Add `animationDuration` property to TabController (#91987)

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

@@ -101,11 +101,12 @@ class TabController extends ChangeNotifier {
   ///
   /// The `initialIndex` must be valid given [length] and must not be null. If
   /// [length] is zero, then `initialIndex` must be 0 (the default).
-  TabController({ int initialIndex = 0, required this.length, required TickerProvider vsync })
+  TabController({ int initialIndex = 0, Duration? animationDuration, required this.length, required TickerProvider vsync})
     : assert(length != null && length >= 0),
       assert(initialIndex != null && initialIndex >= 0 && (length == 0 || initialIndex < length)),
       _index = initialIndex,
       _previousIndex = initialIndex,
+      _animationDuration = animationDuration ?? kTabScrollDuration,
       _animationController = AnimationController.unbounded(
         value: initialIndex.toDouble(),
         vsync: vsync,
@@ -117,14 +118,16 @@ class TabController extends ChangeNotifier {
     required int index,
     required int previousIndex,
     required AnimationController? animationController,
+    required Duration animationDuration,
     required this.length,
   }) : _index = index,
        _previousIndex = previousIndex,
-       _animationController = animationController;
+       _animationController = animationController,
+       _animationDuration = animationDuration;
 
 
-  /// Creates a new [TabController] with `index`, `previousIndex`, and `length`
-  /// if they are non-null.
+  /// Creates a new [TabController] with `index`, `previousIndex`, `length`, and
+  /// `animationDuration` if they are non-null.
   ///
   /// This method is used by [DefaultTabController].
   ///
@@ -134,6 +137,7 @@ class TabController extends ChangeNotifier {
     required int? index,
     required int? length,
     required int? previousIndex,
+    required Duration? animationDuration,
   }) {
     if (index != null) {
       _animationController!.value = index.toDouble();
@@ -143,6 +147,7 @@ class TabController extends ChangeNotifier {
       length: length ?? this.length,
       animationController: _animationController,
       previousIndex: previousIndex ?? _previousIndex,
+      animationDuration: animationDuration ?? _animationDuration,
     );
   }
 
@@ -159,6 +164,12 @@ class TabController extends ChangeNotifier {
   Animation<double>? get animation => _animationController?.view;
   AnimationController? _animationController;
 
+  /// Controls the duration of TabController and TabBarView animations.
+  ///
+  /// Defaults to kTabScrollDuration.
+  Duration get animationDuration => _animationDuration;
+  final Duration _animationDuration;
+
   /// The total number of tabs.
   ///
   /// Typically greater than one. Must match [TabBar.tabs]'s and
@@ -174,7 +185,7 @@ class TabController extends ChangeNotifier {
       return;
     _previousIndex = index;
     _index = value;
-    if (duration != null) {
+    if (duration != null && duration > Duration.zero) {
       _indexIsChangingCount += 1;
       notifyListeners(); // Because the value of indexIsChanging may have changed.
       _animationController!
@@ -228,8 +239,8 @@ class TabController extends ChangeNotifier {
   ///
   /// While the animation is running [indexIsChanging] is true. When the
   /// animation completes [offset] will be 0.0.
-  void animateTo(int value, { Duration duration = kTabScrollDuration, Curve curve = Curves.ease }) {
-    _changeIndex(value, duration: duration, curve: curve);
+  void animateTo(int value, { Duration? duration, Curve curve = Curves.ease }) {
+    _changeIndex(value, duration: duration ?? _animationDuration, curve: curve);
   }
 
   /// The difference between the [animation]'s value and [index].
@@ -333,6 +344,7 @@ class DefaultTabController extends StatefulWidget {
     required this.length,
     this.initialIndex = 0,
     required this.child,
+    this.animationDuration,
   }) : assert(initialIndex != null),
        assert(length >= 0),
        assert(length == 0 || (initialIndex >= 0 && initialIndex < length)),
@@ -349,6 +361,11 @@ class DefaultTabController extends StatefulWidget {
   /// Defaults to zero.
   final int initialIndex;
 
+  /// Controls the duration of DefaultTabController and TabBarView animations.
+  ///
+  /// Defaults to kTabScrollDuration.
+  final Duration? animationDuration;
+
   /// The widget below this widget in the tree.
   ///
   /// Typically a [Scaffold] whose [AppBar] includes a [TabBar].
@@ -384,6 +401,7 @@ class _DefaultTabControllerState extends State<DefaultTabController> with Single
       vsync: this,
       length: widget.length,
       initialIndex: widget.initialIndex,
+      animationDuration: widget.animationDuration,
     );
   }
 
@@ -416,9 +434,19 @@ class _DefaultTabControllerState extends State<DefaultTabController> with Single
       }
       _controller = _controller._copyWith(
         length: widget.length,
+        animationDuration: widget.animationDuration,
         index: newIndex,
         previousIndex: previousIndex,
       );
     }
+
+    if (oldWidget.animationDuration != widget.animationDuration) {
+      _controller = _controller._copyWith(
+        length: widget.length,
+        animationDuration: widget.animationDuration,
+        index: _controller.index,
+        previousIndex: _controller.previousIndex,
+      );
+    }
   }
 }

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

@@ -1392,10 +1392,18 @@ class _TabBarViewState extends State<TabBarView> {
     if (_pageController.page == _currentIndex!.toDouble())
       return Future<void>.value();
 
+    final Duration duration = _controller!.animationDuration;
+
+    if (duration == Duration.zero) {
+      _pageController.jumpToPage(_currentIndex!);
+      return Future<void>.value();
+    }
+
     final int previousIndex = _controller!.previousIndex;
+
     if ((_currentIndex! - previousIndex).abs() == 1) {
       _warpUnderwayCount += 1;
-      await _pageController.animateToPage(_currentIndex!, duration: kTabScrollDuration, curve: Curves.ease);
+      await _pageController.animateToPage(_currentIndex!, duration: duration, curve: Curves.ease);
       _warpUnderwayCount -= 1;
       return Future<void>.value();
     }
@@ -1415,7 +1423,7 @@ class _TabBarViewState extends State<TabBarView> {
     });
     _pageController.jumpToPage(initialPage);
 
-    await _pageController.animateToPage(_currentIndex!, duration: kTabScrollDuration, curve: Curves.ease);
+    await _pageController.animateToPage(_currentIndex!, duration: duration, curve: Curves.ease);
     if (!mounted)
       return Future<void>.value();
     setState(() {

packages/flutter/test/material/tabs_test.dart

@@ -109,9 +109,11 @@ Widget buildFrame({
   required String value,
   bool isScrollable = false,
   Color? indicatorColor,
+  Duration? animationDuration,
 }) {
   return boilerplate(
     child: DefaultTabController(
+      animationDuration: animationDuration,
       initialIndex: tabs.indexOf(value),
       length: tabs.length,
       child: TabBar(
@@ -937,6 +939,262 @@ void main() {
     expect(find.text('Second'), findsNothing);
   });
 
+  testWidgets('TabBar animationDuration sets indicator animation duration', (WidgetTester tester) async {
+    const Duration animationDuration = Duration(milliseconds: 100);
+    final List<String> tabs = <String>['A', 'B', 'C'];
+
+    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'B', animationDuration: animationDuration));
+    final TabController controller = DefaultTabController.of(tester.element(find.text('A')))!;
+
+    await tester.tap(find.text('A'));
+    await tester.pump();
+    expect(controller.indexIsChanging, true);
+    await tester.pump(const Duration(milliseconds: 50));
+    await tester.pump(animationDuration);
+    expect(controller.index, 0);
+    expect(controller.previousIndex, 1);
+    expect(controller.indexIsChanging, false);
+
+    //Test when index diff is greater than 1
+    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'B', animationDuration: animationDuration));
+    await tester.tap(find.text('C'));
+    await tester.pump();
+    expect(controller.indexIsChanging, true);
+    await tester.pump(const Duration(milliseconds: 50));
+    await tester.pump(animationDuration);
+    expect(controller.index, 2);
+    expect(controller.previousIndex, 0);
+    expect(controller.indexIsChanging, false);
+  });
+
+  testWidgets('TabBarView controller sets animation duration', (WidgetTester tester) async {
+    const Duration animationDuration = Duration(milliseconds: 100);
+    final List<String> tabs = <String>['A', 'B', 'C'];
+
+    final TabController tabController = TabController(
+      vsync: const TestVSync(),
+      initialIndex: 1,
+      length: tabs.length,
+      animationDuration: animationDuration,
+    );
+    await tester.pumpWidget(boilerplate(
+      child: Column(
+        children: <Widget>[
+          TabBar(
+            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
+            controller: tabController,
+          ),
+          SizedBox(
+            width: 400.0,
+            height: 400.0,
+            child: TabBarView(
+              controller: tabController,
+              children: const <Widget>[
+                Center(child: Text('0')),
+                Center(child: Text('1')),
+                Center(child: Text('2')),
+              ],
+            ),
+          ),
+        ],
+      ),
+    ));
+
+    expect(tabController.index, 1);
+
+    final PageView pageView = tester.widget(find.byType(PageView));
+    final PageController pageController = pageView.controller;
+    final ScrollPosition position = pageController.position;
+
+    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
+    // page 1 is at 400.0, page 2 is at 800.0.
+    expect(position.pixels, 400);
+    await tester.tap(find.text('C'));
+    await tester.pump();
+    expect(position.pixels, 400);
+    await tester.pump(const Duration(milliseconds: 50));
+    await tester.pump(animationDuration);
+    expect(position.pixels, 800);
+  });
+
+  testWidgets('TabBar tap skips indicator animation when disabled in controller', (WidgetTester tester) async {
+    final List<String> tabs = <String>['A', 'B'];
+
+    const Color indicatorColor = Color(0xFFFF0000);
+    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'A', indicatorColor: indicatorColor, animationDuration: Duration.zero));
+
+    final RenderBox box = tester.renderObject(find.byType(TabBar));
+    final TabIndicatorRecordingCanvas canvas = TabIndicatorRecordingCanvas(indicatorColor);
+    final TestRecordingPaintingContext context = TestRecordingPaintingContext(canvas);
+
+    box.paint(context, Offset.zero);
+    final Rect indicatorRect0 = canvas.indicatorRect;
+    expect(indicatorRect0.left, 0.0);
+    expect(indicatorRect0.width, 400.0);
+    expect(indicatorRect0.height, 2.0);
+
+    await tester.tap(find.text('B'));
+    await tester.pump();
+    box.paint(context, Offset.zero);
+    final Rect indicatorRect2 = canvas.indicatorRect;
+    expect(indicatorRect2.left, 400.0);
+    expect(indicatorRect2.width, 400.0);
+    expect(indicatorRect2.height, 2.0);
+  });
+
+  testWidgets('TabBar tap changes index instantly when animation is disabled in controller', (WidgetTester tester) async {
+    final List<String> tabs = <String>['A', 'B', 'C'];
+
+    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'B', animationDuration: Duration.zero));
+    final TabController controller = DefaultTabController.of(tester.element(find.text('A')))!;
+
+    await tester.tap(find.text('A'));
+    await tester.pump();
+    expect(controller.index, 0);
+    expect(controller.previousIndex, 1);
+    expect(controller.indexIsChanging, false);
+
+    //Test when index diff is greater than 1
+    await tester.pumpWidget(buildFrame(tabs: tabs, value: 'B', animationDuration: Duration.zero));
+    await tester.tap(find.text('C'));
+    await tester.pump();
+    expect(controller.index, 2);
+    expect(controller.previousIndex, 0);
+    expect(controller.indexIsChanging, false);
+  });
+
+  testWidgets('TabBarView skips animation when disabled in controller', (WidgetTester tester) async {
+    final List<String> tabs = <String>['A', 'B', 'C'];
+    final TabController tabController = TabController(
+      vsync: const TestVSync(),
+      initialIndex: 1,
+      length: tabs.length,
+      animationDuration: Duration.zero,
+    );
+    await tester.pumpWidget(boilerplate(
+      child: Column(
+        children: <Widget>[
+          TabBar(
+            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
+            controller: tabController,
+          ),
+          SizedBox(
+            width: 400.0,
+            height: 400.0,
+            child: TabBarView(
+              controller: tabController,
+              children: const <Widget>[
+                Center(child: Text('0')),
+                Center(child: Text('1')),
+                Center(child: Text('2')),
+              ],
+            ),
+          ),
+        ],
+      ),
+    ));
+
+    expect(tabController.index, 1);
+
+    final PageView pageView = tester.widget(find.byType(PageView));
+    final PageController pageController = pageView.controller;
+    final ScrollPosition position = pageController.position;
+
+    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
+    // page 1 is at 400.0, page 2 is at 800.0.
+    expect(position.pixels, 400);
+    await tester.tap(find.text('C'));
+    await tester.pump();
+    expect(position.pixels, 800);
+  });
+
+  testWidgets('TabBarView skips animation when disabled in controller - skip tabs', (WidgetTester tester) async {
+    final List<String> tabs = <String>['A', 'B', 'C'];
+    final TabController tabController = TabController(
+      vsync: const TestVSync(),
+      length: tabs.length,
+      animationDuration: Duration.zero,
+    );
+    await tester.pumpWidget(boilerplate(
+      child: Column(
+        children: <Widget>[
+          TabBar(
+            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
+            controller: tabController,
+          ),
+          SizedBox(
+            width: 400.0,
+            height: 400.0,
+            child: TabBarView(
+              controller: tabController,
+              children: const <Widget>[
+                Center(child: Text('0')),
+                Center(child: Text('1')),
+                Center(child: Text('2')),
+              ],
+            ),
+          ),
+        ],
+      ),
+    ));
+
+    expect(tabController.index, 0);
+
+    final PageView pageView = tester.widget(find.byType(PageView));
+    final PageController pageController = pageView.controller;
+    final ScrollPosition position = pageController.position;
+
+    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
+    // page 1 is at 400.0, page 2 is at 800.0.
+    expect(position.pixels, 0);
+    await tester.tap(find.text('C'));
+    await tester.pump();
+    expect(position.pixels, 800);
+  });
+
+  testWidgets('TabBarView skips animation when disabled in controller - two tabs', (WidgetTester tester) async {
+    final List<String> tabs = <String>['A', 'B'];
+    final TabController tabController = TabController(
+      vsync: const TestVSync(),
+      length: tabs.length,
+      animationDuration: Duration.zero,
+    );
+    await tester.pumpWidget(boilerplate(
+      child: Column(
+        children: <Widget>[
+          TabBar(
+            tabs: tabs.map<Widget>((String tab) => Tab(text: tab)).toList(),
+            controller: tabController,
+          ),
+          SizedBox(
+            width: 400.0,
+            height: 400.0,
+            child: TabBarView(
+              controller: tabController,
+              children: const <Widget>[
+                Center(child: Text('0')),
+                Center(child: Text('1')),
+              ],
+            ),
+          ),
+        ],
+      ),
+    ));
+
+    expect(tabController.index, 0);
+
+    final PageView pageView = tester.widget(find.byType(PageView));
+    final PageController pageController = pageView.controller;
+    final ScrollPosition position = pageController.position;
+
+    // The TabBarView's page width is 400, so page 0 is at scroll offset 0.0,
+    // page 1 is at 400.0, page 2 is at 800.0.
+    expect(position.pixels, 0);
+    await tester.tap(find.text('B'));
+    await tester.pump();
+    expect(position.pixels, 400);
+  });
+
   testWidgets('TabBar tap animates the selection indicator', (WidgetTester tester) async {
     // This is a regression test for https://github.com/flutter/flutter/issues/7479