如何使用Flutter MultiProvider中内建的上下文，在它的子级中？

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        ChangeNotifierProvider(create: (_) => Count()),
      ],
      child: MaterialApp(
        home: MyHomePage(),
      ),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final count = Provider.of<Count>(context);

    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter MultiProvider Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'Count:',
            ),
            Text(
              '${count.value}',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          count.increment();
        },
        child: Icon(Icons.add),
      ),
    );
  }
}