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/*
* 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.
* </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.
*/
public static final int HOST_VIEW_ID = -1;
/**
* Returns an {@link AccessibilityNodeInfo} representing a virtual view,
* i.e. 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;
}
/**
* Performs an accessibility action on a virtual view, i.e. 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 {@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, 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;
}
}
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