如何在Fluttter中调用父组件appbar

import 'package:flutter/material.dart';

class MyParentWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Parent App Bar'),
      ),
      body: MyChildWidget(),
    );
  }
}

class MyChildWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return RaisedButton(
      child: Text('Call Parent AppBar'),
      onPressed: () {
        Scaffold.of(context).showSnackBar(
          SnackBar(
            content: Text('Calling Parent AppBar'),
          ),
        );
      },
    );
  }
}

class MyParentWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Parent App Bar'),
      ),
      body: Builder(
        builder: (BuildContext context) {
          return MyChildWidget();
        },
      ),
    );
  }
}