How to Keep Users Always Logged In [duplicate] - flutter

Question

This question already has answers here:
Persist user Auth Flutter Firebase
(8 answers)
Closed 2 years ago.
I want to keep the user logged in even if the user closes the app. The problem is that if I close the app, I appear in the WelcomePage() instead of the HomePage().
In the main.dart, the initialRoute is the WelcomePage(), but I need it to change once the user has registered or logged in. What do I need to change?
Here's what I have:
import 'package:flutter/material.dart';
import 'pages/account/WelcomePage.dart';
import 'pages/match/HomePage.dart';
void main() => runApp(MyApp());
// Test
class MyApp extends StatelessWidget {
//
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
//
initialRoute: WelcomePage.id,
//
routes: {
WelcomePage.id: (context) => WelcomePage(),
HomePage.id: (context) => HomePage(),
},
);
}
}
Edit: I was reading that the user must be still logged in, so what I have to do here is check if the user is not null, and then pus to the HomePage.id. But to check if the user is logged in I need an async function, and the initialRoute doesn't accept Futures.

Answer 1

Rather than always directly going to the WelcomePage, make a widget that displays a loading indicator until you determine the login state. Once this state is determined you can show either the WelcomePage or HomePage based on this state.
An example of such a widget would be the RootPage from this medium article.
Example from article:
enum AuthStatus {
NOT_DETERMINED,
NOT_LOGGED_IN,
LOGGED_IN,
}
class RootPage extends StatefulWidget {
RootPage({this.auth});
final BaseAuth auth;
#override
State<StatefulWidget> createState() => new _RootPageState();
}
class _RootPageState extends State<RootPage> {
AuthStatus authStatus = AuthStatus.NOT_DETERMINED;
String _userId = "";
#override
void initState() {
super.initState();
widget.auth.getCurrentUser().then((user) {
setState(() {
if (user != null) {
_userId = user?.uid;
}
authStatus =
user?.uid == null ? AuthStatus.NOT_LOGGED_IN : AuthStatus.LOGGED_IN;
});
});
}
void loginCallback() {
widget.auth.getCurrentUser().then((user) {
setState(() {
_userId = user.uid.toString();
});
});
setState(() {
authStatus = AuthStatus.LOGGED_IN;
});
}
void logoutCallback() {
setState(() {
authStatus = AuthStatus.NOT_LOGGED_IN;
_userId = "";
});
}
Widget buildWaitingScreen() {
return Scaffold(
body: Container(
alignment: Alignment.center,
child: CircularProgressIndicator(),
),
);
}
#override
Widget build(BuildContext context) {
switch (authStatus) {
case AuthStatus.NOT_DETERMINED:
return buildWaitingScreen();
break;
case AuthStatus.NOT_LOGGED_IN:
return new LoginSignupPage(
auth: widget.auth,
loginCallback: loginCallback,
);
break;
case AuthStatus.LOGGED_IN:
if (_userId.length > 0 && _userId != null) {
return new HomePage(
userId: _userId,
auth: widget.auth,
logoutCallback: logoutCallback,
);
} else
return buildWaitingScreen();
break;
default:
return buildWaitingScreen();
}
}
}