如何在flutter中创建分层的可滚动页面？

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('分层可滚动页面')),
        body: MyScrollablePage(),
      ),
    );
  }
}

class MyScrollablePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return CustomScrollView(
      slivers: <Widget>[
        SliverAppBar(
          expandedHeight: 200.0,
          floating: false,
          pinned: true,
          flexibleSpace: FlexibleSpaceBar(
            title: Text('应用栏'),
            background: Image.network(
              'https://via.placeholder.com/350x150',
              fit: BoxFit.cover,
            ),
          ),
        ),
        SliverList(
          delegate: SliverChildBuilderDelegate(
            (BuildContext context, int index) {
              return ListTile(title: Text('列表项 $index'));
            },
            childCount: 50,
          ),
        ),
      ],
    );
  }
}