code: protected void onAdsCountChanged() {
          final Context context = mContext.get();
          //context may be null if activity is destroyed
          if(context != null) {
              new Handler(context.getMainLooper()).post(new Runnable() {
                  @Override
                  public void run() {
                      for (AdmobListener listener : mAdNativeListeners)
                          listener.onAdsCountChanged();
                  }
              });
          }
      }
docs: Notifies all registered {@link AdmobListener} on a change of ad count.