Fix DropdownMenu focus (#156412)

Fixes #143505

I am unable to test sending `TextInputClient.performAction` when the
enter key is pressed on desktop platforms. I have created an issue for
this: #156414. The current test approach is to check whether the
`DropdownMenu` has focus.

## 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

---------

Co-authored-by: Bruno Leroux <bruno.leroux@gmail.com>

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

@@ -518,6 +518,7 @@ class _DropdownMenuState<T> extends State<DropdownMenu<T>> {
   double? leadingPadding;
   bool _menuHasEnabledItem = false;
   TextEditingController? _localTextEditingController;
+  final FocusNode _internalFocudeNode = FocusNode();
 
   TextEditingValue get _initialTextEditingValue {
     for (final DropdownMenuEntry<T> entry in filteredEntries) {
@@ -554,6 +555,7 @@ class _DropdownMenuState<T> extends State<DropdownMenu<T>> {
       _localTextEditingController?.dispose();
       _localTextEditingController = null;
     }
+    _internalFocudeNode.dispose();
     super.dispose();
   }
 
@@ -832,10 +834,32 @@ class _DropdownMenuState<T> extends State<DropdownMenu<T>> {
         _enableFilter = false;
       }
       controller.open();
+      _internalFocudeNode.requestFocus();
     }
     setState(() {});
   }
 
+  void _handleEditingComplete() {
+    if (currentHighlight != null) {
+      final DropdownMenuEntry<T> entry = filteredEntries[currentHighlight!];
+      if (entry.enabled) {
+        _localTextEditingController?.value = TextEditingValue(
+          text: entry.label,
+          selection: TextSelection.collapsed(offset: entry.label.length),
+        );
+        widget.onSelected?.call(entry.value);
+      }
+    } else {
+      if (_controller.isOpen) {
+        widget.onSelected?.call(null);
+      }
+    }
+    if (!widget.enableSearch) {
+      currentHighlight = null;
+    }
+    _controller.close();
+  }
+
   @override
   Widget build(BuildContext context) {
     final TextDirection textDirection = Directionality.of(context);
@@ -934,24 +958,7 @@ class _DropdownMenuState<T> extends State<DropdownMenu<T>> {
           textAlignVertical: TextAlignVertical.center,
           style: effectiveTextStyle,
           controller: _localTextEditingController,
-          onEditingComplete: () {
+          onEditingComplete: _handleEditingComplete,
-            if (currentHighlight != null) {
-              final DropdownMenuEntry<T> entry = filteredEntries[currentHighlight!];
-              if (entry.enabled) {
-                _localTextEditingController?.value = TextEditingValue(
-                  text: entry.label,
-                  selection: TextSelection.collapsed(offset: entry.label.length),
-                );
-                widget.onSelected?.call(entry.value);
-              }
-            } else {
-              widget.onSelected?.call(null);
-            }
-            if (!widget.enableSearch) {
-              currentHighlight = null;
-            }
-            controller.close();
-          },
           onTap: !widget.enabled ? null : () {
             handlePressed(controller);
           },
@@ -1041,8 +1048,28 @@ class _DropdownMenuState<T> extends State<DropdownMenu<T>> {
         _ArrowDownIntent: CallbackAction<_ArrowDownIntent>(
           onInvoke: handleDownKeyInvoke,
         ),
+        _EnterIntent: CallbackAction<_EnterIntent>(
+          onInvoke: (_) => _handleEditingComplete(),
+        ),
       },
-      child: menuAnchor,
+      child: Stack(
+        children: <Widget>[
+          // Handling keyboard navigation when the Textfield has no focus.
+          Shortcuts(
+            shortcuts: const <ShortcutActivator, Intent>{
+              SingleActivator(LogicalKeyboardKey.arrowUp): _ArrowUpIntent(),
+              SingleActivator(LogicalKeyboardKey.arrowDown): _ArrowDownIntent(),
+              SingleActivator(LogicalKeyboardKey.enter): _EnterIntent(),
+            },
+            child: Focus(
+              focusNode: _internalFocudeNode,
+              skipTraversal: true,
+              child: const SizedBox.shrink(),
+            ),
+          ),
+          menuAnchor,
+        ],
+      ),
     );
   }
 }
@@ -1062,6 +1089,10 @@ class _ArrowDownIntent extends Intent {
   const _ArrowDownIntent();
 }
 
+class _EnterIntent extends Intent {
+  const _EnterIntent();
+}
+
 class _DropdownMenuBody extends MultiChildRenderObjectWidget {
   const _DropdownMenuBody({
     super.children,

packages/flutter/test/material/dropdown_menu_test.dart

@@ -4,6 +4,7 @@
 
 import 'dart:ui';
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
@@ -1874,8 +1875,7 @@ void main() {
     await tester.pumpAndSettle();
     expect(menuAnchor.controller!.isOpen, true);
 
-    // Simulate `TextInputAction.done` on textfield
+    await tester.sendKeyEvent(LogicalKeyboardKey.enter);
-    await tester.testTextInput.receiveAction(TextInputAction.done);
     await tester.pumpAndSettle();
     expect(menuAnchor.controller!.isOpen, false);
   });
@@ -1915,31 +1915,29 @@ void main() {
     // Open the menu
     await tester.tap(find.byType(DropdownMenu<TestMenu>));
     await tester.pump();
-
     final bool isMobile = switch (themeData.platform) {
       TargetPlatform.android || TargetPlatform.iOS || TargetPlatform.fuchsia => true,
       TargetPlatform.macOS || TargetPlatform.linux || TargetPlatform.windows => false,
     };
-    int expectedCount = isMobile ? 0 : 1;
+    int expectedCount = 1;
 
     // Test onSelected on key press
     await simulateKeyDownEvent(LogicalKeyboardKey.arrowDown);
     await tester.pumpAndSettle();
-    await tester.testTextInput.receiveAction(TextInputAction.done);
+    await tester.sendKeyEvent(LogicalKeyboardKey.enter);
     await tester.pumpAndSettle();
     expect(selectionCount, expectedCount);
-    // The desktop platform closed the menu when a completion action is pressed. So we need to reopen it.
+
-    if (!isMobile) {
+    // Open the menu
-      await tester.tap(find.byType(DropdownMenu<TestMenu>));
+    await tester.tap(find.byType(DropdownMenu<TestMenu>));
-      await tester.pump();
+    await tester.pump();
-    }
 
     // Disabled item doesn't trigger onSelected callback.
     final Finder item1 = findMenuItemButton('Item 1');
     await tester.tap(item1);
     await tester.pumpAndSettle();
 
-    expect(controller.text, isMobile ? '' : 'Item 0');
+    expect(controller.text, 'Item 0');
     expect(selectionCount, expectedCount);
 
     final Finder item2 = findMenuItemButton('Item 2');
@@ -3576,6 +3574,94 @@ void main() {
       expect(tester.getRect(findMenuMaterial()).top, textFieldBottom);
     });
   });
+
+  // Regression test for https://github.com/flutter/flutter/issues/143505.
+  testWidgets('Using keyboard navigation to select', (WidgetTester tester) async {
+    final FocusNode focusNode = FocusNode();
+    addTearDown(focusNode.dispose);
+    TestMenu? selectedMenu;
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Material(
+          child: Center(
+            child: DropdownMenu<TestMenu>(
+              focusNode: focusNode,
+              dropdownMenuEntries: menuChildren,
+              onSelected: (TestMenu? menu) {
+                selectedMenu = menu;
+              },
+            ),
+          ),
+        ),
+      ),
+    );
+    // Pressing the tab key 3 times moves the focus to the icon button.
+    for (int i = 0; i < 3; i++) {
+      await tester.sendKeyEvent(LogicalKeyboardKey.tab);
+      await tester.pump();
+    }
+
+    // Now the focus is on the icon button.
+    final Element iconButton = tester.firstElement(find.byIcon(Icons.arrow_drop_down));
+    expect(Focus.of(iconButton).hasPrimaryFocus, isTrue);
+
+    await tester.sendKeyEvent(LogicalKeyboardKey.enter);
+    await tester.pump();
+
+    await tester.sendKeyEvent(LogicalKeyboardKey.arrowDown);
+    await tester.pump();
+
+    await tester.sendKeyEvent(LogicalKeyboardKey.enter);
+    await tester.pump();
+
+    expect(selectedMenu, TestMenu.mainMenu0);
+  }, variant: TargetPlatformVariant.all());
+
+  // Regression test for https://github.com/flutter/flutter/issues/143505.
+  testWidgets('Using keyboard navigation to select and without setting the FocusNode parameter',
+  (WidgetTester tester) async {
+    TestMenu? selectedMenu;
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Material(
+          child: Center(
+            child: DropdownMenu<TestMenu>(
+              dropdownMenuEntries: menuChildren,
+              onSelected: (TestMenu? menu) {
+                selectedMenu = menu;
+              },
+            ),
+          ),
+        ),
+      ),
+    );
+    // If there is no `FocusNode`, by default, `TextField` can receive focus
+    // on desktop platforms, but not on mobile platforms. Therefore, on desktop
+    // platforms, it takes 3 tabs to reach the icon button.
+    final int tabCount = switch (defaultTargetPlatform) {
+      TargetPlatform.iOS || TargetPlatform.android || TargetPlatform.fuchsia => 2,
+      TargetPlatform.macOS || TargetPlatform.linux || TargetPlatform.windows => 3,
+    };
+    for (int i = 0; i < tabCount; i++) {
+      await tester.sendKeyEvent(LogicalKeyboardKey.tab);
+      await tester.pump();
+    }
+
+    // Now the focus is on the icon button.
+    final Element iconButton = tester.firstElement(find.byIcon(Icons.arrow_drop_down));
+    expect(Focus.of(iconButton).hasPrimaryFocus, isTrue);
+
+    await tester.sendKeyEvent(LogicalKeyboardKey.enter);
+    await tester.pump();
+
+    await tester.sendKeyEvent(LogicalKeyboardKey.arrowDown);
+    await tester.pump();
+
+    await tester.sendKeyEvent(LogicalKeyboardKey.enter);
+    await tester.pump();
+
+    expect(selectedMenu, TestMenu.mainMenu0);
+  }, variant: TargetPlatformVariant.all());
 }
 
 enum TestMenu {