问Scala不会调用publishProgress回调，"onProgressUpdate“

EN

private class FeedLoaderTask(val activity: ActivityFeedReader) 
  extends android.os.AsyncTask[AnyRef, Seq[FeedEntry], Seq[FeedEntry]]
{
  /** @brief dialog to show our progress */
  private var dlgBusy:ProgressDialog = null;


  override def onPreExecute() {
    dlgBusy = ProgressDialog.show(...)
  }

  override protected def doInBackground(params: AnyRef*): Seq[FeedEntry] = {
    // resorted to AnyRef for reasons explained above although
    val url = params.apply(0).asInstanceOf[String]
    log.d("FeedLoaderTask: doInBackground: " + url)
    val feeds = new FeedReader(url).extract
    log.d("Got them, total: " + feeds.length)
    publishProgress()//feeds) // <--- seems to "call" but does not arrive
    feeds
  }

  protected def onProgressUpdate(feeds: Seq[FeedEntry]): Void = {
    // work damn you, WORK!
    log.d("FeedLoaderTask: onProgressUpdate: " + feeds.length)
    return null
  }

  override protected def onPostExecute (feeds: Seq[FeedEntry]) {
    dlgBusy.dismiss()
    dlgBusy = null
    feeds.length match {
    case 0 => messageAndTerminate(R.string.rss_failed_msg)
    case _ =>
      listAdapter = new FeedListAdapter(...)
      activity.setListAdapter(listAdapter)
      ...blah blah more code...
   }
  }
}