使用Flutter和Firebase构建聊天应用：一次快速的五小时学习体验

import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
 
class ChatScreen extends StatefulWidget {
  @override
  _ChatScreenState createState() => _ChatScreenState();
}
 
class _ChatScreenState extends State<ChatScreen> {
  final messageTextController = TextEditingController();
  final _firestore = FirebaseFirestore.instance;
  final _auth = FirebaseAuth.instance;
 
  Future<void> sendMessage() async {
    // 获取当前用户
    final user = _auth.currentUser;
    if (user != null) {
      // 发送消息到Firestore的messages集合
      final message = {
        'text': messageTextController.text,
        'sender': user.email,
      };
      await _firestore.collection('messages').add(message);
      messageTextController.clear();
    }
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Chat Screen'),
      ),
      body: StreamBuilder(
        stream: _firestore.collection('messages').snapshots(),
        builder: (context, snapshot) {
          if (!snapshot.hasData) {
            return Center(
              child: CircularProgressIndicator(),
            );
          }
          final messages = snapshot.data.documents.reversed;
          return Column(
            children: [
              // 循环显示每条消息
              Expanded(
                child: ListView.builder(
                  itemCount: messages.length,
                  itemBuilder: (context, index) => ListTile(
                    title: Text(messages[index]['text']),
                    subtitle: Text(messages[index]['sender']),
                  ),
                ),
              ),
              // 输入消息的文本框和发送按钮
              Divider(),
              Container(
                decoration: BoxDecoration(
                  border: Border(top: BorderSide()),
                ),
                child: Row(
                  children: <Widget>[
                    Expanded(
                      child: TextField(
                        controller: messageTextController,
                        decoration: InputDecoration(hintText: 'Type your message'),