Add convenience accessor for primaryFocus (flutter#43859)

This adds accessors for WidgetsBinding.instance.focusManager and WidgetsBinding.instance.focusManager.primaryFocus so that they can be more easily found in IDEs and accessed.

This adds a top level getter for WidgetsBinding.instance.focusManager.primaryFocus called primaryFocus, and a static accessor FocusManager.instance that returns WidgetsBinding.instance.focusManager.

dev/manual_tests/lib/actions.dart

@@ -101,7 +101,7 @@ class UndoableActionDispatcher extends ActionDispatcher implements Listenable {
   bool get canUndo {
     if (_completedActions.isNotEmpty) {
       final Intent lastIntent = _completedActions.last.invocationIntent;
-      return lastIntent.isEnabled(WidgetsBinding.instance.focusManager.primaryFocus.context);
+      return lastIntent.isEnabled(primaryFocus.context);
     }
     return false;
   }
@@ -110,7 +110,7 @@ class UndoableActionDispatcher extends ActionDispatcher implements Listenable {
   bool get canRedo {
     if (_undoneActions.isNotEmpty) {
       final Intent lastIntent = _undoneActions.last.invocationIntent;
-      return lastIntent.isEnabled(WidgetsBinding.instance.focusManager.primaryFocus?.context);
+      return lastIntent.isEnabled(primaryFocus?.context);
     }
     return false;
   }
@@ -255,14 +255,14 @@ class UndoableFocusActionBase extends UndoableAction {
   @override
   void invoke(FocusNode node, Intent intent) {
     super.invoke(node, intent);
-    _previousFocus = WidgetsBinding.instance.focusManager.primaryFocus;
+    _previousFocus = primaryFocus;
     node.requestFocus();
   }
 
   @override
   void undo() {
     if (_previousFocus == null) {
-      WidgetsBinding.instance.focusManager.primaryFocus?.unfocus();
+      primaryFocus?.unfocus();
       return;
     }
     if (_previousFocus is FocusScopeNode) {
@@ -272,7 +272,7 @@ class UndoableFocusActionBase extends UndoableAction {
 
       // Unfocus the current node to remove it from the focused child list of
       // the scope.
-      WidgetsBinding.instance.focusManager.primaryFocus?.unfocus();
+      primaryFocus?.unfocus();
       // and then let the scope node be focused...
     }
     _previousFocus.requestFocus();

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

@@ -168,8 +168,8 @@ class _CheckboxState extends State<Checkbox> with TickerProviderStateMixin {
       SelectAction.key: _createAction,
       if (!kIsWeb) ActivateAction.key: _createAction,
     };
-    _updateHighlightMode(WidgetsBinding.instance.focusManager.highlightMode);
-    WidgetsBinding.instance.focusManager.addHighlightModeListener(_handleFocusHighlightModeChange);
+    _updateHighlightMode(FocusManager.instance.highlightMode);
+    FocusManager.instance.addHighlightModeListener(_handleFocusHighlightModeChange);
   }
 
   void _actionHandler(FocusNode node, Intent intent){
@@ -198,7 +198,7 @@ class _CheckboxState extends State<Checkbox> with TickerProviderStateMixin {
   }
 
   void _updateHighlightMode(FocusHighlightMode mode) {
-    switch (WidgetsBinding.instance.focusManager.highlightMode) {
+    switch (FocusManager.instance.highlightMode) {
       case FocusHighlightMode.touch:
         _showHighlight = false;
         break;

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

@@ -508,7 +508,7 @@ class _InkResponseState<T extends InkResponse> extends State<T> with AutomaticKe
       SelectAction.key: _createAction,
       if (!kIsWeb) ActivateAction.key: _createAction,
     };
-    WidgetsBinding.instance.focusManager.addHighlightModeListener(_handleFocusHighlightModeChange);
+    FocusManager.instance.addHighlightModeListener(_handleFocusHighlightModeChange);
   }
 
   @override
@@ -522,7 +522,7 @@ class _InkResponseState<T extends InkResponse> extends State<T> with AutomaticKe
 
   @override
   void dispose() {
-    WidgetsBinding.instance.focusManager.removeHighlightModeListener(_handleFocusHighlightModeChange);
+    FocusManager.instance.removeHighlightModeListener(_handleFocusHighlightModeChange);
     super.dispose();
   }
 
@@ -650,7 +650,7 @@ class _InkResponseState<T extends InkResponse> extends State<T> with AutomaticKe
 
   void _updateFocusHighlights() {
     bool showFocus;
-    switch (WidgetsBinding.instance.focusManager.highlightMode) {
+    switch (FocusManager.instance.highlightMode) {
       case FocusHighlightMode.touch:
         showFocus = false;
         break;

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

@@ -196,8 +196,8 @@ class _RadioState<T> extends State<Radio<T>> with TickerProviderStateMixin {
       SelectAction.key: _createAction,
       if (!kIsWeb) ActivateAction.key: _createAction,
     };
-    _updateHighlightMode(WidgetsBinding.instance.focusManager.highlightMode);
-    WidgetsBinding.instance.focusManager.addHighlightModeListener(_handleFocusHighlightModeChange);
+    _updateHighlightMode(FocusManager.instance.highlightMode);
+    FocusManager.instance.addHighlightModeListener(_handleFocusHighlightModeChange);
   }
 
   void _actionHandler(FocusNode node, Intent intent){
@@ -216,7 +216,7 @@ class _RadioState<T> extends State<Radio<T>> with TickerProviderStateMixin {
   }
 
   void _updateHighlightMode(FocusHighlightMode mode) {
-    switch (WidgetsBinding.instance.focusManager.highlightMode) {
+    switch (FocusManager.instance.highlightMode) {
       case FocusHighlightMode.touch:
         _showHighlight = false;
         break;

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

@@ -223,8 +223,8 @@ class _SwitchState extends State<Switch> with TickerProviderStateMixin {
       SelectAction.key: _createAction,
       if (!kIsWeb) ActivateAction.key: _createAction,
     };
-    _updateHighlightMode(WidgetsBinding.instance.focusManager.highlightMode);
-    WidgetsBinding.instance.focusManager.addHighlightModeListener(_handleFocusHighlightModeChange);
+    _updateHighlightMode(FocusManager.instance.highlightMode);
+    FocusManager.instance.addHighlightModeListener(_handleFocusHighlightModeChange);
   }
 
   void _actionHandler(FocusNode node, Intent intent){
@@ -243,7 +243,7 @@ class _SwitchState extends State<Switch> with TickerProviderStateMixin {
   }
 
   void _updateHighlightMode(FocusHighlightMode mode) {
-    switch (WidgetsBinding.instance.focusManager.highlightMode) {
+    switch (FocusManager.instance.highlightMode) {
       case FocusHighlightMode.touch:
         _showHighlight = false;
         break;

packages/flutter/lib/src/widgets/actions.dart

@@ -4,7 +4,6 @@
 
 import 'package:flutter/foundation.dart';
 
-import 'binding.dart';
 import 'focus_manager.dart';
 import 'framework.dart';
 
@@ -153,7 +152,7 @@ class ActionDispatcher extends Diagnosticable {
   bool invokeAction(Action action, Intent intent, {FocusNode focusNode}) {
     assert(action != null);
     assert(intent != null);
-    focusNode ??= WidgetsBinding.instance.focusManager.primaryFocus;
+    focusNode ??= primaryFocus;
     if (action != null && intent.isEnabled(focusNode.context)) {
       action.invoke(focusNode, intent);
       return true;

packages/flutter/lib/src/widgets/focus_manager.dart

@@ -577,7 +577,7 @@ class FocusNode with DiagnosticableTreeMixin, ChangeNotifier {
   bool get hasPrimaryFocus => _manager?.primaryFocus == this;
 
   /// Returns the [FocusHighlightMode] that is currently in effect for this node.
-  FocusHighlightMode get highlightMode => WidgetsBinding.instance.focusManager.highlightMode;
+  FocusHighlightMode get highlightMode => FocusManager.instance.highlightMode;
 
   /// Returns the nearest enclosing scope node above this node, including
   /// this node, if it's a scope.
@@ -1111,15 +1111,18 @@ enum FocusHighlightStrategy {
 /// focus.
 ///
 /// The [FocusManager] is held by the [WidgetsBinding] as
-/// [WidgetsBinding.focusManager]. The [FocusManager] is rarely accessed
-/// directly. Instead, to find the [FocusScopeNode] for a given [BuildContext],
-/// use [FocusScope.of].
+/// [WidgetsBinding.focusManager], and can be conveniently accessed using the
+/// [focusManager] global accessor.
+///
+/// To find the [FocusScopeNode] for a given [BuildContext], use
+/// [FocusScope.of].
 ///
 /// The [FocusManager] knows nothing about [FocusNode]s other than the one that
-/// is currently focused. If a [FocusScopeNode] is removed, then the
-/// [FocusManager] will attempt to focus the next [FocusScopeNode] in the focus
-/// tree that it maintains, but if the current focus in that [FocusScopeNode] is
-/// null, it will stop there, and no [FocusNode] will have focus.
+/// is currently focused (accessible via the [primaryFocus] global accessor). If
+/// a [FocusScopeNode] is removed, then the [FocusManager] will attempt to focus
+/// the next [FocusScopeNode] in the focus tree that it maintains, but if the
+/// current focus in that [FocusScopeNode] is null, it will stop there, and no
+/// [FocusNode] will have focus.
 ///
 /// See also:
 ///
@@ -1130,17 +1133,24 @@ enum FocusHighlightStrategy {
 ///    [BuildContext].
 ///  * [FocusScope.of], which provides the nearest ancestor [FocusScopeNode] for
 ///    a given [BuildContext].
+///  * The [focusManager] and [primaryFocus] global accessors, for convenient
+///    access from anywhere to the current focus manager state.
 class FocusManager with DiagnosticableTreeMixin {
   /// Creates an object that manages the focus tree.
   ///
   /// This constructor is rarely called directly. To access the [FocusManager],
-  /// consider using [WidgetsBinding.focusManager] instead.
+  /// consider using the [focusManager] accessor instead (which gets it from the
+  /// [WidgetsBinding] singleton).
   FocusManager() {
     rootScope._manager = this;
     RawKeyboard.instance.addListener(_handleRawKeyEvent);
     GestureBinding.instance.pointerRouter.addGlobalRoute(_handlePointerEvent);
   }
 
+  /// Provides convenient access to the current [FocusManager] singleton from
+  /// the [WidgetsBinding] instance.
+  static FocusManager get instance => WidgetsBinding.instance.focusManager;
+
   bool _lastInteractionWasTouch = true;
 
   /// Sets the strategy by which [highlightMode] is determined.
@@ -1418,6 +1428,10 @@ class FocusManager with DiagnosticableTreeMixin {
   }
 }
 
+/// Provides convenient access to the current [FocusManager.primaryFocus] from the
+/// [WidgetsBinding] instance.
+FocusNode get primaryFocus => WidgetsBinding.instance.focusManager.primaryFocus;
+
 /// Returns a text representation of the current focus tree, along with the
 /// current attributes on each node.
 ///
@@ -1426,7 +1440,7 @@ String debugDescribeFocusTree() {
   assert(WidgetsBinding.instance != null);
   String result;
   assert(() {
-    result = WidgetsBinding.instance.focusManager.toStringDeep();
+    result = FocusManager.instance.toStringDeep();
     return true;
   }());
   return result ?? '';

packages/flutter/lib/src/widgets/focus_traversal.dart

@@ -9,7 +9,6 @@ import 'package:flutter/painting.dart';
 
 import 'actions.dart';
 import 'basic.dart';
-import 'binding.dart';
 import 'editable_text.dart';
 import 'focus_manager.dart';
 import 'framework.dart';
@@ -623,7 +622,7 @@ class ReadingOrderTraversalPolicy extends FocusTraversalPolicy with DirectionalF
     // If we still didn't find any candidate, use the current node as a
     // fallback.
     candidate ??= currentNode;
-    candidate ??= WidgetsBinding.instance.focusManager.rootScope;
+    candidate ??= FocusManager.instance.rootScope;
     return candidate;
   }
 
@@ -807,7 +806,7 @@ class _RequestFocusActionBase extends Action {
 
   @override
   void invoke(FocusNode node, Intent intent) {
-    _previousFocus = WidgetsBinding.instance.focusManager.primaryFocus;
+    _previousFocus = primaryFocus;
     node.requestFocus();
   }
 

packages/flutter/lib/src/widgets/shortcuts.dart

@@ -9,7 +9,6 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 
 import 'actions.dart';
-import 'binding.dart';
 import 'focus_manager.dart';
 import 'focus_scope.dart';
 import 'framework.dart';
@@ -209,7 +208,7 @@ class ShortcutManager extends ChangeNotifier with DiagnosticableMixin {
       matchedIntent = _shortcuts[LogicalKeySet.fromSet(pseudoKeys)];
     }
     if (matchedIntent != null) {
-      final BuildContext primaryContext = WidgetsBinding.instance.focusManager.primaryFocus?.context;
+      final BuildContext primaryContext = primaryFocus?.context;
       if (primaryContext == null) {
         return false;
       }

packages/flutter/test/material/buttons_test.dart

@@ -315,7 +315,7 @@ void main() {
       ),
     );
 
-    WidgetsBinding.instance.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
+    FocusManager.instance.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
     focusNode.requestFocus();
     await tester.pumpAndSettle();
 

packages/flutter/test/material/ink_well_test.dart

@@ -121,7 +121,7 @@ void main() {
   });
 
   testWidgets('ink response changes color on focus', (WidgetTester tester) async {
-    WidgetsBinding.instance.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
+    FocusManager.instance.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
     final FocusNode focusNode = FocusNode(debugLabel: 'Ink Focus');
     await tester.pumpWidget(
       Material(
@@ -156,7 +156,7 @@ void main() {
   });
 
   testWidgets("ink response doesn't change color on focus when on touch device", (WidgetTester tester) async {
-    WidgetsBinding.instance.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTouch;
+    FocusManager.instance.highlightStrategy = FocusHighlightStrategy.alwaysTouch;
     final FocusNode focusNode = FocusNode(debugLabel: 'Ink Focus');
     await tester.pumpWidget(Material(
       child: Directionality(

packages/flutter/test/material/material_button_test.dart

@@ -133,7 +133,7 @@ void main() {
       ),
     );
 
-    WidgetsBinding.instance.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
+    FocusManager.instance.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
     focusNode.requestFocus();
     await tester.pumpAndSettle();
 
@@ -174,7 +174,7 @@ void main() {
       ),
     );
     await tester.pumpAndSettle();
-    WidgetsBinding.instance.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
+    FocusManager.instance.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
 
     // Base elevation
     Material material = tester.widget<Material>(rawButtonMaterial);

packages/flutter/test/material/raw_material_button_test.dart

@@ -311,7 +311,7 @@ void main() {
     const Key key = Key('test');
     const Color focusColor = Color(0xff00ff00);
 
-    WidgetsBinding.instance.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
+    FocusManager.instance.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
     await tester.pumpWidget(
       MaterialApp(
         home: Center(
@@ -410,7 +410,7 @@ void main() {
     const Key key = Key('test');
     const Color hoverColor = Color(0xff00ff00);
 
-    WidgetsBinding.instance.focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
+    FocusManager.instance.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
     await tester.pumpWidget(
       MaterialApp(
         home: Center(

packages/flutter/test/widgets/focus_manager_test.dart

@@ -585,39 +585,38 @@ void main() {
         callCount++;
       }
 
-      final FocusManager focusManager = WidgetsBinding.instance.focusManager;
-      focusManager.addHighlightModeListener(handleModeChange);
-      addTearDown(() => focusManager.removeHighlightModeListener(handleModeChange));
+      FocusManager.instance.addHighlightModeListener(handleModeChange);
+      addTearDown(() => FocusManager.instance.removeHighlightModeListener(handleModeChange));
       expect(callCount, equals(0));
       expect(lastMode, isNull);
-      focusManager.highlightStrategy = FocusHighlightStrategy.automatic;
-      expect(focusManager.highlightMode, equals(FocusHighlightMode.touch));
+      FocusManager.instance.highlightStrategy = FocusHighlightStrategy.automatic;
+      expect(FocusManager.instance.highlightMode, equals(FocusHighlightMode.touch));
       await tester.sendKeyEvent(LogicalKeyboardKey.metaLeft, platform: 'fuchsia');
       expect(callCount, equals(1));
       expect(lastMode, FocusHighlightMode.traditional);
-      expect(focusManager.highlightMode, equals(FocusHighlightMode.traditional));
+      expect(FocusManager.instance.highlightMode, equals(FocusHighlightMode.traditional));
       await tester.tap(find.byType(Container));
       expect(callCount, equals(2));
       expect(lastMode, FocusHighlightMode.touch);
-      expect(focusManager.highlightMode, equals(FocusHighlightMode.touch));
+      expect(FocusManager.instance.highlightMode, equals(FocusHighlightMode.touch));
       final TestGesture gesture = await tester.startGesture(Offset.zero, kind: PointerDeviceKind.mouse);
       addTearDown(gesture.removePointer);
       await gesture.up();
       expect(callCount, equals(3));
       expect(lastMode, FocusHighlightMode.traditional);
-      expect(focusManager.highlightMode, equals(FocusHighlightMode.traditional));
+      expect(FocusManager.instance.highlightMode, equals(FocusHighlightMode.traditional));
       await tester.tap(find.byType(Container));
       expect(callCount, equals(4));
       expect(lastMode, FocusHighlightMode.touch);
-      expect(focusManager.highlightMode, equals(FocusHighlightMode.touch));
-      focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
+      expect(FocusManager.instance.highlightMode, equals(FocusHighlightMode.touch));
+      FocusManager.instance.highlightStrategy = FocusHighlightStrategy.alwaysTraditional;
       expect(callCount, equals(5));
       expect(lastMode, FocusHighlightMode.traditional);
-      expect(focusManager.highlightMode, equals(FocusHighlightMode.traditional));
-      focusManager.highlightStrategy = FocusHighlightStrategy.alwaysTouch;
+      expect(FocusManager.instance.highlightMode, equals(FocusHighlightMode.traditional));
+      FocusManager.instance.highlightStrategy = FocusHighlightStrategy.alwaysTouch;
       expect(callCount, equals(6));
       expect(lastMode, FocusHighlightMode.touch);
-      expect(focusManager.highlightMode, equals(FocusHighlightMode.touch));
+      expect(FocusManager.instance.highlightMode, equals(FocusHighlightMode.touch));
     });
     testWidgets('implements debugFillProperties', (WidgetTester tester) async {
       final DiagnosticPropertiesBuilder builder = DiagnosticPropertiesBuilder();