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)      {                      }}