FlutterでFutureBuilderを２回以上初期化したい

Question

FlutterでFutureBuilderを２回以上初期化したいです
下記コードは初期表示で
ローディングアニメーション→文章表示というようになりますが
ボタンを押下時も同じように動作させたいです
しかし、ローディングアニメーションが表示されずに、時間が立ってから文章表示となってしまいます。
どうすればボタン押下時にも初期表示と同じ処理を出来ますでしょうか。。。
どなたか教えて下さい！

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  Future<dynamic> _json= fetchBored();

  void _incrementCounter() async {

    setState(() {
          _json = null;

    });

    setState(() {
          _json = fetchBored();
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(

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

        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            FutureBuilder<dynamic>(
                future: _json,
                builder: (context, snapshot) {
                  Widget childWidget;
                  if (snapshot.hasData) {
                    var text = snapshot.data["activity"];
                    childWidget = SelectableText(
                      '$text',
                      style: Theme.of(context).textTheme.headline4,
                    );
                  } else {
                    childWidget = const CircularProgressIndicator();
                  }
                  return childWidget;
                }),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}