populate listfragment from asyntask

Question

I want to create an app which is similer to Gmail app idea ( a navigation drawer to choose category such as inbox or draft and listfragment to show the emails with images in list).

for now i done the following :

a MainActivity.java :

 public class MainActivity extends ActionBarActivity {

 private DrawerLayout mDrawerLayout;
 private ListView mDrawerList;
 private ActionBarDrawerToggle mDrawerToggle;
 private CharSequence mDrawerTitle;
 private CharSequence mTitle;
 private String[] sections_array;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

         ........................
         .............................
          ........a bunch of code...............
.............................
 private class DrawerItemClickListener implements ListView.OnItemClickListener {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            selectItem(position);
        }
    }

    private void selectItem(int position) {
        // update the main content by replacing fragments
        Fragment fragment = null;
        ListFragment lfragment = null;
        switch (position) {
        case 0:
            lfragment = new NewsFragment();
            break;
        case 1:
            fragment = new TvFragment();
  ...............................
  .............................
    .................a bunch of code..............
  ............................. 
    public static class NewsFragment extends ListFragment {

         private ListView listView; 
         private NewsAdapter newsAdapter;
         @Override
         public  View  onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceStatee){
             View rootView = inflater.inflate(R.layout.fragment_news, container, false);
             listView = (ListView) rootView.findViewById(android.R.id.list);
             return rootView;
         }

         @Override
          public void onActivityCreated(Bundle savedInstanceState) {
            super.onActivityCreated(savedInstanceState);

            // URL to the JSON data         
            String strUrl =       "http://wptrafficanalyzer.in/p/demo1/first.php/countries";
         // Creating a new non-ui thread task to download json data 
            GetJSON downloadTask = new GetJSON();

            // Starting the download process
            downloadTask.execute(strUrl);       

          }

    }

GetJson :

         /** AsyncTask to download json data */
        public class GetJSON extends AsyncTask<String, Integer, String>{
  String data = null;
    private ListView listView;  
 private NewsAdapter newsAdapter;

        @Override
        protected String doInBackground(String... url) {
                try{
                    data = downloadUrl(url[0]);

                }catch(Exception e){
                    Log.d("Background Task",e.toString());
                }
                return data;
        }

        @Override
        protected void onPostExecute(String result) {

            try {
                JSONObject jObject;
                jObject = new JSONObject(result);
                JSONArray jCountries =  jObject.getJSONArray("countries");
                ArrayList<String> stringArrayList = new  ArrayList<String>();
                for (int i=0; i < jCountries.length(); i++)
                {
                    try {
                        JSONObject oneObject = jCountries.getJSONObject(i);
                        // Pulling items from the array
                        stringArrayList.add(oneObject.getString("countryname"));



                       /*
                 **How to use NewsAdapter here with     stringArrayList as data to be used**
  */


                    } catch (JSONException e) {
                        // Oops
                    }
                }
                String [] stringArray = stringArrayList.toArray(new String[stringArrayList.size()]);
            } catch (JSONException e) {
                e.printStackTrace();
            }


        }

        /** A method to download json data from url */
        private String downloadUrl(String strUrl) throws IOException{
            String data = "";
            InputStream iStream = null;
            try{
                    URL url = new URL(strUrl);

                    // Creating an http connection to communicate with url 
                    HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

                    // Connecting to url 
                    urlConnection.connect();

                    // Reading data from url 
                    iStream = urlConnection.getInputStream();

                    BufferedReader br = new BufferedReader(new InputStreamReader(iStream));

                    StringBuffer sb  = new StringBuffer();

                    String line = "";
                    while( ( line = br.readLine())  != null){
                        sb.append(line);
                    }

                    data = sb.toString();

                    br.close();

            }catch(Exception e){
                    Log.d("Exception while downloading url", e.toString());
            }finally{
                    iStream.close();
            }

            return data;
        }

        }

NewsAdapter.java :

     public class NewsAdapter extends ArrayAdapter<String> {

private final Context context;
private final String[] values;

public NewsAdapter(Context context, String[] values) {
    super(context, R.layout.drawer_list_item, values);
    this.context = context;
    this.values = values;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    LayoutInflater inflater = (LayoutInflater)          context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            ................................
             ...............
          ...............
                  ...............

stringArrayList inside onPostExecute method is now contain the data which i want to be populated inide the listfragment using NewsAdapter , but the problem is how to use NewsAdapter inside the GetJSON class because i tried several methods but nothing work ?

Answer 1

Try this:

An Interface:

public interface ILoadDataListener {
    public void onComplete(ArrayList<String> data);
}

Your Fragment:

public static class NewsFragment extends ListFragment implements ILoadDataListener {

     @Override
          public void onActivityCreated(Bundle savedInstanceState) {
            super.onActivityCreated(savedInstanceState);

            // URL to the JSON data         
            String strUrl =       "http://wptrafficanalyzer.in/p/demo1/first.php/countries";
         // Creating a new non-ui thread task to download json data 

            GetJSON downloadTask = new GetJSON(this); // 

            // Starting the download process
            downloadTask.execute(strUrl);       

          }

    @Override
    public void onComplete(ArrayList<String> result) {
        YourAdapter adapter = new YourAdapter(..., result);
        yourListView.setAdapter(adapter);
    }
}

Your AsyncTask

public class GetJSON extends AsyncTask<String, Integer, ArrayList<String>>{ // return an ArrayList of String
  //.... Your declaration
   private ILoadDataListener mListener;

   public GetJSON(ILoadDataListener listener) {
       this.mListener = listener;
   }

   @Override
   public void onPostExecute(ArrayList<String> result) {
       if (mListener != null) { 
           mListener.onComplete(result);
       }
   }
}

Your Adapter

Use ArrayList<String> values; instead of String[] values;