Firebase + Flutter：获取用于登录的平台用户

Question

I have an app with 3 sign in methods: Google, Facebook & mail. I want to show the users that are signed in with mail a different screen. Is it possible to get the sign in method form the package firebase authentication?

I know I can fix this by using firestore & checking if a statement is true or false. But that will cost me a read every time a user opens the app...

Answer 1

Firebase has a special property providerId . But, as mentioned @GazihanAlankus it always returns firebase .

And, the property firebaseUser.providerData[1].providerId sometimes not exists (for example when user used anonymous login).

So, we should use appropriate approaches, for example:

FirebaseUser user = await _firebaseAuth.currentUser();

if (user.providerData.length < 2) {
  // do something
}
else {
  print(res.providerId);  
}

The list of values, that are returned by property providerId :

EmailAuthProviderID: password
PhoneAuthProviderID: phone
GoogleAuthProviderID: google.com
FacebookAuthProviderID: facebook.com
TwitterAuthProviderID: twitter.com
GitHubAuthProviderID: github.com
AppleAuthProviderID: apple.com
YahooAuthProviderID: yahoo.com
MicrosoftAuthProviderID: hotmail.com

I got this list from the cool research here What is the full list of provider id's for firebase.UserInfo.providerId?

Answer 2

This seems to be what you want: https://firebase.google.com/docs/reference/android/com/google/firebase/auth/FirebaseUser.html#getProviderData()

In my app where I use Google logins only, I have firebaseUser.providerData[1].providerId == 'google.com' .

Btw, firebaseUser.providerData[0].providerId == 'firebase' .

I guess you could check them all and look for what providers you get for different kinds of users.

Edit: here's what I get when logging in with e-mail: https://postimg.cc/BXWGGN6h

Answer 3

In my app I used FirebaseAuth.instance.currentUser.providerData[0].providerId == 'google.com'. , cause providerData[1] doesn't contain any value

Answer 4

But that will cost me a read every time a user opens the app. THIS IS TRUTH!

Alternatively, you can create your own app DB using SQFLite , and create only one table (user) in that, having a field of signUpMethod having possible values are google, facebook and mail . Whenever you opens the app, first check that in your db, if this is mail , redirect to another screen which you want, else call firebase service

Cheers!

Answer 5

For anyone reading this in 2022, Firebase now has nice new docs for Flutter and in it they have this, which I personally found super useful:

if (user != null) {
    for (final providerProfile in user.providerData) {
        // ID of the provider (google.com, apple.cpm, etc.)
        final provider = providerProfile.providerId;

        // UID specific to the provider
        final uid = providerProfile.uid;

        // Name, email address, and profile photo URL
        final name = providerProfile.displayName;
        final emailAddress = providerProfile.email;
        final profilePhoto = providerProfile.photoURL;
    }
}

Source: Firebase documentation