https://code.i-harness.com/ko/q/23b82a5

public static void  sendRegistrationToServer(final Context context) {

if(Common.getBooleanPerf(context,Constants.isTokenSentToServer,false) ||
        Common.getStringPref(context,Constants.userId,"").isEmpty()){

    return;
}

String token =  FirebaseInstanceId.getInstance().getToken();
String userId = Common.getUserId(context);
if(!userId.isEmpty()) {
    HashMap<String, Object> reqJson = new HashMap<>();
    reqJson.put("deviceToken", token);
    ApiInterface apiService =
            ApiClient.getClient().create(ApiInterface.class);

    Call<JsonElement> call = apiService.updateDeviceToken(reqJson,Common.getUserId(context),Common.getAccessToken(context));
    call.enqueue(new Callback<JsonElement>() {
        @Override
        public void onResponse(Call<JsonElement> call, Response<JsonElement> serverResponse) {

            try {
                JsonElement jsonElement = serverResponse.body();
                JSONObject response = new JSONObject(jsonElement.toString());
                if(context == null ){
                    return;
                }
                if(response.getString(Constants.statusCode).equalsIgnoreCase(Constants.responseStatusSuccess)) {

                    Common.saveBooleanPref(context,Constants.isTokenSentToServer,true);
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }

        @Override
        public void onFailure(Call<JsonElement> call, Throwable throwable) {

            Log.d("", "RetroFit2.0 :getAppVersion: " + "eroorrrrrrrrrrrr");
            Log.e("eroooooooorr", throwable.toString());
        }
    });

}

}

MyFirebaseInstanceIDService 클래스에서

    @Override
public void onTokenRefresh() {
    // Get updated InstanceID token.
    String refreshedToken = FirebaseInstanceId.getInstance().getToken();
    Log.d(TAG, "Refreshed token: " + refreshedToken);

    // If you want to send messages to this application instance or
    // manage this apps subscriptions on the server side, send the
    // Instance ID token to your app server.
    Common.saveBooleanPref(this,Constants.isTokenSentToServer,false);
    Common.sendRegistrationToServer(this);
    FirebaseMessaging.getInstance().subscribeToTopic("bloodRequest");
}