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Android Reference

AccessibilityNodeProvider


android.view.accessibility

Class 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 AccessibilityService explores the window content. Since the virtual View tree does not exist this class is responsible for managing the AccessibilityNodeInfos 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 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 AccessibilityNodeInfos 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;
     
    • Constructor Detail

      • AccessibilityNodeProvider

        public AccessibilityNodeProvider()
    • Method Detail

      • createAccessibilityNodeInfo

        public AccessibilityNodeInfo createAccessibilityNodeInfo(int virtualViewId)
        Returns an 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 View.NO_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.

        Parameters:
        virtualViewId - A client defined virtual view id.
        Returns:
        A populated AccessibilityNodeInfo for a virtual descendant or the host View.
        See Also:
        View.createAccessibilityNodeInfo(), AccessibilityNodeInfo
      • findAccessibilityNodeInfosByText

        public List<AccessibilityNodeInfo> findAccessibilityNodeInfosByText(String text,
                                                                   int virtualViewId)
        Finds AccessibilityNodeInfos 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 View.NO_ID.
        Parameters:
        virtualViewId - A client defined virtual view id which defined the root of the tree in which to perform the search.
        text - The searched text.
        Returns:
        A list of node info.
        See Also:
        createAccessibilityNodeInfo(int), AccessibilityNodeInfo


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