anchor.diff:    @override
     void initState() {
       super.initState();
  -    _tabController = new TabController(vsync: this, length: widget.tabItems.length);
  +    _tabController =
  +        new TabController(vsync: this, length: widget.tabItems.length);
     }
   
     ///整个页面dispose时，记得把控制器也dispose掉，释放内存
  
positive.code:         bottomNavigationBar: new Material(
            //为了适配主题风格，包一层Material实现风格套用
            color: Theme.of(context).primaryColor, //底部导航栏主题颜色
            child: new TabBar(
              //TabBar导航标签，底部导航放到Scaffold的bottomNavigationBar中
              controller: _tabController, //配置控制器
              tabs: widget.tabItems,
              indicatorColor: _indicatorColor,
              onTap: (index) {
                _onPageChanged?.call(index);
                _pageController.jumpTo(MediaQuery.of(context).size.width * index);
              }, //tab标签的下划线颜色
            ),
          ));
    }
  
negative.code:       );
  }
  
  class _GSYTabBarState extends State<GSYTabBarWidget>
      with SingleTickerProviderStateMixin {
    final int _type;
  
    final List<Widget> _tabViews;
  