滚动时UIScrollView对齐位置

Question

我正在尝试实现滚动视图,在滚动时捕捉到点.

我看到的所有帖子都是关于在用户结束拖动滚动后'捕捉到一个点'.我想在拖动过程中使其快速捕捉.

到目前为止,我有这个拖动后停止惯性,它工作正常:

func scrollViewWillEndDragging(scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
      targetContentOffset.memory = scrollView.contentOffset
}

我尝试了这个,但没有按照预期工作:

    var scrollSnapHeight : CGFloat = myScrollView.contentSize.height/10

scrollViewDidScroll:

func scrollViewDidScroll(scrollView: UIScrollView) {
    let remainder : CGFloat = scrollView.contentOffset.y % scrollSnapHeight
    var scrollPoint : CGPoint = scrollView.contentOffset
    if remainder != 0 && scrollView.dragging
    {
        if self.lastOffset > scrollView.contentOffset.y //Scrolling Down
        {
            scrollPoint.y += (scrollSnapHeight - remainder)
            NSLog("scrollDown")
        }
        else //Scrolling Up
        {
            scrollPoint.y -= (scrollSnapHeight - remainder)
        }
        scrollView .setContentOffset(scrollPoint, animated: true)
    }
    self.lastOffset = scrollView.contentOffset.y;
}

Answer 1

这种方法将启用/禁用scrollEnabled属性UIScrollView.

当scrollView在给定的外部滚动时scrollSnapHeight,make scrollEnabledto false.这将停止滚动.然后再次启用滚动以进行下一次拖动.

extension ViewController: UIScrollViewDelegate {

    func scrollViewDidScroll(scrollView: UIScrollView) {

        if scrollView.contentOffset.y > lastOffset + scrollSnapHeight {
            scrollView.scrollEnabled = false
        } else if scrollView.contentOffset.y < lastOffset - scrollSnapHeight {
            scrollView.scrollEnabled = false
        }
    }

    func scrollViewDidEndDragging(scrollView: UIScrollView, willDecelerate decelerate: Bool) {

        guard !decelerate else {
            return
        }

        setContentOffset(scrollView)
    }

    func scrollViewWillBeginDecelerating(scrollView: UIScrollView) {

        setContentOffset(scrollView)
    }
}

func setContentOffset(scrollView: UIScrollView) {

    let stopOver = scrollSnapHeight
    var y = round(scrollView.contentOffset.y / stopOver) * stopOver
    y = max(0, min(y, scrollView.contentSize.height - scrollView.frame.height))
    lastOffset = y

    scrollView.setContentOffset(CGPointMake(scrollView.contentOffset.x, y), animated: true)

    scrollView.scrollEnabled = true
}