What version of the AdMob SDK are you using? This solution will work with Google Play Services.
Lets say that this is how you setup your interstitial:
//Here is where you setup your interstitial
//...
adView.setAdListener(new AdListener() {
@Override
public void onAdLoaded(){
adView.show();
}
});
In your onPause() method you can do the following:
protected void onPause() {
super.onPause();
if(adView != null) {
adView.setAdListener(null);
}
}
This works because by the time the onPause method is called because of a new interstitial, the ad will already be in the process of being shown and will display normally. However, if onPause() is called because of something else, like the Home button being pressed, it will disable new interstitials from being shown.
Only caveat is if you're using other callback methods available from the AdListener.