check already log in or not in main screen flutter firebase auth code example

Example: flutter check if logged in

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  final SharedPreferences prefs = await SharedPreferences.getInstance();
  var isLoggedIn = (prefs.getBool('isLoggedIn') == null) ? false : prefs.getBool('isLoggedIn');
  runApp(MaterialApp(
    debugShowCheckedModeBanner: false,
    home: isLoggedIn ? anotherPage() : loginPage(),
  ));
}