The getter 'email' was called on null. Receiver: null Tried calling: email

Question

I got this error and I'm trying to build a messaging app. All my attempts to solve the problem didn't work

Please see these screenshots to understand the problem well.

The error

When I try to send a message, the message does not appear and all I get is a white screen

I tried to change this part of the code, and what happened is that all of my messages are on the left side of the screen and they are all called anonymous

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

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

The complete code of the chat_screen


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,
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }
}

login_screen code

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);
                  }
                },
              ),
            ],
          ),
        ),
      ),
    );
  }
}

registration_screen code


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);
                  }
                },
              ),
            ],
          ),
        ),
      ),
    );
  }
}

score 0 · Answer 1 · answered Nov 21 '20 at 05:30

0

try to wrap MessagesStream(), with futurebuilder as it depend on async call of getCurrentUser(); which provide authenticated user.

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

answered Nov 21 '20 at 05:30

GJJ2019

4,624
3
12
22

here is api link https://api.flutter.dev/flutter/widgets/FutureBuilder-class.html – GJJ2019 Nov 21 '20 at 05:30
I did not understand what do you mean? What should I change in the code? Can you clarify more? Thank you – Гєстєя Локи Nov 21 '20 at 13:17
i think problem here is your `MessagesStream()` (build method ) get executed before even completion of `getCurrentUser()` method – GJJ2019 Nov 21 '20 at 15:19
this question may help u https://stackoverflow.com/questions/61121266/why-might-a-function-not-get-called-in-initstate-super-initstate-in-flutte/61121682#61121682 – GJJ2019 Nov 21 '20 at 15:22

score 0 · Answer 2 · answered Jan 01 '21 at 14:01

change 'sender': loggedInUser.email to loggedInUser on onPressed of the Flatbutton (Send) of chat Screen. But this method has only one drawback that now if u go to your cloud firestore, you will find out that u aren't getting sender email address's field in messages collection.

The getter 'email' was called on null. Receiver: null Tried calling: email

2 Answers2