class _OrderPageState extends State<OrderPage>{   List _tabLabels = ["坚果", "前端"];      child: Scaffold(        appBar: AppBar(          elevation: 0.0,          backgroundColor: Color.fromRGBO(26, 172, 255, 1),          title: TabBar(            isScrollable: true,            indicator: UnderlineTabIndicator(                borderSide: BorderSide(style: BorderStyle.none)),            tabs: _tabLabels          ),        ),        body: Container(          color: Color.fromRGBO(26, 172, 255, 1),          child: TabBarView(            //TabBarView 默认支持手势滑动，若要禁止设置 NeverScrollableScrollPhysics            physics: NeverScrollableScrollPhysics(),            children: <Widget>[                Center(child:Text('坚果')),                Center(child:Text('前端"')),                        ],          ),        ),      )}

class _GroupInfoState extends BaseState<GroupInfoNeWPage>    with SingleTickerProviderStateMixin{    TabController tabController;      @override  void initState() {    super.initState();    // 添加监听器    tabController = TabController(vsync: this, length: titleTabs.length)      ..addListener(() {          switch (tabController.index) {            case 0:                  print("坚果");                  break;                case 1:                  print("前端")                  break;                     }      });  }    //增加controller    title: TabBar(        controller: tabController,    )    child: TabBarView(        controller: tabController,    )}

//该动画值表示当前TabBar选中的指示器位置以及TabBar和TabBarView的scrollOffsetsanimation → Animation<double>//当前选中Tab的下标。改变index也会更新 previousIndex、设置animation's的value值、重置indexIsChanging为false并且通知监听器index ↔ int//true：当动画从上一个跳到下一个时indexIsChanging → bool//tabs的总数，通常大于1length → int//不同于animation's的value和index。offset value必须在-1.0和1.0之间offset ↔ double//上一个选中tab的index值，最初与index相同previousIndex → int

 tabController = TabController(vsync: this, length: titleTabs.length)      ..addListener(() {          if(tabController.index.toDouble() == tabController.animation.value){            switch (tabController.index) {                case 0:                  print("坚果");                  break;                case 1:                  print("前端")                  break;                            }          }      });