| 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;
| 