The getter 'uid' was called on null error appears between screens - firebase

Question

I am getting an error
The getter 'uid' was called on null.
Receiver: null
Tried calling: uid
this is the code I am using, the problem is auth.currentUser.uid which is returning null when first called, from what I understand the auth.currentUser is null at first then it return the current user
but I don't get how to handle this situation
the error show on the emulator when between the login screen and home screen after I log in, it appear for a second then it's gone and the home screen appears normally
class HomePage extends StatelessWidget {
final FirebaseAuth auth = FirebaseAuth.instance;
static int count;
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
actions: [
GestureDetector(
child: Icon(Icons.logout),
onTap: () async {
await auth.signOut();
Navigator.of(context).push(MaterialPageRoute(builder: (context) {
return LoginPage();
}));
},
),
],
),
floatingActionButton: FloatingActionButton(
child: Icon(Icons.add),
onPressed: () {
print('add button pressed');
Navigator.of(context).push(MaterialPageRoute(builder: (context) {
return NewNote();
}));
},
),
body: SafeArea(
child: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text(
'Notes',
style: TextStyle(
fontSize: 18,
),
),
// Text(count != null ? count.toString() : '0'),
NotesCount(
auth1: auth,
),
Text(auth.currentUser.uid != null ? auth.currentUser.uid : 'No user id'),
SizedBox(
height: 20,
),
NotesGrid(
auth1: auth,
),
],
),
),
),
);
}
}
class NotesCount extends StatelessWidget {
final FirebaseAuth auth1;
NotesCount({this.auth1});
#override
Widget build(BuildContext context) {
CollectionReference notes = FirebaseFirestore.instance.collection('users').doc(auth1.currentUser.uid).collection('notes');
return StreamBuilder<QuerySnapshot>(
stream: notes.snapshots(),
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasError) {
return Text('Something went wrong');
}
if (snapshot.connectionState == ConnectionState.waiting) {
return Text("Loading");
}
return new Text(snapshot.data.docs.length.toString());
},
);
}
}
class NotesGrid extends StatelessWidget {
final FirebaseAuth auth1;
NotesGrid({this.auth1});
#override
Widget build(BuildContext context) {
CollectionReference notes = FirebaseFirestore.instance.collection('users').doc(auth1.currentUser.uid).collection('notes');
return StreamBuilder(
stream: notes.snapshots(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (!snapshot.hasData) {
return Center(child: const Text('Loading events...'));
}
if (snapshot.hasError) {
return Text('Something went wrong');
}
if (snapshot.connectionState == ConnectionState.waiting) {
return Text("Loading");
}
return GridView.builder(
shrinkWrap: true,
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
itemBuilder: (BuildContext context, int index) {
return NoteCard(
note: Note(
title: snapshot.data.documents[index]['title'],
content: snapshot.data.documents[index]['content'],
datetime: snapshot.data.documents[index]['datetime'].toDate(),
id: snapshot.data.documents[index].documentID,
),
);
},
itemCount: snapshot.data.documents.length,
);
},
);
}
}

Answer 1

It's not a good idea to use currentUser as your primary way to find the signed in user account. It will always be null when the app is first launched. The previously signed in user object doesn't become available until some time later. It's better to follow the instructions in the documentation and set up an auth state listener so you can find out when the user object first becomes available.
FirebaseAuth.instance
.authStateChanges()
.listen((User user) {
if (user == null) {
print('User is currently signed out!');
} else {
print('User is signed in!');
}
});
Use this listener to respond to changes in auth state and trigger an update of your UI accordingly.

Answer 2

I tried adding if else before accessing to current user and the error is gone and the user data shows normally after loading it
Text(auth.currentUser != null ? auth.currentUser.uid : 'Loading...')