swift - 实现无限滚动时多次调用 scrollViewDidLoad

Question

我正在尝试在具有自定义布局的 Collection View 上实现无限滚动。

经过搜索我找到了这个方法:

    override func scrollViewDidScroll(_ scrollView: UIScrollView) {

    //make sure collection view is on screen
    if collectionView?.window == nil { return }

    let offsetY = scrollView.contentOffset.y
    let contentHeight = scrollView.contentSize.height

    if offsetY > contentHeight - scrollView.frame.size.height {
        print("scroll ended")
        getNextTenProducts()
        collectionView?.reloadData()
    }

}

然而，多次调用print语句导致在 Collection View 中插入大量单元格，有时甚至连续调用20次。

有解决办法吗？

Answer 1

我找到了解决方案:

    override func scrollViewDidScroll(_ scrollView: UIScrollView) {

    if collectionView?.window == nil { return }

    let offsetTolerance = CGFloat(30)

    let offsetY = scrollView.contentOffset.y
    let contentHeight = scrollView.contentSize.height

    if offsetY > contentHeight - scrollView.frame.size.height + offsetTolerance, !scrollViewReachedBottom {
        print("scroll ended")
        scrollViewReachedBottom = true
    } else if offsetY < contentHeight - scrollView.frame.size.height - offsetTolerance {
        scrollViewReachedBottom = false
    }

}