关于android下实现FTP多线程下载的功能解决思路

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);       
   setContentView(R.layout.main);

    this.pd = ProgressDialog.show(this, "Working...", "*** Downloading Data...", true, false);
    new DownloadTask().execute(" parameters needed for download");
}

private class DownloadTask extends AsyncTask<String, Void, Object> {
     protected Void doInBackground(String... args) {
        //Background thread starting......
         startLongRunningOperation();   
        return null;         
     }

     protected void onPostExecute(Object result) {

         if (Splash.this.pd != null) {
          Splash.this.pd.dismiss();
         }
         updateResultsInUi();

     }
} 


protected void startLongRunningOperation() {
             try
             {
             ftp = new FTPClient();
             ftp.connect(host);
             ftp.login("username", "password");
             ftp.changeDirectory("public_ftp");
       ftp.download("test.txt", new java.io.File("/sdcard/test.txt")); 
             }
      catch(Exception e)
      {                

      }
}