Flutter 滚动时隐藏AppBar

问题：

如何在列表滚动时隐藏 AppBar ?

解决方法：

使用NestedScrollView：

new Scaffold(
  body: new NestedScrollView(
    controller: _scrollViewController,
    headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
      return <Widget>[
        new SliverAppBar(
          title: new Text(widget.title),
          pinned: true,
          floating: true,
          forceElevated: innerBoxIsScrolled,
          bottom: new TabBar(
            tabs: <Tab>[
              new Tab(text: "STATISTICS"),
              new Tab(text: "HISTORY"),
            ],
            controller: _tabController,
          ),
        ),
      ];
    },
    body: new TabBarView(
      children: <Widget>[
        new StatisticsPage(),
        new HistoryPage(),
      ],
      controller: _tabController,
    ),
  ),
);