mAuth = FirebaseAuth.getInstance();
        mAuth.signInAnonymously().addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                if (task.isSuccessful()) {
                    FirebaseUser currentUser = mAuth.getCurrentUser();
                    if (currentUser != null) {
                        String uid = currentUser.getUid();

                    }
                }
            }
        });