更改setContentOffset的速度:动画:？

UIView.animateWithDuration(0.3) {
    self.scrollView.contentOffset = CGPointMake(0, 100)
}

self.scrollView.setContentOffset(CGPointMake(0, 100), animated: true)

let displayLink = CADisplayLink(target: self, selector: #selector(handleDisplayLink(_:)))
displayLink.addToRunLoop(NSRunLoop.currentRunLoop(), forMode: NSRunLoopCommonModes)

@objc private func handleDisplayLink(displayLink: CADisplayLink) {
    let duration = 0.3
    let progress = CGFloat(displayLink.timestamp - startTime) / CGFloat(duration)
    if progress >= 1.0 {
        displayLink.invalidate()
    }
    self.scrollView.contentOffset = CGPointMake(0, startOffset + distance * progress)
}

func scrollViewWillBeginDragging(scrollView: UIScrollView) {
    startOffset = scrollView.contentOffset.y
}

func scrollViewDidScroll(scrollView: UIScrollView) {
    let distance = 100.0
    let progress = min(1.0, max(0.0, scrollView.contentOffset.y - startOffset) / distance)
    scrollView.contentOffset = CGPointMake(0, startOffset + distance * progress)
}