progressdialog - Android Progress Dialog Issue -

i've been trying progressdialog work.

at first, had inside activity, not showing no matter how many permutations , combinations tried.

then moved inside asynctask. i'm initializing , showing in onpreexecute, , dismissing in onpostexecute.

 @override  protected void onpreexecute(){     try {         dialog = new progressdialog(context,                 progressdialog.style_spinner);         dialog.settitle("please wait");         dialog.setprogressstyle(progressdialog.style_spinner);         dialog.seticon(r.drawable.ic_error);         dialog.show();     } catch (exception e) {         log.e(task_tag, exceptionutils.getstacktrace(e));     } } 

however, i'm not sure should used context. when try activity.getapplicationcontext, following exception thrown android.view.windowmanager$badtokenexception: unable add window -- token null not application.

when tried activity, dialog not shown.

when enclose dialog.show in try / catch, doesn't show. when not enclosed, seems exception takes down app.

i have few questions -

1. what recommended way of showing progress dialog? through async task?
2. if yes, should used context?
3. if 1 of 2 choices mentioned, why app throwing these exceptions?

i recommend using progressdialog inside asynctask, asynctask , activity not linked, it's possible activity dies , asynctask continues execution.

new yourasynctask(context).execute(...); 

you have create custom contructor asynctask:

private class yourasynctask extends asynctask<url, integer, long> {       private context context;      private dialog dialog;       public yourasynctask(context context){         this.context = context;      }       @override      protected void onpreexecute(){         try {            dialog = new progressdialog(context,                 progressdialog.style_spinner);            dialog.settitle("please wait");            dialog.setprogressstyle(progressdialog.style_spinner);            dialog.seticon(r.drawable.ic_error);            dialog.show();         } catch (exception e) {             log.e(task_tag, exceptionutils.getstacktrace(e));         }      }       protected long doinbackground(url... urls) {          ...      }        protected void onpostexecute(long result) {          if(dialog != null && dialog.isshowing()){              dialog.dismiss();          }          ....      }  }