Fix the issue where DropdownMenu does not gain focus when tapped. (#162874)

Fixes: #162539
Fixes: #162897

*If you had to change anything in the [flutter/tests] repo, include a
link to the migration guide as per the [breaking change policy].*

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] 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/blob/main/docs/contributing/Tree-hygiene.md#overview
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md
[Data Driven Fixes]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

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

@@ -879,7 +879,7 @@ class _DropdownMenuState<T> extends State<DropdownMenu<T>> {
     });
   }
 
-  void handlePressed(MenuController controller) {
+  void handlePressed(MenuController controller, {bool focusForKeyboard = true}) {
     if (controller.isOpen) {
       currentHighlight = null;
       controller.close();
@@ -889,7 +889,9 @@ class _DropdownMenuState<T> extends State<DropdownMenu<T>> {
         _enableFilter = false;
       }
       controller.open();
-      _internalFocudeNode.requestFocus();
+      if (focusForKeyboard) {
+        _internalFocudeNode.requestFocus();
+      }
     }
     setState(() {});
   }
@@ -1047,7 +1049,7 @@ class _DropdownMenuState<T> extends State<DropdownMenu<T>> {
               !widget.enabled
                   ? null
                   : () {
-                    handlePressed(controller);
+                    handlePressed(controller, focusForKeyboard: !canRequestFocus());
                   },
           onChanged: (String text) {
             controller.open();

packages/flutter/test/material/dropdown_menu_test.dart

@@ -2169,7 +2169,8 @@ void main() {
     await tester.pumpAndSettle();
     expect(menuAnchor.controller!.isOpen, true);
 
-    await tester.sendKeyEvent(LogicalKeyboardKey.enter);
+    // Simulate `TextInputAction.done` on textfield
+    await tester.testTextInput.receiveAction(TextInputAction.done);
     await tester.pumpAndSettle();
     expect(menuAnchor.controller!.isOpen, false);
   });
@@ -2222,7 +2223,15 @@ void main() {
     // Test onSelected on key press
     await simulateKeyDownEvent(LogicalKeyboardKey.arrowDown);
     await tester.pumpAndSettle();
-    await tester.sendKeyEvent(LogicalKeyboardKey.enter);
+
+    // On mobile platforms, the TextField cannot gain focus by default; the focus is
+    // on a FocusNode specifically used for keyboard navigation. Therefore,
+    // LogicalKeyboardKey.enter should be used.
+    if (isMobile) {
+      await tester.sendKeyEvent(LogicalKeyboardKey.enter);
+    } else {
+      await tester.testTextInput.receiveAction(TextInputAction.done);
+    }
     await tester.pumpAndSettle();
     expect(selectionCount, expectedCount);
 
@@ -4011,6 +4020,27 @@ void main() {
     expect(textField.textInputAction, TextInputAction.next);
   });
 
+  // Regression test for https://github.com/flutter/flutter/issues/162539
+  testWidgets(
+    'When requestFocusOnTap is true, the TextField should gain focus after being tapped.',
+    (WidgetTester tester) async {
+      await tester.pumpWidget(
+        MaterialApp(
+          home: Scaffold(
+            body: DropdownMenu<TestMenu>(
+              dropdownMenuEntries: menuChildren,
+              requestFocusOnTap: true,
+            ),
+          ),
+        ),
+      );
+      await tester.tap(find.byType(TextField));
+      await tester.pumpAndSettle();
+      final Element textField = tester.firstElement(find.byType(TextField));
+      expect(Focus.of(textField).hasFocus, isTrue);
+    },
+  );
+
   testWidgets('items can be constrainted to be smaller than the text field with menuStyle', (
     WidgetTester tester,
   ) async {