Flutter Firebase身份验证: StreamBuilder中的authStateChanges()方法无法从LoginScreen更改为仪表板

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: StreamBuilder<User>(
        stream: FirebaseAuth.instance.authStateChanges(),
        builder: (BuildContext context, AsyncSnapshot<User> snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            // 如果身份验证状态正在加载中，则显示加载指示器
            return CircularProgressIndicator();
          } else {
            if (snapshot.hasData) {
              // 如果用户已经登录，则导航到仪表板
              return DashboardScreen();
            } else {
              // 如果用户未登录，则导航到登录屏幕
              return LoginScreen();
            }
          }
        },
      ),
    );
  }
}

class LoginScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('登录'),
      ),
      body: Center(
        child: RaisedButton(
          child: Text('登录'),
          onPressed: () {
            // 执行登录操作
            // 可以使用Firebase Auth的signInWithEmailAndPassword()方法进行电子邮件/密码登录
          },
        ),
      ),
    );
  }
}

class DashboardScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('仪表板'),
      ),
      body: Center(
        child: Text('欢迎来到仪表板！'),
      ),
    );
  }
}

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