问当调用SetState()时，如何避免UniqueKey闪烁的颤动FutureBuilder？

EN

void main() async {
  runApp(
    MaterialApp(
      title: 'Test',
      home: Scaffold(
        body: Bar(),
      ),
    ),
  );
}

class Bar extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _BarState();
}

class _BarState extends State<Bar> {
  List<Widget> pages;

  final controller = PageController(initialPage: 0, keepPage: true);
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    pages = [
      Center(child: PageWithFutureBuilder(key: UniqueKey())),
      Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          PageWithFutureBuilder(key: UniqueKey()),
          RaisedButton(
            onPressed: () {
              refresh();
            },
            child: new Icon(
              Icons.refresh,
              color: Colors.blue,
              size: 30.0,
            ),
          )
        ],
      ),
    ];
    return PageView(
      controller: controller,
      children: pages,
    );
  }

  void refresh() async {
    setState(() {});
  }
}

class PageWithFutureBuilder extends StatefulWidget {
  PageWithFutureBuilder({Key key}) : super(key: key);
  @override
  State<StatefulWidget> createState() => _PageWithFutureBuilderState();
}

Future test() async {
  return;
}

class _PageWithFutureBuilderState extends State<PageWithFutureBuilder> {
  Future future;
  @override
  void initState() {
    future = test();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
      future: future,
      builder: (ocntext, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting)
          return Container(
            color: Colors.black,
            child: Center(child: CircularProgressIndicator()),
          );
        else if (snapshot.connectionState == ConnectionState.done) {
          return Center(child: Text('test text'));
        } else
          return Container();
      },
    );
  }
}