UIScrollViewDelegate

    @available(iOS 2.0, *)
    optional func scrollViewDidScroll(_ scrollView: UIScrollView) // any offset changes
    @available(iOS 3.2, *)
    optional func scrollViewDidZoom(_ scrollView: UIScrollView) // any zoom scale changes
    // called on start of dragging (may require some time and or distance to move)
    @available(iOS 2.0, *)
    optional func scrollViewWillBeginDragging(_ scrollView: UIScrollView)
    // called on finger up if the user dragged. velocity is in points/millisecond. targetContentOffset may be changed to adjust where the scroll view comes to rest
    @available(iOS 5.0, *)
    optional func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>)
    // called on finger up if the user dragged. decelerate is true if it will continue moving afterwards
    @available(iOS 2.0, *)
    optional func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool)
    @available(iOS 2.0, *)
    optional func scrollViewWillBeginDecelerating(_ scrollView: UIScrollView) // called on finger up as we are moving
    @available(iOS 2.0, *)
    optional func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) // called when scroll view grinds to a halt
    @available(iOS 2.0, *)
    optional func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) // called when setContentOffset/scrollRectVisible:animated: finishes. not called if not animating
    @available(iOS 2.0, *)
    optional func viewForZooming(in scrollView: UIScrollView) -> UIView? // return a view that will be scaled. if delegate returns nil, nothing happens
    @available(iOS 3.2, *)
    optional func scrollViewWillBeginZooming(_ scrollView: UIScrollView, with view: UIView?) // called before the scroll view begins zooming its content
    @available(iOS 2.0, *)
    optional func scrollViewDidEndZooming(_ scrollView: UIScrollView, with view: UIView?, atScale scale: CGFloat) // scale between minimum and maximum. called after any 'bounce' animations
    @available(iOS 2.0, *)
    optional func scrollViewShouldScrollToTop(_ scrollView: UIScrollView) -> Bool // return a yes if you want to scroll to the top. if not defined, assumes YES
    @available(iOS 2.0, *)
    optional func scrollViewDidScrollToTop(_ scrollView: UIScrollView) // called when scrolling animation finished. may be called immediately if already at top
    /* Also see -[UIScrollView adjustedContentInsetDidChange]
     */
    @available(iOS 11.0, *)
    optional func scrollViewDidChangeAdjustedContentInset(_ scrollView: UIScrollView)

• func scrollViewDidScroll : 스크롤 할때마다 계속 호출

@available(iOS 2.0, *)
optional func scrollViewDidScroll(_ scrollView: UIScrollView) // any offset changes

• func scrollViewWillBeginDragging : 스크롤뷰에서 드래그하기 시작할 때 한번만 호출

// called on start of dragging (may require some time and or distance to move)
@available(iOS 2.0, *)
optional func scrollViewWillBeginDragging(_ scrollView: UIScrollView)

• func scrollViewWillEndDragging : 손을 땠을 때 한번 호출, 뗐을 때의 속도(방향 포함)를 알 수 있다.

// called on finger up if the user dragged. velocity is in points/millisecond. targetContentOffset may be changed to adjust where the scroll view comes to rest
@available(iOS 5.0, *)
optional func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>)

• func scrollViewDidEndDragging : 손을 땠을 때 한번 호출, 테이블 뷰의 스크롤 모션의 감속 여부를 알 수 있다.

// called on finger up if the user dragged. decelerate is true if it will continue moving afterwards
@available(iOS 2.0, *)
optional func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool)

• func scrollViewWillBeginDecelerating

@available(iOS 2.0, *)
optional func scrollViewWillBeginDecelerating(_ scrollView: UIScrollView) // called on finger up as we are moving

• func scrollViewDidEndDecelerating

@available(iOS 2.0, *)
optional func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) // called when scroll view grinds to a halt

위 두함수는 말로 설명하기가 힘들다 ; 한번 보는게 빠를 듯,,!

• func scrollViewDidEndScrollingAnimation : setContentOffset 또는 scrollRectVisible 이 사용될 때 호출됨

@available(iOS 2.0, *)
optional func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) // called when setContentOffset/scrollRectVisible:animated: finishes. not called if not animating

• func scrollViewShouldScrollToTop : 맨위를 누르면 Top으로 올라가는 액션을 허용할껀지 안할껀지 정할 수 있음

@available(iOS 2.0, *)
optional func scrollViewShouldScrollToTop(_ scrollView: UIScrollView) -> Bool // return a yes if you want to scroll to the top. if not defined, assumes YES

• func scrollViewDidScrollToTop : 맨위로 누르면 Top으로 올라가는 이벤트가 발생할 때 호출

@available(iOS 2.0, *)
optional func scrollViewDidScrollToTop(_ scrollView: UIScrollView) // called when scrolling animation finished. may be called immediately if already at top

#iOS/스터디