fix animateTo bug when new index > 1 tab away

Author: qixotic

example/lib/default_appbar_demo.dart

@@ -163,11 +163,12 @@ class _State extends State<DefaultAppBarDemo>
               color: Colors.white,
               tooltip: "convex button example",
               onPressed: () => Navigator.of(context).pushNamed('/fab'),
-            ), IconButton(
-              icon: Icon(Icons.radio_button_checked),
+            ),
+            IconButton(
+              icon: Icon(Icons.looks_two),
               color: Colors.white,
               tooltip: "change tab by controller",
-              onPressed: (){
+              onPressed: () {
                 _tabController?.animateTo(2);
               },
             )
@@ -195,7 +196,11 @@ class _State extends State<DefaultAppBarDemo>
                 onTap: (int i) => debugPrint('select index=$i'),
               )
             : ConvexAppBar.badge(
-                {3: _badge!.text, 4: Icons.assistant_photo, 2: Colors.redAccent},
+                {
+                  3: _badge!.text,
+                  4: Icons.assistant_photo,
+                  2: Colors.redAccent
+                },
                 badgePadding: _badge!.padding,
                 badgeColor: _badge!.badgeColor,
                 badgeBorderRadius: _badge!.borderRadius,
@@ -221,9 +226,7 @@ class _State extends State<DefaultAppBarDemo>
     });
   }
 
-  void _onNothing(ChoiceValue<TabStyle>? value) {
-
-  }
+  void _onNothing(ChoiceValue<TabStyle>? value) {}
 
   void _onStyleChanged(ChoiceValue<TabStyle>? value) {
     if (value == null) {

lib/src/bar.dart

@@ -361,6 +361,7 @@ class ConvexAppBar extends StatefulWidget {
 class ConvexAppBarState extends State<ConvexAppBar>
     with TickerProviderStateMixin {
   int? _currentIndex;
+  int? get currentIndex => _currentIndex;
   int _warpUnderwayCount = 0;
   Animation<double>? _animation;
   AnimationController? _animationController;
@@ -403,17 +404,14 @@ class ConvexAppBarState extends State<ConvexAppBar>
     if (c == null) {
       return;
     }
-    // Workaround for TabController, see https://github.com/hacktons/convex_bottom_bar/issues/59
-    var _diff = (c.index - _currentIndex!).abs();
-    if (_diff == 1) {
-      if (_blockEvent(c.index)) return;
-      final previousIndex = c.previousIndex;
-      final index = c.index;
-      _warpUnderwayCount += 1;
-      await animateTo(index, from: previousIndex);
-      _warpUnderwayCount -= 1;
-      return Future<void>.value();
-    }
+    if (_blockEvent(c.index)) return;
+    final previousIndex = c.previousIndex;
+    final index = c.index;
+    // Counter to avoid repeat calls to animateTo in the middle of a transition.
+    _warpUnderwayCount += 1;
+    await animateTo(index, from: previousIndex);
+    _warpUnderwayCount -= 1;
+    return Future<void>.value();
   }
 
   /// change active tab index; can be used with [PageView].
@@ -465,15 +463,15 @@ class ConvexAppBarState extends State<ConvexAppBar>
     super.dispose();
   }
 
-  TabController? get _takeControllerRef {
+  TabController? get _currentControllerRef {
     if (widget.disableDefaultTabController == true) {
       return widget.controller;
     }
     return widget.controller ?? DefaultTabController.of(context);
   }
 
   void _updateTabController() {
-    final newController = _takeControllerRef;
+    final newController = _currentControllerRef;
     assert(() {
       if (newController != null &&
           widget.controller == null &&
@@ -505,7 +503,7 @@ class ConvexAppBarState extends State<ConvexAppBar>
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
-    if (_controller != _takeControllerRef) {
+    if (_controller != _currentControllerRef) {
       _updateTabController();
       _resetState();
     }
@@ -625,8 +623,13 @@ class ConvexAppBarState extends State<ConvexAppBar>
 
   void _onTabClick(int i) {
     if (_blockEvent(i)) return;
-    animateTo(i);
-    _controller?.animateTo(i);
+    if (_controller == null) {
+      animateTo(i);
+    } else {
+      // animation listener [_handleTabControllerAnimationTick] will drive the
+      // internal animateTo() via [_warpToCurrentIndex].
+      _controller!.animateTo(i);
+    }
     widget.onTap?.call(i);
   }
 

test/widget_test.dart

@@ -188,39 +188,70 @@ void main() {
   testWidgets('Test tab controller', (WidgetTester tester) async {
     var controller =
         TabController(length: 3, vsync: TestVSync(), initialIndex: 2);
-    var key = GlobalKey(debugLabel: 'appbar');
+    var key = GlobalKey<ConvexAppBarState>(debugLabel: 'appbar');
     var appbar = ConvexAppBar.builder(
       key: key,
       controller: controller,
       itemBuilder: Builder(),
       count: 3,
       top: -20,
       onTap: (i) {
-        assert(i == 1);
+        expect(i, 1);
       },
     );
     await tester.pumpWidget(
-      material(appbar),
+      // material(appbar),
+      material(Scaffold(
+        body: TabBarView(
+          controller: controller,
+          children: const <Widget>[
+            Center(child: Text('CHILD 0')),
+            Center(child: Text('CHILD 1')),
+            Center(child: Text('CHILD 2')),
+          ],
+        ),
+        bottomNavigationBar: appbar,
+      )),
       Duration(milliseconds: 300),
     );
+    expect(key.currentState?.currentIndex, 2);
     expect(find.text('TAB 0'), findsOneWidget);
     expect(find.text('TAB 1'), findsOneWidget);
+    expect(find.text('TAB 2'), findsOneWidget);
+    expect(find.text('CHILD 2'), findsOneWidget);
+
     await tester.tap(find.text('TAB 1'));
     await tester.tap(find.text('TAB 1'));
     await tester.pumpAndSettle(Duration(milliseconds: 300));
-    await tester.startGesture(Offset(0, 100)).then((g) {
-      return g.moveTo(Offset(500, 100));
-    });
-    await tester.startGesture(Offset(0, 100)).then((g) {
-      return g.moveTo(Offset(100, 100));
-    });
-    controller.index = 1;
+    expect(controller.index, 1);
+    expect(key.currentState?.currentIndex, 1);
+
+    await tester.drag(find.text('CHILD 1'), Offset(1000, 0));
     await tester.pumpAndSettle(Duration(milliseconds: 300));
+    expect(controller.index, 0);
+    expect(key.currentState?.currentIndex, 0);
+
+    controller.animateTo(2);
+    await tester.pumpAndSettle(Duration(milliseconds: 300));
+    expect(controller.index, 2);
+    expect(key.currentState?.currentIndex, 2);
+
+    // Test a custom controller accidentally used with the DefaultTabController
+    controller.index = 2;
     await tester.pumpWidget(
       material(DefaultTabController(
-          initialIndex: 2,
-          length: 3,
-          child: ConvexAppBar.builder(
+        initialIndex: 0,
+        length: 3,
+        child: material(Scaffold(
+          body: TabBarView(
+            controller: controller,
+            children: const <Widget>[
+              Center(child: Text('CHILD 0')),
+              Center(child: Text('CHILD 1')),
+              Center(child: Text('CHILD 2')),
+            ],
+          ),
+          bottomNavigationBar: ConvexAppBar.builder(
             key: key,
             controller: controller,
             itemBuilder: Builder(),
@@ -229,10 +260,16 @@ void main() {
             onTap: (i) {
               assert(i == 1);
             },
-          ))),
+          ),
+        )),
+      )),
       Duration(milliseconds: 300),
     );
-    controller.index = 1;
+    expect(key.currentState?.currentIndex, 2);
+    await tester.flingFrom(Offset(0, 100), const Offset(600, 100), 10000.0);
+    await tester.pumpAndSettle(Duration(milliseconds: 300));
+    expect(controller.index, 1);
+    expect(key.currentState?.currentIndex, 1);
   });
 
   testWidgets('Add badge on AppBar', (WidgetTester tester) async {