如何使用ChangeNotifier在颤动中收听多个信号源？

import 'package:flutter/material.dart';

class MyProvider extends ChangeNotifier {
  String _message = '';

  String get message => _message;

  void setMessage(String newMessage) {
    _message = newMessage;
    notifyListeners();
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('ChangeNotifier Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Consumer<MyProvider>(
              builder: (context, provider, child) {
                return Text(provider.message);
              },
            ),
            RaisedButton(
              child: Text('Change Message'),
              onPressed: () {
                Provider.of<MyProvider>(context, listen: false)
                    .setMessage('New Message');
              },
            ),
          ],
        ),
      ),
    );
  }
}

void main() {
  runApp(
    ChangeNotifierProvider(
      create: (context) => MyProvider(),
      child: MaterialApp(
        home: MyWidget(),
      ),
    ),
  );
}