Android RecyclerView not updating items

问题

I have a RecyclerView on my tabview fragment Activity. iam using arrayList to fill items on the recyclerview. Those JSON data are taken from this URL through volley library.

Here is my code

            public class EditorsChoiceFragment extends Fragment {
            private RecyclerView mRecyclerView;
            private RecyclerView.Adapter mAdapter;
            private RecyclerView.LayoutManager mLayoutManager;
            private static String LOG_TAG = "EditorsChoiceFragment";
            private String urlJsonArry = "http://checkthisphone.com/black.apps/get_apps/editor.php";
            private ProgressDialog pDialog;
            private String jsonResponse;
            private static String TAG = EditorsChoiceFragment.class.getSimpleName();

            private String appTitle;
            private String appDescription;

            private JSONArray appDetails=null;
            ArrayList<DataObject> results = new ArrayList<DataObject>();

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


                View view = inflater.inflate(R.layout.editor_choice_layout, container, false);
                makeJsonArrayRequest();
                pDialog = new ProgressDialog(getContext());
                pDialog.setMessage("Please wait...");
                pDialog.setCancelable(false);
                mRecyclerView = (RecyclerView)view.findViewById(R.id.my_recycler_view);
                mRecyclerView.setHasFixedSize(true);
                mLayoutManager = new LinearLayoutManager(getContext());
                mRecyclerView.setLayoutManager(mLayoutManager);

              //  mAdapter.notifyDataSetChanged();
                makeJsonArrayRequest();
                mAdapter = new MyRecyclerViewAdapter(results);
                mAdapter.notifyDataSetChanged();
                mRecyclerView.setAdapter(mAdapter);
               mAdapter.notifyDataSetChanged();

                return view;

            }

            @Override
            public void onResume() {
                super.onResume();
              /*((MyRecyclerViewAdapter) mAdapter).setOnItemClickListener(new MyRecyclerViewAdapter
                        .MyClickListener() {
                    @Override
                    public void onItemClick(int position, View v) {
                        Log.i(LOG_TAG, " Clicked on Item " + position);
                    }
                });*/
            }



            private void makeJsonArrayRequest() {

        //       showpDialog();
                JsonArrayRequest req = new JsonArrayRequest(urlJsonArry,
                        new Response.Listener<JSONArray>() {
                            @Override
                            public void onResponse(JSONArray response) {
                                Log.d(TAG, response.toString());


                                try {
                                    for (int i = 0; i < response.length(); i++) {

                                        JSONObject person = (JSONObject) response.get(i);

                                        String title = person.getString("title");
                                        String description = person.getString("description");
                                        DataObject obj = new DataObject(title, description);
                                        results.add(i, obj);

                                    }


                                } catch (JSONException e) {
                                    e.printStackTrace();
                                    Toast.makeText(getContext(),
                                            "Error: " + e.getMessage(),
                                            Toast.LENGTH_LONG).show();
                                    Log.d(TAG, e.getMessage());
                                }

                                hidepDialog();
                            }


                        }, new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        VolleyLog.d(TAG, "Error: " + error.getMessage());
                        Toast.makeText(getContext(),
                                error.getMessage(), Toast.LENGTH_SHORT).show();
                        hidepDialog();
                    }
                });



                // Adding request to request queue
                AppController.getInstance().addToRequestQueue(req);


            }

            private void showpDialog() {
                if (!pDialog.isShowing())
                    pDialog.show();
            }

            private void hidepDialog() {
                if (pDialog.isShowing())
                    pDialog.dismiss();
            }




        }

Log file indicates data coming correctly but recyclerview is not updating. I have used .notifyDataSetChanged(); but still it shows blank. Please me to find the error..

回答1:

I didn't view your codes each line by line but what I can suggest is refactor these codes as a method like here

public void setAdapter(ArrayList<DataObject> results){
    mAdapter = new MyRecyclerViewAdapter(results);
    mRecyclerView.setAdapter(mAdapter);
    mAdapter.notifyDataSetChanged();
}

Call this in onCreateView once and again call this after retrieving the results that means inside onResponse method like here

  try {
        for (int i = 0; i < response.length(); i++) {
            JSONObject person = (JSONObject) response.get(i);
            String title = person.getString("title");
            String description = person.getString("description");
            DataObject obj = new DataObject(title, description);
            results.add(i, obj);
        }
      }
      catch (JSONException e) {
        e.printStackTrace();
        Toast.makeText(getContext(),
                "Error: " + e.getMessage(),
                Toast.LENGTH_LONG).show();
        Log.d(TAG, e.getMessage());
    }
  //Call method here
     setAdapter(results)

回答2:

Please remove notifyDataSetChanged from the below places.

            makeJsonArrayRequest();
            mAdapter = new MyRecyclerViewAdapter(results);
            mAdapter.notifyDataSetChanged();
            mRecyclerView.setAdapter(mAdapter);
           mAdapter.notifyDataSetChanged();

notifyDataSetChanged should be called when you have changed the data in your adapter and want the adapter to know that data has been changes. So in this case you will call it some data added to your results array list.

So once you add data to your results in makeJsonArrayRequest() call

          mAdapter.notifyDataSetChanged(); 

after the for loop.

Also in your adapter constructor make sure you are not creating a new array list and are reusing results as follows.

      ArrayList<DataObject> results;

      MyRecyclerViewAdapter(results){
             this.results = results;
      }

Let me know if this works. If it does not please post your adapter code so i can further debug.

回答3:

You should notify DatasetChanged in onRequestFinished method of volley.

in MainActivity.java

 RequestListener listener;
 listener = new RequestListener();
 volley_queue.addRequestFinishedListener(listener);

RequestListner class

 class RequestListener implements RequestQueue.RequestFinishedListener     {
    @Override
    public void onRequestFinished(Request request) {
         mAdapter.notifyDataSetChanged();
   }
}

回答4:

try {
     for (int i = 0; i < response.length(); i++) {        
        JSONObject person = (JSONObject) response.get(i);
        String title = person.getString("title");
        String description = person.getString("description");
        DataObject obj = new DataObject(title, description);
        results.add(i, obj);
        mAdapter.notifyItemInserted(i);
    }

回答5:

try 
{
    for (int i = 0; i < response.length(); i++) 
    {    
         JSONObject person = (JSONObject) response.get(i);    
         String title = person.getString("title");
         String description = person.getString("description");
         DataObject obj = new DataObject(title, description);
         results.add(i, obj);    
    }
} 
catch (JSONException e) 
{
    e.printStackTrace();
    Toast.makeText(getContext(),"Error: " + e.getMessage(),Toast.LENGTH_LONG).show();
    Log.d(TAG, e.getMessage());
}
mAdapter.notifyDataSetChanged();
hidepDialog();

来源：https://stackoverflow.com/questions/35884118/android-recyclerview-not-updating-items