title: UISlider sliding event when its continuous set to No
body: <p>How to detect the event when I slide the UISlider(not release, keep slide), I know <code>setContinues</code> can do so. </p>
  
  <p>But my slider can't be set to continues, because I need the slider change once a time(that is touch-slide-slide-...-slide-stop only change its value for one time). Is there any way can do this ?</p>