java - Notify a Fragment of onPostExecute from MainActivity -

in android, i'm having trouble figuring out how, when asynctask complete, notify fragment listening. seems usual java stuff, propertychangelistener not available. in onpostexecute, want fire event , have otherfragment see that.

how do this?

    public class mainactivity extends fragmentactivity {          <stuff>          private class consumewebservice extends asynctask                   <string,   // type of parameters sent task upon execution - doinbackground()                   integer,  // type of progress units published during background computation -onprogressupdate()                   string> {               public consumewebservice(somekindoflistener listener){                     this.mylistener = listener;             }              protected string doinbackground(string... urls) {                    < json data restful service>                   < create , populate sqlite db wit json data>                    return jsondata;             }              @override             protected void onpostexecute(string result) {                      try {                          <fire kind of event>                      }                       catch (exception e) {                      }             }         }     }      public class otherfragment extends fragment implements somekindoflistener {          @override         public void somekindofchange(somekindofchangeevent arg0) {             < stuff want do>         }      }      public interface somekindoflistener {           void onpostexecutedone();     } 

i this:

1 - have interface

public interface onxlistener {     void onx(object data); } 

2- have fragment implement it

public class myfragment extends fragment implements onxlistener{     public void onx(object data) {         dosomething(data);     }     public void dosomething(data) {         /do real thing     } } 

3- call in actvitiy when asynctask done

public class myactivity extends activity {     fragment mmyfragment fragment;     //stuff, initializate fragment, show fragment, etc.      private class myasynctask extends asynctask {         //stuff         @override         protected void onpostexecute(object result) {            ((onxlistener) myactivity.this.mmyfragment).onx(result);         }     } }