iOS tableview如何检查它是否向上或向下滚动 [英] iOS tableview how can I check if it is scrolling up or down

问题描述

我正在学习如何使用TableViews，我想知道如何判断tableView是向上还是向下滚动？我一直在尝试各种各样的东西，比如这个但是没有用，因为下面是滚动视图，我有一个TableView。任何建议都会很棒，因为我是新手......

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 ...

  func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
    if scrollView.panGestureRecognizer.translation(in: scrollView).y < 0 {
        print("down")
    } else {
        print("up")
    }
}

这是我在tableView代码中的内容

This is what I have in my tableView code

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
    }

推荐答案

<像@maddy在你的问题的评论中所说，你可以使用 UIScrollViewDelegate UITableView 是否在滚动>还有更多你可以通过使用 scrollViewDidScroll 和 scrollViewWillBeginDragging 函数

Like @maddy said in the comment of your question, you can check if your UITableView is scrolling by using the UIScrollViewDelegate and further more you could check which direction it scrolls to by using both scrollViewDidScroll and scrollViewWillBeginDragging functions

// 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) {
        // moved to top
    } else if (self.lastContentOffset > scrollView.contentOffset.y) {
        // moved to bottom
    } else {
        // didn't move
    }
}

此外：您不需要将 UIViewController 继承为 UIScrollViewDelegate 如果你'已经使用 UITableViewDelegate 将您的 UIViewController 子类化，因为 UITableViewDelegate 已经 UIScrollViewDelegate的子类

Furthermore: You don't need to subclass your UIViewController with UIScrollViewDelegate if you've already subclassed your UIViewController with UITableViewDelegate because UITableViewDelegate is already a subclass of UIScrollViewDelegate

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