flutter rebuild future

class _MyHomePageState extends State<MyHomePage> {

  String display;

  Widget futureBuilder() {

 return new FutureBuilder<String>(builder: (context, snapshot) {
 // if(snapshot.hasData){return new Text(display);}    //does not display updated text
 if (display != null) {
  return new Text(display);
  // return your createListView(context, snapshot);

  }
  return new Text("no data yet");
  });
}

  @override
  Widget build(BuildContext context) {

    return new Scaffold(
      appBar: new AppBar(
        title: new Text("Home Page"),
      ),
      body: Center(
             child: Column(
                 mainAxisAlignment: MainAxisAlignment.center,
                 children: <Widget>[
                        FlatButton(onPressed: () async{
                            result = await _getData();
                            print(result);
                                // Result will be your json response

                            setState(() {
                                display = result; //assign any string value from result to display variable.
                            });
                        },
                        child: new Text("Get Data")
                        ),
                        futureBuilder()
                ],
            ),
        ),

    );
  }

  Future<List<String>> _getData() async {
    var values = new List<String>();

    await new Future.delayed(new Duration(seconds: 5));

    return values;
  }

  Widget createListView(BuildContext context, AsyncSnapshot snapshot) {

  }
}