Allow TalkBack navigation while a platform view is rendered (#21719)

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

@@ -28,6 +28,7 @@ import androidx.annotation.RequiresApi;
 import androidx.annotation.VisibleForTesting;
 import io.flutter.BuildConfig;
 import io.flutter.Log;
+import io.flutter.embedding.android.FlutterActivity;
 import io.flutter.embedding.engine.systemchannels.AccessibilityChannel;
 import io.flutter.plugin.platform.PlatformViewsAccessibilityDelegate;
 import io.flutter.util.Predicate;
@@ -541,12 +542,22 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
       return null;
     }
 
+    // Generate accessibility node for platform views using a virtual display.
+    //
+    // In this case, register the accessibility node in the view embedder,
+    // so the accessibility tree can be mirrored as a subtree of the Flutter accessibility tree.
+    // This is in constrast to hybrid composition where the embeded view is in the view hiearchy,
+    // so it doesn't need to be mirrored.
+    //
+    // See the case down below for how hybrid composition is handled.
     if (semanticsNode.platformViewId != -1) {
-      // For platform views we delegate the node creation to the accessibility view embedder.
       View embeddedView =
           platformViewsAccessibilityDelegate.getPlatformViewById(semanticsNode.platformViewId);
-      Rect bounds = semanticsNode.getGlobalRect();
-      return accessibilityViewEmbedder.getRootNode(embeddedView, semanticsNode.id, bounds);
+      boolean childUsesVirtualDisplay = !(embeddedView.getContext() instanceof FlutterActivity);
+      if (childUsesVirtualDisplay) {
+        Rect bounds = semanticsNode.getGlobalRect();
+        return accessibilityViewEmbedder.getRootNode(embeddedView, semanticsNode.id, bounds);
+      }
     }
 
     AccessibilityNodeInfo result =
@@ -823,11 +834,28 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
     }
 
     for (SemanticsNode child : semanticsNode.childrenInTraversalOrder) {
-      if (!child.hasFlag(Flag.IS_HIDDEN)) {
-        result.addChild(rootAccessibilityView, child.id);
+      if (child.hasFlag(Flag.IS_HIDDEN)) {
+        continue;
+      }
+      if (child.platformViewId != -1) {
+        View embeddedView =
+            platformViewsAccessibilityDelegate.getPlatformViewById(child.platformViewId);
+
+        // Add the embeded view as a child of the current accessibility node if it's using
+        // hybrid composition.
+        //
+        // In this case, the view is in the Activity's view hierarchy, so it doesn't need to be
+        // mirrored.
+        //
+        // See the case above for how virtual displays are handled.
+        boolean childUsesHybridComposition = embeddedView.getContext() instanceof FlutterActivity;
+        if (childUsesHybridComposition) {
+          result.addChild(embeddedView);
+          continue;
+        }
       }
+      result.addChild(rootAccessibilityView, child.id);
     }
-
     return result;
   }
 

shell/platform/android/test/io/flutter/view/AccessibilityBridgeTest.java

@@ -5,6 +5,7 @@
 package io.flutter.view;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.any;
 import static org.mockito.Mockito.anyInt;
@@ -16,14 +17,17 @@ import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 import android.annotation.TargetApi;
+import android.app.Activity;
 import android.content.ContentResolver;
 import android.content.Context;
+import android.graphics.Rect;
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewParent;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityManager;
 import android.view.accessibility.AccessibilityNodeInfo;
+import io.flutter.embedding.android.FlutterActivity;
 import io.flutter.embedding.engine.systemchannels.AccessibilityChannel;
 import io.flutter.plugin.platform.PlatformViewsAccessibilityDelegate;
 import java.nio.ByteBuffer;
@@ -33,6 +37,7 @@ import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.ArgumentCaptor;
 import org.robolectric.RobolectricTestRunner;
+import org.robolectric.RuntimeEnvironment;
 import org.robolectric.annotation.Config;
 
 @Config(manifest = Config.NONE)
@@ -198,6 +203,81 @@ public class AccessibilityBridgeTest {
     accessibilityBridge.onAccessibilityHoverEvent(MotionEvent.obtain(1, 1, 1, -10, -10, 0));
   }
 
+  @Test
+  public void itProducesPlatformViewNodeForHybridComposition() {
+    PlatformViewsAccessibilityDelegate accessibilityDelegate =
+        mock(PlatformViewsAccessibilityDelegate.class);
+
+    Context context = RuntimeEnvironment.application.getApplicationContext();
+    View rootAccessibilityView = new View(context);
+    AccessibilityViewEmbedder accessibilityViewEmbedder = mock(AccessibilityViewEmbedder.class);
+    AccessibilityBridge accessibilityBridge =
+        setUpBridge(
+            rootAccessibilityView,
+            /*accessibilityChannel=*/ null,
+            /*accessibilityManager=*/ null,
+            /*contentResolver=*/ null,
+            accessibilityViewEmbedder,
+            accessibilityDelegate);
+
+    TestSemanticsNode root = new TestSemanticsNode();
+    root.id = 0;
+
+    TestSemanticsNode platformView = new TestSemanticsNode();
+    platformView.id = 1;
+    platformView.platformViewId = 1;
+    root.addChild(platformView);
+
+    TestSemanticsUpdate testSemanticsRootUpdate = root.toUpdate();
+    accessibilityBridge.updateSemantics(
+        testSemanticsRootUpdate.buffer, testSemanticsRootUpdate.strings);
+
+    TestSemanticsUpdate testSemanticsPlatformViewUpdate = platformView.toUpdate();
+    accessibilityBridge.updateSemantics(
+        testSemanticsPlatformViewUpdate.buffer, testSemanticsPlatformViewUpdate.strings);
+
+    View embeddedView = mock(View.class);
+    when(accessibilityDelegate.getPlatformViewById(1)).thenReturn(embeddedView);
+
+    when(embeddedView.getContext()).thenReturn(mock(FlutterActivity.class));
+
+    AccessibilityNodeInfo nodeInfo = mock(AccessibilityNodeInfo.class);
+    when(embeddedView.createAccessibilityNodeInfo()).thenReturn(nodeInfo);
+
+    AccessibilityNodeInfo result = accessibilityBridge.createAccessibilityNodeInfo(0);
+    assertNotNull(result);
+    assertEquals(result.getChildCount(), 1);
+    assertEquals(result.getClassName(), "android.view.View");
+  }
+
+  @Test
+  public void itProducesPlatformViewNodeForVirtualDisplay() {
+    PlatformViewsAccessibilityDelegate accessibilityDelegate =
+        mock(PlatformViewsAccessibilityDelegate.class);
+    AccessibilityViewEmbedder accessibilityViewEmbedder = mock(AccessibilityViewEmbedder.class);
+    AccessibilityBridge accessibilityBridge =
+        setUpBridge(
+            /*rootAccessibilityView=*/ null,
+            /*accessibilityChannel=*/ null,
+            /*accessibilityManager=*/ null,
+            /*contentResolver=*/ null,
+            accessibilityViewEmbedder,
+            accessibilityDelegate);
+
+    TestSemanticsNode platformView = new TestSemanticsNode();
+    platformView.platformViewId = 1;
+
+    TestSemanticsUpdate testSemanticsUpdate = platformView.toUpdate();
+    accessibilityBridge.updateSemantics(testSemanticsUpdate.buffer, testSemanticsUpdate.strings);
+
+    View embeddedView = mock(View.class);
+    when(accessibilityDelegate.getPlatformViewById(1)).thenReturn(embeddedView);
+    when(embeddedView.getContext()).thenReturn(mock(Activity.class));
+
+    accessibilityBridge.createAccessibilityNodeInfo(0);
+    verify(accessibilityViewEmbedder).getRootNode(eq(embeddedView), eq(0), any(Rect.class));
+  }
+
   @Test
   public void releaseDropsChannelMessageHandler() {
     AccessibilityChannel mockChannel = mock(AccessibilityChannel.class);
@@ -317,6 +397,10 @@ public class AccessibilityBridgeTest {
     float right = 0.0f;
     float bottom = 0.0f;
     final List<TestSemanticsNode> children = new ArrayList<TestSemanticsNode>();
+
+    public void addChild(TestSemanticsNode child) {
+      children.add(child);
+    }
     // custom actions not supported.
 
     TestSemanticsUpdate toUpdate() {