TabBar 头部切换嵌套实现无缝隙切换

Scaffold(
      // appBar: AppBar(
      //   // title: ,
      // ),
      body: Container(
        child: Column(
          children: <Widget>[
            Container(
              height: 105,
              color: Colors.green[200],
              child: Stack(
                fit: StackFit.loose,
                children: <Widget>[
                  // Container(
                  //   child: Text('4444'),
                  // ),
                  Positioned(
                    top: 49,
                    left: -5,
                    child: IconButton(
                      onPressed: (){
                        AppNavigator.pop(context);
                      },
                      icon: Icon(Icons.chevron_left, color: Colors.red, size: 38,),
                    ),
                  ),
                  Positioned(
                    // top: 49,
                    left: 50,
                    right: 50,
                    child: Container(
                    padding: EdgeInsets.only(top: 45),
                    height: 105,
                    width: width * 100,
                    color: Colors.blue[600],
                    alignment: Alignment.center,
                    child: TabBar(
                      isScrollable:  true,
                      controller: _controller,
                      indicatorSize: TabBarIndicatorSize.label,
                      indicator: UnderlineTabIndicator(
                          borderSide: BorderSide(color: Color(0xffFF3700), width: 2, ),
                          insets: EdgeInsets.only(  top: 1, left: 1, right :1),
                      ),
                      tabs: <Widget>[
                        Tab(
                          text: "精英版集群",
                        ),
                        Tab(
                          text: "超算版集群",
                        )
                      ],
                    ),
                 ),
                  )
                ],
              ),
            )
          ],
        ),
      ),
    );