AsyncTask在后台运行时看不到ProgressDialog

首先，请注意所有AsyncTask实现的方法附带的“ @override”标头，例如

private class loadMoreListView extends AsyncTask<Void, Void, Void> {    ProgressDialog pDialog;    @Override    protected void onPreExecute() {        // TODO Auto-generated method stub        super.onPreExecute();        pDialog = new ProgressDialog(SingleMenuItemActivity.this);        pDialog.setMessage("Please Wait ...");        pDialog.isIndeterminate();        pDialog.setCancelable(false);        pDialog.show();    }    @Override    protected Void doInBackground(Void... params) {        // TODO Auto-generated method stub        return null;    }    @Override    protected void onPostExecute(Void result) {        // TODO Auto-generated method stub        super.onPostExecute(result);        pDialog.cancel();    }}

除非您必须在UI上执行某些操作，否则还要从doInBackground中删除它。

runonUiThread(new Runnable() {        public void run() {       // do something for downloading    }    });

您无法在runOnUiThread上进行任何下载操作。doInBackground用于运行后台任务，例如对UI不可见的下载等。