void NotifyScreenChangeListener(int whichScreen, bool changeComplete)
 {
     if (mOnScreenChangeListener != null)
     {
         if (changeComplete)
         {
             mOnScreenChangeListener.OnScreenChanged(GetScreenAt(whichScreen), whichScreen);
         }
         else
         {
             mOnScreenChangeListener.OnScreenChanging(GetScreenAt(whichScreen), whichScreen);
         }
     }
     if (mOnScrollListener != null)
     {
         mOnScrollListener.OnScroll(GetCurrentScreenFraction());
     }
 }