Change UI based on change to provided value - flutter

Question

I have a screen from which I want to navigate to a new screen if a provided boolean value(isLoggedIn) gets changed to true. The first build method below is not possible since Navigator cannot be called during build. I attempted to do this in build because I need access to context to use my provider. The value of isLoggedIn coming from the provider of Authorization can potentially change at any time, so I would have to check for this.
How can I solve this using provider and navigator?
//Not working solution
Widget build(BuildContext context) {
Authorization auth = Provider.of<Authorization>(context);
return Scaffold(
body: Center(
child: auth.isLoggedIn
? Text(
"Logged In",
)
: Navigator.pushReplacementNamed(context, 'sign-in')),
);
}
I can do it without Navigator like this:
//Working solution
class SplashScreen extends StatelessWidget {
static const routeName = 'splash';
#override
Widget build(BuildContext context) {
final auth = Provider.of<Authorization>(context);
return auth.isLoggedIn ? HomeScreen() : SignInScreen();
}
}
But I do not now if that is a solid approach.

Answer 1

Here is an approach to solving your problem.
enum AuthStatus {
NOT_DETERMINED,
NOT_LOGGED_IN,
LOGGED_IN,
}//Always define this outside the class.
AuthStatus authStatus = AuthStatus.NOT_DETERMINED;
#override
void initState() {
super.initState();
getCurrentUser().then((user) {
setState(() {
if (user != null) {
_userId = user?.uid;
}
authStatus =
user?.uid == null ? AuthStatus.NOT_LOGGED_IN : AuthStatus.LOGGED_IN;
});
});
}
Future<FirebaseUser> getCurrentUser() async {
FirebaseUser user = await _firebaseAuth.currentUser();
return user;
}
void loginCallback() {
getCurrentUser().then((user) {
setState(() {
_userId = user.uid.toString();
authStatus = AuthStatus.LOGGED_IN;
Navigator.of(context).pushReplacementNamed('/');
});
});
}
Widget buildWaitingScreen() {
return Scaffold(
body: Container(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
child: CircleAvatar(
backgroundColor: Colors.transparent,
radius: 70.0,
child: Image.asset('assets/icons/icon.png'),
),
),
);
}
#override
Widget build(BuildContext context) {
switch (authStatus) {
case AuthStatus.NOT_DETERMINED:
return buildWaitingScreen();
break;
case AuthStatus.NOT_LOGGED_IN:
return new LoginSignUpPage();
break;
case AuthStatus.LOGGED_IN:
if (_userId.length > 0 && _userId != null) {
return new HomePage();
} else
return buildWaitingScreen();
break;
default:
return buildWaitingScreen();
}
}
}
To navigate use this in initState
void loginCallback() {
getCurrentUser().then((user) {
setState(() {
_userId = user.uid.toString();
authStatus = AuthStatus.LOGGED_IN;
});});
if(authStatus==AuthStatus.LOGGED_IN){
Navigator.pushReplacementNamed(context, 'sign-in')} }