FirebaseUser is not null after anonymous authentication is signed out

问题

I have 2 activities in my app. I also have a sign-in button that when clicked this method is called:

private void signIn() {
    firebaseAuth.signInAnonymously().addOnCompleteListener(this, task -> {
        if (task.isSuccessful()) {
            FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();
            if (firebaseUser != null) {
                goToSecondActivity();
            }
        }
    });
}

This my goToSecondActivity() method:

private void goToSecondActivity() {
    startActivity(new Intent(FirstActivity.this, SecondActivity.class));
    finish();
}

As specified in the official doc, in onStart(), I check the firebaseUser object for nullity like this:

FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();
if (firebaseUser != null) {
    goToMapActivity();
}

In the second activity I'm trying to get the uid of the user like this:

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();

If I try to print this uid, everything works fine, the uid is printed. If I try to sign-out (in the SecondActivity) and sign-in again, a new uid is generated, which is correct. The problem is if I sign-out again and uninstall the app and launch it again, an old user is used, even if I wait for 5 hours.

How can I solve this, so if I sign-out, next time I use my app to use the last generated user and not a very old one?

回答1:

It's because Android 6 has the automatic backup. You need to tune android:allowBackup and android:fullBackupContent in your manifest application> tag if you don't want your data backed up or if you want to include or exclude some resources. It's not a bug.

You can find more info here

In short to avoid this behaviour it is necessary to put android:allowBackup="false" and android:fullBackupContent="false" in manifest.xml

来源：https://stackoverflow.com/questions/50622674/firebaseuser-is-not-null-after-anonymous-authentication-is-signed-out