https://source.android.com/ 
/*
 * Copyright (C) 2011 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.accessibility;

import android.accessibilityservice.AccessibilityService;
import android.os.Bundle;
import android.view.View;

import java.util.List;


This class is the contract a client should implement to enable support of a virtual view hierarchy rooted at a given view for accessibility purposes. A virtual view hierarchy is a tree of imaginary Views that is reported as a part of the view hierarchy when an AccessibilityService explores the window content. Since the virtual View tree does not exist this class is responsible for managing the AccessibilityNodeInfos describing that tree to accessibility services. 



The main use case of these APIs is to enable a custom view that draws complex content,
for example a monthly calendar grid, to be presented as a tree of logical nodes,
for example month days each containing events, thus conveying its logical structure.



 A typical use case is to override View.getAccessibilityNodeProvider() of the View that is a root of a virtual View hierarchy to return an instance of this class. In such a case this instance is responsible for managing AccessibilityNodeInfos describing the virtual sub-tree rooted at the View including the one representing the View itself. Similarly the returned instance is responsible for performing accessibility actions on any virtual view or the root view itself. For example: 


    getAccessibilityNodeProvider(
        if (mAccessibilityNodeProvider == null) {
            mAccessibilityNodeProvider = new AccessibilityNodeProvider() {
                public boolean performAction(int action, int virtualDescendantId) {
                    // Implementation.
                    return false;
                }
                public List findAccessibilityNodeInfosByText(String text,
                        int virtualDescendantId) {
                    // Implementation.
                    return null;
                }
                public AccessibilityNodeInfo createAccessibilityNodeInfo(int virtualDescendantId) {
                    // Implementation.
                    return null;
                }
            });
    return mAccessibilityNodeProvider;



/**
 * This class is the contract a client should implement to enable support of a
 * virtual view hierarchy rooted at a given view for accessibility purposes. A virtual
 * view hierarchy is a tree of imaginary Views that is reported as a part of the view
 * hierarchy when an {@link AccessibilityService} explores the window content.
 * Since the virtual View tree does not exist this class is responsible for
 * managing the {@link AccessibilityNodeInfo}s describing that tree to accessibility
 * services.
 * </p>
 * <p>
 * The main use case of these APIs is to enable a custom view that draws complex content,
 * for example a monthly calendar grid, to be presented as a tree of logical nodes,
 * for example month days each containing events, thus conveying its logical structure.
 * <p>
 * <p>
 * A typical use case is to override {@link View#getAccessibilityNodeProvider()} of the
 * View that is a root of a virtual View hierarchy to return an instance of this class.
 * In such a case this instance is responsible for managing {@link AccessibilityNodeInfo}s
 * describing the virtual sub-tree rooted at the View including the one representing the
 * View itself. Similarly the returned instance is responsible for performing accessibility
 * actions on any virtual view or the root view itself. For example:
 * </p>
 * <pre>
 *     getAccessibilityNodeProvider(
 *         if (mAccessibilityNodeProvider == null) {
 *             mAccessibilityNodeProvider = new AccessibilityNodeProvider() {
 *                 public boolean performAction(int action, int virtualDescendantId) {
 *                     // Implementation.
 *                     return false;
 *                 }
 *
 *                 public List<AccessibilityNodeInfo> findAccessibilityNodeInfosByText(String text,
 *                         int virtualDescendantId) {
 *                     // Implementation.
 *                     return null;
 *                 }
 *
 *                 public AccessibilityNodeInfo createAccessibilityNodeInfo(int virtualDescendantId) {
 *                     // Implementation.
 *                     return null;
 *                 }
 *             });
 *     return mAccessibilityNodeProvider;
 * </pre>
 */
public abstract class AccessibilityNodeProvider {

    
The virtual id for the hosting View.

/**
     * The virtual id for the hosting View.
     */
    public static final int HOST_VIEW_ID = -1;

    
Returns an AccessibilityNodeInfo representing a virtual view, such as a descendant of the host View, with the given virtualViewId
or the host View itself if virtualViewId equals to HOST_VIEW_ID. 

A virtual descendant is an imaginary View that is reported as a part of the view
hierarchy for accessibility purposes. This enables custom views that draw complex
content to report them selves as a tree of virtual views, thus conveying their
logical structure.




The implementer is responsible for obtaining an accessibility node info from the
pool of reusable instances and setting the desired properties of the node info
before returning it.



Params:
  • virtualViewId – A client defined virtual view id.
See Also:
Returns:A populated AccessibilityNodeInfo for a virtual descendant or the host View.
/**
     * Returns an {@link AccessibilityNodeInfo} representing a virtual view,
     * such as a descendant of the host View, with the given <code>virtualViewId</code>
     * or the host View itself if <code>virtualViewId</code> equals to {@link #HOST_VIEW_ID}.
     * <p>
     * A virtual descendant is an imaginary View that is reported as a part of the view
     * hierarchy for accessibility purposes. This enables custom views that draw complex
     * content to report them selves as a tree of virtual views, thus conveying their
     * logical structure.
     * </p>
     * <p>
     * The implementer is responsible for obtaining an accessibility node info from the
     * pool of reusable instances and setting the desired properties of the node info
     * before returning it.
     * </p>
     *
     * @param virtualViewId A client defined virtual view id.
     * @return A populated {@link AccessibilityNodeInfo} for a virtual descendant or the
     *     host View.
     *
     * @see View#createAccessibilityNodeInfo()
     * @see AccessibilityNodeInfo
     */
    public AccessibilityNodeInfo createAccessibilityNodeInfo(int virtualViewId) {
        return null;
    }

    
Adds extra data to an AccessibilityNodeInfo based on an explicit request for the additional data. 

This method only needs to be implemented if a virtual view offers to provide additional
data.



Params:
  • virtualViewId – The virtual view id used to create the node
  • info – The info to which to add the extra data
  • extraDataKey – A key specifying the type of extra data to add to the info. The extra data should be added to the Bundle returned by the info's AccessibilityNodeInfo.getExtras method.
  • arguments – A Bundle holding any arguments relevant for this request.
See Also:
  • AccessibilityNodeInfo.setExtraAvailableData
/**
     * Adds extra data to an {@link AccessibilityNodeInfo} based on an explicit request for the
     * additional data.
     * <p>
     * This method only needs to be implemented if a virtual view offers to provide additional
     * data.
     * </p>
     *
     * @param virtualViewId The virtual view id used to create the node
     * @param info The info to which to add the extra data
     * @param extraDataKey A key specifying the type of extra data to add to the info. The
     *                     extra data should be added to the {@link Bundle} returned by
     *                     the info's {@link AccessibilityNodeInfo#getExtras} method.
     * @param arguments A {@link Bundle} holding any arguments relevant for this request.
     *
     * @see AccessibilityNodeInfo#setExtraAvailableData
     */
    public void addExtraDataToAccessibilityNodeInfo(
            int virtualViewId, AccessibilityNodeInfo info, String extraDataKey, Bundle arguments) {
    }

    
Performs an accessibility action on a virtual view, such as a descendant of the
host View, with the given virtualViewId or the host View itself
if virtualViewId equals to HOST_VIEW_ID. 
Params:
  • virtualViewId – A client defined virtual view id.
  • action – The action to perform.
  • arguments – Optional action arguments.
See Also:
Returns:True if the action was performed.
/**
     * Performs an accessibility action on a virtual view, such as a descendant of the
     * host View, with the given <code>virtualViewId</code> or the host View itself
     * if <code>virtualViewId</code> equals to {@link #HOST_VIEW_ID}.
     *
     * @param virtualViewId A client defined virtual view id.
     * @param action The action to perform.
     * @param arguments Optional action arguments.
     * @return True if the action was performed.
     *
     * @see View#performAccessibilityAction(int, Bundle)
     * @see #createAccessibilityNodeInfo(int)
     * @see AccessibilityNodeInfo
     */
    public boolean performAction(int virtualViewId, int action, Bundle arguments) {
        return false;
    }

    
Finds AccessibilityNodeInfos by text. The match is case insensitive containment. The search is relative to the virtual view, i.e. a descendant of the host View, with the given virtualViewId or the host View itself
virtualViewId equals to HOST_VIEW_ID. 
Params:
  • virtualViewId – A client defined virtual view id which defined
    the root of the tree in which to perform the search.
  • text – The searched text.
See Also:
Returns:A list of node info.
/**
     * Finds {@link AccessibilityNodeInfo}s by text. The match is case insensitive
     * containment. The search is relative to the virtual view, i.e. a descendant of the
     * host View, with the given <code>virtualViewId</code> or the host View itself
     * <code>virtualViewId</code> equals to {@link #HOST_VIEW_ID}.
     *
     * @param virtualViewId A client defined virtual view id which defined
     *     the root of the tree in which to perform the search.
     * @param text The searched text.
     * @return A list of node info.
     *
     * @see #createAccessibilityNodeInfo(int)
     * @see AccessibilityNodeInfo
     */
    public List<AccessibilityNodeInfo> findAccessibilityNodeInfosByText(String text,
            int virtualViewId) {
        return null;
    }

    
Find the virtual view, such as a descendant of the host View, that has the
specified focus type.

Params:
See Also:
Returns:The node info of the focused view or null.
/**
     * Find the virtual view, such as a descendant of the host View, that has the
     * specified focus type.
     *
     * @param focus The focus to find. One of
     *            {@link AccessibilityNodeInfo#FOCUS_INPUT} or
     *            {@link AccessibilityNodeInfo#FOCUS_ACCESSIBILITY}.
     * @return The node info of the focused view or null.
     * @see AccessibilityNodeInfo#FOCUS_INPUT
     * @see AccessibilityNodeInfo#FOCUS_ACCESSIBILITY
     */
    public AccessibilityNodeInfo findFocus(int focus) {
        return null;
    }
}