public class MyFirebaseInstanceIDService extends FirebaseInstanceIdService {
    @Override
    public void onTokenRefresh() {
        String refreshedToken = FirebaseInstanceId.getInstance().getToken();

        // Check if the user is logged in. If so,
        // send the Firebase token to the server.
        if (PreferenceUtils.isLoggedIn(this)) {
            ApiInterface apiService = ApiClient.createService(ApiInterface.class, PreferenceUtils.getAuthToken(context));

            Call<BasicResponse> call = apiService.sendDeviceToken(token);
            call.enqueue(new Callback<BasicResponse>() {
                @Override
                public void onResponse(Call<BasicResponse> call, Response<BasicResponse> response) {
                    if (!response.isSuccessful()) {

                        // WHAT SHOULD I DO IF THE TOKEN FAILS TO GET SENT TO THE SERVER?

                    }
                }

                @Override
                public void onFailure(Call<BasicResponse> call, Throwable t) {
                    //
                }
            });
        }
    }
}