Flutter：如何共享有状态小部件的实例？

Question

I have a "WidgetBackGround" statefullwidget that return an animated background for my app,

I use it like this :

Scaffold( resizeToAvoidBottomInset: false, body: WidgetBackGround( child: Container(),),)

The problem is when I use navigator to change screen and reuse WidgetBackGround an other instance is created and the animation is not a the same state that previous screen.

I want to have the same animated background on all my app, is it possible to instance it one time and then just reuse it ?

WidgetBackGround.dart look like this:

  final Widget child;

  WidgetBackGround({this.child = const SizedBox.expand()});

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

class _WidgetBackGroundState extends State<WidgetBackGround> {
  double iter = 0.0;

  @override
  void initState() {
    Future.delayed(Duration(seconds: 1)).then((value) async {
      for (int i = 0; i < 2000000; i++) {
        setState(() {
          iter = iter + 0.000001;
        });
        await Future.delayed(Duration(milliseconds: 50));
      }
    });
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return CustomPaint(painter: SpaceBackGround(iter), child: widget.child);
  }
}

Answer 1

1. this is not a solution, but maybe a valid workaround:

   try making the iter a static variable, this of course won't preserve the state of WidgetBackGround but will let the animation continue from its last value in the previous screen

2. A valid solution (not sure if it's the best out there):

   is to use some dependency injection tool (for example get_it ) and provide your WidgetBackGround object as a singleton for every scaffold in your app