Touch exploration feature, event bubling, refactor

1. Added an Input Filter that interprets the touch screen motion
   events to perfrom accessibility exploration. One finger explores.
   Tapping within a given time and distance slop on the last exlopred
   location does click and long press, respectively. Two fingers close
   and in the same diretion drag. Multiple finglers or two fingers in
   different directions or two fingers too far away are delegated to
   the view hierarchy. Non moving fingers "accidentally grabbed the
   device for the scrren" are ignored.

2. Added accessibility events for hover enter, hover exit, touch
   exoloration gesture start, and end. Accessibility hover events
   are fired by the hover pipeline. An accessibility event is
   dispatched up the view tree and the topmost view fires it.
   Thus predecessors can augment the fired event. An accessibility
   event has several records and a predecessor can optionally
   modify, delete, and add such to the event.

3. Added onPopulateAccessibilityEvent and refactored the existing
   accessibility code to use it.

4. Added API for querying the currently enabled accessibility services
   by feedback type.

Change-Id: Iec03c6c3fe298de3f14cb6efdbb9b198cd531a0c

1 files changed, 16 insertions, 12 deletions

diff --git a/core/java/android/widget/AdapterView.java b/core/java/android/widget/AdapterView.java
index f16efbdeb7be..060f1a9b2bc0 100644
--- a/core/java/android/widget/AdapterView.java
+++ b/core/java/android/widget/AdapterView.java
@@ -876,7 +876,6 @@ public abstract class AdapterView<T extends Adapter> extends ViewGroup {
 
     @Override
     public boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event) {
-        boolean populated = false;
         // This is an exceptional case which occurs when a window gets the
         // focus and sends a focus event via its focused child to announce
         // current focus/selection. AdapterView fires selection but not focus
@@ -885,22 +884,27 @@ public abstract class AdapterView<T extends Adapter> extends ViewGroup {
             event.setEventType(AccessibilityEvent.TYPE_VIEW_SELECTED);
         }
 
-        // we send selection events only from AdapterView to avoid
-        // generation of such event for each child
+        // We first get a chance to populate the event.
+        onPopulateAccessibilityEvent(event);
+
+        // We send selection events only from AdapterView to avoid
+        // generation of such event for each child.
         View selectedView = getSelectedView();
         if (selectedView != null) {
-            populated = selectedView.dispatchPopulateAccessibilityEvent(event);
+            return selectedView.dispatchPopulateAccessibilityEvent(event);
         }
 
-        if (!populated) {
-            if (selectedView != null) {
-                event.setEnabled(selectedView.isEnabled());
-            }
-            event.setItemCount(getCount());
-            event.setCurrentItemIndex(getSelectedItemPosition());
-        }
+        return false;
+    }
 
-        return populated;
+    @Override
+    public void onPopulateAccessibilityEvent(AccessibilityEvent event) {
+        View selectedView = getSelectedView();
+        if (selectedView != null) {
+            event.setEnabled(selectedView.isEnabled());
+        }
+        event.setItemCount(getCount());
+        event.setCurrentItemIndex(getSelectedItemPosition());
     }
 
     @Override