android - Interstitial Ad onBackPressed from default video player -

i making tv channel streaming app when click on channel list view goes activity , pop of player selection comes , after selecting player plays video. implementing admob interstitial ad should displayed directly onbackpressed , after closing ad goes "activity a" (first activity) , not second activity b. works flawelessly when press backbutton goes second activity blank screen , on press ad.how can show ad on backpress default selected video player. here code

activty a

case 1:                     = new intent(a.this, b.class);                     i.putextra("channel","http://id=hbo");                     startactivity(i);                     break; 

activity b

bundle bundle = getintent().getextras();     string channel = bundle.getstring("channel");     uri uri = uri.parse(channel);     intent intent = new intent(intent.action_view, uri);     intent.setdataandtype(uri, "video/mp4");     startactivity(intent); 

and onbackpressed

@override public void onbackpressed() {     if (interstitial.isloaded()) {         interstitial.show();     }     super.onbackpressed(); } 

if ad loaded show fine, still call through super.onbackpressed(). causes activity finish , return last activity.

what need add else clause call super.onbackpressed(); if ad not loaded.

then need add listener interstitial ad listen ad closed event , call finish(); there.