从 firebase 获取用户时完全跳过 addOnCompleteListener

Question

I have the following in a login activity that gets triggered to sign in a user to my app:

   mAuth.signInWithEmailAndPassword(email, password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
        @Override
        public void onComplete(@NonNull Task<AuthResult> task) {
            if (task.isSuccessful()) {
                ...
                LoggedInUser loggedInUser = LoggedInUser.getInstance();

                Toast.makeText(LoginActivity.this, getString(R.string.welcome_back) + loggedInUser.getUser().name, Toast.LENGTH_LONG).show();

The sign in and the listener above are successfully triggered. However, I am having an issue occur on that Toast line where I call loggedInUser.getUser().name

    public User getUser() {
    if (user == null) {
        FirebaseAuth mAuth = FirebaseAuth.getInstance();
        String userID = mAuth.getCurrentUser().getUid();
        DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("Users").child(userID);

        databaseReference.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
            @Override
            public void onComplete(@NonNull Task<DataSnapshot> task) {
                if (!task.isSuccessful()) {
                    Log.e("firebase", "Error getting data", task.getException());
                }
                else {
                    User currUser = task.getResult().getValue(User.class);
                    user = currUser;
                }
            }
        });
    }

    return user;
}

What happens here is that databaseReference.get().addOnCompleteListener never gets triggered so user is never set, it returns null and the app crashes.

I utilized the same code I have in getUser to set a user elsewhere with no issues so I am not sure what I am missing here that is causing the listener to be skipped. I am new to firebase so any help to understand and fix this is appreciated!

Answer 1

Not sure if I fully understand your code but you can get your user object from mAuth.getCurrentUser() inside signInWithEmailAndPassword .

Refer to the docs .

Also bear in mind that calls to the Firebase database are asynchronous. So this means in your getUser() method, you'll probably get a null return when you enter the if == null block ie your addOnCompleteListener executes after your return user statement.