java - Interstitial ad black screen -

i imported interstitial ad on android application. when shows press button remove , screen stays black, put code on on create method , there possibility call in different way. in advance, me please tried lot still black screen appears after press button remove it, here main activity

interstitialad = new interstitialad(this);      interstitialad.setadunitid(ad_unit_id);     adrequest adrequest = new adrequest.builder().build();      interstitialad.loadad(adrequest);      interstitialad.setadlistener(new adlistener() {         @override         public void onadloaded() {              if (interstitialad.isloaded()) {                 interstitialad.show();             }          }          @override         public void onadopened() {           }          @override         public void onadfailedtoload(int errorcode) {          }     });