Fixes dialog title announce twice (#90075)

packages/flutter/lib/src/material/dialog.dart

@@ -499,7 +499,9 @@ class AlertDialog extends StatelessWidget {
         child: DefaultTextStyle(
           style: titleTextStyle ?? dialogTheme.titleTextStyle ?? theme.textTheme.headline6!,
           child: Semantics(
-            namesRoute: label == null,
+            // For iOS platform, the focus always lands on the title.
+            // Set nameRoute to false to avoid title being announce twice.
+            namesRoute: label == null && theme.platform != TargetPlatform.iOS,
             container: true,
             child: title,
           ),
@@ -843,17 +845,15 @@ class SimpleDialog extends StatelessWidget {
     final ThemeData theme = Theme.of(context);
 
     String? label = semanticLabel;
-    if (title == null) {
-      switch (theme.platform) {
-        case TargetPlatform.macOS:
-        case TargetPlatform.iOS:
-          break;
-        case TargetPlatform.android:
-        case TargetPlatform.fuchsia:
-        case TargetPlatform.linux:
-        case TargetPlatform.windows:
-          label = semanticLabel ?? MaterialLocalizations.of(context).dialogLabel;
-      }
+    switch (theme.platform) {
+      case TargetPlatform.macOS:
+      case TargetPlatform.iOS:
+        break;
+      case TargetPlatform.android:
+      case TargetPlatform.fuchsia:
+      case TargetPlatform.linux:
+      case TargetPlatform.windows:
+        label ??= MaterialLocalizations.of(context).dialogLabel;
     }
 
     // The paddingScaleFactor is used to adjust the padding of Dialog
@@ -874,7 +874,9 @@ class SimpleDialog extends StatelessWidget {
         child: DefaultTextStyle(
           style: titleTextStyle ?? DialogTheme.of(context).titleTextStyle ?? theme.textTheme.headline6!,
           child: Semantics(
-            namesRoute: label == null,
+            // For iOS platform, the focus always lands on the title.
+            // Set nameRoute to false to avoid title being announce twice.
+            namesRoute: label == null && theme.platform != TargetPlatform.iOS,
             container: true,
             child: title,
           ),

packages/flutter/test/material/dialog_test.dart

@@ -1319,54 +1319,6 @@ void main() {
     );
   });
 
-  testWidgets('AlertDialog widget contains route semantics from title for iOS', (WidgetTester tester) async {
-    final SemanticsTester semantics = SemanticsTester(tester);
-
-    await tester.pumpWidget(
-      MaterialApp(
-        theme: ThemeData(platform: TargetPlatform.iOS),
-        home: Material(
-          child: Builder(
-            builder: (BuildContext context) {
-              return Center(
-                child: ElevatedButton(
-                  child: const Text('X'),
-                  onPressed: () {
-                    showDialog<void>(
-                      context: context,
-                      builder: (BuildContext context) {
-                        return const AlertDialog(
-                          title: Text('Title'),
-                          content: Text('Y'),
-                          actions: <Widget>[],
-                        );
-                      },
-                    );
-                  },
-                ),
-              );
-            },
-          ),
-        ),
-      ),
-    );
-
-    expect(semantics, isNot(includesNodeWith(
-      label: 'Title',
-      flags: <SemanticsFlag>[SemanticsFlag.namesRoute],
-    )));
-
-    await tester.tap(find.text('X'));
-    await tester.pumpAndSettle();
-
-    expect(semantics, includesNodeWith(
-      label: 'Title',
-      flags: <SemanticsFlag>[SemanticsFlag.namesRoute],
-    ));
-
-    semantics.dispose();
-  });
-
   // Regression test for https://github.com/flutter/flutter/issues/78229.
   testWidgets('AlertDialog has correct semantics for content in iOS', (WidgetTester tester) async {
     final SemanticsTester semantics = SemanticsTester(tester);
@@ -1400,7 +1352,6 @@ void main() {
                       children: <TestSemantics>[
                         TestSemantics(
                           id: 5,
-                          flags: <SemanticsFlag>[SemanticsFlag.namesRoute],
                           label: 'title',
                           textDirection: TextDirection.ltr,
                         ),
@@ -1569,7 +1520,6 @@ void main() {
                         // node 4.
                         TestSemantics(
                           id: 5,
-                          flags: <SemanticsFlag>[SemanticsFlag.namesRoute],
                           label: 'title',
                           textDirection: TextDirection.ltr,
                         ),