main_collapsing_toolbar.dart

 @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: DefaultTabController(
        length: 2,
        child: NestedScrollView(
          headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
            return <Widget>[
              SliverAppBar(
                expandedHeight: 200.0,
                floating: false,
                pinned: true,
                flexibleSpace: FlexibleSpaceBar(
                    centerTitle: true,
                    title: Text("Collapsing Toolbar",
                        style: TextStyle(
                          color: Colors.white,
                          fontSize: 16.0,
                        )),
                    background: Image.network(
                      "https://images.pexels.com/photos/396547/pexels-photo-396547.jpeg?auto=compress&cs=tinysrgb&h=350",
                      fit: BoxFit.cover,
                    )),
              ),
              new SliverPadding(
                padding: new EdgeInsets.all(16.0),
                sliver: new SliverList(
                  delegate: new SliverChildListDelegate([
                    TabBar(
                      labelColor: Colors.black87,
                      unselectedLabelColor: Colors.grey,
                      tabs: [
                        new Tab(icon: new Icon(Icons.info), text: "Tab 1"),
                        new Tab(
                            icon: new Icon(Icons.lightbulb_outline),
                            text: "Tab 2"),
                      ],
                    ),
                  ]),
                ),
              ),
            ];
          },
          body: Center(
            child: Text("Sample text"),
          ),
        ),
      ),
    );