Need Help in Downloading in Background Images in Android?

The best way to download it using the service like i have done to download the file from server and put in SD card also use the notification for it.
It is quite long code but i think the perfect one,if did not understand any thing then please go to android developer blog for services.

public class DownloadService extends Service{

     SharedPreferences preferences;

    private static final String DOCUMENT_VIEW_STATE_PREFERENCES = "DjvuDocumentViewState";

      private Looper mServiceLooper;
      private ServiceHandler mServiceHandler;
      private NotificationManager mNM;
      String downloadUrl;
      public static boolean serviceState=false;

      // Handler that receives messages from the thread
      private final class ServiceHandler extends Handler {
          public ServiceHandler(Looper looper) {
              super(looper);
          }
          @Override
          public void handleMessage(Message msg) {
              downloadFile();
              showNotification(getResources().getString(R.string.notification_catalog_downloaded),"VVS");
              stopSelf(msg.arg1);
          }
      }


    @Override
        public void onCreate() {
            serviceState=true;
            mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
            HandlerThread thread = new HandlerThread("ServiceStartArguments",1);
            thread.start();

            // Get the HandlerThread's Looper and use it for our Handler 
            mServiceLooper = thread.getLooper();
            mServiceHandler = new ServiceHandler(mServiceLooper);

        }



     @Override
        public int onStartCommand(Intent intent, int flags, int startId) {
             Log.d("SERVICE-ONCOMMAND","onStartCommand");  

               Bundle extra = intent.getExtras();
               if(extra != null){
                   String downloadUrl = extra.getString("downloadUrl");
                   Log.d("URL",downloadUrl);

                   this.downloadUrl=downloadUrl;
               }

              Message msg = mServiceHandler.obtainMessage();
              msg.arg1 = startId;
              mServiceHandler.sendMessage(msg);

              // If we get killed, after returning from here, restart
              return START_STICKY;
          }



     @Override
          public void onDestroy() {

             Log.d("SERVICE-DESTROY","DESTORY");
             serviceState=false;
            //Toast.makeText(this, "service done", Toast.LENGTH_SHORT).show(); 
          }


     @Override
      public IBinder onBind(Intent intent) {
          // We don't provide binding, so return null
          return null;
      }


      public void downloadFile(){

            downloadFile(this.downloadUrl,fileName);


      }



        void showNotification(String message,String title) {
        // In this sample, we'll use the same text for the ticker and the expanded notification
        CharSequence text = message;

        // Set the icon, scrolling text and timestamp
       Notification notification = new Notification(R.drawable.icon, "vvs",
                System.currentTimeMillis());
        notification.flags |= Notification.FLAG_AUTO_CANCEL;
        Intent intent = new Intent(this, HomeScreenActivity.class);
        intent.setFlags (Intent.FLAG_ACTIVITY_CLEAR_TOP);
         //The PendingIntent to launch our activity if the user selects this notification
        PendingIntent contentIntent = PendingIntent.getActivity(this.getBaseContext(), 0,
              intent, PendingIntent.FLAG_CANCEL_CURRENT);

        // Set the info for the views that show in the notification panel.
        notification.setLatestEventInfo(this, title,
                      text, contentIntent);
        // Send the notification.
        // We use a layout id because it is a unique number.  We use it later to cancel.
        mNM.notify(R.string.app_name, notification);
    }

  public void downloadFile(String fileURL, String fileName) {

    StatFs stat_fs = new StatFs(Environment.getExternalStorageDirectory().getPath());
    double avail_sd_space = (double)stat_fs.getAvailableBlocks() *(double)stat_fs.getBlockSize();
    //double GB_Available = (avail_sd_space / 1073741824);
    double MB_Available = (avail_sd_space / 10485783);
    //System.out.println("Available MB : " + MB_Available);
    Log.d("MB",""+MB_Available);
   try {
        File root =new File(Environment.getExternalStorageDirectory()+"/vvveksperten");
        if(root.exists() && root.isDirectory()) {

        }else{
            root.mkdir();
        }
        Log.d("CURRENT PATH",root.getPath());
        URL u = new URL(fileURL);
        HttpURLConnection c = (HttpURLConnection) u.openConnection();
        c.setRequestMethod("GET");
        c.setDoOutput(true);
        c.connect();
          int fileSize  = c.getContentLength()/1048576;
          Log.d("FILESIZE",""+fileSize);
          if(MB_Available <= fileSize ){
               this.showNotification(getResources().getString(R.string.notification_no_memory),getResources().getString(R.string.notification_error));
              c.disconnect();
              return;
          } 

        FileOutputStream f = new FileOutputStream(new File(root.getPath(), fileName));

        InputStream in = c.getInputStream();


        byte[] buffer = new byte[1024];
        int len1 = 0;
        while ((len1 = in.read(buffer)) > 0) {
            f.write(buffer, 0, len1);
        }
        f.close();
        File file = new File(root.getAbsolutePath() + "https://stackoverflow.com/" + "some.pdf");
        if(file.exists()){
            file.delete();
            Log.d("FILE-DELETE","YES");
        }else{
            Log.d("FILE-DELETE","NO");
        }
        File from =new File(root.getAbsolutePath() + "https://stackoverflow.com/" + fileName);
        File to = new File(root.getAbsolutePath() + "https://stackoverflow.com/" + "some.pdf");


        } catch (Exception e) {
        Log.d("Downloader", e.getMessage());

    }