在SliverAppBar中使用FutureBuilder

import 'package:flutter/material.dart';

class MyApp extends StatelessWidget {
  Future<String> fetchData() async {
    // 模拟异步操作，例如网络请求
    await Future.delayed(Duration(seconds: 2));
    return 'Hello, World!';
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: CustomScrollView(
        slivers: <Widget>[
          SliverAppBar(
            title: Text('My App'),
            expandedHeight: 200,
            flexibleSpace: FutureBuilder<String>(
              future: fetchData(),
              builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
                if (snapshot.connectionState == ConnectionState.waiting) {
                  return Center(child: CircularProgressIndicator());
                } else if (snapshot.connectionState == ConnectionState.done) {
                  if (snapshot.hasError) {
                    return Center(child: Text('Error: ${snapshot.error}'));
                  } else {
                    return FlexibleSpaceBar(
                      title: Text(snapshot.data),
                      background: Image.network('https://example.com/image.jpg'),
                    );
                  }
                } else {
                  return Container();
                }
              },
            ),
          ),
          // 其他Sliver组件
        ],
      ),
    );
  }
}