如何在flutter中使用流构建器刷新小部件

import 'dart:async';
import 'package:flutter/material.dart';

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  StreamController<String> _streamController = StreamController<String>();

  @override
  void dispose() {
    _streamController.close();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<String>(
      stream: _streamController.stream,
      builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
        if (snapshot.hasData) {
          // 数据已加载完成，更新小部件
          return Text(snapshot.data);
        } else if (snapshot.hasError) {
          // 发生错误，显示错误信息
          return Text('Error: ${snapshot.error}');
        } else {
          // 数据还未加载完成，显示加载中的状态
          return CircularProgressIndicator();
        }
      },
    );
  }
}