如何在 Swift 中的 UITableView 底部显示“下拉刷新”元素

Question

我需要在UITableView 的底部显示UIRefreshControl，就像在以下Objective-C 库中一样：

• https://github.com/emenegro/bottom-pull-to-refresh
• https://github.com/vlasov/CCBottomRefreshControl

但我使用的是 Swift，并注意到在将 "Bridging-Header.h" 文件与这些库一起使用时出现了一些问题。

实现这种行为的替代方法和最简单的方法是什么？

提前致谢。

Answer 1

我在我的项目中遇到了同样的问题，并找到了this answer。你可以在表格底部添加一个UIActivityIndicatorView实例，最初是隐藏的，当它进入上面的if条件时，取消隐藏并开始动画。

您可能需要更改表格的底部偏移量，在加载时为其添加“1 个单元格”高度，并在 if 条件内完成时将其放回。

在 Swift 3 中：

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

    // Use this 'canLoadFromBottom' variable only if you want to load from bottom iff content > table size
    let contentSize = scrollView.contentSize.height
    let tableSize = scrollView.frame.size.height - scrollView.contentInset.top - scrollView.contentInset.bottom
    let canLoadFromBottom = contentSize > tableSize

    // Offset
    let currentOffset = scrollView.contentOffset.y
    let maximumOffset = scrollView.contentSize.height - scrollView.frame.size.height
    let difference = maximumOffset - currentOffset

    // Difference threshold as you like. -120.0 means pulling the cell up 120 points
    if canLoadFromBottom, difference <= -120.0 {

        // Save the current bottom inset
        let previousScrollViewBottomInset = scrollView.contentInset.bottom
        // Add 50 points to bottom inset, avoiding it from laying over the refresh control.
        scrollView.contentInset.bottom = previousScrollViewBottomInset + 50

        // loadMoreData function call
        loadMoreDataFunction(){ result in
            // Reset the bottom inset to its original value
            scrollView.contentInset.bottom = previousScrollViewBottomInset
        }
    }
}

Answer 2

var refreshControl: UIRefreshControl!

//Pull to refresh
self.refreshControl = UIRefreshControl()
self.refreshControl.attributedTitle = NSAttributedString(string: "Pull to refresh")
self.refreshControl.addTarget(self, action: "pullToRefresh:", forControlEvents: UIControlEvents.ValueChanged)
self.messageTableView.addSubview(refreshControl)

//Refresh the table view (pull to refresh)
func pullToRefresh(sender:AnyObject)
{
    print("pull to refresh...")
}