How to check if User is Signed In in Flutter Firebase - flutter

Question

Hy here everyone. I am new to flutter and i want to check if User is SignedIn. If so the user navigate to HomeScreen else SplashScreen.
Here is my main.dart
void main() async{
runApp(MyApp());
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp();
}
// ignore: must_be_immutable
class MyApp extends StatelessWidget {
String initRoute;
User user = FirebaseAuth.instance.currentUser;
getUser(){
if (user != null) {
initRoute = MainScreen.routeName;
} else {
initRoute = SplashScreen.routeName;
}
}
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Instant Tasker',
theme: theme(),
initialRoute: initRoute,
routes: routes,
);
}
}

Answer 1

The proper way that I see is through the Firebase plugin, here is how it looks like.
in main.dart
void main() async {
WidgetsFlutterBinding.ensureInitialized();
Firebase.initializeApp().then((value) => print(value));
runApp(MyApp());
}
final FirebaseAuth auth = FirebaseAuth.instance;
String userData() {
final User user = auth.currentUser;
final uid = user.uid;
return uid;
}
if a user is logged in it will return uid(String) otherwise null

Answer 2

The easiest and the best way to identify if a user is already signed in or not is via using Shared Preferences.
Just add this dependency in your pubspec.yaml file.
Every time a user logs in a particular device you can save some value as a key value pair in the phone's storage using Shared Preferences.
Next time whenever a user opens the app you can just check if any value is available in the shared preferences. If so then open the Home Screen else open the Splash Screen.
This is by far the cleanest solution.
You can read more about shared Preferences here.
If you still need a sample code. Drop a comment and I will edit the answer.
Thanks

Answer 3

you should right function getuser with return statement of widget that contains return Statement of mainScreen if user signed in or else splashscreen and use this function in home:
Widget getUser(){
if (user != null) {
mainScreen();
} else {
splashScreen();
}
}
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Instant Tasker',
theme: theme(),
home:getUser(),
);
}
}

Answer 4

Thank you every one i solved my problem. Everyone on stackoverflow was providing complex solutions but still didn't solve the problem. The mistake everyone was making is they were using Firebase before the 'FirebaseApp initialize'. So i simply call the runApp when the FirebaseApp is initialized.cHere is my code
void main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp().then((value) {
runApp(MyApp());
});
}
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
User user = FirebaseAuth.instance.currentUser;
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Instant Tasker',
theme: theme(),
initialRoute: user != null ? MainScreen.routeName : SplashScreen.routeName,
routes: routes,
);
}
}