Send TYPE_VIEW_FOCUSED for views with input focus. (#12410)

This change modifies the accessibility bridge so that if a node has input focus, then it will tell TalkBack so that it will request the accessibility focus for the view.

It also sets the content change types bit field to include CONTENT_CHANGE_TYPE_SUBTREE to indicate that the subtree for the view has changed for API levels after, and including, KitKat (19)

shell/platform/android/io/flutter/view/AccessibilityBridge.java

@@ -519,6 +519,10 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
         result.setClassName("android.view.View");
         result.setSource(rootAccessibilityView, virtualViewId);
         result.setFocusable(semanticsNode.isFocusable());
+        if (semanticsNode.isFocusable()) {
+           result.addAction(AccessibilityNodeInfo.ACTION_FOCUS);
+        }
+
         if (inputFocusedSemanticsNode != null) {
             result.setFocused(inputFocusedSemanticsNode.id == virtualViewId);
         }
@@ -1228,6 +1232,11 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
             }
             if (semanticsNode.hasFlag(Flag.IS_FOCUSED)) {
                 inputFocusedSemanticsNode = semanticsNode;
+                AccessibilityEvent event = obtainAccessibilityEvent(
+                    inputFocusedSemanticsNode.id,
+                    AccessibilityEvent.TYPE_VIEW_FOCUSED
+                );
+                sendAccessibilityEvent(event);
             }
             if (semanticsNode.hadPreviousConfig) {
                 updated.add(semanticsNode);
@@ -1271,7 +1280,7 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
         }
         if (lastAdded != null && lastAdded.id != previousRouteId) {
             previousRouteId = lastAdded.id;
-            createAndSendWindowChangeEvent(lastAdded);
+            sendWindowChangeEvent(lastAdded);
         }
         flutterNavigationStack.clear();
         for (SemanticsNode semanticsNode : newRoutes) {
@@ -1290,7 +1299,7 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
 
         // TODO(goderbauer): Send this event only once (!) for changed subtrees,
         //     see https://github.com/flutter/flutter/issues/14534
-        sendAccessibilityEvent(0, AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED);
+        sendWindowContentChangeEvent(0);
 
         for (SemanticsNode object : updated) {
             if (object.didScroll()) {
@@ -1362,13 +1371,13 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
                 String label = object.label == null ? "" : object.label;
                 String previousLabel = object.previousLabel == null ? "" : object.label;
                 if (!label.equals(previousLabel) || !object.hadFlag(Flag.IS_LIVE_REGION)) {
-                    sendAccessibilityEvent(object.id, AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED);
+                    sendWindowContentChangeEvent(object.id);
                 }
             } else if (object.hasFlag(Flag.IS_TEXT_FIELD) && object.didChangeLabel()
                     && inputFocusedSemanticsNode != null && inputFocusedSemanticsNode.id == object.id) {
                 // Text fields should announce when their label changes while focused. We use a live
                 // region tag to do so, and this event triggers that update.
-                sendAccessibilityEvent(object.id, AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED);
+                sendWindowContentChangeEvent(object.id);
             }
             if (accessibilityFocusedSemanticsNode != null && accessibilityFocusedSemanticsNode.id == object.id
                     && !object.hadFlag(Flag.IS_SELECTED) && object.hasFlag(Flag.IS_SELECTED)) {
@@ -1472,13 +1481,13 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
     }
 
     /**
-     * Factory method that creates a {@link AccessibilityEvent#TYPE_WINDOW_STATE_CHANGED} and sends
-     * the event to Android's accessibility system.
+     * Creates a {@link AccessibilityEvent#TYPE_WINDOW_STATE_CHANGED} and sends the event to
+     * Android's accessibility system.
      *
      * The given {@code route} should be a {@link SemanticsNode} that represents a navigation route
      * in the Flutter app.
      */
-    private void createAndSendWindowChangeEvent(@NonNull SemanticsNode route) {
+    private void sendWindowChangeEvent(@NonNull SemanticsNode route) {
         AccessibilityEvent event = obtainAccessibilityEvent(
             route.id,
             AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED
@@ -1488,6 +1497,27 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
         sendAccessibilityEvent(event);
     }
 
+    /**
+     * Creates a {@link AccessibilityEvent#TYPE_WINDOW_CONTENT_CHANGED} and sends the event to
+     * Android's accessibility system.
+     *
+     * It sets the content change types to {@link AccessibilityEvent#CONTENT_CHANGE_TYPE_SUBTREE}
+     * when supported by the API level.
+     *
+     * The given {@code virtualViewId} should be a {@link SemanticsNode} below which the content has
+     * changed.
+     */
+    private void sendWindowContentChangeEvent(int virtualViewId) {
+        AccessibilityEvent event = obtainAccessibilityEvent(
+            virtualViewId,
+            AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED
+        );
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
+            event.setContentChangeTypes(AccessibilityEvent.CONTENT_CHANGE_TYPE_SUBTREE);
+        }
+        sendAccessibilityEvent(event);
+    }
+
     /**
      * Factory method that creates a new {@link AccessibilityEvent} that is configured to represent
      * the Flutter {@link SemanticsNode} represented by the given {@code virtualViewId}, categorized
@@ -1559,7 +1589,7 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
         }
         accessibilityFocusedSemanticsNode = null;
         hoveredObject = null;
-        sendAccessibilityEvent(0, AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED);
+        sendWindowContentChangeEvent(0);
     }
 
     /**