java - In-app purchase cause error -

i'm trying make in app purchase in application wrong. made tutorial: http://developer.android.com/training/in-app-billing/purchase-iab-products.html , stackoverflows solutions id didnt , i'm still getting error after run application: java.lang.illegalstateexception: iab helper not set up. can't perform operation: queryinventory caused response result_billing_unavailable it's happening after call method mhelper.queryinventoryasync(mgotinventorylistener); code oncreate in activity:

    mhelper = new iabhelper(this, string1 + string2 + string3);     mhelper.enabledebuglogging(true);     mhelper.startsetup(new iabhelper.oniabsetupfinishedlistener() {         public void oniabsetupfinished(iabresult result) {             if (!result.issuccess()) {                 log.d(tag, "problem setting in-app billing: " + result);             }             if (mhelper == null) return;             log.d(tag, "setup successful. querying inventory.");             mhelper.queryinventoryasync(mgotinventorylistener);         }     }); 

and variable definition in activity:

iabhelper.queryinventoryfinishedlistener mgotinventorylistener = new    iabhelper.queryinventoryfinishedlistener() {     public void onqueryinventoryfinished(iabresult result, inventory inventory) {         log.d(tag, "query inventory finished.");         if (mhelper == null) return;          if (result.isfailure()) {             log.e(tag, "**** trivialdrive error: " + "failed query inventory: " + result);             return;         }          log.d(tag, "query inventory successful.");          purchase farmpurchase = inventory.getpurchase(constants.sku_farm);         isfarm = (farmpurchase != null);         log.d(tag, "user " + (isfarm ? "farm" : "not farm"));          purchase birdspurchase = inventory.getpurchase(constants.sku_birds);         isbirds = (birdspurchase != null);         log.d(tag, "user " + (isbirds ? "birds" : "not birds"));          log.d(tag, "initial inventory query finished; enabling main ui.");     } }; 

do missed important?