flutter操作提示栏SnackBar

class SnackBarDemo extends StatefulWidget {
  @override
  _SnackBarDemoState createState() => _SnackBarDemoState();
}

class _SnackBarDemoState extends State<SnackBarDemo> {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('SnackBarDemo'), elevation: 0.0,),
      body: Container(
        padding: EdgeInsets.all(16.0),
        child: Column(
          mainAxisAlignment:  MainAxisAlignment.center,
          children: <Widget>[
            Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                SnackBarButton(),
              ],
            ),
          ],
        ),
      ),
    );
  }
}

class SnackBarButton extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return FlatButton(onPressed: () {
      Scaffold.of(context).showSnackBar( // 打开操作提示栏
        SnackBar(
          content: Text('Processing...'),
          action: SnackBarAction(label: 'OK', onPressed: () {}),
        )
      );
    }, child: Text('Open SnackBar'));
  }
}