Laden asynchrone Bilder in einem GridView (Android)

Ich habe eine GridView mit Bilder/text, geladen von verschiedenen Servern (ich kenne nur die URL).
Ich habe versucht, zu ändern, mein code basiert auf das tutorial von ryac.

In meiner Aktivität Datei, habe ich die GAdapter zu meinem GridView wie diese:

GridView mGridMain = (GridView)findViewById(R.id.gvMain);
mGridMain.setAdapter(new GAdapter(this, listAppInfo));

Habe ich geändert meine eigenen adapter und versuchen Sie anzupassen:

public class GAdapter extends BaseAdapter {

 private Context mContext;
 private List<SiteStaff> mListAppInfo;
 private HashMap<Integer, ImageView> views;

 /**
  * @param context
  * @param list
  */
 public GAdapter(Context context, List<SiteStaff> list) {
  mContext = context;
  mListAppInfo = list;  
 }

 @Override
 public int getCount() {
  return mListAppInfo.size();
 }

 @Override
 public Object getItem(int position) {
  return mListAppInfo.get(position);
 }

 @Override
 public long getItemId(int position) {
  return position;
 }

 @Override
 public View getView(int position, View convertView, ViewGroup parent) {

  SiteStaff entry = mListAppInfo.get(position);

  if(convertView == null) {
   LayoutInflater inflater = LayoutInflater.from(mContext);
   convertView = inflater.inflate(R.layout.list_g, null);
  }

  ImageView v;

  //get the ImageView for this position in the GridView..
  v = (ImageView)convertView.findViewById(R.id.ivIcon);

  //set default image
  v.setImageResource(android.R.drawable.ic_menu_gallery);

  TextView tvName = (TextView)convertView.findViewById(R.id.tvName);
  tvName.setText(entry.getName());


  Bundle b = new Bundle ();
  b.putString("file", "http://www.test.com/mypict.jpg");
  b.putInt("pos", position);

  //this executes a new thread, passing along the file
  //to load and the position via the Bundle..
  new LoadImage().execute(b);

  //puts this new ImageView and position in the HashMap.
  views.put(position, v);


  //return the view to the GridView..
  //at this point, the ImageView is only displaying the
  //default icon..
  return v;

 }




 //this is the class that handles the loading of images from the cloud
 //inside another thread, separate from the main UI thread..
 private class LoadImage extends AsyncTask<Bundle, Void, Bundle> {

  @Override
  protected Bundle doInBackground(Bundle... b) {

   //get the file that was passed from the bundle..
   String file = b[0].getString("file");

   URL UrlImage;
   Bitmap bm=null;
   try {
    UrlImage = new URL (file);
    HttpURLConnection connection;
    connection = (HttpURLConnection) UrlImage.openConnection(); 
    bm= BitmapFactory.decodeStream(connection.getInputStream());

   } catch (MalformedURLException e) {
    //TODO Auto-generated catch block
    e.printStackTrace();
   } catch (IOException e) {
    //TODO Auto-generated catch block
    e.printStackTrace();
   }   


   //now that we have the bitmap (bm), we'll
   //create another bundle to pass to 'onPostExecute'.
   //this is the method that is called at the end of 
   //our task. like a callback function..
   //this time, we're not passing the filename to this
   //method, but the actual bitmap, not forgetting to
   //pass the same position along..

   Bundle bundle = new Bundle();
   bundle.putParcelable("bm", bm);
   bundle.putInt("pos", b[0].getInt("pos"));
   bundle.putString("file", file); //this is only used for testing..

   return bundle;
  }

  @Override
  protected void onPostExecute(Bundle result) {
   super.onPostExecute(result);

   //just a test to make sure that the position and
   //file name are matching before and after the
   //image has loaded..
   Log.d("test", "*after: " + result.getInt("pos") + " | " + result.getString("file"));

   //here's where the photo gets put into the
   //appropriate ImageView. we're retrieving the
   //ImageView from the HashMap according to
   //the position..
   ImageView view = views.get(result.getInt("pos"));

   //then we set the bitmap into that view. and that's it.
   view.setImageBitmap((Bitmap) result.getParcelable("bm"));
  }

 }

}

Aber die folgende Fehlermeldung wird angezeigt:

11-16 06:16:08.285: E/AndroidRuntime(517): FATAL EXCEPTION: main
11-16 06:16:08.285: E/AndroidRuntime(517): java.lang.NullPointerException
11-16 06:16:08.285: E/AndroidRuntime(517):  at common.adapter.GAdapter.getView(GAdapter.java:139)
11-16 06:16:08.285: E/AndroidRuntime(517):  at android.widget.AbsListView.obtainView(AbsListView.java:1315)
11-16 06:16:08.285: E/AndroidRuntime(517):  at android.widget.GridView.onMeasure(GridView.java:932)
11-16 06:16:08.285: E/AndroidRuntime(517):  at android.view.View.measure(View.java:8171)
11-16 06:16:08.285: E/AndroidRuntime(517):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
11-16 06:16:08.285: E/AndroidRuntime(517):  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1012)
11-16 06:16:08.285: E/AndroidRuntime(517):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:381)
11-16 06:16:08.285: E/AndroidRuntime(517):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
11-16 06:16:08.285: E/AndroidRuntime(517):  at android.view.View.measure(View.java:8171)
11-16 06:16:08.285: E/AndroidRuntime(517):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
11-16 06:16:08.285: E/AndroidRuntime(517):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
11-16 06:16:08.285: E/AndroidRuntime(517):  at android.view.View.measure(View.java:8171)

Ich bis jetzt nie benutzt Threads in Android. Ich wäre dankbar, wenn mir jemand helfen kann.