[Android] Send " did gain focus" message from engine to framework (#47114)

issue:flutter/flutter#97747

framework pr:flutter/flutter#135771

## Pre-launch Checklist

- [ ] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [ ] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [ ] I read and followed the [Flutter Style Guide] and the [C++,
Objective-C, Java style guides].
- [ ] I listed at least one issue that this PR fixes in the description
above.
- [ ] I added new tests to check the change I am making or feature I am
adding, or the PR is [test-exempt]. See [testing the engine] for
instructions on writing and running engine tests.
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [ ] I signed the [CLA].
- [ ] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[C++, Objective-C, Java style guides]:
https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style
[testing the engine]:
https://github.com/flutter/flutter/wiki/Testing-the-engine
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat

---------

Co-authored-by: Reid Baker <[email protected]>

Author: hannah-hyj

shell/platform/android/io/flutter/embedding/engine/systemchannels/AccessibilityChannel.java

@@ -2,6 +2,7 @@
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
 import io.flutter.Log;
 import io.flutter.embedding.engine.FlutterJNI;
 import io.flutter.embedding.engine.dart.DartExecutor;
@@ -102,6 +103,13 @@ public AccessibilityChannel(@NonNull DartExecutor dartExecutor, @NonNull Flutter
     this.flutterJNI = flutterJNI;
   }
 
+  @VisibleForTesting
+  public AccessibilityChannel(
+      @NonNull BasicMessageChannel<Object> channel, @NonNull FlutterJNI flutterJNI) {
+    this.channel = channel;
+    this.flutterJNI = flutterJNI;
+  }
+
   /**
    * Informs Flutter that the Android OS currently has accessibility enabled.
    *

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

@@ -1166,6 +1166,12 @@ public boolean performAction(
 
           accessibilityChannel.dispatchSemanticsAction(
               virtualViewId, Action.DID_GAIN_ACCESSIBILITY_FOCUS);
+
+          HashMap<String, Object> message = new HashMap<>();
+          message.put("type", "didGainFocus");
+          message.put("nodeId", semanticsNode.id);
+          accessibilityChannel.channel.send(message);
+
           sendAccessibilityEvent(virtualViewId, AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUSED);
 
           if (semanticsNode.hasAction(Action.INCREASE)

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

@@ -1187,7 +1187,9 @@ public void itCanPredictSetSelection() {
 
   @Test
   public void itPerformsClearAccessibilityFocusCorrectly() {
-    AccessibilityChannel mockChannel = mock(AccessibilityChannel.class);
+    BasicMessageChannel mockChannel = mock(BasicMessageChannel.class);
+    AccessibilityChannel accessibilityChannel =
+        new AccessibilityChannel(mockChannel, mock(FlutterJNI.class));
     AccessibilityViewEmbedder mockViewEmbedder = mock(AccessibilityViewEmbedder.class);
     AccessibilityManager mockManager = mock(AccessibilityManager.class);
     View mockRootView = mock(View.class);
@@ -1197,7 +1199,7 @@ public void itPerformsClearAccessibilityFocusCorrectly() {
     AccessibilityBridge accessibilityBridge =
         setUpBridge(
             /*rootAccessibilityView=*/ mockRootView,
-            /*accessibilityChannel=*/ mockChannel,
+            /*accessibilityChannel=*/ accessibilityChannel,
             /*accessibilityManager=*/ mockManager,
             /*contentResolver=*/ null,
             /*accessibilityViewEmbedder=*/ mockViewEmbedder,
@@ -1220,6 +1222,11 @@ public void itPerformsClearAccessibilityFocusCorrectly() {
     accessibilityBridge.performAction(0, AccessibilityNodeInfo.ACTION_ACCESSIBILITY_FOCUS, null);
     AccessibilityNodeInfo nodeInfo = accessibilityBridge.createAccessibilityNodeInfo(0);
     assertTrue(nodeInfo.isAccessibilityFocused());
+
+    HashMap<String, Object> message = new HashMap<>();
+    message.put("type", "didGainFocus");
+    message.put("nodeId", 0);
+    verify(mockChannel).send(message);
     // Clear focus on non-focused node shouldn't do anything
     accessibilityBridge.performAction(
         1, AccessibilityNodeInfo.ACTION_CLEAR_ACCESSIBILITY_FOCUS, null);
@@ -1310,7 +1317,10 @@ public void itSetsBoldTextFlagCorrectly() {
 
   @Test
   public void itSetsFocusedNodeBeforeSendingEvent() {
-    AccessibilityChannel mockChannel = mock(AccessibilityChannel.class);
+    BasicMessageChannel mockChannel = mock(BasicMessageChannel.class);
+    AccessibilityChannel accessibilityChannel =
+        new AccessibilityChannel(mockChannel, mock(FlutterJNI.class));
+
     AccessibilityViewEmbedder mockViewEmbedder = mock(AccessibilityViewEmbedder.class);
     AccessibilityManager mockManager = mock(AccessibilityManager.class);
     View mockRootView = mock(View.class);
@@ -1320,7 +1330,7 @@ public void itSetsFocusedNodeBeforeSendingEvent() {
     AccessibilityBridge accessibilityBridge =
         setUpBridge(
             /*rootAccessibilityView=*/ mockRootView,
-            /*accessibilityChannel=*/ mockChannel,
+            /*accessibilityChannel=*/ accessibilityChannel,
             /*accessibilityManager=*/ mockManager,
             /*contentResolver=*/ null,
             /*accessibilityViewEmbedder=*/ mockViewEmbedder,
@@ -1361,11 +1371,18 @@ public boolean verify(InvocationOnMock invocation) {
         .thenAnswer(invocation -> verifier.verify(invocation));
     accessibilityBridge.performAction(0, AccessibilityNodeInfo.ACTION_ACCESSIBILITY_FOCUS, null);
     assertTrue(verifier.verified);
+
+    HashMap<String, Object> message = new HashMap<>();
+    message.put("type", "didGainFocus");
+    message.put("nodeId", 0);
+    verify(mockChannel).send(message);
   }
 
   @Test
   public void itClearsFocusedNodeBeforeSendingEvent() {
-    AccessibilityChannel mockChannel = mock(AccessibilityChannel.class);
+    BasicMessageChannel mockChannel = mock(BasicMessageChannel.class);
+    AccessibilityChannel accessibilityChannel =
+        new AccessibilityChannel(mockChannel, mock(FlutterJNI.class));
     AccessibilityViewEmbedder mockViewEmbedder = mock(AccessibilityViewEmbedder.class);
     AccessibilityManager mockManager = mock(AccessibilityManager.class);
     View mockRootView = mock(View.class);
@@ -1375,7 +1392,7 @@ public void itClearsFocusedNodeBeforeSendingEvent() {
     AccessibilityBridge accessibilityBridge =
         setUpBridge(
             /*rootAccessibilityView=*/ mockRootView,
-            /*accessibilityChannel=*/ mockChannel,
+            /*accessibilityChannel=*/ accessibilityChannel,
             /*accessibilityManager=*/ mockManager,
             /*contentResolver=*/ null,
             /*accessibilityViewEmbedder=*/ mockViewEmbedder,
@@ -1395,6 +1412,10 @@ public void itClearsFocusedNodeBeforeSendingEvent() {
     accessibilityBridge.performAction(0, AccessibilityNodeInfo.ACTION_ACCESSIBILITY_FOCUS, null);
     AccessibilityNodeInfo nodeInfo = accessibilityBridge.createAccessibilityNodeInfo(0);
     assertTrue(nodeInfo.isAccessibilityFocused());
+    HashMap<String, Object> message = new HashMap<>();
+    message.put("type", "didGainFocus");
+    message.put("nodeId", 0);
+    verify(mockChannel).send(message);
 
     class Verifier {
       public Verifier(AccessibilityBridge accessibilityBridge) {