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AccessibilityNodeProvider.javaAPI DocAndroid 5.1 API6432Thu Mar 12 22:22:10 GMT 2015android.view.accessibility

AccessibilityNodeProvider

public abstract class AccessibilityNodeProvider extends Object
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;

Fields Summary
public static final int
HOST_VIEW_ID
The virtual id for the hosting View.
Constructors Summary
Methods Summary
public AccessibilityNodeInfocreateAccessibilityNodeInfo(int virtualViewId)
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 #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.

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


                                                                                                                                               
        
        return null;
    
public java.util.ListfindAccessibilityNodeInfosByText(java.lang.String text, int virtualViewId)
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 #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

        return null;
    
public AccessibilityNodeInfofindFocus(int focus)
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

        return null;
    
public booleanperformAction(int virtualViewId, int action, android.os.Bundle arguments)
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 #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

        return false;