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Commit 2f69c16c authored by Phil Weaver's avatar Phil Weaver
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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 a4002c8d)
parent 82b0d17b

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

+11 −3
Original line number Diff line number Diff line
@@ -418,20 +418,28 @@ public class AccessibilityCache { 
     *

     * @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

+20 −0
Original line number Diff line number Diff line
@@ -299,6 +299,26 @@ public class AccessibilityCacheTest { 
        }

    }



    @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