commit 2f69c16c3dd0ea9522deebd9141ccc189b4a118e
author Phil Weaver <pweaver@google.com> Tue Jul 17 12:28:24 2018 -0700
committer Phil Weaver <pweaver@google.com> Thu Sep 20 23:46:25 2018 +0000
tree dac9338de36dede11b386aa070779b61c5ed155d
parent 82b0d17b393783c5259bf183a7ded118d28e50cc

Fix a11y cache correctness bug

If two views change, their common ancestor can send
a subtree_changed event. But the cache is dropping
events that come from views that it hasn't cached.

Now clearing the cache entirely when a node not in
the cache sends a subtree changed event, since we
don't know which nodes are descendents and which
may have changed.

I'm not thrilled with this change, since it may
degrade performance, but I want to fix the correctness
problem quickly.

Bug: 111554539
Test: atest AccessibilityCacheTest
Change-Id: Ib32d3622cddd7001663943eff71e823d21f5e500
(cherry picked from commit a4002c8daf272f550787d94bed8e81749a891e66)

core/java/android/view/accessibility/AccessibilityCache.java

diff --git a/core/java/android/view/accessibility/AccessibilityCache.java b/core/java/android/view/accessibility/AccessibilityCache.java
index da5a1cd..0e1e379 100644
--- a/core/java/android/view/accessibility/AccessibilityCache.java
+++ b/core/java/android/view/accessibility/AccessibilityCache.java
@@ -418,20 +418,28 @@
      *
      * @param nodes The nodes in the hosting window.
      * @param rootNodeId The id of the root to evict.
+     *
+     * @return {@code true} if the cache was cleared
      */
-    private void clearSubTreeRecursiveLocked(LongSparseArray<AccessibilityNodeInfo> nodes,
+    private boolean clearSubTreeRecursiveLocked(LongSparseArray<AccessibilityNodeInfo> nodes,
             long rootNodeId) {
         AccessibilityNodeInfo current = nodes.get(rootNodeId);
         if (current == null) {
-            return;
+            // The node isn't in the cache, but its descendents might be.
+            clear();
+            return true;
         }
         nodes.remove(rootNodeId);
         final int childCount = current.getChildCount();
         for (int i = 0; i < childCount; i++) {
             final long childNodeId = current.getChildId(i);
-            clearSubTreeRecursiveLocked(nodes, childNodeId);
+            if (clearSubTreeRecursiveLocked(nodes, childNodeId)) {
+                current.recycle();
+                return true;
+            }
         }
         current.recycle();
+        return false;
     }
 
     /**

core/tests/coretests/src/android/view/accessibility/AccessibilityCacheTest.java

diff --git a/core/tests/coretests/src/android/view/accessibility/AccessibilityCacheTest.java b/core/tests/coretests/src/android/view/accessibility/AccessibilityCacheTest.java
index 4de8155..993378d 100644
--- a/core/tests/coretests/src/android/view/accessibility/AccessibilityCacheTest.java
+++ b/core/tests/coretests/src/android/view/accessibility/AccessibilityCacheTest.java
@@ -300,6 +300,26 @@
     }
 
     @Test
+    public void subTreeChangeEventFromUncachedNode_clearsNodeInCache() {
+        AccessibilityNodeInfo nodeInfo = getNodeWithA11yAndWindowId(CHILD_VIEW_ID, WINDOW_ID_1);
+        long id = nodeInfo.getSourceNodeId();
+        mAccessibilityCache.add(nodeInfo);
+        nodeInfo.recycle();
+
+        AccessibilityEvent event = AccessibilityEvent
+                .obtain(AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED);
+        event.setContentChangeTypes(AccessibilityEvent.CONTENT_CHANGE_TYPE_SUBTREE);
+        event.setSource(getMockViewWithA11yAndWindowIds(PARENT_VIEW_ID, WINDOW_ID_1));
+
+        mAccessibilityCache.onAccessibilityEvent(event);
+        AccessibilityNodeInfo shouldBeNull = mAccessibilityCache.getNode(WINDOW_ID_1, id);
+        if (shouldBeNull != null) {
+            shouldBeNull.recycle();
+        }
+        assertNull(shouldBeNull);
+    }
+
+    @Test
     public void scrollEvent_clearsNodeAndChild() {
         AccessibilityEvent event = AccessibilityEvent
                 .obtain(AccessibilityEvent.TYPE_VIEW_SCROLLED);