/* * 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 {@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. *

*

* 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 {@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: *

*
 *     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;
 * 
*/ public abstract class AccessibilityNodeProvider { /** * Returns an {@link AccessibilityNodeInfo} representing a virtual view, * i.e. a descendant of the host View, with the given virtualViewId * or the host View itself if virtualViewId equals to {@link View#NO_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. *

* * @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; } /** * Performs an accessibility action on a virtual view, i.e. a descendant of the * host View, with the given virtualViewId or the host View itself * if virtualViewId equals to {@link View#NO_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 {@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 virtualViewId or the host View itself * virtualViewId equals to {@link View#NO_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 findAccessibilityNodeInfosByText(String text, int virtualViewId) { return null; } /** * Find the virtual view, i.e. 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; } }