fix On iOS, dialog titles are announced twice (#19826)

Author: chunhtai

shell/platform/darwin/ios/framework/Source/SemanticsObject.h

@@ -93,7 +93,7 @@ constexpr int32_t kRootNodeId = 0;
 - (BOOL)nodeWillCauseScroll:(const flutter::SemanticsNode*)node;
 - (BOOL)nodeShouldTriggerAnnouncement:(const flutter::SemanticsNode*)node;
 - (void)collectRoutes:(NSMutableArray<SemanticsObject*>*)edges;
-- (NSString*)routeName;
+- (SemanticsObject*)routeFocusObject;
 - (BOOL)onCustomAccessibilityAction:(FlutterCustomAccessibilityAction*)action;
 
 @end

shell/platform/darwin/ios/framework/Source/SemanticsObject.mm

@@ -282,20 +282,21 @@ - (BOOL)onCustomAccessibilityAction:(FlutterCustomAccessibilityAction*)action {
   return YES;
 }
 
-- (NSString*)routeName {
-  // Returns the first non-null and non-empty semantic label of a child
-  // with an NamesRoute flag. Otherwise returns nil.
+- (SemanticsObject*)routeFocusObject {
+  // Returns the first SemanticObject in this branch that has
+  // the NamesRoute flag with a non-nil semantic label. Otherwise
+  // returns nil.
   if ([self node].HasFlag(flutter::SemanticsFlags::kNamesRoute)) {
     NSString* newName = [self accessibilityLabel];
     if (newName != nil && [newName length] > 0) {
-      return newName;
+      return self;
     }
   }
   if ([self hasChildren]) {
     for (SemanticsObject* child in self.children) {
-      NSString* newName = [child routeName];
-      if (newName != nil && [newName length] > 0) {
-        return newName;
+      SemanticsObject* focusObject = [child routeFocusObject];
+      if (focusObject != nil) {
+        return focusObject;
       }
     }
   }

shell/platform/darwin/ios/framework/Source/accessibility_bridge.mm

@@ -199,9 +199,8 @@ void PostAccessibilityNotification(UIAccessibilityNotifications notification,
   layoutChanged = layoutChanged || [doomed_uids count] > 0;
   if (routeChanged) {
     if (!ios_delegate_->IsFlutterViewControllerPresentingModalViewController(view_)) {
-      NSString* routeName = [lastAdded routeName];
       ios_delegate_->PostAccessibilityNotification(UIAccessibilityScreenChangedNotification,
-                                                   routeName);
+                                                   [lastAdded routeFocusObject]);
     }
   } else if (layoutChanged) {
     // TODO(goderbauer): figure out which node to focus next.

shell/platform/darwin/ios/framework/Source/accessibility_bridge_test.mm

@@ -311,7 +311,9 @@ - (void)testAnnouncesRouteChanges {
   bridge->UpdateSemantics(/*nodes=*/nodes, /*actions=*/actions);
 
   XCTAssertEqual([accessibility_notifications count], 1ul);
-  XCTAssertEqualObjects(accessibility_notifications[0][@"argument"], @"route");
+  SemanticsObject* focusObject = accessibility_notifications[0][@"argument"];
+  XCTAssertEqual([focusObject uid], 1);
+  XCTAssertEqualObjects([focusObject accessibilityLabel], @"route");
   XCTAssertEqual([accessibility_notifications[0][@"notification"] unsignedIntValue],
                  UIAccessibilityScreenChangedNotification);
 }