Refresh/Reset StreamProvider - Flutter Firebase - firebase

Question

In my app, I have the following providers.
#override
Widget build(BuildContext context) {
return OverlaySupport.global(
child: MultiProvider(
providers: [userLoggedIn, currentUserData],
child: MaterialApp(...)))
}
var userLoggedIn = StreamProvider<User?>.value(
value: FirebaseAuth.instance.authStateChanges(), initialData: null);
var currentUserData = StreamProvider<FrediUser>.value(
updateShouldNotify: (_, __) => true,
initialData: FrediUser(
loginProvider: '',
email: '',
admin: false,
profileSettings: [],
profileChips: [],
profileStats: [],
id: 'loading',
imageUrl: 'loading',
bio: 'loading',
username: 'loading'),
value: currentUserID != null ? currentUserDataStream() : null,
);
PROBLEM
When the user logs out (or logs in for the first time), the provider is either:
Containing old user data (until a hot restart is done, when the providers are called again and reloaded)
Null or empty, because there was no user before.
What I want to do is to refresh or call the Stream Providers again once I have a new user, or delete all the data once a user logs off.
Thank you!

Answer 1

You can listen to the changes of auth state like this.
FirebaseAuth.instance
.authStateChanges()
.listen((User? user) {
if (user == null) {
print('User is currently signed out!');
} else {
print('User is signed in!');
}
});

Answer 2

I've been facing a similar problem as you are, I've come up with a work-around although not sure how "valid" it is according to the Provider architecture
The Problem
I've got a DatabaseService class which has a stream function of type Stream<CustomUser> function, and I used it like this:
//--- main.dart ---//
runApp(MultiProvider(
providers: [
// ..some other providers.. //
// data provider
Provider<DatabaseService?>(
create: (_) => databaseService,
),
// data provider
StreamProvider<CustomUser?>(
create: (context) => databaseService.getCurrUserFromDb(),
lazy: false,
initialData: null,
updateShouldNotify: (_, __) => true,
),
],
child: MyApp(
initPage: initPage,
)
));
Stream Function:
//--- database_service.dart ---//
// gets the user from database and
// assigns it to the variable _user.
Stream<CustomUser?> getCurrUserFromDB() async* {
try {
CustomUser? currUser;
if (_user != null) {
await for (DocumentSnapshot<Object?> event
in users.doc(user.uid).snapshots()) {
final jsonMap = event.data() as Map<String, dynamic>;
currUser = CustomUser.fromJson(jsonMap);
_user = currUser;
CustomPreferences.setCurrUser(_user);
yield currUser;
}
}
} catch (e) {
rethrow;
}
}
databaseService is the DatabaseService class with named constructors.
This was not causing the widgets to rebuild at the start nor when the stream has a new value
Solution:
Created a StreamController in the DatabaseService class, and when the user signs in I add the stream function:getCurrUserFromDB() to the StreamController like this
//--- authentication_screen.dart ---//
...
ElevatedButton(
child: const Text("Sign In"),
onPressed: () async {
final user = await AuthService().googleSignIn();
if (user != null) {
final dbProvider = context.read<DatabaseService?>();
await dbProvider?.setInitUser(user, context);
await dbProvider?.cusUserController
.addStream(dbProvider.getCurrUserFromDB());
}
}),
...
setInitUser(CustomUser? user) is used set the value of the _user variable in DatabaseService and user is used to get this variable.
Reasoning
I am creating a StreamProvider at the start of the app, and its source the StreamController needs to have a stream to listen so I give it when I am trying to sign in.
Or even cleaner solution would be to do it in the constructor of DatabaseService Class like this:
//--- database_service.dart ---//
// method to add the stream to controller //
Future<void> addStream() async {
if (!_cusUserController.isClosed && !_cusUserController.isPaused) {
await _cusUserController.addStream(getCurrUserFromDB());
}
}
// constructor //
DatabaseService._init(CustomUser cusUser) {
addStream();
_user = cusUser;
}
And one last thing to note is that I don't make the declare the Controller as final. When I had it declared as final the streams weren't updating, so it looks like this now:
//--- database_service.dart ---//
StreamController<CustomUser?> _cusUserController = StreamController();
TL;DR
I created a StreamProvider which returns a StreamController in its create property and later down the life cycle of the app I gave the controller a Stream using the addStream method.
Sorry for the wall of text I just wanted to come out as clear as possible.