异步函数完成后的Flutter setState()

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('异步函数完成后调用setState()')),
        body: AsyncDemo(),
      ),
    );
  }
}

class AsyncDemo extends StatefulWidget {
  @override
  _AsyncDemoState createState() => _AsyncDemoState();
}

class _AsyncDemoState extends State<AsyncDemo> {
  String data = '加载中...';

  void fetchData() async {
    // 模拟异步操作，例如从API获取数据
    await Future.delayed(Duration(seconds: 2));
    // 异步操作完成后，调用setState()更新UI
    setState(() {
      data = '数据加载完成';
    });
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Text(data),
          SizedBox(height: 20),
          ElevatedButton(
            onPressed: fetchData,
            child: Text('获取数据'),
          ),
        ],
      ),
    );
  }
}