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      * The virtual id for the hosting View.
74      */
75     public static final int HOST_VIEW_ID = -1;
76 
77     /**
78      * Returns an {@link AccessibilityNodeInfo} representing a virtual view,
79      * i.e. a descendant of the host View, with the given <code>virtualViewId</code>
80      * or the host View itself if <code>virtualViewId</code> equals to {@link #HOST_VIEW_ID}.
81      * <p>
82      * A virtual descendant is an imaginary View that is reported as a part of the view
83      * hierarchy for accessibility purposes. This enables custom views that draw complex
84      * content to report them selves as a tree of virtual views, thus conveying their
85      * logical structure.
86      * </p>
87      * <p>
88      * The implementer is responsible for obtaining an accessibility node info from the
89      * pool of reusable instances and setting the desired properties of the node info
90      * before returning it.
91      * </p>
92      *
93      * @param virtualViewId A client defined virtual view id.
94      * @return A populated {@link AccessibilityNodeInfo} for a virtual descendant or the
95      *     host View.
96      *
97      * @see View#createAccessibilityNodeInfo()
98      * @see AccessibilityNodeInfo
99      */
createAccessibilityNodeInfo(int virtualViewId)100     public AccessibilityNodeInfo createAccessibilityNodeInfo(int virtualViewId) {
101         return null;
102     }
103 
104     /**
105      * Adds extra data to an {@link AccessibilityNodeInfo} based on an explicit request for the
106      * additional data.
107      * <p>
108      * This method only needs to be implemented if a virtual view offers to provide additional
109      * data.
110      * </p>
111      *
112      * @param virtualViewId The virtual view id used to create the node
113      * @param info The info to which to add the extra data
114      * @param extraDataKey A key specifying the type of extra data to add to the info. The
115      *                     extra data should be added to the {@link Bundle} returned by
116      *                     the info's {@link AccessibilityNodeInfo#getExtras} method.
117      * @param arguments A {@link Bundle} holding any arguments relevant for this request.
118      *
119      * @see AccessibilityNodeInfo#setExtraAvailableData
120      */
addExtraDataToAccessibilityNodeInfo( int virtualViewId, AccessibilityNodeInfo info, String extraDataKey, Bundle arguments)121     public void addExtraDataToAccessibilityNodeInfo(
122             int virtualViewId, AccessibilityNodeInfo info, String extraDataKey, Bundle arguments) {
123     }
124 
125     /**
126      * Performs an accessibility action on a virtual view, i.e. a descendant of the
127      * host View, with the given <code>virtualViewId</code> or the host View itself
128      * if <code>virtualViewId</code> equals to {@link #HOST_VIEW_ID}.
129      *
130      * @param virtualViewId A client defined virtual view id.
131      * @param action The action to perform.
132      * @param arguments Optional action arguments.
133      * @return True if the action was performed.
134      *
135      * @see View#performAccessibilityAction(int, Bundle)
136      * @see #createAccessibilityNodeInfo(int)
137      * @see AccessibilityNodeInfo
138      */
performAction(int virtualViewId, int action, Bundle arguments)139     public boolean performAction(int virtualViewId, int action, Bundle arguments) {
140         return false;
141     }
142 
143     /**
144      * Finds {@link AccessibilityNodeInfo}s by text. The match is case insensitive
145      * containment. The search is relative to the virtual view, i.e. a descendant of the
146      * host View, with the given <code>virtualViewId</code> or the host View itself
147      * <code>virtualViewId</code> equals to {@link #HOST_VIEW_ID}.
148      *
149      * @param virtualViewId A client defined virtual view id which defined
150      *     the root of the tree in which to perform the search.
151      * @param text The searched text.
152      * @return A list of node info.
153      *
154      * @see #createAccessibilityNodeInfo(int)
155      * @see AccessibilityNodeInfo
156      */
findAccessibilityNodeInfosByText(String text, int virtualViewId)157     public List<AccessibilityNodeInfo> findAccessibilityNodeInfosByText(String text,
158             int virtualViewId) {
159         return null;
160     }
161 
162     /**
163      * Find the virtual view, i.e. a descendant of the host View, that has the
164      * specified focus type.
165      *
166      * @param focus The focus to find. One of
167      *            {@link AccessibilityNodeInfo#FOCUS_INPUT} or
168      *            {@link AccessibilityNodeInfo#FOCUS_ACCESSIBILITY}.
169      * @return The node info of the focused view or null.
170      * @see AccessibilityNodeInfo#FOCUS_INPUT
171      * @see AccessibilityNodeInfo#FOCUS_ACCESSIBILITY
172      */
findFocus(int focus)173     public AccessibilityNodeInfo findFocus(int focus) {
174         return null;
175     }
176 }
177