Firebase android : make username unique

Question

Parse will shut down at the end of the year, so I decided to start using Firebase. I need to implement a register process with 3 fields : email, username, password (

Answer 1

I dont know much about firebase security yet, but I may have solved the problem using Java. I have posted it below.

my data structure is

myapp
{
  users: {
          
          { username: "example.username" }
}
}


public boolean isUsernameExists(final String enteredUsername) {
        final Boolean[] isExist = {false};
        FBref.child("users").addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot userSnapshot : dataSnapshot.getChildren()) {
                    String existingUsername = (String) userSnapshot.child("userName").getValue();
                    if (existingUsername.equals(enteredUsername)) {
                        isExist[0] = true;
                    }
                }
            }
            @Override
            public void onCancelled(FirebaseError firebaseError) {
                //some error thrown here
            }
        });
        return isExist[0];
    }