[State Restoration] Scaffold.drawer and Scaffold.endDrawer (#72788)

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

@@ -231,6 +231,7 @@ class DrawerController extends StatefulWidget {
     GlobalKey? key,
     required this.child,
     required this.alignment,
+    this.isDrawerOpen = false,
     this.drawerCallback,
     this.dragStartBehavior = DragStartBehavior.start,
     this.scrimColor,
@@ -298,6 +299,14 @@ class DrawerController extends StatefulWidget {
   /// 20.0 will be added to `MediaQuery.of(context).padding.left`.
   final double? edgeDragWidth;
 
+  /// Whether or not the drawer is opened or closed.
+  ///
+  /// This parameter is primarily used by the state restoration framework
+  /// to restore the drawer's animation controller to the open or closed state
+  /// depending on what was last saved to the target platform before the
+  /// application was killed.
+  final bool isDrawerOpen;
+
   @override
   DrawerControllerState createState() => DrawerControllerState();
 }
@@ -310,7 +319,12 @@ class DrawerControllerState extends State<DrawerController> with SingleTickerPro
   void initState() {
     super.initState();
     _scrimColorTween = _buildScrimColorTween();
-    _controller = AnimationController(duration: _kBaseSettleDuration, vsync: this)
+    _controller = AnimationController(
+      value: widget.isDrawerOpen ? 1.0 : 0.0,
+      duration: _kBaseSettleDuration,
+      vsync: this,
+    );
+    _controller
       ..addListener(_animationChanged)
       ..addStatusListener(_animationStatusChanged);
   }
@@ -327,6 +341,16 @@ class DrawerControllerState extends State<DrawerController> with SingleTickerPro
     super.didUpdateWidget(oldWidget);
     if (widget.scrimColor != oldWidget.scrimColor)
       _scrimColorTween = _buildScrimColorTween();
+    if (widget.isDrawerOpen != oldWidget.isDrawerOpen) {
+      switch(_controller.status) {
+        case AnimationStatus.completed:
+        case AnimationStatus.dismissed:
+          _controller.value = widget.isDrawerOpen ? 1.0 : 0.0;
+          break;
+        default:
+          break;
+      }
+    }
   }
 
   void _animationChanged() {

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

@@ -1459,6 +1459,7 @@ class Scaffold extends StatefulWidget {
     this.drawerEdgeDragWidth,
     this.drawerEnableOpenDragGesture = true,
     this.endDrawerEnableOpenDragGesture = true,
+    this.restorationId,
   }) : assert(primary != null),
        assert(extendBody != null),
        assert(extendBodyBehindAppBar != null),
@@ -1783,6 +1784,20 @@ class Scaffold extends StatefulWidget {
   /// By default, the drag gesture is enabled.
   final bool endDrawerEnableOpenDragGesture;
 
+  /// Restoration ID to save and restore the state of the [Scaffold].
+  ///
+  /// If it is non-null, the scaffold will persist and restore whether the
+  /// [drawer] and [endDrawer] was open or closed.
+  ///
+  /// The state of this widget is persisted in a [RestorationBucket] claimed
+  /// from the surrounding [RestorationScope] using the provided restoration ID.
+  ///
+  /// See also:
+  ///
+  ///  * [RestorationManager], which explains how state restoration works in
+  ///    Flutter.
+  final String? restorationId;
+
   /// Finds the [ScaffoldState] from the closest instance of this class that
   /// encloses the given context.
   ///
@@ -2055,7 +2070,15 @@ class Scaffold extends StatefulWidget {
 ///
 /// Can display [BottomSheet]s. Retrieve a [ScaffoldState] from the current
 /// [BuildContext] using [Scaffold.of].
-class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
+class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin, RestorationMixin {
+  @override
+  String? get restorationId => widget.restorationId;
+
+  @override
+  void restoreState(RestorationBucket? oldBucket, bool initialRestore) {
+    registerForRestoration(_drawerOpened, 'drawer_open');
+    registerForRestoration(_endDrawerOpened, 'end_drawer_open');
+  }
 
   // DRAWER API
 
@@ -2076,8 +2099,8 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
   ///
   /// This is based on the appBar preferred height plus the top padding.
   double? get appBarMaxHeight => _appBarMaxHeight;
-  bool _drawerOpened = false;
-  bool _endDrawerOpened = false;
+  final RestorableBool _drawerOpened = RestorableBool(false);
+  final RestorableBool _endDrawerOpened = RestorableBool(false);
 
   /// Whether the [Scaffold.drawer] is opened.
   ///
@@ -2085,7 +2108,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
   ///
   ///  * [ScaffoldState.openDrawer], which opens the [Scaffold.drawer] of a
   ///    [Scaffold].
-  bool get isDrawerOpen => _drawerOpened;
+  bool get isDrawerOpen => _drawerOpened.value;
 
   /// Whether the [Scaffold.endDrawer] is opened.
   ///
@@ -2093,18 +2116,18 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
   ///
   ///  * [ScaffoldState.openEndDrawer], which opens the [Scaffold.endDrawer] of
   ///    a [Scaffold].
-  bool get isEndDrawerOpen => _endDrawerOpened;
+  bool get isEndDrawerOpen => _endDrawerOpened.value;
 
   void _drawerOpenedCallback(bool isOpened) {
     setState(() {
-      _drawerOpened = isOpened;
+      _drawerOpened.value = isOpened;
     });
     widget.onDrawerChanged?.call(isOpened);
   }
 
   void _endDrawerOpenedCallback(bool isOpened) {
     setState(() {
-      _endDrawerOpened = isOpened;
+      _endDrawerOpened.value = isOpened;
     });
     widget.onEndDrawerChanged?.call(isOpened);
   }
@@ -2122,7 +2145,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
   ///
   /// See [Scaffold.of] for information about how to obtain the [ScaffoldState].
   void openDrawer() {
-    if (_endDrawerKey.currentState != null && _endDrawerOpened)
+    if (_endDrawerKey.currentState != null && _endDrawerOpened.value)
       _endDrawerKey.currentState!.close();
     _drawerKey.currentState?.open();
   }
@@ -2140,7 +2163,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
   ///
   /// See [Scaffold.of] for information about how to obtain the [ScaffoldState].
   void openEndDrawer() {
-    if (_drawerKey.currentState != null && _drawerOpened)
+    if (_drawerKey.currentState != null && _drawerOpened.value)
       _drawerKey.currentState!.close();
     _endDrawerKey.currentState?.open();
   }
@@ -2859,6 +2882,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
           scrimColor: widget.drawerScrimColor,
           edgeDragWidth: widget.drawerEdgeDragWidth,
           enableOpenDragGesture: widget.endDrawerEnableOpenDragGesture,
+          isDrawerOpen: _endDrawerOpened.value,
         ),
         _ScaffoldSlot.endDrawer,
         // remove the side padding from the side we're not touching
@@ -2884,6 +2908,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
           scrimColor: widget.drawerScrimColor,
           edgeDragWidth: widget.drawerEdgeDragWidth,
           enableOpenDragGesture: widget.drawerEnableOpenDragGesture,
+          isDrawerOpen: _drawerOpened.value,
         ),
         _ScaffoldSlot.drawer,
         // remove the side padding from the side we're not touching
@@ -3145,7 +3170,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
         break;
     }
 
-    if (_endDrawerOpened) {
+    if (_endDrawerOpened.value) {
       _buildDrawer(children, textDirection);
       _buildEndDrawer(children, textDirection);
     } else {

packages/flutter/test/material/drawer_test.dart

@@ -215,4 +215,173 @@ void main() {
     expect(state.isDrawerOpen, equals(false));
     expect(state.isEndDrawerOpen, equals(false));
   });
+
+  testWidgets('Scaffold.drawer - null restorationId ', (WidgetTester tester) async {
+    final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
+    await tester.pumpWidget(
+      MaterialApp(
+        restorationScopeId: 'app',
+        home: Scaffold(
+          key: scaffoldKey,
+          drawer: const Text('drawer'),
+          body: Container(),
+        ),
+      ),
+    );
+    await tester.pump(); // no effect
+    expect(find.text('drawer'), findsNothing);
+    scaffoldKey.currentState!.openDrawer();
+    await tester.pumpAndSettle();
+    expect(find.text('drawer'), findsOneWidget);
+
+    await tester.restartAndRestore();
+    // Drawer state should not have been saved.
+    expect(find.text('drawer'), findsNothing);
+  });
+
+  testWidgets('Scaffold.endDrawer - null restorationId ', (WidgetTester tester) async {
+    final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
+    await tester.pumpWidget(
+      MaterialApp(
+        restorationScopeId: 'app',
+        home: Scaffold(
+          key: scaffoldKey,
+          drawer: const Text('endDrawer'),
+          body: Container(),
+        ),
+      ),
+    );
+    await tester.pump(); // no effect
+    expect(find.text('endDrawer'), findsNothing);
+    scaffoldKey.currentState!.openDrawer();
+    await tester.pumpAndSettle();
+    expect(find.text('endDrawer'), findsOneWidget);
+
+    await tester.restartAndRestore();
+    // Drawer state should not have been saved.
+    expect(find.text('endDrawer'), findsNothing);
+  });
+
+  testWidgets('Scaffold.drawer state restoration test', (WidgetTester tester) async {
+    final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
+    await tester.pumpWidget(
+      MaterialApp(
+        restorationScopeId: 'app',
+        home: Scaffold(
+          key: scaffoldKey,
+          restorationId: 'scaffold',
+          drawer: const Text('drawer'),
+          body: Container(),
+        ),
+      ),
+    );
+    await tester.pump(); // no effect
+    expect(find.text('drawer'), findsNothing);
+    scaffoldKey.currentState!.openDrawer();
+    await tester.pumpAndSettle();
+    expect(find.text('drawer'), findsOneWidget);
+
+    await tester.restartAndRestore();
+    expect(find.text('drawer'), findsOneWidget);
+
+    final TestRestorationData data = await tester.getRestorationData();
+    await tester.tapAt(const Offset(750.0, 100.0)); // on the mask
+    await tester.pumpAndSettle();
+    expect(find.text('drawer'), findsNothing);
+
+    await tester.restoreFrom(data);
+    expect(find.text('drawer'), findsOneWidget);
+  });
+
+  testWidgets('Scaffold.endDrawer state restoration test', (WidgetTester tester) async {
+    final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
+    await tester.pumpWidget(
+      MaterialApp(
+        restorationScopeId: 'app',
+        home: Scaffold(
+          key: scaffoldKey,
+          restorationId: 'scaffold',
+          endDrawer: const Text('endDrawer'),
+          body: Container(),
+        ),
+      ),
+    );
+    await tester.pump(); // no effect
+    expect(find.text('endDrawer'), findsNothing);
+    scaffoldKey.currentState!.openEndDrawer();
+    await tester.pumpAndSettle();
+    expect(find.text('endDrawer'), findsOneWidget);
+
+    await tester.restartAndRestore();
+    expect(find.text('endDrawer'), findsOneWidget);
+
+    final TestRestorationData data = await tester.getRestorationData();
+    await tester.tapAt(const Offset(750.0, 100.0)); // on the mask
+    await tester.pumpAndSettle();
+    expect(find.text('endDrawer'), findsNothing);
+
+    await tester.restoreFrom(data);
+    expect(find.text('endDrawer'), findsOneWidget);
+  });
+
+  testWidgets('Both drawer and endDrawer state restoration test', (WidgetTester tester) async {
+    final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
+    await tester.pumpWidget(
+      MaterialApp(
+        restorationScopeId: 'app',
+        home: Scaffold(
+          restorationId: 'scaffold',
+          key: scaffoldKey,
+          drawer: const Text('drawer'),
+          endDrawer: const Text('endDrawer'),
+          body: Container(),
+        ),
+      ),
+    );
+    await tester.pump(); // no effect
+    expect(find.text('drawer'), findsNothing);
+    expect(find.text('endDrawer'), findsNothing);
+    scaffoldKey.currentState!.openDrawer();
+    await tester.pumpAndSettle();
+    expect(find.text('drawer'), findsOneWidget);
+    expect(find.text('endDrawer'), findsNothing);
+
+    await tester.restartAndRestore();
+    expect(find.text('drawer'), findsOneWidget);
+    expect(find.text('endDrawer'), findsNothing);
+
+    TestRestorationData data = await tester.getRestorationData();
+    await tester.tapAt(const Offset(750.0, 100.0)); // on the mask
+    await tester.pumpAndSettle();
+    expect(find.text('drawer'), findsNothing);
+    expect(find.text('endDrawer'), findsNothing);
+
+    await tester.restoreFrom(data);
+    expect(find.text('drawer'), findsOneWidget);
+    expect(find.text('endDrawer'), findsNothing);
+
+    await tester.tapAt(const Offset(750.0, 100.0)); // on the mask
+    await tester.pumpAndSettle();
+    expect(find.text('drawer'), findsNothing);
+    expect(find.text('endDrawer'), findsNothing);
+
+    scaffoldKey.currentState!.openEndDrawer();
+    await tester.pumpAndSettle();
+    expect(find.text('drawer'), findsNothing);
+    expect(find.text('endDrawer'), findsOneWidget);
+
+    await tester.restartAndRestore();
+    expect(find.text('drawer'), findsNothing);
+    expect(find.text('endDrawer'), findsOneWidget);
+
+    data = await tester.getRestorationData();
+    await tester.tapAt(const Offset(750.0, 100.0)); // on the mask
+    await tester.pumpAndSettle();
+    expect(find.text('drawer'), findsNothing);
+    expect(find.text('endDrawer'), findsNothing);
+
+    await tester.restoreFrom(data);
+    expect(find.text('drawer'), findsNothing);
+    expect(find.text('endDrawer'), findsOneWidget);
+  });
 }