1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.view.accessibility; 18 19 import android.accessibilityservice.AccessibilityService; 20 import android.os.Bundle; 21 import android.view.View; 22 23 import java.util.List; 24 25 /** 26 * This class is the contract a client should implement to enable support of a 27 * virtual view hierarchy rooted at a given view for accessibility purposes. A virtual 28 * view hierarchy is a tree of imaginary Views that is reported as a part of the view 29 * hierarchy when an {@link AccessibilityService} explores the window content. 30 * Since the virtual View tree does not exist this class is responsible for 31 * managing the {@link AccessibilityNodeInfo}s describing that tree to accessibility 32 * services. 33 * </p> 34 * <p> 35 * The main use case of these APIs is to enable a custom view that draws complex content, 36 * for example a monthly calendar grid, to be presented as a tree of logical nodes, 37 * for example month days each containing events, thus conveying its logical structure. 38 * <p> 39 * <p> 40 * A typical use case is to override {@link View#getAccessibilityNodeProvider()} of the 41 * View that is a root of a virtual View hierarchy to return an instance of this class. 42 * In such a case this instance is responsible for managing {@link AccessibilityNodeInfo}s 43 * describing the virtual sub-tree rooted at the View including the one representing the 44 * View itself. Similarly the returned instance is responsible for performing accessibility 45 * actions on any virtual view or the root view itself. For example: 46 * </p> 47 * <pre> 48 * getAccessibilityNodeProvider( 49 * if (mAccessibilityNodeProvider == null) { 50 * mAccessibilityNodeProvider = new AccessibilityNodeProvider() { 51 * public boolean performAction(int action, int virtualDescendantId) { 52 * // Implementation. 53 * return false; 54 * } 55 * 56 * public List<AccessibilityNodeInfo> findAccessibilityNodeInfosByText(String text, 57 * int virtualDescendantId) { 58 * // Implementation. 59 * return null; 60 * } 61 * 62 * public AccessibilityNodeInfo createAccessibilityNodeInfo(int virtualDescendantId) { 63 * // Implementation. 64 * return null; 65 * } 66 * }); 67 * return mAccessibilityNodeProvider; 68 * </pre> 69 */ 70 public abstract class AccessibilityNodeProvider { 71 72 /** 73 * Returns an {@link AccessibilityNodeInfo} representing a virtual view, 74 * i.e. a descendant of the host View, with the given <code>virtualViewId</code> 75 * or the host View itself if <code>virtualViewId</code> equals to {@link View#NO_ID}. 76 * <p> 77 * A virtual descendant is an imaginary View that is reported as a part of the view 78 * hierarchy for accessibility purposes. This enables custom views that draw complex 79 * content to report them selves as a tree of virtual views, thus conveying their 80 * logical structure. 81 * </p> 82 * <p> 83 * The implementer is responsible for obtaining an accessibility node info from the 84 * pool of reusable instances and setting the desired properties of the node info 85 * before returning it. 86 * </p> 87 * 88 * @param virtualViewId A client defined virtual view id. 89 * @return A populated {@link AccessibilityNodeInfo} for a virtual descendant or the 90 * host View. 91 * 92 * @see View#createAccessibilityNodeInfo() 93 * @see AccessibilityNodeInfo 94 */ 95 public AccessibilityNodeInfo createAccessibilityNodeInfo(int virtualViewId) { 96 return null; 97 } 98 99 /** 100 * Performs an accessibility action on a virtual view, i.e. a descendant of the 101 * host View, with the given <code>virtualViewId</code> or the host View itself 102 * if <code>virtualViewId</code> equals to {@link View#NO_ID}. 103 * 104 * @param virtualViewId A client defined virtual view id. 105 * @param action The action to perform. 106 * @param arguments Optional action arguments. 107 * @return True if the action was performed. 108 * 109 * @see View#performAccessibilityAction(int, Bundle) 110 * @see #createAccessibilityNodeInfo(int) 111 * @see AccessibilityNodeInfo 112 */ 113 public boolean performAction(int virtualViewId, int action, Bundle arguments) { 114 return false; 115 } 116 117 /** 118 * Finds {@link AccessibilityNodeInfo}s by text. The match is case insensitive 119 * containment. The search is relative to the virtual view, i.e. a descendant of the 120 * host View, with the given <code>virtualViewId</code> or the host View itself 121 * <code>virtualViewId</code> equals to {@link View#NO_ID}. 122 * 123 * @param virtualViewId A client defined virtual view id which defined 124 * the root of the tree in which to perform the search. 125 * @param text The searched text. 126 * @return A list of node info. 127 * 128 * @see #createAccessibilityNodeInfo(int) 129 * @see AccessibilityNodeInfo 130 */ 131 public List<AccessibilityNodeInfo> findAccessibilityNodeInfosByText(String text, 132 int virtualViewId) { 133 return null; 134 } 135 } 136
