class _MyHomePageState extends State<MyHomePage> {

final RoundedLoadingButtonController _btnController = new RoundedLoadingButtonController();

void _doSomething() async {
    Timer(Duration(seconds: 3), () {
    _btnController.success();
    });
}

@override
Widget build(BuildContext context) {

    return Scaffold(
    appBar: AppBar(

        title: Text(widget.title),
    ),
    body: Center(
        child: Column(

        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
            RoundedLoadingButton(
            child: Text('Tap me!', style: TextStyle(color: Colors.white)),
            controller: _btnController,
            onPressed: _doSomething,
            )
        ],
        ),
    )
    );
}
}