InheritedNotificationListener with subclass and event blubbling

main.dart

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class _InheritedNotificationListener extends InheritedWidget {
  _InheritedNotificationListener({
    Key key,
    this.maybeNotify,
    Widget child,
  }) : super(key: key, child: child);

  final bool Function(Object value) maybeNotify;

  @override
  bool updateShouldNotify(InheritedWidget oldWidget) {
    return false;
  }
}

class InheritedNotificationListener<T> extends StatelessWidget {
  const InheritedNotificationListener({
    Key key,
    this.onNotification,
    this.child,
  }) : super(key: key);

  static void dispatch(BuildContext context, Object value) {
    bool shouldStop = false;
    while (!shouldStop) {
      final element = context.ancestorInheritedElementForWidgetOfExactType(
          _InheritedNotificationListener);
      final widget = element?.widget as _InheritedNotificationListener;

      shouldStop = widget?.maybeNotify(value) ?? true;
      element?.visitAncestorElements((e) {
        context = e;
        return false;
      });
    }
  }

  final Widget child;
  final bool Function(T value) onNotification;

  @override
  Widget build(BuildContext context) {
    return _InheritedNotificationListener(
      maybeNotify: _maybeNotify,
      child: child,
    );
  }

  bool _maybeNotify(Object value) {
    if (value is T) {
      return onNotification(value);
    }
    return false;
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return InheritedNotificationListener(
      onNotification: (int value) {
        print('received int  $value');
        return false; // bubble
      },
      child: InheritedNotificationListener(
        onNotification: (num value) {
          print('received num $value');
          return false; // bubble
        },
        child: MaterialApp(
          title: 'Flutter Demo',
          debugShowCheckedModeBanner: false,
          theme: ThemeData(
            primarySwatch: Colors.blue,
          ),
          home: MyHomePage(title: 'Flutter Demo Home Page'),
        ),
      ),
    );
  }
}

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

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: RaisedButton(
          onPressed: () {
            InheritedNotificationListener.dispatch(context, 42);
          },
          child: Text('dispatch'),
        ),
      ),
    );
  }
}