after to retrieving data from DataBase by the withOutAsyncTask( )..... then use RXAndroid to parse them to the UI

rxAndroidClientSample.java

      subscription = Observable.just(fetchDataHttpCall())
                .map(new Func1<String, List<GRO_VO>>() {
                    @Override
                    public List<GRO_VO> call(String jsonIn) {
                        Gson gson = new Gson();
                        Type listType = new TypeToken<List<GRO_VO>>() {

                        }.getType();
                        return gson.fromJson(jsonIn, listType);
                    }


                })
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Action1<List<GRO_VO>>() {
                    @Override
                    public void call(List<GRO_VO> groVoList) {
                        Log.d("RX", ".subscribe");
                        recyclerView.setAdapter(new EventJoinAdapter(groVoList));
                    }
                });


 public String fetchDataHttpCall() {
        String GroURL = theURL.URL + "GroupServlet";
        String mem_noMy1 = "6";

        Log.d(TAG, "GroURL=" + GroURL);
       
        String jsonIn = "";
        JsonObject jsonObject = new JsonObject();
        jsonObject.addProperty("action", "getEventOthersHostNotOver");
        jsonObject.addProperty("mem_no", mem_noMy1);


        try {
            jsonIn = okHttpPost(GroURL, jsonObject.toString());

        } catch (IOException e) {
            Log.d(TAG, e.getMessage());
        }
        return jsonIn;

    }