java - android.view.WindowManager$BadTokenException: Unable to add window — token null is not valid -

i error whenever try start window class. using separate class, , not method within game class, cause need disable button on popup window. calling class button. code works fine if use within game class, not in separate class. here code:

public class popup_pogresno extends activity implements onclicklistener{      private popupwindow pwindow;      @override     protected void oncreate(bundle savedinstancestate) {         // todo auto-generated method stub         super.oncreate(savedinstancestate);          layoutinflater layoutinflater           = (layoutinflater)popup_pogresno.this           .getsystemservice(layout_inflater_service);           view popupview = layoutinflater.inflate(r.layout.popup, null);                    pwindow  = new popupwindow(popupview, 300, 170, true);                   button btndismiss = (button)popupview.findviewbyid(r.id.bpopupok);                  btndismiss.setonclicklistener(new button.onclicklistener(){           public void onclick(view v) {           // todo auto-generated method stub              pwindow.dismiss();          }});                   pwindow.showatlocation(popupview, gravity.center, 0, 0);         }      public void onclick(view v) {         // todo auto-generated method stub      }     @override     public void onbackpressed() {      } } 

you not calling setcontentview(r.layout.mylayout) in oncreate(bundle) method. call right after super.oncreate(savedinstancestate);.

this activity resource page on android developers site:

there 2 methods subclasses of activity implement:

oncreate(bundle) initialize activity. importantly, here call setcontentview(int) layout resource defining ui, , using findviewbyid(int) retrieve widgets in ui need interact programmatically.

onpause() deal user leaving activity. importantly, changes made user should @ point committed (usually contentprovider holding data).

edit 1:

replace:

pwindow.showatlocation(popupview, gravity.center, 0, 0); 

with:

new handler().postdelayed(new runnable(){      public void run() {         pwindow.showatlocation(popupview, gravity.center, 0, 0);     }  }, 100l);