我正在尝试创建下载进度。我有扩展AsyncTask的类(class):公共(public)类DownloadFileTask扩展AsyncTask当下载开始时，我想创建进度:@OverrideprotectedvoidonPreExecute(){progressDialog=newProgressDialog(whatContext);progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);progressDialog.setMessage("Loading...");progressDialog.setCan