Android Runtime exception : An error occur while executing doinbackground-Collection of common programming errors

I am parsing online Xml using XmlPullParserFactory and showing the details in a listview. I have put the condition for checking internet, but sometimes it takes time to fetch data and crashes.The code which I am using is below.

      private void runningABackProcess() {
      Handler mHandler = new Handler(Looper.getMainLooper());
      Runnable myRunnable = new Runnable() {                        
      public void run() {
       try{
             //Thread.sleep(5000);

         new DoSomeTask().execute();                           

                  }catch(Exception e){}
                           // myPd_ring.dismiss();
              }
           };
           mHandler.post(myRunnable);

    }
         private class DoSomeTask extends AsyncTask
     {


        @Override
         protected Void doInBackground(Void... arg0) {
                        try { 
         isInternetPresent = icd.isConnectingToInternet
         if(isInternetPresent){                             
              URL url = new     URL("njhgjghjkjhkjl");                                 
              XmlPullParserFactory factory=XmlPullParserFactory.newInstance();  
              XmlPullParser xpp=factory.newPullParser();      
              xpp.setInput(getInputStream(url), "UTF_8");                                   
              int eventType=xpp.getEventType(); 
              if(eventType!=XmlPullParser.END_DOCUMENT)
                  {
            if(eventType==XmlPullParser.START_DOCUMENT)     
                 {       
                 while(eventType!=XmlPullParser.END_DOCUMENT )              
                  {              
                              xpp_name=xpp.getName();                                   
                      if((xpp_name!=null) ) 
                                {
                                   --------------------
                                   -------------------------
                                }
                            }
                    }
               }

and

      public InputStream getInputStream(URL url) {
  try {  
       InputStream str=null;
       isInternetPresent=icd.isConnectingToInternet();
      if(isInternetPresent)
           {    
         str=url.openConnection().getInputStream(); 
         if(str!= null)
             {
             return str; 
          }else{
         new AlertDialogBox(getActivity()).show(getFragmentManager(),"MyDialog");
          }
    }else{
    new AlertDialogBox(getActivity()).show(getFragmentManager(), "MyDialog");
                            }
                                return    str;              
                            //}
                        } catch (IOException e) {

                            return null;
                          }

                     }

Below is the erroe I am getting: