public InterstitialClient(string adAppId, string adUnitId)
 {
     interstitialClientPtr = (IntPtr)GCHandle.Alloc(this);
     InterstitialPtr       = Externs.ZPLADCreateInterstitial(interstitialClientPtr, adAppId, adUnitId);
     Externs.ZPLADSetInterstitialAdCallbacks(
         InterstitialPtr,
         InterstitialDidReceivedAdCallback,
         InterstitialDidFailToReceiveAdWithErrorCallback,
         InterstitialVideoDidStartPlayingCallback,
         InterstitiaDidClickCallback,
         InterstitialVideoDidCloseCallback,
         InterstitialDidCompleteCallback
         );
 }