getter 'email' 被調用為 null。 接收方：空嘗試調用：電子郵件

Question

我遇到了這個錯誤，我正在嘗試構建一個消息傳遞應用程序。 我解決問題的所有嘗試都沒有奏效

請查看這些屏幕截圖以很好地理解問題。

我試圖改變這部分代碼，結果是我的所有消息都在屏幕左側，並且都被稱為匿名

final messageText = message.data()['text'];
final messagesendar = message.data()['Sender'] ?? 'Anonymous'; // If null then use 'Anonymous'

final messagebubble = Messagebubble(
  sendar: messagesendar,
  text: messageText,
);

chat_screen 的完整代碼

import 'package:flutter/material.dart';
import 'package:flash_chat/constants.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

final _firestore = Firestore.instance;
FirebaseUser loggedInUser;

class ChatScreen extends StatefulWidget {
  static const String id = 'chat_screen';
  @override
  _ChatScreenState createState() => _ChatScreenState();
}

class _ChatScreenState extends State<ChatScreen> {
  final messageTextController = TextEditingController();
  final _auth = FirebaseAuth.instance;

  String messageText;

  @override
  void initState() {
    super.initState();

    getCurrentUser();
  }

  void getCurrentUser() async {
    try {
      final user = await _auth.currentUser;
      if (user != null) {
        loggedInUser = user;
      }
    } catch (e) {
      print(e);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        leading: null,
        actions: <Widget>[
          IconButton(
              icon: Icon(Icons.close),
              onPressed: () {
                _auth.signOut();
                Navigator.pop(context);
              }),
        ],
        title: Text('⚡️Chat'),
        backgroundColor: Colors.lightBlueAccent,
      ),
      body: SafeArea(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: <Widget>[
            MessagesStream(),
            Container(
              decoration: kMessageContainerDecoration,
              child: Row(
                crossAxisAlignment: CrossAxisAlignment.center,
                children: <Widget>[
                  Expanded(
                    child: TextField(
                      controller: messageTextController,
                      onChanged: (value) {
                        messageText = value;
                      },
                      decoration: kMessageTextFieldDecoration,
                    ),
                  ),
                  FlatButton(
                    onPressed: () {
                      messageTextController.clear();
                      _firestore.collection('messages').add({
                        'text': messageText,
                        'sender': loggedInUser.email,
                      });
                    },
                    child: Text(
                      'Send',
                      style: kSendButtonTextStyle,
                    ),
                  ),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class MessagesStream extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return StreamBuilder<QuerySnapshot>(
      stream: _firestore.collection('messages').snapshots(),
      builder: (context, snapshot) {
        if (!snapshot.hasData) {
          return Center(
            child: CircularProgressIndicator(
              backgroundColor: Colors.lightBlueAccent,
            ),
          );
        }
        final messages = snapshot.data.documents.reversed;
        List<MessageBubble> messageBubbles = [];
        for (var message in messages) {
          final messageText = message.data()['text'];
          final messageSender = message.data()['sender'];

          final currentUser = loggedInUser.email;

          final messageBubble = MessageBubble(
            sender: messageSender,
            text: messageText,
            isMe: currentUser == messageSender,
          );

          messageBubbles.add(messageBubble);
        }
        return Expanded(
          child: ListView(
            reverse: true,
            padding: EdgeInsets.symmetric(horizontal: 10.0, vertical: 20.0),
            children: messageBubbles,
          ),
        );
      },
    );
  }
}

class MessageBubble extends StatelessWidget {
  MessageBubble({this.sender, this.text, this.isMe});

  final String sender;
  final String text;
  final bool isMe;

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: EdgeInsets.all(10.0),
      child: Column(
        crossAxisAlignment:
            isMe ? CrossAxisAlignment.end : CrossAxisAlignment.start,
        children: <Widget>[
          Text(
            sender,
            style: TextStyle(
              fontSize: 12.0,
              color: Colors.black54,
            ),
          ),
          Material(
            borderRadius: isMe
                ? BorderRadius.only(
                    topLeft: Radius.circular(30.0),
                    bottomLeft: Radius.circular(30.0),
                    bottomRight: Radius.circular(30.0))
                : BorderRadius.only(
                    bottomLeft: Radius.circular(30.0),
                    bottomRight: Radius.circular(30.0),
                    topRight: Radius.circular(30.0),
                  ),
            elevation: 5.0,
            color: isMe ? Colors.lightBlueAccent : Colors.white,
            child: Padding(
              padding: EdgeInsets.symmetric(vertical: 10.0, horizontal: 20.0),
              child: Text(
                text,
                style: TextStyle(
                  color: isMe ? Colors.white : Colors.black54,
                  fontSize: 15.0,
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }
}

登錄屏幕代碼

import 'dart:math';
import 'package:modal_progress_hud/modal_progress_hud.dart';

import 'package:flash_chat/component/Roundedbutton.dart';
import 'package:flash_chat/screens/chat_screen.dart';
import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';

import '../constants.dart';

class LoginScreen extends StatefulWidget {
  static const Id = 'login_screen';
  @override
  _LoginScreenState createState() => _LoginScreenState();
}

class _LoginScreenState extends State<LoginScreen> {
  final _auth = FirebaseAuth.instance;
  bool showSpinner = false;
  String email;
  String password;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      body: ModalProgressHUD(
        inAsyncCall: showSpinner,
        child: Padding(
          padding: EdgeInsets.symmetric(horizontal: 24.0),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: <Widget>[
              Flexible(
                child: Hero(
                  tag: 'logo',
                  child: Container(
                    height: 200.0,
                    child: Image.asset('images/logo.png'),
                  ),
                ),
              ),
              SizedBox(
                height: 48.0,
              ),
              TextField(
                  keyboardType: TextInputType.emailAddress,
                  textAlign: TextAlign.center,
                  onChanged: (value) {
                    email = value;
                  },
                  decoration: KTextfieldDecoration.copyWith(
                      hintText: 'Enter your email')),
              SizedBox(
                height: 8.0,
              ),
              TextField(
                  obscureText: true,
                  textAlign: TextAlign.center,
                  onChanged: (value) {
                    password = value;
                  },
                  decoration: KTextfieldDecoration.copyWith(
                      hintText: 'Enter your password')),
              SizedBox(
                height: 24.0,
              ),
              Roundedbutton(
                titel: 'Login',
                colourl: Colors.blueAccent,
                onPressed: () async {
                  setState(() {
                    showSpinner = true;
                  });
                  try {
                    final user = await _auth.signInWithEmailAndPassword(
                      email: email,
                      password: password,
                    );
                    if (user != null) {
                      Navigator.pushNamed(
                        context,
                        ChatScreen.id,
                      );
                    }
                    setState(() {
                      showSpinner = false;
                    });
                  } catch (a) {
                    print(e);
                  }
                },
              ),
            ],
          ),
        ),
      ),
    );
  }
}

注冊_屏幕代碼

import 'package:flash_chat/component/Roundedbutton.dart';
import 'package:flash_chat/constants.dart';
import 'package:flash_chat/screens/chat_screen.dart';
import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'chat_screen.dart';
import 'package:modal_progress_hud/modal_progress_hud.dart';

class RegistrationScreen extends StatefulWidget {
  static const String Id = 'registration_screen';
  @override
  _RegistrationScreenState createState() => _RegistrationScreenState();
}

class _RegistrationScreenState extends State<RegistrationScreen> {
  final _auth = FirebaseAuth.instance;
  bool showSpinner = false;
  String email;
  String password;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      body: ModalProgressHUD(
        inAsyncCall: showSpinner,
        child: Padding(
          padding: EdgeInsets.symmetric(horizontal: 24.0),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: <Widget>[
              Flexible(
                child: Hero(
                  tag: 'logo',
                  child: Container(
                    height: 200.0,
                    child: Image.asset('images/logo.png'),
                  ),
                ),
              ),
              SizedBox(
                height: 48.0,
              ),
              TextField(
                  keyboardType: TextInputType.emailAddress,
                  textAlign: TextAlign.center,
                  onChanged: (value) {
                    email = value;
                  },
                  decoration: KTextfieldDecoration.copyWith(
                      hintText: 'Enter your email')),
              SizedBox(
                height: 8.0,
              ),
              TextField(
                  obscureText: true,
                  textAlign: TextAlign.center,
                  onChanged: (value) {
                    password = value;
                  },
                  decoration: KTextfieldDecoration.copyWith(
                      hintText: 'Enter your password')),
              SizedBox(
                height: 24.0,
              ),
              Roundedbutton(
                titel: 'Register',
                colourl: Colors.blueAccent,
                onPressed: () async {
                  setState(() {
                    showSpinner = true;
                  });
                  try {
                    final newUser = await _auth.createUserWithEmailAndPassword(
                        email: email, password: password);
                    if (newUser != null) {
                      Navigator.pushNamed(context, ChatScreen.id);
                    }
                    setState(() {
                      showSpinner = false;
                    });
                  } catch (e) {
                    print(e);
                  }
                },
              ),
            ],
          ),
        ),
      ),
    );
  }
}

Answer 1

嘗試使用futurebuilder包裝MessagesStream(),因為它依賴於getCurrentUser();異步調用getCurrentUser(); 提供經過身份驗證的用戶。

FutureBuilder<>(
  future: getCurrentUser,
  builder:(_, __) {}
);

Answer 2

在聊天屏幕的平面按鈕（發送）的 onPressed 上將“sender”：loggedInUser.email 更改為 loggingInUser。 但是這種方法只有一個缺點，現在如果你去你的雲防火牆，你會發現你沒有在郵件收集中獲得發件人電子郵件地址的字段。