我正在尝试实现一个滚动视图,在滚动时捕捉到点。
我在这里看到的所有帖子都是关于在用户结束拖动滚动条“之后”捕捉到某个点的。 我想让它在拖动过程中对齐。到目前为止,我已经用它来停止拖动后的惯性,并且效果很好:
func scrollViewWillEndDragging(scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
targetContentOffset.memory = scrollView.contentOffset
}
我尝试过这个,但没有按预期工作:
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;
}
scrollEnabled
的
UIScrollView
属性。当scrollView滚动到给定的
scrollSnapHeight
之外时,使
scrollEnabled
变为
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
}
将
snapPoint 设置为您想要捕捉中心所在的内容偏移量。
将snapOffset 设置为您想要在 snapPoint 周围发生捕捉的半径。
如果您需要知道scrollView是否已对齐,只需检查isSnapped变量即可。
class UIScrollViewSnapping : UIScrollView {
public var snapPoint: CGPoint?
public var snapOffset: CGFloat?
public var isSnapped = false
public override var contentOffset: CGPoint {
set {
if let snapPoint = self.snapPoint,
let snapOffset = self.snapOffset,
newValue.x > snapPoint.x - snapOffset,
newValue.x < snapPoint.x + snapOffset {
self.isSnapped = true
super.contentOffset = snapPoint
}
else {
self.isSnapped = false
super.contentOffset = newValue
}
}
get {
return super.contentOffset
}
}
}