https://source.android.com/ 
/*
 * Copyright (C) 2013 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 com.android.internal.widget;

import android.content.Context;
import android.graphics.Rect;
import android.os.Bundle;
import android.util.IntArray;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewParent;
import android.view.accessibility.AccessibilityEvent;
import android.view.accessibility.AccessibilityManager;
import android.view.accessibility.AccessibilityNodeInfo;
import android.view.accessibility.AccessibilityNodeInfo.AccessibilityAction;
import android.view.accessibility.AccessibilityNodeProvider;


ExploreByTouchHelper is a utility class for implementing accessibility support in custom Views that represent a collection of View-like logical items. It extends AccessibilityNodeProvider and simplifies many aspects of providing information to accessibility services and managing accessibility focus. This class does not currently support hierarchies of logical items. 
 This should be applied to the parent view using View.setAccessibilityDelegate: 
mAccessHelper = ExploreByTouchHelper.create(someView, mAccessHelperCallback);
ViewCompat.setAccessibilityDelegate(someView, mAccessHelper);



/**
 * ExploreByTouchHelper is a utility class for implementing accessibility
 * support in custom {@link android.view.View}s that represent a collection of View-like
 * logical items. It extends {@link android.view.accessibility.AccessibilityNodeProvider} and
 * simplifies many aspects of providing information to accessibility services
 * and managing accessibility focus. This class does not currently support
 * hierarchies of logical items.
 * <p>
 * This should be applied to the parent view using
 * {@link android.view.View#setAccessibilityDelegate}:
 *
 * <pre>
 * mAccessHelper = ExploreByTouchHelper.create(someView, mAccessHelperCallback);
 * ViewCompat.setAccessibilityDelegate(someView, mAccessHelper);
 * </pre>
 */
public abstract class ExploreByTouchHelper extends View.AccessibilityDelegate {
    
Virtual node identifier value for invalid nodes. 
/** Virtual node identifier value for invalid nodes. */
    public static final int INVALID_ID = Integer.MIN_VALUE;

    
Virtual node identifier value for the host view's node. 
/** Virtual node identifier value for the host view's node. */
    public static final int HOST_ID = View.NO_ID;

    
Default class name used for virtual views. 
/** Default class name used for virtual views. */
    private static final String DEFAULT_CLASS_NAME = View.class.getName();

    
Default bounds used to determine if the client didn't set any. 
/** Default bounds used to determine if the client didn't set any. */
    private static final Rect INVALID_PARENT_BOUNDS = new Rect(
            Integer.MAX_VALUE, Integer.MAX_VALUE, Integer.MIN_VALUE, Integer.MIN_VALUE);

    // Lazily-created temporary data structures used when creating nodes.
    private Rect mTempScreenRect;
    private Rect mTempParentRect;
    private int[] mTempGlobalRect;

    
Lazily-created temporary data structure used to compute visibility. 
/** Lazily-created temporary data structure used to compute visibility. */
    private Rect mTempVisibleRect;

    
Lazily-created temporary data structure used to obtain child IDs. 
/** Lazily-created temporary data structure used to obtain child IDs. */
    private IntArray mTempArray;

    
System accessibility manager, used to check state and send events. 
/** System accessibility manager, used to check state and send events. */
    private final AccessibilityManager mManager;

    
View whose internal structure is exposed through this helper. 
/** View whose internal structure is exposed through this helper. */
    private final View mView;

    
Context of the host view. 
/** Context of the host view. **/
    private final Context mContext;

    
Node provider that handles creating nodes and performing actions. 
/** Node provider that handles creating nodes and performing actions. */
    private ExploreByTouchNodeProvider mNodeProvider;

    
Virtual view id for the currently focused logical item. 
/** Virtual view id for the currently focused logical item. */
    private int mFocusedVirtualViewId = INVALID_ID;

    
Virtual view id for the currently hovered logical item. 
/** Virtual view id for the currently hovered logical item. */
    private int mHoveredVirtualViewId = INVALID_ID;

    
Factory method to create a new ExploreByTouchHelper. 
Params:
  • forView – View whose logical children are exposed by this helper.
/**
     * Factory method to create a new {@link ExploreByTouchHelper}.
     *
     * @param forView View whose logical children are exposed by this helper.
     */
    public ExploreByTouchHelper(View forView) {
        if (forView == null) {
            throw new IllegalArgumentException("View may not be null");
        }

        mView = forView;
        mContext = forView.getContext();
        mManager = (AccessibilityManager) mContext.getSystemService(Context.ACCESSIBILITY_SERVICE);
    }

    
Returns the AccessibilityNodeProvider for this helper. 
Params:
  • host – View whose logical children are exposed by this helper.
Returns:The accessibility node provider for this helper.
/**
     * Returns the {@link android.view.accessibility.AccessibilityNodeProvider} for this helper.
     *
     * @param host View whose logical children are exposed by this helper.
     * @return The accessibility node provider for this helper.
     */
    @Override
    public AccessibilityNodeProvider getAccessibilityNodeProvider(View host) {
        if (mNodeProvider == null) {
            mNodeProvider = new ExploreByTouchNodeProvider();
        }
        return mNodeProvider;
    }

    
Dispatches hover MotionEvents to the virtual view hierarchy when the Explore by Touch feature is enabled. 
 This method should be called by overriding View.dispatchHoverEvent: 
@Override
public boolean dispatchHoverEvent(MotionEvent event) {
  if (mHelper.dispatchHoverEvent(this, event) {
    return true;
  }
  return super.dispatchHoverEvent(event);
}



Params:
  • event – The hover event to dispatch to the virtual view hierarchy.
Returns:Whether the hover event was handled.
/**
     * Dispatches hover {@link android.view.MotionEvent}s to the virtual view hierarchy when
     * the Explore by Touch feature is enabled.
     * <p>
     * This method should be called by overriding
     * {@link View#dispatchHoverEvent}:
     *
     * <pre>&#64;Override
     * public boolean dispatchHoverEvent(MotionEvent event) {
     *   if (mHelper.dispatchHoverEvent(this, event) {
     *     return true;
     *   }
     *   return super.dispatchHoverEvent(event);
     * }
     * </pre>
     *
     * @param event The hover event to dispatch to the virtual view hierarchy.
     * @return Whether the hover event was handled.
     */
    public boolean dispatchHoverEvent(MotionEvent event) {
        if (!mManager.isEnabled() || !mManager.isTouchExplorationEnabled()) {
            return false;
        }

        switch (event.getAction()) {
            case MotionEvent.ACTION_HOVER_MOVE:
            case MotionEvent.ACTION_HOVER_ENTER:
                final int virtualViewId = getVirtualViewAt(event.getX(), event.getY());
                updateHoveredVirtualView(virtualViewId);
                return (virtualViewId != INVALID_ID);
            case MotionEvent.ACTION_HOVER_EXIT:
                if (mFocusedVirtualViewId != INVALID_ID) {
                    updateHoveredVirtualView(INVALID_ID);
                    return true;
                }
                return false;
            default:
                return false;
        }
    }

    
Populates an event of the specified type with information about an item
and attempts to send it up through the view hierarchy.


You should call this method after performing a user action that normally
fires an accessibility event, such as clicking on an item.

public void performItemClick(T item) {
  ...
  sendEventForVirtualViewId(item.id, AccessibilityEvent.TYPE_VIEW_CLICKED);
}



Params:
  • virtualViewId – The virtual view id for which to send an event.
  • eventType – The type of event to send.
Returns:true if the event was sent successfully.
/**
     * Populates an event of the specified type with information about an item
     * and attempts to send it up through the view hierarchy.
     * <p>
     * You should call this method after performing a user action that normally
     * fires an accessibility event, such as clicking on an item.
     *
     * <pre>public void performItemClick(T item) {
     *   ...
     *   sendEventForVirtualViewId(item.id, AccessibilityEvent.TYPE_VIEW_CLICKED);
     * }
     * </pre>
     *
     * @param virtualViewId The virtual view id for which to send an event.
     * @param eventType The type of event to send.
     * @return true if the event was sent successfully.
     */
    public boolean sendEventForVirtualView(int virtualViewId, int eventType) {
        if ((virtualViewId == INVALID_ID) || !mManager.isEnabled()) {
            return false;
        }

        final ViewParent parent = mView.getParent();
        if (parent == null) {
            return false;
        }

        final AccessibilityEvent event = createEvent(virtualViewId, eventType);
        return parent.requestSendAccessibilityEvent(mView, event);
    }

    
Notifies the accessibility framework that the properties of the parent
view have changed.


You must call this method after adding or removing items from the
parent view.

/**
     * Notifies the accessibility framework that the properties of the parent
     * view have changed.
     * <p>
     * You <b>must</b> call this method after adding or removing items from the
     * parent view.
     */
    public void invalidateRoot() {
        invalidateVirtualView(HOST_ID, AccessibilityEvent.CONTENT_CHANGE_TYPE_SUBTREE);
    }

    
Notifies the accessibility framework that the properties of a particular
item have changed.


You must call this method after changing any of the properties set in onPopulateNodeForVirtualView. 
Params:
  • virtualViewId – The virtual view id to invalidate, or HOST_ID to invalidate the root view.
See Also:
/**
     * Notifies the accessibility framework that the properties of a particular
     * item have changed.
     * <p>
     * You <b>must</b> call this method after changing any of the properties set
     * in {@link #onPopulateNodeForVirtualView}.
     *
     * @param virtualViewId The virtual view id to invalidate, or
     *                      {@link #HOST_ID} to invalidate the root view.
     * @see #invalidateVirtualView(int, int)
     */
    public void invalidateVirtualView(int virtualViewId) {
        invalidateVirtualView(virtualViewId,
                AccessibilityEvent.CONTENT_CHANGE_TYPE_UNDEFINED);
    }

    
Notifies the accessibility framework that the properties of a particular
item have changed.


You must call this method after changing any of the properties set in onPopulateNodeForVirtualView. 
Params:
/**
     * Notifies the accessibility framework that the properties of a particular
     * item have changed.
     * <p>
     * You <b>must</b> call this method after changing any of the properties set
     * in {@link #onPopulateNodeForVirtualView}.
     *
     * @param virtualViewId The virtual view id to invalidate, or
     *                      {@link #HOST_ID} to invalidate the root view.
     * @param changeTypes The bit mask of change types. May be {@code 0} for the
     *                    default (undefined) change type or one or more of:
     *         <ul>
     *         <li>{@link AccessibilityEvent#CONTENT_CHANGE_TYPE_CONTENT_DESCRIPTION}
     *         <li>{@link AccessibilityEvent#CONTENT_CHANGE_TYPE_SUBTREE}
     *         <li>{@link AccessibilityEvent#CONTENT_CHANGE_TYPE_TEXT}
     *         <li>{@link AccessibilityEvent#CONTENT_CHANGE_TYPE_UNDEFINED}
     *         </ul>
     */
    public void invalidateVirtualView(int virtualViewId, int changeTypes) {
        if (virtualViewId != INVALID_ID && mManager.isEnabled()) {
            final ViewParent parent = mView.getParent();
            if (parent != null) {
                final AccessibilityEvent event = createEvent(virtualViewId,
                        AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED);
                event.setContentChangeTypes(changeTypes);
                parent.requestSendAccessibilityEvent(mView, event);
            }
        }
    }

    
Returns the virtual view id for the currently focused item,

Returns:A virtual view id, or INVALID_ID if no item is currently focused.
/**
     * Returns the virtual view id for the currently focused item,
     *
     * @return A virtual view id, or {@link #INVALID_ID} if no item is
     *         currently focused.
     */
    public int getFocusedVirtualView() {
        return mFocusedVirtualViewId;
    }

    
Sets the currently hovered item, sending hover accessibility events as
necessary to maintain the correct state.

Params:
  • virtualViewId – The virtual view id for the item currently being hovered, or INVALID_ID if no item is hovered within the parent view.
/**
     * Sets the currently hovered item, sending hover accessibility events as
     * necessary to maintain the correct state.
     *
     * @param virtualViewId The virtual view id for the item currently being
     *            hovered, or {@link #INVALID_ID} if no item is hovered within
     *            the parent view.
     */
    private void updateHoveredVirtualView(int virtualViewId) {
        if (mHoveredVirtualViewId == virtualViewId) {
            return;
        }

        final int previousVirtualViewId = mHoveredVirtualViewId;
        mHoveredVirtualViewId = virtualViewId;

        // Stay consistent with framework behavior by sending ENTER/EXIT pairs
        // in reverse order. This is accurate as of API 18.
        sendEventForVirtualView(virtualViewId, AccessibilityEvent.TYPE_VIEW_HOVER_ENTER);
        sendEventForVirtualView(previousVirtualViewId, AccessibilityEvent.TYPE_VIEW_HOVER_EXIT);
    }

    
Constructs and returns an AccessibilityEvent for the specified virtual view id, which includes the host view (HOST_ID). 
Params:
  • virtualViewId – The virtual view id for the item for which to
           construct an event.
  • eventType – The type of event to construct.
Returns:An AccessibilityEvent populated with information about the specified item.
/**
     * Constructs and returns an {@link AccessibilityEvent} for the specified
     * virtual view id, which includes the host view ({@link #HOST_ID}).
     *
     * @param virtualViewId The virtual view id for the item for which to
     *            construct an event.
     * @param eventType The type of event to construct.
     * @return An {@link AccessibilityEvent} populated with information about
     *         the specified item.
     */
    private AccessibilityEvent createEvent(int virtualViewId, int eventType) {
        switch (virtualViewId) {
            case HOST_ID:
                return createEventForHost(eventType);
            default:
                return createEventForChild(virtualViewId, eventType);
        }
    }

    
Constructs and returns an AccessibilityEvent for the host node. 
Params:
  • eventType – The type of event to construct.
Returns:An AccessibilityEvent populated with information about the specified item.
/**
     * Constructs and returns an {@link AccessibilityEvent} for the host node.
     *
     * @param eventType The type of event to construct.
     * @return An {@link AccessibilityEvent} populated with information about
     *         the specified item.
     */
    private AccessibilityEvent createEventForHost(int eventType) {
        final AccessibilityEvent event = AccessibilityEvent.obtain(eventType);
        mView.onInitializeAccessibilityEvent(event);

        // Allow the client to populate the event.
        onPopulateEventForHost(event);

        return event;
    }

    
Constructs and returns an AccessibilityEvent populated with information about the specified item. 
Params:
  • virtualViewId – The virtual view id for the item for which to
           construct an event.
  • eventType – The type of event to construct.
Returns:An AccessibilityEvent populated with information about the specified item.
/**
     * Constructs and returns an {@link AccessibilityEvent} populated with
     * information about the specified item.
     *
     * @param virtualViewId The virtual view id for the item for which to
     *            construct an event.
     * @param eventType The type of event to construct.
     * @return An {@link AccessibilityEvent} populated with information about
     *         the specified item.
     */
    private AccessibilityEvent createEventForChild(int virtualViewId, int eventType) {
        final AccessibilityEvent event = AccessibilityEvent.obtain(eventType);
        event.setEnabled(true);
        event.setClassName(DEFAULT_CLASS_NAME);

        // Allow the client to populate the event.
        onPopulateEventForVirtualView(virtualViewId, event);

        // Make sure the developer is following the rules.
        if (event.getText().isEmpty() && (event.getContentDescription() == null)) {
            throw new RuntimeException("Callbacks must add text or a content description in "
                    + "populateEventForVirtualViewId()");
        }

        // Don't allow the client to override these properties.
        event.setPackageName(mView.getContext().getPackageName());
        event.setSource(mView, virtualViewId);

        return event;
    }

    
Constructs and returns an AccessibilityNodeInfo for the specified virtual view id, which includes the host view (HOST_ID). 
Params:
  • virtualViewId – The virtual view id for the item for which to
           construct a node.
Returns:An AccessibilityNodeInfo populated with information about the specified item.
/**
     * Constructs and returns an {@link android.view.accessibility.AccessibilityNodeInfo} for the
     * specified virtual view id, which includes the host view
     * ({@link #HOST_ID}).
     *
     * @param virtualViewId The virtual view id for the item for which to
     *            construct a node.
     * @return An {@link android.view.accessibility.AccessibilityNodeInfo} populated with information
     *         about the specified item.
     */
    private AccessibilityNodeInfo createNode(int virtualViewId) {
        switch (virtualViewId) {
            case HOST_ID:
                return createNodeForHost();
            default:
                return createNodeForChild(virtualViewId);
        }
    }

    
Constructs and returns an AccessibilityNodeInfo for the host view populated with its virtual descendants. 
Returns:An AccessibilityNodeInfo for the parent node.
/**
     * Constructs and returns an {@link AccessibilityNodeInfo} for the
     * host view populated with its virtual descendants.
     *
     * @return An {@link AccessibilityNodeInfo} for the parent node.
     */
    private AccessibilityNodeInfo createNodeForHost() {
        final AccessibilityNodeInfo node = AccessibilityNodeInfo.obtain(mView);
        mView.onInitializeAccessibilityNodeInfo(node);
        final int realNodeCount = node.getChildCount();

        // Allow the client to populate the host node.
        onPopulateNodeForHost(node);

        // Add the virtual descendants.
        if (mTempArray == null) {
            mTempArray = new IntArray();
        } else {
            mTempArray.clear();
        }
        final IntArray virtualViewIds = mTempArray;
        getVisibleVirtualViews(virtualViewIds);
        if (realNodeCount > 0 && virtualViewIds.size() > 0) {
            throw new RuntimeException("Views cannot have both real and virtual children");
        }

        final int N = virtualViewIds.size();
        for (int i = 0; i < N; i++) {
            node.addChild(mView, virtualViewIds.get(i));
        }

        return node;
    }

    
Constructs and returns an AccessibilityNodeInfo for the specified item. Automatically manages accessibility focus actions. 

Allows the implementing class to specify most node properties, but
overrides the following:



 Uses the bounds of the parent view and the parent-relative bounding rectangle specified by AccessibilityNodeInfo.getBoundsInParent to automatically update the following properties: 


Params:
  • virtualViewId – The virtual view id for item for which to construct
           a node.
Returns:An AccessibilityNodeInfo for the specified item.
/**
     * Constructs and returns an {@link AccessibilityNodeInfo} for the
     * specified item. Automatically manages accessibility focus actions.
     * <p>
     * Allows the implementing class to specify most node properties, but
     * overrides the following:
     * <ul>
     * <li>{@link AccessibilityNodeInfo#setPackageName}
     * <li>{@link AccessibilityNodeInfo#setClassName}
     * <li>{@link AccessibilityNodeInfo#setParent(View)}
     * <li>{@link AccessibilityNodeInfo#setSource(View, int)}
     * <li>{@link AccessibilityNodeInfo#setVisibleToUser}
     * <li>{@link AccessibilityNodeInfo#setBoundsInScreen(Rect)}
     * </ul>
     * <p>
     * Uses the bounds of the parent view and the parent-relative bounding
     * rectangle specified by
     * {@link AccessibilityNodeInfo#getBoundsInParent} to automatically
     * update the following properties:
     * <ul>
     * <li>{@link AccessibilityNodeInfo#setVisibleToUser}
     * <li>{@link AccessibilityNodeInfo#setBoundsInParent}
     * </ul>
     *
     * @param virtualViewId The virtual view id for item for which to construct
     *            a node.
     * @return An {@link AccessibilityNodeInfo} for the specified item.
     */
    private AccessibilityNodeInfo createNodeForChild(int virtualViewId) {
        ensureTempRects();
        final Rect tempParentRect = mTempParentRect;
        final int[] tempGlobalRect = mTempGlobalRect;
        final Rect tempScreenRect = mTempScreenRect;

        final AccessibilityNodeInfo node = AccessibilityNodeInfo.obtain();

        // Ensure the client has good defaults.
        node.setEnabled(true);
        node.setClassName(DEFAULT_CLASS_NAME);
        node.setBoundsInParent(INVALID_PARENT_BOUNDS);

        // Allow the client to populate the node.
        onPopulateNodeForVirtualView(virtualViewId, node);

        // Make sure the developer is following the rules.
        if ((node.getText() == null) && (node.getContentDescription() == null)) {
            throw new RuntimeException("Callbacks must add text or a content description in "
                    + "populateNodeForVirtualViewId()");
        }

        node.getBoundsInParent(tempParentRect);
        if (tempParentRect.equals(INVALID_PARENT_BOUNDS)) {
            throw new RuntimeException("Callbacks must set parent bounds in "
                    + "populateNodeForVirtualViewId()");
        }

        final int actions = node.getActions();
        if ((actions & AccessibilityNodeInfo.ACTION_ACCESSIBILITY_FOCUS) != 0) {
            throw new RuntimeException("Callbacks must not add ACTION_ACCESSIBILITY_FOCUS in "
                    + "populateNodeForVirtualViewId()");
        }
        if ((actions & AccessibilityNodeInfo.ACTION_CLEAR_ACCESSIBILITY_FOCUS) != 0) {
            throw new RuntimeException("Callbacks must not add ACTION_CLEAR_ACCESSIBILITY_FOCUS in "
                    + "populateNodeForVirtualViewId()");
        }

        // Don't allow the client to override these properties.
        node.setPackageName(mView.getContext().getPackageName());
        node.setSource(mView, virtualViewId);
        node.setParent(mView);

        // Manage internal accessibility focus state.
        if (mFocusedVirtualViewId == virtualViewId) {
            node.setAccessibilityFocused(true);
            node.addAction(AccessibilityAction.ACTION_CLEAR_ACCESSIBILITY_FOCUS);
        } else {
            node.setAccessibilityFocused(false);
            node.addAction(AccessibilityAction.ACTION_ACCESSIBILITY_FOCUS);
        }

        // Set the visibility based on the parent bound.
        if (intersectVisibleToUser(tempParentRect)) {
            node.setVisibleToUser(true);
            node.setBoundsInParent(tempParentRect);
        }

        // Calculate screen-relative bound.
        mView.getLocationOnScreen(tempGlobalRect);
        final int offsetX = tempGlobalRect[0];
        final int offsetY = tempGlobalRect[1];
        tempScreenRect.set(tempParentRect);
        tempScreenRect.offset(offsetX, offsetY);
        node.setBoundsInScreen(tempScreenRect);

        return node;
    }

    private void ensureTempRects() {
        mTempGlobalRect = new int[2];
        mTempParentRect = new Rect();
        mTempScreenRect = new Rect();
    }

    private boolean performAction(int virtualViewId, int action, Bundle arguments) {
        switch (virtualViewId) {
            case HOST_ID:
                return performActionForHost(action, arguments);
            default:
                return performActionForChild(virtualViewId, action, arguments);
        }
    }

    private boolean performActionForHost(int action, Bundle arguments) {
        return mView.performAccessibilityAction(action, arguments);
    }

    private boolean performActionForChild(int virtualViewId, int action, Bundle arguments) {
        switch (action) {
            case AccessibilityNodeInfo.ACTION_ACCESSIBILITY_FOCUS:
            case AccessibilityNodeInfo.ACTION_CLEAR_ACCESSIBILITY_FOCUS:
                return manageFocusForChild(virtualViewId, action);
            default:
                return onPerformActionForVirtualView(virtualViewId, action, arguments);
        }
    }

    private boolean manageFocusForChild(int virtualViewId, int action) {
        switch (action) {
            case AccessibilityNodeInfo.ACTION_ACCESSIBILITY_FOCUS:
                return requestAccessibilityFocus(virtualViewId);
            case AccessibilityNodeInfo.ACTION_CLEAR_ACCESSIBILITY_FOCUS:
                return clearAccessibilityFocus(virtualViewId);
            default:
                return false;
        }
    }

    
Computes whether the specified Rect intersects with the visible portion of its parent View. Modifies localRect to contain only the visible portion. 
Params:
  • localRect – A rectangle in local (parent) coordinates.
Returns:Whether the specified Rect is visible on the screen.
/**
     * Computes whether the specified {@link Rect} intersects with the visible
     * portion of its parent {@link View}. Modifies {@code localRect} to contain
     * only the visible portion.
     *
     * @param localRect A rectangle in local (parent) coordinates.
     * @return Whether the specified {@link Rect} is visible on the screen.
     */
    private boolean intersectVisibleToUser(Rect localRect) {
        // Missing or empty bounds mean this view is not visible.
        if ((localRect == null) || localRect.isEmpty()) {
            return false;
        }

        // Attached to invisible window means this view is not visible.
        if (mView.getWindowVisibility() != View.VISIBLE) {
            return false;
        }

        // An invisible predecessor means that this view is not visible.
        ViewParent viewParent = mView.getParent();
        while (viewParent instanceof View) {
            final View view = (View) viewParent;
            if ((view.getAlpha() <= 0) || (view.getVisibility() != View.VISIBLE)) {
                return false;
            }
            viewParent = view.getParent();
        }

        // A null parent implies the view is not visible.
        if (viewParent == null) {
            return false;
        }

        // If no portion of the parent is visible, this view is not visible.
        if (mTempVisibleRect == null) {
            mTempVisibleRect = new Rect();
        }
        final Rect tempVisibleRect = mTempVisibleRect;
        if (!mView.getLocalVisibleRect(tempVisibleRect)) {
            return false;
        }

        // Check if the view intersects the visible portion of the parent.
        return localRect.intersect(tempVisibleRect);
    }

    
Returns whether this virtual view is accessibility focused.

Returns:True if the view is accessibility focused.
/**
     * Returns whether this virtual view is accessibility focused.
     *
     * @return True if the view is accessibility focused.
     */
    private boolean isAccessibilityFocused(int virtualViewId) {
        return (mFocusedVirtualViewId == virtualViewId);
    }

    
Attempts to give accessibility focus to a virtual view.

 A virtual view will not actually take focus if AccessibilityManager.isEnabled() returns false, AccessibilityManager.isTouchExplorationEnabled() returns false, or the view already has accessibility focus. 
Params:
  • virtualViewId – The id of the virtual view on which to place
           accessibility focus.
Returns:Whether this virtual view actually took accessibility focus.
/**
     * Attempts to give accessibility focus to a virtual view.
     * <p>
     * A virtual view will not actually take focus if
     * {@link AccessibilityManager#isEnabled()} returns false,
     * {@link AccessibilityManager#isTouchExplorationEnabled()} returns false,
     * or the view already has accessibility focus.
     *
     * @param virtualViewId The id of the virtual view on which to place
     *            accessibility focus.
     * @return Whether this virtual view actually took accessibility focus.
     */
    private boolean requestAccessibilityFocus(int virtualViewId) {
        final AccessibilityManager accessibilityManager =
                (AccessibilityManager) mContext.getSystemService(Context.ACCESSIBILITY_SERVICE);

        if (!mManager.isEnabled()
                || !accessibilityManager.isTouchExplorationEnabled()) {
            return false;
        }
        // TODO: Check virtual view visibility.
        if (!isAccessibilityFocused(virtualViewId)) {
            // Clear focus from the previously focused view, if applicable.
            if (mFocusedVirtualViewId != INVALID_ID) {
                sendEventForVirtualView(mFocusedVirtualViewId,
                        AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUS_CLEARED);
            }

            // Set focus on the new view.
            mFocusedVirtualViewId = virtualViewId;

            // TODO: Only invalidate virtual view bounds.
            mView.invalidate();
            sendEventForVirtualView(virtualViewId,
                    AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUSED);
            return true;
        }
        return false;
    }

    
Attempts to clear accessibility focus from a virtual view.

Params:
  • virtualViewId – The id of the virtual view from which to clear
           accessibility focus.
Returns:Whether this virtual view actually cleared accessibility focus.
/**
     * Attempts to clear accessibility focus from a virtual view.
     *
     * @param virtualViewId The id of the virtual view from which to clear
     *            accessibility focus.
     * @return Whether this virtual view actually cleared accessibility focus.
     */
    private boolean clearAccessibilityFocus(int virtualViewId) {
        if (isAccessibilityFocused(virtualViewId)) {
            mFocusedVirtualViewId = INVALID_ID;
            mView.invalidate();
            sendEventForVirtualView(virtualViewId,
                    AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUS_CLEARED);
            return true;
        }
        return false;
    }

    
Provides a mapping between view-relative coordinates and logical
items.

Params:
  • x – The view-relative x coordinate
  • y – The view-relative y coordinate
Returns:virtual view identifier for the logical item under
        coordinates (x,y)
/**
     * Provides a mapping between view-relative coordinates and logical
     * items.
     *
     * @param x The view-relative x coordinate
     * @param y The view-relative y coordinate
     * @return virtual view identifier for the logical item under
     *         coordinates (x,y)
     */
    protected abstract int getVirtualViewAt(float x, float y);

    
Populates a list with the view's visible items. The ordering of items within virtualViewIds specifies order of accessibility focus traversal. 
Params:
  • virtualViewIds – The list to populate with visible items
/**
     * Populates a list with the view's visible items. The ordering of items
     * within {@code virtualViewIds} specifies order of accessibility focus
     * traversal.
     *
     * @param virtualViewIds The list to populate with visible items
     */
    protected abstract void getVisibleVirtualViews(IntArray virtualViewIds);

    
Populates an AccessibilityEvent with information about the specified item. 

Implementations must populate the following required fields:




The helper class automatically populates the following fields with
default values, but implementations may optionally override them:




The following required fields are automatically populated by the
helper class and may not be overridden:



Params:
  • virtualViewId – The virtual view id for the item for which to
           populate the event
  • event – The event to populate
/**
     * Populates an {@link AccessibilityEvent} with information about the
     * specified item.
     * <p>
     * Implementations <b>must</b> populate the following required fields:
     * <ul>
     * <li>event text, see {@link AccessibilityEvent#getText} or
     * {@link AccessibilityEvent#setContentDescription}
     * </ul>
     * <p>
     * The helper class automatically populates the following fields with
     * default values, but implementations may optionally override them:
     * <ul>
     * <li>item class name, set to android.view.View, see
     * {@link AccessibilityEvent#setClassName}
     * </ul>
     * <p>
     * The following required fields are automatically populated by the
     * helper class and may not be overridden:
     * <ul>
     * <li>package name, set to the package of the host view's
     * {@link Context}, see {@link AccessibilityEvent#setPackageName}
     * <li>event source, set to the host view and virtual view identifier,
     * see {@link android.view.accessibility.AccessibilityRecord#setSource(View, int)}
     * </ul>
     *
     * @param virtualViewId The virtual view id for the item for which to
     *            populate the event
     * @param event The event to populate
     */
    protected abstract void onPopulateEventForVirtualView(
            int virtualViewId, AccessibilityEvent event);

    
Populates an AccessibilityEvent with information about the host view. 

The default implementation is a no-op.

Params:
  • event – the event to populate with information about the host view
/**
     * Populates an {@link AccessibilityEvent} with information about the host
     * view.
     * <p>
     * The default implementation is a no-op.
     *
     * @param event the event to populate with information about the host view
     */
    protected void onPopulateEventForHost(AccessibilityEvent event) {
        // Default implementation is no-op.
    }

    
Populates an AccessibilityNodeInfo with information about the specified item. 

Implementations must populate the following required fields:




The helper class automatically populates the following fields with
default values, but implementations may optionally override them:




The following required fields are automatically populated by the
helper class and may not be overridden:



 Additionally, the helper class automatically handles accessibility focus management by adding the appropriate AccessibilityNodeInfo.ACTION_ACCESSIBILITY_FOCUS or AccessibilityNodeInfo.ACTION_CLEAR_ACCESSIBILITY_FOCUS action. Implementations must never manually add these actions.


The helper class also automatically modifies parent- and
screen-relative bounds to reflect the portion of the item visible
within its parent.

Params:
  • virtualViewId – The virtual view identifier of the item for
           which to populate the node
  • node – The node to populate
/**
     * Populates an {@link AccessibilityNodeInfo} with information
     * about the specified item.
     * <p>
     * Implementations <b>must</b> populate the following required fields:
     * <ul>
     * <li>event text, see {@link AccessibilityNodeInfo#setText} or
     * {@link AccessibilityNodeInfo#setContentDescription}
     * <li>bounds in parent coordinates, see
     * {@link AccessibilityNodeInfo#setBoundsInParent}
     * </ul>
     * <p>
     * The helper class automatically populates the following fields with
     * default values, but implementations may optionally override them:
     * <ul>
     * <li>enabled state, set to true, see
     * {@link AccessibilityNodeInfo#setEnabled}
     * <li>item class name, identical to the class name set by
     * {@link #onPopulateEventForVirtualView}, see
     * {@link AccessibilityNodeInfo#setClassName}
     * </ul>
     * <p>
     * The following required fields are automatically populated by the
     * helper class and may not be overridden:
     * <ul>
     * <li>package name, identical to the package name set by
     * {@link #onPopulateEventForVirtualView}, see
     * {@link AccessibilityNodeInfo#setPackageName}
     * <li>node source, identical to the event source set in
     * {@link #onPopulateEventForVirtualView}, see
     * {@link AccessibilityNodeInfo#setSource(View, int)}
     * <li>parent view, set to the host view, see
     * {@link AccessibilityNodeInfo#setParent(View)}
     * <li>visibility, computed based on parent-relative bounds, see
     * {@link AccessibilityNodeInfo#setVisibleToUser}
     * <li>accessibility focus, computed based on internal helper state, see
     * {@link AccessibilityNodeInfo#setAccessibilityFocused}
     * <li>bounds in screen coordinates, computed based on host view bounds,
     * see {@link AccessibilityNodeInfo#setBoundsInScreen}
     * </ul>
     * <p>
     * Additionally, the helper class automatically handles accessibility
     * focus management by adding the appropriate
     * {@link AccessibilityNodeInfo#ACTION_ACCESSIBILITY_FOCUS} or
     * {@link AccessibilityNodeInfo#ACTION_CLEAR_ACCESSIBILITY_FOCUS}
     * action. Implementations must <b>never</b> manually add these actions.
     * <p>
     * The helper class also automatically modifies parent- and
     * screen-relative bounds to reflect the portion of the item visible
     * within its parent.
     *
     * @param virtualViewId The virtual view identifier of the item for
     *            which to populate the node
     * @param node The node to populate
     */
    protected abstract void onPopulateNodeForVirtualView(
            int virtualViewId, AccessibilityNodeInfo node);

    
Populates an AccessibilityNodeInfo with information about the host view. 

The default implementation is a no-op.

Params:
  • node – the node to populate with information about the host view
/**
     * Populates an {@link AccessibilityNodeInfo} with information about the
     * host view.
     * <p>
     * The default implementation is a no-op.
     *
     * @param node the node to populate with information about the host view
     */
    protected void onPopulateNodeForHost(AccessibilityNodeInfo node) {
        // Default implementation is no-op.
    }

    
Performs the specified accessibility action on the item associated with the virtual view identifier. See AccessibilityNodeInfo.performAction(int, Bundle) for more information. 

Implementations must handle any actions added manually in onPopulateNodeForVirtualView. 
 The helper class automatically handles focus management resulting from AccessibilityNodeInfo.ACTION_ACCESSIBILITY_FOCUS and AccessibilityNodeInfo.ACTION_CLEAR_ACCESSIBILITY_FOCUS actions. 
Params:
  • virtualViewId – The virtual view identifier of the item on which
           to perform the action
  • action – The accessibility action to perform
  • arguments – (Optional) A bundle with additional arguments, or
           null
Returns:true if the action was performed
/**
     * Performs the specified accessibility action on the item associated
     * with the virtual view identifier. See
     * {@link AccessibilityNodeInfo#performAction(int, Bundle)} for
     * more information.
     * <p>
     * Implementations <b>must</b> handle any actions added manually in
     * {@link #onPopulateNodeForVirtualView}.
     * <p>
     * The helper class automatically handles focus management resulting
     * from {@link AccessibilityNodeInfo#ACTION_ACCESSIBILITY_FOCUS}
     * and
     * {@link AccessibilityNodeInfo#ACTION_CLEAR_ACCESSIBILITY_FOCUS}
     * actions.
     *
     * @param virtualViewId The virtual view identifier of the item on which
     *            to perform the action
     * @param action The accessibility action to perform
     * @param arguments (Optional) A bundle with additional arguments, or
     *            null
     * @return true if the action was performed
     */
    protected abstract boolean onPerformActionForVirtualView(
            int virtualViewId, int action, Bundle arguments);

    
Exposes a virtual view hierarchy to the accessibility framework. Only
used in API 16+.

/**
     * Exposes a virtual view hierarchy to the accessibility framework. Only
     * used in API 16+.
     */
    private class ExploreByTouchNodeProvider extends AccessibilityNodeProvider {
        @Override
        public AccessibilityNodeInfo createAccessibilityNodeInfo(int virtualViewId) {
            return ExploreByTouchHelper.this.createNode(virtualViewId);
        }

        @Override
        public boolean performAction(int virtualViewId, int action, Bundle arguments) {
            return ExploreByTouchHelper.this.performAction(virtualViewId, action, arguments);
        }
    }
}