iOS tableview 如何检查它是向上还是向下滚动
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iOS tableview how can I check if it is scrolling up or down
提问by Rome Torres
I am learning how to work with TableViews and I am wondering how can I figure out if the tableView is scrolling up or down ? I been trying various things such as this but it hasn't worked granted that below is for a scrollview and I have a TableView . Any suggestions would be great as I am new at this ...
我正在学习如何使用 TableViews，我想知道如何确定 tableView 是向上还是向下滚动？我一直在尝试诸如此类的各种事情，但它没有奏效，因为下面是滚动视图并且我有一个 TableView 。任何建议都会很棒，因为我是新手...
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
if scrollView.panGestureRecognizer.translation(in: scrollView).y < 0 {
print("down")
} else {
print("up")
}
}
This is what I have in my tableView code
这就是我的 tableView 代码中的内容
func tableView(_ tableView:UITableView, numberOfRowsInSection section:Int) -> Int {
return Locations.count
}
func tableView(tableView: UITableView, willDisplayCell cell: UITableViewCell, forRowAtIndexPath indexPath: NSIndexPath) {
if indexPath.row == self.Posts.count - 4 {
reloadTable(latmin: self.latmin,latmax: self.latmax,lonmin: self.lonmin,lonmax: self.lonmax,my_id: myID)
print("Load More")
}
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "HomePageTVC", for: indexPath) as! NewCell
cell.post.text = Posts[indexPath.row]
cell.fullname.setTitle(FullName[indexPath.row],for: UIControlState.normal)
return cell
}
回答by Zonily Jame
Like @maddy said in the comment of your question, you can check if your UITableViewis scrolling by using the UIScrollViewDelegateand further more you could check which direction it scrolls to by using both scrollViewDidScrolland scrollViewWillBeginDraggingfunctions
就像@maddy 在您的问题的评论中所说的那样，您可以使用和函数来检查您UITableView是否正在滚动UIScrollViewDelegate，此外，您还可以使用scrollViewDidScroll和scrollViewWillBeginDragging函数来检查它滚动到的方向
// we set a variable to hold the contentOffSet before scroll view scrolls
var lastContentOffset: CGFloat = 0
// this delegate is called when the scrollView (i.e your UITableView) will start scrolling
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
self.lastContentOffset = scrollView.contentOffset.y
}
// while scrolling this delegate is being called so you may now check which direction your scrollView is being scrolled to
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if self.lastContentOffset < scrollView.contentOffset.y {
// did move up
} else if self.lastContentOffset > scrollView.contentOffset.y {
// did move down
} else {
// didn't move
}
}
Furthermore: You don't need to subclass your UIViewControllerwith UIScrollViewDelegateif you've already subclassed your UIViewControllerwith UITableViewDelegatebecause UITableViewDelegateis already a subclass of UIScrollViewDelegate
此外：如果您已经对您的UIViewControllerwith进行了子类化，UIScrollViewDelegate则不需要将您的with子类化UIViewController， UITableViewDelegate因为UITableViewDelegate它已经是UIScrollViewDelegate
回答by Alexandre Lara
You can implement scrollViewWillEndDraggingmethod:
您可以实现scrollViewWillEndDragging方法：
func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
if targetContentOffset.pointee.y < scrollView.contentOffset.y {
// it's going up
} else {
// it's going down
}
}
回答by sadegh bitarafan
first we should make two property for last Offset and Current Offset
首先我们应该为 last Offset 和 Current Offset 设置两个属性
var lastOffset = CGFloat()
var currentOffset = CGFloat()
then in the Scrollview VC call the scrollViewWillBeginDragging for get current offset
然后在 Scrollview VC 中调用 scrollViewWillBeginDragging 以获取当前偏移量
override func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
self.lastOffset = scrollView.contentOffset.y
}
and scrollViewWillBeginDecelerating for get last offset
和 scrollViewWillBeginDecelerating 获取最后一个偏移量
override func scrollViewWillBeginDecelerating(_ scrollView: UIScrollView) {
self.lastOffset = scrollView.contentOffset.y
viewStatus(scrollView: scrollView)
}
then with this two variable you can know your scrollview W here it goes????
然后用这两个变量你可以知道你的滚动视图 W 在这里？？？？
???let isScrollUp = scrollView.contentOffset.y > self.lastOffset
let isScrollDown = scrollView.contentOffset.y < self.lastOffset
