具有ProgressDialog的外部AsyncTask类[更新：并返回？

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ProgressDialog

public class AsyncClass extends AsyncTask<Void, String, Void> {    private Context context;    ProgressDialog dialog;        public AsyncClass(Context cxt) { context = cxt; dialog = new ProgressDialog(context);        }        @Override        protected void onPreExecute() { dialog.setTitle("Please wait"); dialog.show();        }        @Override        protected Void doInBackground(Void... unused) { SystemClock.sleep(2000); return (null);        }        @Override        protected void onPostExecute(Void unused) { dialog.dismiss();        }    }