Make tab highlighting work properly only with _handleTabControllerIndexChangeStarted

giantsol · giantsol · commit db8400a16ead · 2020-08-13T00:20:26.000+09:00
diff --git a/packages/flutter/lib/src/material/tabs.dart b/packages/flutter/lib/src/material/tabs.dart
@@ -453,32 +453,8 @@ class _IndicatorPainter extends CustomPainter {
   }
 }
 
-class _ChangeAnimation extends Animation<double> with AnimationWithParentMixin<double> {
-  _ChangeAnimation(this.controller);
-
-  final TabController controller;
-
-  @override
-  Animation<double> get parent => controller.animation;
-
-  @override
-  void removeStatusListener(AnimationStatusListener listener) {
-    if (parent != null)
-      super.removeStatusListener(listener);
-  }
-
-  @override
-  void removeListener(VoidCallback listener) {
-    if (parent != null)
-      super.removeListener(listener);
-  }
-
-  @override
-  double get value => _indexChangeProgress(controller);
-}
-
-class _DragAnimation extends Animation<double> with AnimationWithParentMixin<double> {
-  _DragAnimation(this.controller, this.index);
+class _TabChangeAnimation extends Animation<double> with AnimationWithParentMixin<double> {
+  _TabChangeAnimation(this.controller, this.index);
 
   final TabController controller;
   final int index;
@@ -500,7 +476,6 @@ class _DragAnimation extends Animation<double> with AnimationWithParentMixin<dou
 
   @override
   double get value {
-    assert(!controller.indexIsChanging);
     return (controller.animation.value - index.toDouble()).abs().clamp(0.0, 1.0) as double;
   }
 }
@@ -860,13 +835,11 @@ class _TabBarState extends State<TabBar> {
 
     if (_controllerIsValid) {
       _controller.animation.removeListener(_handleTabControllerAnimationTick);
-      _controller.removeListener(_handleTabControllerTick);
       _controller.removeIndexChangeStartedListener(_handleTabControllerIndexChangeStarted);
     }
     _controller = newController;
     if (_controller != null) {
       _controller.animation.addListener(_handleTabControllerAnimationTick);
-      _controller.addListener(_handleTabControllerTick);
       _controller.addIndexChangeStartedListener(_handleTabControllerIndexChangeStarted);
       _currentIndex = _controller.index;
     }
@@ -916,7 +889,6 @@ class _TabBarState extends State<TabBar> {
     _indicatorPainter.dispose();
     if (_controllerIsValid) {
       _controller.animation.removeListener(_handleTabControllerAnimationTick);
-      _controller.removeListener(_handleTabControllerTick);
       _controller.removeIndexChangeStartedListener(_handleTabControllerIndexChangeStarted);
     }
     _controller = null;
@@ -985,16 +957,11 @@ class _TabBarState extends State<TabBar> {
     }
   }
 
-  void _handleTabControllerTick() {
-    setState(() {
-      // Rebuild the tabs after a (potentially animated) index change
-      // has completed.
-    });
-  }
-
   void _handleTabControllerIndexChangeStarted(int index, Duration duration, Curve curve) {
     if (index != _currentIndex) {
-      _currentIndex = index;
+      setState(() {
+        _currentIndex = index;
+      });
       if (widget.isScrollable)
         _scrollToCurrentIndex(duration, curve);
     }
@@ -1070,28 +1037,24 @@ class _TabBarState extends State<TabBar> {
     // controller during a Hero transition. See https://github.com/flutter/flutter/issues/213.
     if (_controller != null) {
       final int previousIndex = _controller.previousIndex;
-
-      if (_controller.indexIsChanging) {
-        // The user tapped on a tab, the tab controller's animation is running.
-        assert(_currentIndex != previousIndex);
-        final Animation<double> animation = _ChangeAnimation(_controller);
-        wrappedTabs[_currentIndex] = _buildStyledTab(wrappedTabs[_currentIndex], true, animation);
+      // Need to check range because tabs size could have been changed.
+      if (previousIndex >= 0 && previousIndex < widget.tabs.length) {
+        final Animation<double> animation = ReverseAnimation(_TabChangeAnimation(_controller, previousIndex));
         wrappedTabs[previousIndex] = _buildStyledTab(wrappedTabs[previousIndex], false, animation);
-      } else {
-        // The user is dragging the TabBarView's PageView left or right.
-        final int tabIndex = _currentIndex;
-        final Animation<double> centerAnimation = _DragAnimation(_controller, tabIndex);
-        wrappedTabs[tabIndex] = _buildStyledTab(wrappedTabs[tabIndex], true, centerAnimation);
-        if (_currentIndex > 0) {
-          final int tabIndex = _currentIndex - 1;
-          final Animation<double> previousAnimation = ReverseAnimation(_DragAnimation(_controller, tabIndex));
-          wrappedTabs[tabIndex] = _buildStyledTab(wrappedTabs[tabIndex], false, previousAnimation);
-        }
-        if (_currentIndex < widget.tabs.length - 1) {
-          final int tabIndex = _currentIndex + 1;
-          final Animation<double> nextAnimation = ReverseAnimation(_DragAnimation(_controller, tabIndex));
-          wrappedTabs[tabIndex] = _buildStyledTab(wrappedTabs[tabIndex], false, nextAnimation);
-        }
+      }
+
+      final int tabIndex = _currentIndex;
+      final Animation<double> centerAnimation = _TabChangeAnimation(_controller, tabIndex);
+      wrappedTabs[tabIndex] = _buildStyledTab(wrappedTabs[tabIndex], true, centerAnimation);
+      if (_currentIndex > 0) {
+        final int tabIndex = _currentIndex - 1;
+        final Animation<double> previousAnimation = ReverseAnimation(_TabChangeAnimation(_controller, tabIndex));
+        wrappedTabs[tabIndex] = _buildStyledTab(wrappedTabs[tabIndex], false, previousAnimation);
+      }
+      if (_currentIndex < widget.tabs.length - 1) {
+        final int tabIndex = _currentIndex + 1;
+        final Animation<double> nextAnimation = ReverseAnimation(_TabChangeAnimation(_controller, tabIndex));
+        wrappedTabs[tabIndex] = _buildStyledTab(wrappedTabs[tabIndex], false, nextAnimation);
       }
     }
 
