The getter 'email' was called on null - firebase

Question

I'm trying to make a chat between two people using Flutter and Firebase but I'm facing an error when I connect into my app using Firebase's signInWithEmailAndPassword, it tells me:
The getter 'email' was called on null. Receiver: null Tried calling:
email
And Flutter also tells me the error come from the MaterialApp widget from my main.dart which doesn't help me to find the error..
import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:social/responsive/size_config.dart';
import 'settings.dart';
import 'home.dart';
final _firestore = Firestore.instance;
FirebaseUser loggedInUser;
class ActivityFeed extends StatefulWidget {
static const String id = 'activity_feed_screen';
#override
_ActivityFeedState createState() => _ActivityFeedState();
}
class _ActivityFeedState extends State<ActivityFeed> {
final _auth = FirebaseAuth.instance;
#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(
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Expanded(
child: Container(
color: Colors.red,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
UserInfo(),
FlatButton(
child: Icon(
Icons.settings,
color: Colors.white,
),
onPressed: () {
Navigator.pushNamed(context, Settings.id);
},
),
FlatButton(
child: Icon(
Icons.not_interested,
color: Colors.white,
),
onPressed: () {
_auth.signOut();
Navigator.pushNamed(context, Home.id);
},
),
],
),
),
)
],
),
);
}
}
class UserInfo extends StatefulWidget {
#override
_UserInfoState createState() => _UserInfoState();
}
class _UserInfoState extends State<UserInfo> {
String email = loggedInUser.email;
String username;
#override
void initState() {
super.initState();
getUsername();
}
void getUsername() async {
DocumentReference docRef = _firestore.collection('users').document(email);
docRef.get().then((snapshot) {
if (snapshot.exists) {
username = snapshot.data['username'];
}
});
}
#override
Widget build(BuildContext context) {
SizeConfig().init(context);
return Column(
children: <Widget>[
Text(
'Welcome $username',
style: TextStyle(
fontFamily: 'Amatic',
fontSize: SizeConfig.safeBlockHorizontal * 10),
),
],
)
;
}
}
So basically what I am just trying to display 'Welcome' + the username, but it doesn't want,
my Firebase Database have one collection named 'users', where the document names are the email the user used when he created his account.
All the Register/Log-In process seems to work fine.
If someone has a clue of what is happening that would be awesome, thanks.

Answer 1

You initialize username as null. You can either check it on the widget tree
username != null ? Text(
'Welcome $username',
style: TextStyle(
fontFamily: 'Amatic',
fontSize: SizeConfig.safeBlockHorizontal * 10),
) : CircularProgressIndicator()
and set it via setState()
setState(() {
username = snapshot.data['username'];
});
Another solution is to change
String username;
to
String username = '';
You should use a state management method by the way. setState() is very primitive and you will end up having sphagetti code if you use it as a state management solution.