i'm new to android programming and i learn material design with this post.
but i have a problem when i'm trying to populate RecyclerView with json and
get nullPointerException in getItemCount method in the RecyclerViewAdapter.
this fragment load the recyclerView and Parse the json
package supporter.majid.com.supporter;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import supporter.majid.com.supporter.app.AppController;
/**
* Created by majid on 11/25/2015.
*/
public class SupporterFragment extends Fragment {
private static final String TAB_POSITION = "tab_position";
String url ="http://javatechig.com/?json=get_recent_posts&count=20";
ArrayList<String> aTitle;
ArrayList<String> aAuthor;
//ArrayList<String> aUrl;
//constructor
public SupporterFragment() {
}
//new instance
public static SupporterFragment newInstance(int tabPosition) {
Bundle args = new Bundle();
SupporterFragment fragment = new SupporterFragment();
args.putInt(TAB_POSITION ,tabPosition);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
sendJsonRequest();
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
Bundle args = getArguments();
int tabPosition = args.getInt(TAB_POSITION);
View view = inflater.inflate(R.layout.fragment_list_view , container ,false);
RecyclerView cRecyclerView = (RecyclerView) view.findViewById(R.id.recyclerViewFragmentXml);
cRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
cRecyclerView.setAdapter(new SupporterRecyclerAdapter(aTitle ,aAuthor ));
return view;
}
// ==========================================sendJsonRequest method
public void sendJsonRequest(){
JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, (String) null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
parsJsonResponse(response);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
error.printStackTrace();
Toast.makeText(getActivity(),"We have a problem in error listener" , Toast.LENGTH_SHORT).show();
}
});
AppController.getInstance().addToRequestQueue(request);
}
// ================================ #send Json Request methoe
private void parsJsonResponse(JSONObject response){
aTitle = new ArrayList<String>();
aAuthor = new ArrayList<String>();
//aUrl = new ArrayList<String>();
if(response == null || response.length() == 0){
return;
}
if(response.has("posts")){
try {
JSONArray arrayPosts = response.getJSONArray("posts");
for (int i=0; i<arrayPosts.length();i++){
JSONObject currentPost = arrayPosts.getJSONObject(i);
//get Title post
String title = currentPost.getString("title");
//add to array list
aTitle.add(title);
//get JsonObjectAuthor
JSONObject authorObject = currentPost.getJSONObject("author");
//get Author first name
String authorFirstName = authorObject.getString("first_name");
//add to author array list
aAuthor.add(authorFirstName);
// //getting url string
// //get thumbnail_images object
// JSONObject objectthumbnail_images = currentPost.getJSONObject("thumbnail_images");
// //get JsonObject thumbnail
// JSONObject objectThumbnail = objectthumbnail_images.getJSONObject("thumbnail");
// //get thumbnail url
// String url = objectThumbnail.getString("url");
// //add to url array list
// aUrl.add(url);
}
} catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getActivity(),"We have a JsonException" , Toast.LENGTH_SHORT).show();
}
}
}
// ================================================= #parsJsonResponse
}
and This is the SupporterRecyclerViewAdapter
package supporter.majid.com.supporter;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.List;
/**
* Created by majid on 11/26/2015.
*/
public class SupporterRecyclerAdapter extends RecyclerView.Adapter<SupporterRecyclerAdapter.ViewHolder> {
private List<String> cTitle;
private List<String> cDesc;
private List<Integer> cImageProduct;
//constructor
SupporterRecyclerAdapter(List<String> title, List<String> Desc ) {
cTitle = title;
cDesc = Desc;
//cImageProduct = ImgProduct;
}
//on create View Holder
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_row, parent, false);
return new ViewHolder(view);
}
//onBindViewHolder
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
String title = cTitle.get(position);
String desc = cDesc.get(position);
//int imgProduct = cImageProduct.get(position);
holder.vTxtTitle.setText(title);
holder.vTxtDesc.setText(desc);
// holder.vImageView.setImageResource(imgProduct);
}
//getItemCount
@Override
public int getItemCount() {
return cTitle.size();
}
//View Holder Pattern
public class ViewHolder extends RecyclerView.ViewHolder {
//private final ImageView vImageView;
private final TextView vTxtDesc;
private final TextView vTxtTitle;
public ViewHolder(View itemView) {
super(itemView);
//vImageView = (ImageView) itemView.findViewById(R.id.imgListRowXml);
vTxtTitle = (TextView) itemView.findViewById(R.id.txtTitleListRowXml);
vTxtDesc = (TextView) itemView.findViewById(R.id.txtDescListRowXml);
}
}
}
when i populate this recyclerView with static data every thing is ok but now i have a problem Thankyou.
