进度对话框未显示在AsyncTask上

我想从http提取json（视频详细信息）数据，并添加到数组列表中，以根据用户选择的类别显示在活动的listview上。但是我想在从互联网上获取数据时显示进度对话框

public class GetOnlineData extends AsyncTask<String, Integer,   ArrayList<McuVideo>> {
private Activity activity; 
private  ArrayList<McuVideo> arrayvid;
private String sdcard_path;
private ProgressDialog pdialog;
public GetOnlineData(Activity activity)
{
    this.activity=activity;
     sdcard_path=Environment.getExternalStorageDirectory()+File.separator
     +"McuVideos";  arrayvid=new ArrayList<McuVideo>();

}
@Override
protected void onPreExecute()
{
super.onPreExecute();
pdialog = new ProgressDialog(activity);
Log.d("pre", "pre");
pdialog.setMessage("Please waiit");
pdialog.setTitle("Loading");
pdialog.setIndeterminate(true);
pdialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
//  dialog.setCancelable(false);
//  dialog.setCanceledOnTouchOutside(false);
pdialog.show();
}
@Override
protected void onPostExecute(ArrayList<McuVideo> result)
{
    super.onPostExecute(result);
    if(pdialog.isShowing())
    pdialog.dismiss();
    Log.d("post", "post");
}
@Override
protected void onProgressUpdate(Integer... progress)
{
super.onProgressUpdate(progress);
pdialog.setProgress(progress[0]);
Log.d("pupdate", ""+progress[0]);
}
@Override
protected ArrayList<McuVideo> doInBackground(String... address) {
    StringBuilder builder = new StringBuilder();
    HttpClient client = new DefaultHttpClient();
    HttpGet httpGet = new HttpGet(address[0]);
    try{
        HttpResponse response = client.execute(httpGet);
        StatusLine statusLine = response.getStatusLine();
        int statusCode = statusLine.getStatusCode();
        if(statusCode == 200){
            HttpEntity entity = response.getEntity();
            //Log.d("context length",""+entity.getContentLength());
            InputStream content = entity.getContent();

BufferedReader reader = new BufferedReader(new   InputStreamReader(content));
            String line;
            int i=0;
            while((line = reader.readLine()) != null){

                builder.append(line);
                Log.d("line length",""+line.length());
                i++;
    //  publishProgress(builder.length());

            }
        } else {
            MyToast.makeToast(activity,"failed to load data",MyToast.ERROR, MyToast.DURATION_LONG).show();
            Log.e(MainActivity.class.toString(),"Failedet JSON object");
            //super.onCancelled();
            cancel(true);
        }
    } catch (Exception e){
    Toast.makeText(activity,e.toString(), Toast.LENGTH_LONG).show();

    }

     try{
            if(builder.length()>15)
            {
     //          Log.d("query",query[0]);
     JSONObject  jsonRootObject = new JSONObject(builder.toString());
     JSONArray jsonArray = jsonRootObject.optJSONArray("videos");
                 for(int i=1; i <jsonArray.length(); i++)
                             {
               JSONObject jsonObject = jsonArray.getJSONObject(i);
 Long vid =Long.parseLong(jsonObject.optString("vid").toString());
 String title = jsonObject.optString("title").toString();
 //String path =context.getResources().getString(R.string.base_web_url)+       jsonObject.optString("path").toString();
  String description = jsonObject.optString("description").toString();//.substring(0, 20);
                                     String path =      jsonObject.optString("path").toString();

                                    // String duration=jsonObject.optString("duration").toString();
                                     String duration=jsonObject.optString("upload_date").toString();
                                     String category=jsonObject.optString("category").toString();
                                //  URL url = new URL(context.getResources().getString(R.string.web_url)+"/thumnails/"+vid+".jpg");
                                 // Bitmap  bmp = BitmapFactory.decodeStream(url.openConnection().getInputStream());
                                     //String thumnail_path=context.getResources().getString(R.string.web_url)+"/thumnails/"+vid+".jpg";
                                   //  String thumnail_path="http://sugamgroups.com/mcu/thumnails/"+vid+".jpg";
                                 //    String thumnail_path=GlobalData.t
                              URL url = new URL (activity.getApplicationContext().getResources().getString(R.string.base_web_url)+"/thumbnails/"+vid+".jpg"); 
                             //        URL url = new URL(thumnail_path);
                                    File file = new File(sdcard_path+File.separator+vid+".jpg");

                                 // long startTime = System.currentTimeMillis();
                                 // Log.d("DownloadFile", "Begin Download URL: " + url + " Filename: " + fileName);
                                    try
                                    {
                                    URLConnection ucon = url.openConnection();
                                    InputStream is = ucon.getInputStream();
                                    BufferedInputStream bis = new BufferedInputStream(is);
                                    ByteArrayBuffer baf = new ByteArrayBuffer(50);
                                    int current = 0;
                                    while ((current = bis.read()) != -1)
                                        baf.append((byte) current);
                                    FileOutputStream fos = new FileOutputStream(file);
                                    fos.write(baf.toByteArray());
                                    fos.flush();
                                    fos.close();
                                    }
                                    catch(Exception e)
                                    {
                                    Log.e("1",e.toString());
                                    }
                                 // Toast.makeText(activity, "file download",Toast.LENGTH_LONG).show();
                                    //bmp.compress(Bitmap.CompressFormat.JPEG ,Bitmap., stream)*/
                                    arrayvid.add(new McuVideo(vid,path,duration,title,description,category));
                                //    Thread.sleep(1000);
                             publishProgress((int)i*100/jsonArray.length());


                                 }
            }

                    } 
                 catch(Exception e)
                    {
                //   Log.e(GetOnlineVideos.this.toString(), e.toString());
                        MyToast.makeToast(activity, e.toString(), MyToast.ERROR, MyToast.DURATION_LONG).show();
                   }


                  return arrayvid;




}

 }