn. At this point,
views cannot be modified in any way.
Unlike with OnPreDrawListener, this method cannot be used to cancel the current drawing pass.
An OnDrawListener listener cannot be added or removed
from this method.
See Also:
View.onMeasure
View.onLayout
View.onDraw/**
         * <p>Callback method to be invoked when the view tree is about to be drawn. At this point,
         * views cannot be modified in any way.</p>
         * 
         * <p>Unlike with {@link OnPreDrawListener}, this method cannot be used to cancel the
         * current drawing pass.</p>
         * 
         * <p>An {@link OnDrawListener} listener <strong>cannot be added or removed</strong>
         * from this method.</p>
         *
         * @see android.view.View#onMeasure
         * @see android.view.View#onLayout
         * @see android.view.View#onDraw
         */
        public void onDraw();
    }

    
Interface definition for a callback to be invoked when the touch mode changes.
/**
     * Interface definition for a callback to be invoked when the touch mode changes.
     */
    public interface OnTouchModeChangeListener {
        
Callback method to be invoked when the touch mode changes.
Params:
isInTouchMode – True if the view hierarchy is now in touch mode, false  otherwise./**
         * Callback method to be invoked when the touch mode changes.
         *
         * @param isInTouchMode True if the view hierarchy is now in touch mode, false  otherwise.
         */
        public void onTouchModeChanged(boolean isInTouchMode);
    }

    
Interface definition for a callback to be invoked when
something in the view tree has been scrolled.
/**
     * Interface definition for a callback to be invoked when
     * something in the view tree has been scrolled.
     */
    public interface OnScrollChangedListener {
        
Callback method to be invoked when something in the view tree
has been scrolled.
/**
         * Callback method to be invoked when something in the view tree
         * has been scrolled.
         */
        public void onScrollChanged();
    }

    
Interface definition for a callback noting when a system window has been displayed.
This is only used for non-Activity windows. Activity windows can use
Activity.onEnterAnimationComplete() to get the same signal.
@hide
/**
     * Interface definition for a callback noting when a system window has been displayed.
     * This is only used for non-Activity windows. Activity windows can use
     * Activity.onEnterAnimationComplete() to get the same signal.
     * @hide
     */
    public interface OnWindowShownListener {
        
Callback method to be invoked when a non-activity window is fully shown.
/**
         * Callback method to be invoked when a non-activity window is fully shown.
         */
        void onWindowShown();
    }

    
Parameters used with OnComputeInternalInsetsListener.
We are not yet ready to commit to this API and support it, so
@hide
/**
     * Parameters used with OnComputeInternalInsetsListener.
     * 
     * We are not yet ready to commit to this API and support it, so
     * @hide
     */
    public final static class InternalInsetsInfo {
        
Offsets from the frame of the window at which the content of
windows behind it should be placed.
/**
         * Offsets from the frame of the window at which the content of
         * windows behind it should be placed.
         */
        public final Rect contentInsets = new Rect();

        
Offsets from the frame of the window at which windows behind it
are visible.
/**
         * Offsets from the frame of the window at which windows behind it
         * are visible.
         */
        public final Rect visibleInsets = new Rect();

        
Touchable region defined relative to the origin of the frame of the window. Only used when setTouchableInsets(int) is called with the option TOUCHABLE_INSETS_REGION. /**
         * Touchable region defined relative to the origin of the frame of the window.
         * Only used when {@link #setTouchableInsets(int)} is called with
         * the option {@link #TOUCHABLE_INSETS_REGION}.
         */
        public final Region touchableRegion = new Region();

        
Option for setTouchableInsets(int): the entire window frame can be touched. /**
         * Option for {@link #setTouchableInsets(int)}: the entire window frame
         * can be touched.
         */
        public static final int TOUCHABLE_INSETS_FRAME = 0;

        
Option for setTouchableInsets(int): the area inside of the content insets can be touched. /**
         * Option for {@link #setTouchableInsets(int)}: the area inside of
         * the content insets can be touched.
         */
        public static final int TOUCHABLE_INSETS_CONTENT = 1;

        
Option for setTouchableInsets(int): the area inside of the visible insets can be touched. /**
         * Option for {@link #setTouchableInsets(int)}: the area inside of
         * the visible insets can be touched.
         */
        public static final int TOUCHABLE_INSETS_VISIBLE = 2;

        
Option for setTouchableInsets(int): the area inside of the provided touchable region in touchableRegion can be touched. /**
         * Option for {@link #setTouchableInsets(int)}: the area inside of
         * the provided touchable region in {@link #touchableRegion} can be touched.
         */
        public static final int TOUCHABLE_INSETS_REGION = 3;

        
Set which parts of the window can be touched: either TOUCHABLE_INSETS_FRAME, TOUCHABLE_INSETS_CONTENT, TOUCHABLE_INSETS_VISIBLE, or TOUCHABLE_INSETS_REGION. /**
         * Set which parts of the window can be touched: either
         * {@link #TOUCHABLE_INSETS_FRAME}, {@link #TOUCHABLE_INSETS_CONTENT},
         * {@link #TOUCHABLE_INSETS_VISIBLE}, or {@link #TOUCHABLE_INSETS_REGION}.
         */
        public void setTouchableInsets(int val) {
            mTouchableInsets = val;
        }

        int mTouchableInsets;

        void reset() {
            contentInsets.setEmpty();
            visibleInsets.setEmpty();
            touchableRegion.setEmpty();
            mTouchableInsets = TOUCHABLE_INSETS_FRAME;
        }

        boolean isEmpty() {
            return contentInsets.isEmpty()
                    && visibleInsets.isEmpty()
                    && touchableRegion.isEmpty()
                    && mTouchableInsets == TOUCHABLE_INSETS_FRAME;
        }

        @Override
        public int hashCode() {
            int result = contentInsets.hashCode();
            result = 31 * result + visibleInsets.hashCode();
            result = 31 * result + touchableRegion.hashCode();
            result = 31 * result + mTouchableInsets;
            return result;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;

            InternalInsetsInfo other = (InternalInsetsInfo)o;
            return mTouchableInsets == other.mTouchableInsets &&
                    contentInsets.equals(other.contentInsets) &&
                    visibleInsets.equals(other.visibleInsets) &&
                    touchableRegion.equals(other.touchableRegion);
        }

        void set(InternalInsetsInfo other) {
            contentInsets.set(other.contentInsets);
            visibleInsets.set(other.visibleInsets);
            touchableRegion.set(other.touchableRegion);
            mTouchableInsets = other.mTouchableInsets;
        }
    }

    
Interface definition for a callback to be invoked when layout has
completed and the client can compute its interior insets.
We are not yet ready to commit to this API and support it, so
@hide
/**
     * Interface definition for a callback to be invoked when layout has
     * completed and the client can compute its interior insets.
     * 
     * We are not yet ready to commit to this API and support it, so
     * @hide
     */
    public interface OnComputeInternalInsetsListener {
        
Callback method to be invoked when layout has completed and the
client can compute its interior insets.
Params:
inoutInfo – Should be filled in by the implementation with
the information about the insets of the window.  This is called
with whatever values the previous OnComputeInternalInsetsListener
returned, if there are multiple such listeners in the window./**
         * Callback method to be invoked when layout has completed and the
         * client can compute its interior insets.
         *
         * @param inoutInfo Should be filled in by the implementation with
         * the information about the insets of the window.  This is called
         * with whatever values the previous OnComputeInternalInsetsListener
         * returned, if there are multiple such listeners in the window.
         */
        public void onComputeInternalInsets(InternalInsetsInfo inoutInfo);
    }

    
@hide
/**
     * @hide
     */
    public interface OnEnterAnimationCompleteListener {
        public void onEnterAnimationComplete();
    }

    
Creates a new ViewTreeObserver. This constructor should not be called
/**
     * Creates a new ViewTreeObserver. This constructor should not be called
     */
    ViewTreeObserver(Context context) {
        sIllegalOnDrawModificationIsFatal =
                context.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.O;
    }

    
Merges all the listeners registered on the specified observer with the listeners registered on this object. After this method is invoked, the specified observer will return false in isAlive() and should not be used anymore. 
Params:
observer – The ViewTreeObserver whose listeners must be added to this observer/**
     * Merges all the listeners registered on the specified observer with the listeners
     * registered on this object. After this method is invoked, the specified observer
     * will return false in {@link #isAlive()} and should not be used anymore.
     *
     * @param observer The ViewTreeObserver whose listeners must be added to this observer
     */
    void merge(ViewTreeObserver observer) {
        if (observer.mOnWindowAttachListeners != null) {
            if (mOnWindowAttachListeners != null) {
                mOnWindowAttachListeners.addAll(observer.mOnWindowAttachListeners);
            } else {
                mOnWindowAttachListeners = observer.mOnWindowAttachListeners;
            }
        }

        if (observer.mOnWindowFocusListeners != null) {
            if (mOnWindowFocusListeners != null) {
                mOnWindowFocusListeners.addAll(observer.mOnWindowFocusListeners);
            } else {
                mOnWindowFocusListeners = observer.mOnWindowFocusListeners;
            }
        }

        if (observer.mOnGlobalFocusListeners != null) {
            if (mOnGlobalFocusListeners != null) {
                mOnGlobalFocusListeners.addAll(observer.mOnGlobalFocusListeners);
            } else {
                mOnGlobalFocusListeners = observer.mOnGlobalFocusListeners;
            }
        }

        if (observer.mOnGlobalLayoutListeners != null) {
            if (mOnGlobalLayoutListeners != null) {
                mOnGlobalLayoutListeners.addAll(observer.mOnGlobalLayoutListeners);
            } else {
                mOnGlobalLayoutListeners = observer.mOnGlobalLayoutListeners;
            }
        }

        if (observer.mOnPreDrawListeners != null) {
            if (mOnPreDrawListeners != null) {
                mOnPreDrawListeners.addAll(observer.mOnPreDrawListeners);
            } else {
                mOnPreDrawListeners = observer.mOnPreDrawListeners;
            }
        }

        if (observer.mOnDrawListeners != null) {
            if (mOnDrawListeners != null) {
                mOnDrawListeners.addAll(observer.mOnDrawListeners);
            } else {
                mOnDrawListeners = observer.mOnDrawListeners;
            }
        }

        if (observer.mOnTouchModeChangeListeners != null) {
            if (mOnTouchModeChangeListeners != null) {
                mOnTouchModeChangeListeners.addAll(observer.mOnTouchModeChangeListeners);
            } else {
                mOnTouchModeChangeListeners = observer.mOnTouchModeChangeListeners;
            }
        }

        if (observer.mOnComputeInternalInsetsListeners != null) {
            if (mOnComputeInternalInsetsListeners != null) {
                mOnComputeInternalInsetsListeners.addAll(observer.mOnComputeInternalInsetsListeners);
            } else {
                mOnComputeInternalInsetsListeners = observer.mOnComputeInternalInsetsListeners;
            }
        }

        if (observer.mOnScrollChangedListeners != null) {
            if (mOnScrollChangedListeners != null) {
                mOnScrollChangedListeners.addAll(observer.mOnScrollChangedListeners);
            } else {
                mOnScrollChangedListeners = observer.mOnScrollChangedListeners;
            }
        }

        if (observer.mOnWindowShownListeners != null) {
            if (mOnWindowShownListeners != null) {
                mOnWindowShownListeners.addAll(observer.mOnWindowShownListeners);
            } else {
                mOnWindowShownListeners = observer.mOnWindowShownListeners;
            }
        }

        observer.kill();
    }

    
Register a callback to be invoked when the view hierarchy is attached to a window.
Params:
listener – The callback to add
Throws:
IllegalStateException – If isAlive() returns false/**
     * Register a callback to be invoked when the view hierarchy is attached to a window.
     *
     * @param listener The callback to add
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     */
    public void addOnWindowAttachListener(OnWindowAttachListener listener) {
        checkIsAlive();

        if (mOnWindowAttachListeners == null) {
            mOnWindowAttachListeners
                    = new CopyOnWriteArrayList<OnWindowAttachListener>();
        }

        mOnWindowAttachListeners.add(listener);
    }

    
Remove a previously installed window attach callback.
Params:
victim – The callback to remove
Throws:
IllegalStateException – If isAlive() returns false
See Also:
addOnWindowAttachListener(OnWindowAttachListener)/**
     * Remove a previously installed window attach callback.
     *
     * @param victim The callback to remove
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     *
     * @see #addOnWindowAttachListener(android.view.ViewTreeObserver.OnWindowAttachListener)
     */
    public void removeOnWindowAttachListener(OnWindowAttachListener victim) {
        checkIsAlive();
        if (mOnWindowAttachListeners == null) {
            return;
        }
        mOnWindowAttachListeners.remove(victim);
    }

    
Register a callback to be invoked when the window focus state within the view tree changes.
Params:
listener – The callback to add
Throws:
IllegalStateException – If isAlive() returns false/**
     * Register a callback to be invoked when the window focus state within the view tree changes.
     *
     * @param listener The callback to add
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     */
    public void addOnWindowFocusChangeListener(OnWindowFocusChangeListener listener) {
        checkIsAlive();

        if (mOnWindowFocusListeners == null) {
            mOnWindowFocusListeners
                    = new CopyOnWriteArrayList<OnWindowFocusChangeListener>();
        }

        mOnWindowFocusListeners.add(listener);
    }

    
Remove a previously installed window focus change callback.
Params:
victim – The callback to remove
Throws:
IllegalStateException – If isAlive() returns false
See Also:
addOnWindowFocusChangeListener(OnWindowFocusChangeListener)/**
     * Remove a previously installed window focus change callback.
     *
     * @param victim The callback to remove
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     *
     * @see #addOnWindowFocusChangeListener(android.view.ViewTreeObserver.OnWindowFocusChangeListener)
     */
    public void removeOnWindowFocusChangeListener(OnWindowFocusChangeListener victim) {
        checkIsAlive();
        if (mOnWindowFocusListeners == null) {
            return;
        }
        mOnWindowFocusListeners.remove(victim);
    }

    
Register a callback to be invoked when the focus state within the view tree changes.
Params:
listener – The callback to add
Throws:
IllegalStateException – If isAlive() returns false/**
     * Register a callback to be invoked when the focus state within the view tree changes.
     *
     * @param listener The callback to add
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     */
    public void addOnGlobalFocusChangeListener(OnGlobalFocusChangeListener listener) {
        checkIsAlive();

        if (mOnGlobalFocusListeners == null) {
            mOnGlobalFocusListeners = new CopyOnWriteArrayList<OnGlobalFocusChangeListener>();
        }

        mOnGlobalFocusListeners.add(listener);
    }

    
Remove a previously installed focus change callback.
Params:
victim – The callback to remove
Throws:
IllegalStateException – If isAlive() returns false
See Also:
addOnGlobalFocusChangeListener(OnGlobalFocusChangeListener)/**
     * Remove a previously installed focus change callback.
     *
     * @param victim The callback to remove
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     *
     * @see #addOnGlobalFocusChangeListener(OnGlobalFocusChangeListener)
     */
    public void removeOnGlobalFocusChangeListener(OnGlobalFocusChangeListener victim) {
        checkIsAlive();
        if (mOnGlobalFocusListeners == null) {
            return;
        }
        mOnGlobalFocusListeners.remove(victim);
    }

    
Register a callback to be invoked when the global layout state or the visibility of views
within the view tree changes
Params:
listener – The callback to add
Throws:
IllegalStateException – If isAlive() returns false/**
     * Register a callback to be invoked when the global layout state or the visibility of views
     * within the view tree changes
     *
     * @param listener The callback to add
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     */
    public void addOnGlobalLayoutListener(OnGlobalLayoutListener listener) {
        checkIsAlive();

        if (mOnGlobalLayoutListeners == null) {
            mOnGlobalLayoutListeners = new CopyOnWriteArray<OnGlobalLayoutListener>();
        }

        mOnGlobalLayoutListeners.add(listener);
    }

    
Remove a previously installed global layout callback
Params:
victim – The callback to remove
Throws:
IllegalStateException – If isAlive() returns false
See Also:
addOnGlobalLayoutListener(OnGlobalLayoutListener)
Deprecated:
Use #removeOnGlobalLayoutListener instead/**
     * Remove a previously installed global layout callback
     *
     * @param victim The callback to remove
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     * 
     * @deprecated Use #removeOnGlobalLayoutListener instead
     *
     * @see #addOnGlobalLayoutListener(OnGlobalLayoutListener)
     */
    @Deprecated
    public void removeGlobalOnLayoutListener(OnGlobalLayoutListener victim) {
        removeOnGlobalLayoutListener(victim);
    }

    
Remove a previously installed global layout callback
Params:
victim – The callback to remove
Throws:
IllegalStateException – If isAlive() returns false
See Also:
addOnGlobalLayoutListener(OnGlobalLayoutListener)/**
     * Remove a previously installed global layout callback
     *
     * @param victim The callback to remove
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     * 
     * @see #addOnGlobalLayoutListener(OnGlobalLayoutListener)
     */
    public void removeOnGlobalLayoutListener(OnGlobalLayoutListener victim) {
        checkIsAlive();
        if (mOnGlobalLayoutListeners == null) {
            return;
        }
        mOnGlobalLayoutListeners.remove(victim);
    }

    
Register a callback to be invoked when the view tree is about to be drawn
Params:
listener – The callback to add
Throws:
IllegalStateException – If isAlive() returns false/**
     * Register a callback to be invoked when the view tree is about to be drawn
     *
     * @param listener The callback to add
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     */
    public void addOnPreDrawListener(OnPreDrawListener listener) {
        checkIsAlive();

        if (mOnPreDrawListeners == null) {
            mOnPreDrawListeners = new CopyOnWriteArray<OnPreDrawListener>();
        }

        mOnPreDrawListeners.add(listener);
    }

    
Remove a previously installed pre-draw callback
Params:
victim – The callback to remove
Throws:
IllegalStateException – If isAlive() returns false
See Also:
addOnPreDrawListener(OnPreDrawListener)/**
     * Remove a previously installed pre-draw callback
     *
     * @param victim The callback to remove
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     *
     * @see #addOnPreDrawListener(OnPreDrawListener)
     */
    public void removeOnPreDrawListener(OnPreDrawListener victim) {
        checkIsAlive();
        if (mOnPreDrawListeners == null) {
            return;
        }
        mOnPreDrawListeners.remove(victim);
    }

    
Register a callback to be invoked when the view tree window has been shown
Params:
listener – The callback to add
Throws:
IllegalStateException – If isAlive() returns false
@hide
/**
     * Register a callback to be invoked when the view tree window has been shown
     *
     * @param listener The callback to add
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     * @hide
     */
    public void addOnWindowShownListener(OnWindowShownListener listener) {
        checkIsAlive();

        if (mOnWindowShownListeners == null) {
            mOnWindowShownListeners = new CopyOnWriteArray<OnWindowShownListener>();
        }

        mOnWindowShownListeners.add(listener);
        if (mWindowShown) {
            listener.onWindowShown();
        }
    }

    
Remove a previously installed window shown callback
Params:
victim – The callback to remove
Throws:
IllegalStateException – If isAlive() returns false
See Also:
addOnWindowShownListener(OnWindowShownListener)
@hide
/**
     * Remove a previously installed window shown callback
     *
     * @param victim The callback to remove
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     *
     * @see #addOnWindowShownListener(OnWindowShownListener)
     * @hide
     */
    public void removeOnWindowShownListener(OnWindowShownListener victim) {
        checkIsAlive();
        if (mOnWindowShownListeners == null) {
            return;
        }
        mOnWindowShownListeners.remove(victim);
    }

    
Register a callback to be invoked when the view tree is about to be drawn.
Note: this method cannot be invoked from OnDrawListener.onDraw().
Params:
listener – The callback to add
Throws:
IllegalStateException – If isAlive() returns false/**
     * <p>Register a callback to be invoked when the view tree is about to be drawn.</p>
     * <p><strong>Note:</strong> this method <strong>cannot</strong> be invoked from
     * {@link android.view.ViewTreeObserver.OnDrawListener#onDraw()}.</p>
     *
     * @param listener The callback to add
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     */
    public void addOnDrawListener(OnDrawListener listener) {
        checkIsAlive();

        if (mOnDrawListeners == null) {
            mOnDrawListeners = new ArrayList<OnDrawListener>();
        }

        if (mInDispatchOnDraw) {
            IllegalStateException ex = new IllegalStateException(
                    "Cannot call addOnDrawListener inside of onDraw");
            if (sIllegalOnDrawModificationIsFatal) {
                throw ex;
            } else {
                Log.e("ViewTreeObserver", ex.getMessage(), ex);
            }
        }
        mOnDrawListeners.add(listener);
    }

    
Remove a previously installed pre-draw callback.
Note: this method cannot be invoked from OnDrawListener.onDraw().
Params:
victim – The callback to remove
Throws:
IllegalStateException – If isAlive() returns false
See Also:
addOnDrawListener(OnDrawListener)/**
     * <p>Remove a previously installed pre-draw callback.</p>
     * <p><strong>Note:</strong> this method <strong>cannot</strong> be invoked from
     * {@link android.view.ViewTreeObserver.OnDrawListener#onDraw()}.</p>
     *
     * @param victim The callback to remove
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     *
     * @see #addOnDrawListener(OnDrawListener)
     */
    public void removeOnDrawListener(OnDrawListener victim) {
        checkIsAlive();
        if (mOnDrawListeners == null) {
            return;
        }
        if (mInDispatchOnDraw) {
            IllegalStateException ex = new IllegalStateException(
                    "Cannot call removeOnDrawListener inside of onDraw");
            if (sIllegalOnDrawModificationIsFatal) {
                throw ex;
            } else {
                Log.e("ViewTreeObserver", ex.getMessage(), ex);
            }
        }
        mOnDrawListeners.remove(victim);
    }

    
Register a callback to be invoked when a view has been scrolled.
Params:
listener – The callback to add
Throws:
IllegalStateException – If isAlive() returns false/**
     * Register a callback to be invoked when a view has been scrolled.
     *
     * @param listener The callback to add
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     */
    public void addOnScrollChangedListener(OnScrollChangedListener listener) {
        checkIsAlive();

        if (mOnScrollChangedListeners == null) {
            mOnScrollChangedListeners = new CopyOnWriteArray<OnScrollChangedListener>();
        }

        mOnScrollChangedListeners.add(listener);
    }

    
Remove a previously installed scroll-changed callback
Params:
victim – The callback to remove
Throws:
IllegalStateException – If isAlive() returns false
See Also:
addOnScrollChangedListener(OnScrollChangedListener)/**
     * Remove a previously installed scroll-changed callback
     *
     * @param victim The callback to remove
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     *
     * @see #addOnScrollChangedListener(OnScrollChangedListener)
     */
    public void removeOnScrollChangedListener(OnScrollChangedListener victim) {
        checkIsAlive();
        if (mOnScrollChangedListeners == null) {
            return;
        }
        mOnScrollChangedListeners.remove(victim);
    }

    
Register a callback to be invoked when the invoked when the touch mode changes.
Params:
listener – The callback to add
Throws:
IllegalStateException – If isAlive() returns false/**
     * Register a callback to be invoked when the invoked when the touch mode changes.
     *
     * @param listener The callback to add
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     */
    public void addOnTouchModeChangeListener(OnTouchModeChangeListener listener) {
        checkIsAlive();

        if (mOnTouchModeChangeListeners == null) {
            mOnTouchModeChangeListeners = new CopyOnWriteArrayList<OnTouchModeChangeListener>();
        }

        mOnTouchModeChangeListeners.add(listener);
    }

    
Remove a previously installed touch mode change callback
Params:
victim – The callback to remove
Throws:
IllegalStateException – If isAlive() returns false
See Also:
addOnTouchModeChangeListener(OnTouchModeChangeListener)/**
     * Remove a previously installed touch mode change callback
     *
     * @param victim The callback to remove
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     *
     * @see #addOnTouchModeChangeListener(OnTouchModeChangeListener)
     */
    public void removeOnTouchModeChangeListener(OnTouchModeChangeListener victim) {
        checkIsAlive();
        if (mOnTouchModeChangeListeners == null) {
            return;
        }
        mOnTouchModeChangeListeners.remove(victim);
    }

    
Register a callback to be invoked when the invoked when it is time to
compute the window's internal insets.
Params:
listener – The callback to add
Throws:
IllegalStateException – If isAlive() returns false We are not yet ready to commit to this API and support it, so
@hide
/**
     * Register a callback to be invoked when the invoked when it is time to
     * compute the window's internal insets.
     *
     * @param listener The callback to add
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     * 
     * We are not yet ready to commit to this API and support it, so
     * @hide
     */
    public void addOnComputeInternalInsetsListener(OnComputeInternalInsetsListener listener) {
        checkIsAlive();

        if (mOnComputeInternalInsetsListeners == null) {
            mOnComputeInternalInsetsListeners =
                    new CopyOnWriteArray<OnComputeInternalInsetsListener>();
        }

        mOnComputeInternalInsetsListeners.add(listener);
    }

    
Remove a previously installed internal insets computation callback
Params:
victim – The callback to remove
Throws:
IllegalStateException – If isAlive() returns false
See Also:

We are not yet ready to commit to this API and support it, so
@hide
/**
     * Remove a previously installed internal insets computation callback
     *
     * @param victim The callback to remove
     *
     * @throws IllegalStateException If {@link #isAlive()} returns false
     *
     * @see #addOnComputeInternalInsetsListener(OnComputeInternalInsetsListener)
     * 
     * We are not yet ready to commit to this API and support it, so
     * @hide
     */
    public void removeOnComputeInternalInsetsListener(OnComputeInternalInsetsListener victim) {
        checkIsAlive();
        if (mOnComputeInternalInsetsListeners == null) {
            return;
        }
        mOnComputeInternalInsetsListeners.remove(victim);
    }

    
@hide
/**
     * @hide
     */
    public void addOnEnterAnimationCompleteListener(OnEnterAnimationCompleteListener listener) {
        checkIsAlive();
        if (mOnEnterAnimationCompleteListeners == null) {
            mOnEnterAnimationCompleteListeners =
                    new CopyOnWriteArrayList<OnEnterAnimationCompleteListener>();
        }
        mOnEnterAnimationCompleteListeners.add(listener);
    }

    
@hide
/**
     * @hide
     */
    public void removeOnEnterAnimationCompleteListener(OnEnterAnimationCompleteListener listener) {
        checkIsAlive();
        if (mOnEnterAnimationCompleteListeners == null) {
            return;
        }
        mOnEnterAnimationCompleteListeners.remove(listener);
    }

    private void checkIsAlive() {
        if (!mAlive) {
            throw new IllegalStateException("This ViewTreeObserver is not alive, call "
                    + "getViewTreeObserver() again");
        }
    }

    
Indicates whether this ViewTreeObserver is alive. When an observer is not alive,
any call to a method (except this one) will throw an exception.
If an application keeps a long-lived reference to this ViewTreeObserver, it should
always check for the result of this method before calling any other method.
Returns:
True if this object is alive and be used, false otherwise./**
     * Indicates whether this ViewTreeObserver is alive. When an observer is not alive,
     * any call to a method (except this one) will throw an exception.
     *
     * If an application keeps a long-lived reference to this ViewTreeObserver, it should
     * always check for the result of this method before calling any other method.
     *
     * @return True if this object is alive and be used, false otherwise.
     */
    public boolean isAlive() {
        return mAlive;
    }

    
Marks this ViewTreeObserver as not alive. After invoking this method, invoking any other method but isAlive() and kill() will throw an Exception. 
@hide
/**
     * Marks this ViewTreeObserver as not alive. After invoking this method, invoking
     * any other method but {@link #isAlive()} and {@link #kill()} will throw an Exception.
     *
     * @hide
     */
    private void kill() {
        mAlive = false;
    }

    
Notifies registered listeners that window has been attached/detached.
/**
     * Notifies registered listeners that window has been attached/detached.
     */
    final void dispatchOnWindowAttachedChange(boolean attached) {
        // NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to
        // perform the dispatching. The iterator is a safe guard against listeners that
        // could mutate the list by calling the various add/remove methods. This prevents
        // the array from being modified while we iterate it.
        final CopyOnWriteArrayList<OnWindowAttachListener> listeners
                = mOnWindowAttachListeners;
        if (listeners != null && listeners.size() > 0) {
            for (OnWindowAttachListener listener : listeners) {
                if (attached) listener.onWindowAttached();
                else listener.onWindowDetached();
            }
        }
    }

    
Notifies registered listeners that window focus has changed.
/**
     * Notifies registered listeners that window focus has changed.
     */
    final void dispatchOnWindowFocusChange(boolean hasFocus) {
        // NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to
        // perform the dispatching. The iterator is a safe guard against listeners that
        // could mutate the list by calling the various add/remove methods. This prevents
        // the array from being modified while we iterate it.
        final CopyOnWriteArrayList<OnWindowFocusChangeListener> listeners
                = mOnWindowFocusListeners;
        if (listeners != null && listeners.size() > 0) {
            for (OnWindowFocusChangeListener listener : listeners) {
                listener.onWindowFocusChanged(hasFocus);
            }
        }
    }

    
Notifies registered listeners that focus has changed.
/**
     * Notifies registered listeners that focus has changed.
     */
    final void dispatchOnGlobalFocusChange(View oldFocus, View newFocus) {
        // NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to
        // perform the dispatching. The iterator is a safe guard against listeners that
        // could mutate the list by calling the various add/remove methods. This prevents
        // the array from being modified while we iterate it.
        final CopyOnWriteArrayList<OnGlobalFocusChangeListener> listeners = mOnGlobalFocusListeners;
        if (listeners != null && listeners.size() > 0) {
            for (OnGlobalFocusChangeListener listener : listeners) {
                listener.onGlobalFocusChanged(oldFocus, newFocus);
            }
        }
    }

    
Notifies registered listeners that a global layout happened. This can be called
manually if you are forcing a layout on a View or a hierarchy of Views that are
not attached to a Window or in the GONE state.
/**
     * Notifies registered listeners that a global layout happened. This can be called
     * manually if you are forcing a layout on a View or a hierarchy of Views that are
     * not attached to a Window or in the GONE state.
     */
    public final void dispatchOnGlobalLayout() {
        // NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to
        // perform the dispatching. The iterator is a safe guard against listeners that
        // could mutate the list by calling the various add/remove methods. This prevents
        // the array from being modified while we iterate it.
        final CopyOnWriteArray<OnGlobalLayoutListener> listeners = mOnGlobalLayoutListeners;
        if (listeners != null && listeners.size() > 0) {
            CopyOnWriteArray.Access<OnGlobalLayoutListener> access = listeners.start();
            try {
                int count = access.size();
                for (int i = 0; i < count; i++) {
                    access.get(i).onGlobalLayout();
                }
            } finally {
                listeners.end();
            }
        }
    }

    
Returns whether there are listeners for on pre-draw events.
/**
     * Returns whether there are listeners for on pre-draw events.
     */
    final boolean hasOnPreDrawListeners() {
        return mOnPreDrawListeners != null && mOnPreDrawListeners.size() > 0;
    }

    
Notifies registered listeners that the drawing pass is about to start. If a
listener returns true, then the drawing pass is canceled and rescheduled. This can
be called manually if you are forcing the drawing on a View or a hierarchy of Views
that are not attached to a Window or in the GONE state.
Returns:
True if the current draw should be canceled and resceduled, false otherwise./**
     * Notifies registered listeners that the drawing pass is about to start. If a
     * listener returns true, then the drawing pass is canceled and rescheduled. This can
     * be called manually if you are forcing the drawing on a View or a hierarchy of Views
     * that are not attached to a Window or in the GONE state.
     *
     * @return True if the current draw should be canceled and resceduled, false otherwise.
     */
    @SuppressWarnings("unchecked")
    public final boolean dispatchOnPreDraw() {
        boolean cancelDraw = false;
        final CopyOnWriteArray<OnPreDrawListener> listeners = mOnPreDrawListeners;
        if (listeners != null && listeners.size() > 0) {
            CopyOnWriteArray.Access<OnPreDrawListener> access = listeners.start();
            try {
                int count = access.size();
                for (int i = 0; i < count; i++) {
                    cancelDraw |= !(access.get(i).onPreDraw());
                }
            } finally {
                listeners.end();
            }
        }
        return cancelDraw;
    }

    
Notifies registered listeners that the window is now shown
@hide
/**
     * Notifies registered listeners that the window is now shown
     * @hide
     */
    @SuppressWarnings("unchecked")
    public final void dispatchOnWindowShown() {
        mWindowShown = true;
        final CopyOnWriteArray<OnWindowShownListener> listeners = mOnWindowShownListeners;
        if (listeners != null && listeners.size() > 0) {
            CopyOnWriteArray.Access<OnWindowShownListener> access = listeners.start();
            try {
                int count = access.size();
                for (int i = 0; i < count; i++) {
                    access.get(i).onWindowShown();
                }
            } finally {
                listeners.end();
            }
        }
    }

    
Notifies registered listeners that the drawing pass is about to start.
/**
     * Notifies registered listeners that the drawing pass is about to start.
     */
    public final void dispatchOnDraw() {
        if (mOnDrawListeners != null) {
            mInDispatchOnDraw = true;
            final ArrayList<OnDrawListener> listeners = mOnDrawListeners;
            int numListeners = listeners.size();
            for (int i = 0; i < numListeners; ++i) {
                listeners.get(i).onDraw();
            }
            mInDispatchOnDraw = false;
        }
    }

    
Notifies registered listeners that the touch mode has changed.
Params:
inTouchMode – True if the touch mode is now enabled, false otherwise./**
     * Notifies registered listeners that the touch mode has changed.
     *
     * @param inTouchMode True if the touch mode is now enabled, false otherwise.
     */
    final void dispatchOnTouchModeChanged(boolean inTouchMode) {
        final CopyOnWriteArrayList<OnTouchModeChangeListener> listeners =
                mOnTouchModeChangeListeners;
        if (listeners != null && listeners.size() > 0) {
            for (OnTouchModeChangeListener listener : listeners) {
                listener.onTouchModeChanged(inTouchMode);
            }
        }
    }

    
Notifies registered listeners that something has scrolled.
/**
     * Notifies registered listeners that something has scrolled.
     */
    final void dispatchOnScrollChanged() {
        // NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to
        // perform the dispatching. The iterator is a safe guard against listeners that
        // could mutate the list by calling the various add/remove methods. This prevents
        // the array from being modified while we iterate it.
        final CopyOnWriteArray<OnScrollChangedListener> listeners = mOnScrollChangedListeners;
        if (listeners != null && listeners.size() > 0) {
            CopyOnWriteArray.Access<OnScrollChangedListener> access = listeners.start();
            try {
                int count = access.size();
                for (int i = 0; i < count; i++) {
                    access.get(i).onScrollChanged();
                }
            } finally {
                listeners.end();
            }
        }
    }

    
Returns whether there are listeners for computing internal insets.
/**
     * Returns whether there are listeners for computing internal insets.
     */
    final boolean hasComputeInternalInsetsListeners() {
        final CopyOnWriteArray<OnComputeInternalInsetsListener> listeners =
                mOnComputeInternalInsetsListeners;
        return (listeners != null && listeners.size() > 0);
    }

    
Calls all listeners to compute the current insets.
/**
     * Calls all listeners to compute the current insets.
     */
    final void dispatchOnComputeInternalInsets(InternalInsetsInfo inoutInfo) {
        // NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to
        // perform the dispatching. The iterator is a safe guard against listeners that
        // could mutate the list by calling the various add/remove methods. This prevents
        // the array from being modified while we iterate it.
        final CopyOnWriteArray<OnComputeInternalInsetsListener> listeners =
                mOnComputeInternalInsetsListeners;
        if (listeners != null && listeners.size() > 0) {
            CopyOnWriteArray.Access<OnComputeInternalInsetsListener> access = listeners.start();
            try {
                int count = access.size();
                for (int i = 0; i < count; i++) {
                    access.get(i).onComputeInternalInsets(inoutInfo);
                }
            } finally {
                listeners.end();
            }
        }
    }

    
@hide
/**
     * @hide
     */
    public final void dispatchOnEnterAnimationComplete() {
        // NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to
        // perform the dispatching. The iterator is a safe guard against listeners that
        // could mutate the list by calling the various add/remove methods. This prevents
        // the array from being modified while we iterate it.
        final CopyOnWriteArrayList<OnEnterAnimationCompleteListener> listeners =
                mOnEnterAnimationCompleteListeners;
        if (listeners != null && !listeners.isEmpty()) {
            for (OnEnterAnimationCompleteListener listener : listeners) {
                listener.onEnterAnimationComplete();
            }
        }
    }

    
Copy on write array. This array is not thread safe, and only one loop can
iterate over this array at any given time. This class avoids allocations
until a concurrent modification happens.
Usage:
CopyOnWriteArray.Access access = array.start();
try {
    for (int i = 0; i < access.size(); i++) {
        MyData d = access.get(i);
    }
} finally {
    access.end();
}
/**
     * Copy on write array. This array is not thread safe, and only one loop can
     * iterate over this array at any given time. This class avoids allocations
     * until a concurrent modification happens.
     * 
     * Usage:
     * 
     * CopyOnWriteArray.Access<MyData> access = array.start();
     * try {
     *     for (int i = 0; i < access.size(); i++) {
     *         MyData d = access.get(i);
     *     }
     * } finally {
     *     access.end();
     * }
     */
    static class CopyOnWriteArray<T> {
        private ArrayList<T> mData = new ArrayList<T>();
        private ArrayList<T> mDataCopy;

        private final Access<T> mAccess = new Access<T>();

        private boolean mStart;

        static class Access<T> {
            private ArrayList<T> mData;
            private int mSize;

            T get(int index) {
                return mData.get(index);
            }

            int size() {
                return mSize;
            }
        }

        CopyOnWriteArray() {
        }

        private ArrayList<T> getArray() {
            if (mStart) {
                if (mDataCopy == null) mDataCopy = new ArrayList<T>(mData);
                return mDataCopy;
            }
            return mData;
        }

        Access<T> start() {
            if (mStart) throw new IllegalStateException("Iteration already started");
            mStart = true;
            mDataCopy = null;
            mAccess.mData = mData;
            mAccess.mSize = mData.size();
            return mAccess;
        }

        void end() {
            if (!mStart) throw new IllegalStateException("Iteration not started");
            mStart = false;
            if (mDataCopy != null) {
                mData = mDataCopy;
                mAccess.mData.clear();
                mAccess.mSize = 0;
            }
            mDataCopy = null;
        }

        int size() {
            return getArray().size();
        }

        void add(T item) {
            getArray().add(item);
        }

        void addAll(CopyOnWriteArray<T> array) {
            getArray().addAll(array.mData);
        }

        void remove(T item) {
            getArray().remove(item);
        }

        void clear() {
            getArray().clear();
        }
    }
}