Notify parent widget from sub children widgets

Question

I am trying to refresh the parent widget from sub children widget. Actually, there are a number of widgets in between like A uses B and B uses C. I would like to refresh A widget on an event in C widget.I researched a lot but couldn't find an exact answer. A code snipped will be really helpful. Thanks in advance

Answer 1

There are a few solutions:

• A pass a callback that does a setState to B, which then pass it to C:

class A extends StatefulWidget {
  @override
  _AState createState() => _AState();
}

class _AState extends State<A> {
  @override
  Widget build(BuildContext context) {
    return B(
      onSomething: () => setState(() {}),
    );
  }
}

class B extends StatelessWidget {
  final VoidCallback onSomething;

  const B({Key key, this.onSomething}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return C(onSomething: onSomething);
  }
}

class C extends StatelessWidget {
  final VoidCallback onSomething;

  const C({Key key, this.onSomething}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return RaisedButton(
      onPressed: onSomething,
    );
  }
}

• use NotificationListener in A, and dispatch a Notification from C:

class MyNotification extends Notification {}

class A extends StatefulWidget {
  @override
  _AState createState() => _AState();
}

class _AState extends State<A> {
  @override
  Widget build(BuildContext context) {
    return NotificationListener<MyNotification>(
      onNotification: (_) {
        setState(() {});
      },
      child: B(),
    );
  }
}

class C extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return RaisedButton(
      onPressed: () {
        MyNotification().dispatch(context);
      },
    );
  }
}