Cannot Login using Firebase - firebase

Question

I'm having issues with logging into my app using Firebase Authentication. I got it to work before, but I can't figure out what changes I've made that ended up breaking the code.
Below are the relevant classes-main for controlling what screens are loaded and LoginScreen to sign the user in. Creating new users work, and I can access MyHomePage() after a new user is created. The StreamBuilder part of the code in main also works since the if(userSnapshot.hasData) of code is reached and executed. The screen however just stays on the LoginScreen. There are no platform exception errors either and the console prints out:
Update The issue was because I implemented signOut() incorrectly. I navigated the app screen to the LoginScreen before auth.FirebaseAuth.instance.signOut(). Since StreamBuilder is used to listen for authStateChanges, that navigation to the LoginScreen isn't necessary.
D/FirebaseAuth(31169): Notifying id token listeners about user ( fK9nC6AFGmew1GLsXgj6FxK1zIg2 ). D/FirebaseAuth(31169): Notifying auth state listeners about user ( fK9nC6AFGmew1GLsXgj6FxK1zIg2 ).
void main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp();
SystemChrome.setPreferredOrientations(
[DeviceOrientation.portraitUp, DeviceOrientation.portraitDown]);
runApp(MyApp());
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MultiProvider(
providers: [
ChangeNotifierProvider(
create: (context) => MyUser(),
),
ChangeNotifierProvider(
create: (context) => Cities(),
),
],
child: MaterialApp(
debugShowCheckedModeBanner: false,
title: 'TestApp',
home: StreamBuilder(
stream: FirebaseAuth.instance.authStateChanges(),
builder: (ctx, userSnapshot) {
if (userSnapshot.hasData) {
return MyHomePage();
}
return LoginScreen();
},
),
),
);
}
}
class LoginScreen extends StatefulWidget {
#override
_LoginScreenState createState() => _LoginScreenState();
}
class _LoginScreenState extends State<LoginScreen> {
final _auth = auth.FirebaseAuth.instance;
var message = '';
void _login(User myUser, BuildContext ctx) async {
try {
await _auth.signInWithEmailAndPassword(
email: myUser.userEmail,
password: myUser.userPassword,
);
} on PlatformException catch (err) {
if (err.message != null) {
message = err.message;
}
} catch (err) {
print(err);
}
}
#override
Widget build(BuildContext context) {
return Scaffold(body: InputForm(_login));
}
}

Answer 1

There's no appear to be error in login
Just add LoginScreen as default in Home like this
child: MaterialApp(
debugShowCheckedModeBanner: false,
title: 'TestApp',
home: LoginScreen(),
),
and then in your logic, after you call signInWithEmailAndPassword firebase method use the Navigator method like this
Navigator.push(
context,
MaterialPageRoute(builder: (context) => MyHomePage()),
);
For more details read this Flutter navigation

Answer 2

Your code seems to work fine except that you're not doing anything (except assigning the value to the message variable which isn't doing anything here) with the PlatformExceptions when you catch them in the block of code below.
on PlatformException catch (err) {
if (err.message != null) {
message = err.message;
}
}
So even if you have a PlatformException, you will not see anything in the console which means the sign in can fail silently.
Solution:
If you want the final catch block to handle all exceptions, you can use the catch block directly.
try {
await _auth.signInWithEmailAndPassword(
email: myUser.userEmail,
password: myUser.userPassword,
);
} catch (err) {
print(err);
}
If you want to print the PlatformException, you can add a print statement like you did in the catch block:
on PlatformException catch (err) {
print(err);
}