Не удается заполнить данные из Asynctask?

Question

В моем приложении я анализирую данные из файла Json. Он работает Fine.Now, я изменил код из моего основного потока на Asynctask. Я новичок в Asynctask, поэтому я не могу найти, где я сделал ошибку. Но в logcat он показывает, что ошибка находится в DoInBackground. Спасибо заранее!

СТАРЫЙ КОД

private void parseJsonFeed(JSONObject response) { 
    try { 
     JSONArray feedArray = response.getJSONArray("feed"); 

     for (int i = 0; i < feedArray.length(); i++) { 
      JSONObject feedObj = (JSONObject) feedArray.get(i); 

      FeedItem item = new FeedItem(); 
      item.setId(feedObj.getInt("id")); 
      item.setName(feedObj.getString("name")); 

      // Image might be null sometimes 
      String image = feedObj.isNull("image") ? null : feedObj 
        .getString("image"); 
      item.setImageUrl(image); 
      item.setStatus(feedObj.getString("status")); 
      item.setProfilePic(feedObj.getString("profilePic")); 
      item.setTimeStamp(feedObj.getString("timeStamp")); 

      // url might be null sometimes 
      String feedUrl = feedObj.isNull("url") ? null : feedObj 
        .getString("url"); 
      item.setUrl(feedUrl); 

      feedItems.add(item); 
     } 

     // notify data changes to list adapater 
     listAdapter.notifyDataSetChanged(); 
    } catch (JSONException e) { 
     e.printStackTrace(); 
    } 
} 

AsyncTask Код

public class News extends AsyncTask<JSONObject, Void, FeedListAdapter> { 

     JSONObject response; 

     protected FeedListAdapter doInBackground(JSONObject... params) { 
      try { 
       JSONArray feedArray = response.getJSONArray("feed"); 

       for (int i = 0; i < feedArray.length(); i++) { 
        JSONObject feedObj = (JSONObject) feedArray.get(i); 

        FeedItem item = new FeedItem(); 
        item.setId(feedObj.getInt("id")); 
        item.setName(feedObj.getString("name")); 

        // Image might be null sometimes 
        String image = feedObj.isNull("image") ? null : feedObj 
          .getString("image"); 
        item.setImageUrl(image); 
        item.setStatus(feedObj.getString("status")); 
        item.setProfilePic(feedObj.getString("profilePic")); 
        item.setTimeStamp(feedObj.getString("timeStamp")); 

        // url might be null sometimes 
        String feedUrl = feedObj.isNull("url") ? null : feedObj 
          .getString("url"); 
        item.setUrl(feedUrl); 

        feedItems.add(item); 
       } 
      } catch (JSONException e) { 
       e.printStackTrace(); 
      } 
      return null; 
     } 

     protected void onPostExecute(FeedListAdapter result) { 
      super.onPostExecute(result); 
      listAdapter.notifyDataSetChanged(); 
     } 

    } 

Мой класс

public class FeedListActivity extends BaseActivity { 
    private static final String TAG = "FeedListActivity"; 

    private ListView NewsView; 
    private FeedListAdapter listAdapter; 
    private List<FeedItem> feedItems; 
    News mynews; 
    private String URL_FEED = "http://www.amsonsindia.net/ins/news.json"; 

    @SuppressLint("NewApi") 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_feed_list); 
     setTitle(R.string.feed_list_demo); 

     mynews=new News(); 
     mynews.execute(); 

     NewsView = (ListView) findViewById(R.id.feed_list); 
     feedItems = new ArrayList<FeedItem>(); 
     listAdapter = new FeedListAdapter(this, feedItems); 
     NewsView.setAdapter(listAdapter); 

     // making fresh volley request and getting json 
     GsonRequest<FeedResult> gsonRequest = new GsonRequest<FeedResult>(URL_FEED, FeedResult.class, 
       new Response.Listener<FeedResult>() { 
        @Override 
        public void onResponse(FeedResult response) { 
         feedItems = response.getFeedItems(); 
         listAdapter.setData(feedItems); 
         listAdapter.notifyDataSetChanged(); 
        } 
       }, 
       new Response.ErrorListener() { 
        @Override 
        public void onErrorResponse(VolleyError error) { 
         Log.d(TAG, "Error: " + error.getMessage()); 
        } 
       }); 

     // Adding request to volley request queue 
     AppController.getInstance().addRequest(gsonRequest, TAG); 
     getimg(); 
    } 

LogCat

Process: io.bxbxbai.feedlistviewdemo, PID: 2245 
    java.lang.RuntimeException: An error occured while executing doInBackground() 
      at android.os.AsyncTask$3.done(AsyncTask.java:300) 
      at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355) 
      at java.util.concurrent.FutureTask.setException(FutureTask.java:222) 
      at java.util.concurrent.FutureTask.run(FutureTask.java:242) 
      at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 
      at java.lang.Thread.run(Thread.java:841) 
    Caused by: java.lang.NullPointerException 
      at io.bxbxbai.androiddemos.activity.FeedListActivity$News.doInBackground(FeedListActivity.java:123) 
      at io.bxbxbai.androiddemos.activity.FeedListActivity$News.doInBackground(FeedListActivity.java:117) 
      at android.os.AsyncTask$2.call(AsyncTask.java:288) 
      at java.util.concurrent.FutureTask.run(FutureTask.java:237) 
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 
            at java.lang.Thread.run(Thread.java:841) 

Answer 1

В методе doInBackground вы не можете обновить пользовательский интерфейс

изменение doinbackground код как this--

  for (int i = 0; i < feedArray.length(); i++) 
     { 
     JSONObject feedObj = (JSONObject) feedArray.get(i);  

     publishProgress(feedObj.getInt("id"), feedObj.getString("status"); 
     //so on.. 
     }  

и в aynctask добавить

protected void onProgressUpdate(final String... message) { 
     try { 

       FeedItem item = new FeedItem(); 
       item.setId(message[0]); 
       item.setName(message[1); 
       and so on 


       feedItems.add(item); 



     } catch (Exception e) { 
      if (pd != null) { 
       pd.dismiss(); 
      } 
     } 
    } 

Answer 2

public class FeedListActivity extends BaseActivity { 
     private static final String TAG = "FeedListActivity"; 

     private ListView NewsView; 
     private FeedListAdapter listAdapter; 
     private List<FeedItem> feedItems; 
     News mynews; 
     private String URL_FEED = "http://www.amsonsindia.net/ins/news.json"; 

     @SuppressLint("NewApi") 
     @Override 
     protected void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 
      setContentView(R.layout.activity_feed_list); 
      setTitle(R.string.feed_list_demo); 
      feedItems = new ArrayList<FeedItem>(); 
      listAdapter = new FeedListAdapter(this, feedItems); 
// i just change feeditem position here 
      mynews=new News(); 
      mynews.execute(); 

      NewsView = (ListView) findViewById(R.id.feed_list); 

      NewsView.setAdapter(listAdapter); 

      // making fresh volley request and getting json 
      GsonRequest<FeedResult> gsonRequest = new GsonRequest<FeedResult>(URL_FEED, FeedResult.class, 
        new Response.Listener<FeedResult>() { 
         @Override 
         public void onResponse(FeedResult response) { 
          feedItems = response.getFeedItems(); 
          listAdapter.setData(feedItems); 
          listAdapter.notifyDataSetChanged(); 
         } 
        }, 
        new Response.ErrorListener() { 
         @Override 
         public void onErrorResponse(VolleyError error) { 
          Log.d(TAG, "Error: " + error.getMessage()); 
         } 
        }); 

      // Adding request to volley request queue 
      AppController.getInstance().addRequest(gsonRequest, TAG); 
      getimg(); 
     } 


    ---------- 
    Replace your my class with above and put debug in doinbackgroud 
    and postexecute