func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let contentOffset = scrollView.contentOffset
    let contentSize = scrollView.contentSize
    let scrollViewBounds = scrollView.bounds
    let contentViewBounds = scrollView.contentView.bounds
    
    // 判断是否到达顶部
    let atTop: Bool = scrollView.contentOffset.y <= contentViewBounds.maxY
    if atTop {
        print("已到达顶部")
    }
}

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let contentOffset = scrollView.contentOffset
    let contentSize = scrollView.contentSize
    let scrollViewBounds = scrollView.bounds
    let contentViewBounds = scrollView.contentView.bounds
    
    // 判断是否到达底部
    let atBottom: Bool = scrollView.contentOffset.y + scrollViewBounds.size.height >= contentSize.height
    if atBottom {
        print("已到达底部")
    }
}