ken:

I organize all the Api Calling method of my app inside a separate Class.So when I get the response from the server,I insert it into a Model class.But the problem is,I cant notifyDataSetChanged()(from the class I parsing the JSON) after I parsing all the JSON. Therefore,my adapter's getItemCount() value is always be 0.Ended up the recyclerView never have data.

Here is my Fragment.class

RecyclerView recyclerView;
LatestAdapter latestAdapter;
List latestItems;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) { 

     // Inflate the layout for this fragment
    View view =  inflater.inflate(R.layout.fragment_latest, container, false);

    // Initilize the RecyclerView and Adapter  
    recyclerView =(RecyclerView)view.findViewById(R.id.recycler_view);
    latestAdapter = new LatestAdapter(getContext(),latestItems);
    final LinearLayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
    recyclerView.setLayoutManager(mLayoutManager);
    recyclerView.setAdapter(latestAdapter);

    fetchIntialPost();
} 

private void fetchIntialPost() {
    //here I make API call in another class,which is all API calling method in that class 
    ApiHelper apiHelper = new ApiHelper();
    apiHelper.fetchIntialPost();
}

Here my ApiHelper (This class contains all the API calling method using Volley )

public class ApiHelper {
   public void fetchIntialPost(){
        JsonObjectRequest jsonReq = new JsonObjectRequest(Request.Method.GET, MY_URL ,null, new Response.Listener() {

            @Override
            public void onResponse(JSONObject response) {
                Log.d("Volley response 123",response.toString()); 

                //here I parse the response in another class
                //this class only doing JSON parsing operation 

                ItemHelper itemHelper = new ItemHelper();
                itemHelper.parseItemJsonFeed(response);
            }
        }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {
                //  VolleyLog.d(AppController.TAG, "Error: " + error.getMessage());
            }
        }) {
            @Override
            public Map getHeaders() throws AuthFailureError {

                Map headers = new HashMap();
                Context applicationContext = MainActivity.getContextOfApplication();

                SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(applicationContext);
                String apiKey = preferences.getString("apiKey","");
                headers.put("Content-Type", "application/json");
                headers.put("authorization",apiKey);
                return  headers;
            }
        };

        // Adding request to volley request queue
        AppController.getInstance().addToRequestQueue(jsonReq);
}


}

Here is my ItemHelper class (The class only using to JSON parsing)

public class ItemHelper {
private List items = new ArrayList();

public List getList() {
    return items;
}

public void parseItemJsonFeed (JSONObject response){

    try {

        JSONObject jObj = response.getJSONObject("return_data");

        //here parsing all the data from the response 
        ******      

        //After all the parsing,I save it to the model 
        //here set all the data to the model
        setItemToFeedArrayList(id);

        //****** here is the problem,I can `notifyDataSetChanged()` 
        //*****For the adapter in Fragment Class
        //I cant access from this class here 

        Fragment fragment = new Fragment();
        fragment.getLatestAdapter().notifyDataSetChanged();


    } catch (JSONException e) {
        e.printStackTrace();
    }

}

private void setItemToFeedArrayList(int id ) {
    Item item = new Item();
    item.setId(id);

    //add item to the list
    items.add(item);
}

Problems:

My problems now is,I cant access the LatestAdapter object in my Fragment.class .Therefore I cant call notifyDataSetChanged() after I parsing response Json.

What I tried

I tried to make a method like below in ItemHelper Class :

public List getList() {
    return items;
}

In LatestAdapter,I also create a method like this:

public void setItem(List item) {
  this.latestItems = item;
  notifyDataSetChanged();
}

And then in Fragment.class I access it like this

ItemHelper itemHelper = new ItemHelper();
latestItems = itemHelper.getList();
latestAdapter.setPosts(latestItems);

With what I tried above,the getItemCount() of LatestAdapter still 0,after the API call.

So somebody please give me a hint to solve this problem

,or a better solution for organize all API calling method in 1 class,all Json Parsing Operation in 1 class.At the same time can notifyDataSetChanged() for the adapter as well.