title: UISlider is difficult to drag in UIScrollView
body: <p>I have a <code>UISlider</code> in <code>UIScrollView</code> and find it's difficult to drag. I have set right <code>contentSize</code> of scroll view, so the scroll view is only able to scroll vertical. </p>
  
  <p>I guess there is a conflict between scroll view and slider when they detect the gesture. Does anyone have idea on this? </p>