android - Ask in runtime permission for push notification -

i'm workin app , when app start, need ask @ user if want receive push notification. know push notification aren't dangerous permission need show popup possibility chose. manifest

<uses-permission android:name="android.permission.bind_notification_listener_service"/> 

and runtime method should show popup

public void receivenotification(view v) {      boolean haspermission = (contextcompat.checkselfpermission(mainactivity.this, manifest.permission.bind_notification_listener_service) == packagemanager.permission_granted);      if (haspermission) {          string token = firebaseinstanceid.getinstance().gettoken();         log.d(tag, "token"+token);         toast.maketext(mainactivity.this, token, toast.length_short).show();      }     else {          activitycompat.requestpermissions(mainactivity.this, new string[]{manifest.permission.bind_notification_listener_service}, request_code_ask_permissions);      } }   @override public void onrequestpermissionsresult(int requestcode, @nonnull string[] permissions,                                        @nonnull int[] grantresults) {     super.onrequestpermissionsresult(requestcode, permissions, grantresults);       if (requestcode == request_code_ask_permissions) {         if (grantresults[0] == packagemanager.permission_granted) {              string token = firebaseinstanceid.getinstance().gettoken();             log.d(tag, "token"+token);             toast.maketext(mainactivity.this, token, toast.length_short).show();          }         else  {             // permission denied             toast.maketext(mainactivity.this, "message", toast.length_short)                     .show();         }      } } 

someone has idea how can show popup? it's importat :) thanks!