Android Firebase Authentication

MainActivity.java

// Firebase instance variables
    private FirebaseAuth mFirebaseAuth;
    private FirebaseUser mFirebaseUser;
    private String mUsername;
    private String mPhotoUrl;

    @Override
    protected void onCreate(Bundle savedInstanceState){
        // Initialize Firebase Auth
        mFirebaseAuth = FirebaseAuth.getInstance();
        mFirebaseUser = mFirebaseAuth.getCurrentUser();
        if(mFirebaseUser == null){
            // Not signed in, launch the Sign In activity
            startActivity(new Intent(this, SignInActivity.class));
            finish();
            return;
        }else{
            mUsername = mFirebaseUser.getDisplayName();
            if(mFirebaseUser.getPhotoUrl() != null){
                mPhotoUrl = mFirebaseUser.getPhotoUrl().toString();
            }
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()){
            case R.id.sign_out_menu:
                mFirebaseAuth.signOut();
                Auth.GoogleSignInApi.signOut(mGoogleApiClient);
                mUsername = ANONYMOUS;
                startActivity(new Intent(this, SignIntActivity.class));
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }