在firebaseAuth Flutter中显示空的未来构建器的主屏幕

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

class HomeScreen extends StatelessWidget {
  final FirebaseAuth _auth = FirebaseAuth.instance;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Home'),
      ),
      body: FutureBuilder(
        future: _auth.currentUser(),
        builder: (BuildContext context, AsyncSnapshot<FirebaseUser> snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            // 数据加载中，显示加载指示器
            return Center(
              child: CircularProgressIndicator(),
            );
          } else {
            if (snapshot.hasData) {
              // 用户已登录，显示用户数据
              return Center(
                child: Text('Welcome, ${snapshot.data.displayName}!'),
              );
            } else {
              // 用户未登录，显示登录按钮
              return Center(
                child: RaisedButton(
                  child: Text('Login'),
                  onPressed: () {
                    // 处理登录逻辑
                  },
                ),
              );
            }
          }
        },
      ),
    );
  }
}