Show the introduction page only when the user logs in for the first time for a Flutter app - flutter

Question

I have used the below code to show the introduction page only when the user logs in for the first time and second time when the user logs in the user should be taken directly to the homepage.
But this does not work after my first try. Now every time a new user logs in it goes directly to the homepage but not to the introduction page. Please let me know if I am doing anything wrong.
Here is my Code:
class OneTimeScreen extends StatefulWidget {
#override
OneTimeScreenState createState() => new OneTimeScreenState();
}
class OneTimeScreenState extends State<OneTimeScreen>
with AfterLayoutMixin<OneTimeScreen> {
Future checkFirstSeen() async {
SharedPreferences prefs = await SharedPreferences.getInstance();
bool _seen = (prefs.getBool('seen') ?? false);
if (_seen) {
Navigator.of(context)
.pushReplacement(MaterialPageRoute(builder: (context) => HomePage()));
} else {
await prefs.setBool('seen', true);
Navigator.of(context).pushReplacement(
MaterialPageRoute(builder: (context) => IntroVideoPage()));
}
}
#override
void afterFirstLayout(BuildContext context) => checkFirstSeen();
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: CircularProgressIndicator(),
),
);
}
}

Answer 1

This is because the scope of the boolean which you are storing in SharedPreferences as seen is app-wide. It does not differentiate if userA or userB logs in. It is a single boolean for both.
To make that boolean user specific, we can add a unique userID as a prefix to the key seen like..
bool _seen = (prefs.getBool(userID + 'seen') ?? false);
prefs.setBool(userID + 'seen', true);
This will ensure storing different boolean for each user.