class PostScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: NestedScrollView(
        headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
          return <Widget>[
            SliverAppBar(
              floating: true,
              pinned: false,
              snap: true,
              title: Text('News'),
              forceElevated: true,
              actions: [
                IconButton(
                  icon: Icon(Icons.share),
                  tooltip: 'Share',
                  onPressed: () {
                    // TODO
                  },
                ),
              ],
            ),
          ];
        },
        body: ListView(
          padding: EdgeInsets.all(0),
          children: <Widget>[
            // ...
          ],
        ),
      ),
    );
  }
}

SystemChrome.setEnabledSystemUIOverlays([SystemUiOverlay.bottom]),