Custom notifications in Flutter

main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  MyApp();

  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State {
  String message = 'no option selected';

  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(),
        body: NotificationListener<MyNotification>(
          onNotification: (notification) {
            setState(() {
              message = 'You selected option ${notification.data}';
            });
            return true;
          },
          child: Center(
            child: Column(
              children: [
                Text(message),
                MyWidget(),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

class MyNotification extends Notification {
  final String data;
  MyNotification(this.data);
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        RaisedButton(
          child: Text('Option A'),
          onPressed: () {
            MyNotification('A').dispatch(context);
          },
        ),
        RaisedButton(
          child: Text('Option B'),
          onPressed: () {
            MyNotification('B').dispatch(context);
          },
        ),
      ],
    );
  }
}