flutter firebase auth current user email for appbar title

Question

User already login to the app by using firebase email login. How to make the appbar title to be the current user email?

class _HomePageState extends State<HomePage> {

  final  Future<String> userEmail = FirebaseAuth.instance.currentUser().then((FirebaseUser user) => user.email);
  var e = "";

  @override
  Widget build(BuildContext context) {

    return new Scaffold(
        appBar: new AppBar(
        backgroundColor: Colors.black,
          title: Text('userEmail'),
          actions: <Widget>[
            new FlatButton(
                onPressed: _signOut,
                child: new Text('logout', style: new TextStyle(fontSize: 17.0, color: Colors.white))
            ),

          ],
        ),
        body: new Center(
          child: new Text(
            e,
            style: new TextStyle(fontSize: 32.0),
          ),
        )
    );
  }
}

Ashton Thomas Ashton Thomas · Accepted Answer · 2018-09-06T18:49:21

You need to call setState() after you have the new user.

In your code, you create the Future<String> email but aren't able to capitalize on the eventual user.email evaluation.

I recommend creating a non-final variable to hold your FirebaseUser and then trigger the request for this in the State's initState() method.

FirebaseUser currentUser; // not final

The goal is to eventually be able to call setState() after receiving the FirebaseUser (since that's asynchronous).

FirebaseAuth.instance.currentUser().then((FirebaseUser user) {
   setState(() { // call setState to rebuild the view
     this.currentUser = user;
   });
});

An important thing to note is that you have to build your UI for all the possible states of currentUser which are:

null (before the call completes)
and, well, not null.

So you need to make sure you handle the null case with logic similar to:

String _email() {
    if (currentUser != null) {
      return currentUser.email;
    } else {
      return "no current user";
    }
}

Below is an example adapted from your code:

class _HomePageState extends State<HomePage> {
  FirebaseUser currentUser;

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

  void _loadCurrentUser() {
    FirebaseAuth.instance.currentUser().then((FirebaseUser user) {
      setState(() { // call setState to rebuild the view
        this.currentUser = user;
      });
    });
  }

  String _email() {
    if (currentUser != null) {
      return currentUser.email;
    } else {
      return "no current user";
    }
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          backgroundColor: Colors.black,
          title: Text('userEmail'),
          actions: <Widget>[
            new FlatButton(
                onPressed: _signOut,
                child: new Text('logout',
                    style: new TextStyle(fontSize: 17.0, color: Colors.white))),
          ],
        ),
        body: new Center(
          child: new Text(
            _email(),
            style: new TextStyle(fontSize: 32.0),
          ),
        ));
  }
}

flutter firebase auth current user email for appbar title

1 Answers