如果你以某种方式改变scrollView contentSize(例如，添加一些东西到stackView是在scrollView)，你必须调用scrollView. layoutifneeded()在滚动之前，否则它什么都不做。

例子:

scrollView.layoutIfNeeded()
let bottomOffset = CGPoint(x: 0, y: scrollView.contentSize.height - scrollView.bounds.size.height + scrollView.contentInset.bottom)
if(bottomOffset.y > 0) {
    scrollView.setContentOffset(bottomOffset, animated: true)
}

如果contentSize低于边界怎么办?

对于Swift来说，它是:

scrollView.setContentOffset(CGPointMake(0, max(scrollView.contentSize.height - scrollView.bounds.size.height, 0) ), animated: true)

滚动到顶部

- CGPoint topOffset = CGPointMake(0, 0);
- [scrollView setContentOffset:topOffset animated:YES];

滚动到底部

- CGPoint bottomOffset = CGPointMake(0, scrollView.contentSize.height - self.scrollView.bounds.size.height);
 - [scrollView setContentOffset:bottomOffset animated:YES];

使用(可选)footerView和contentInset，解决方案是:

CGPoint bottomOffset = CGPointMake(0, _tableView.contentSize.height - tableView.frame.size.height + _tableView.contentInset.bottom);
if (bottomOffset.y > 0) [_tableView setContentOffset: bottomOffset animated: YES];

扩展UIScrollView添加一个scrollToBottom方法:

extension UIScrollView {
    func scrollToBottom(animated:Bool) {
        let offset = self.contentSize.height - self.visibleSize.height
        if offset > self.contentOffset.y {
            self.setContentOffset(CGPoint(x: 0, y: offset), animated: animated)
        }
    }
}

滚动到表的最后一项的解决方案

Swift 3:

if self.items.count > 0 {
        self.tableView.scrollToRow(at:  IndexPath.init(row: self.items.count - 1, section: 0), at: UITableViewScrollPosition.bottom, animated: true)
}