如果您想在swift中检测它们：

override func scrollViewDidScroll(scrollView: UIScrollView) {

if (scrollView.contentOffset.y >= (scrollView.contentSize.height - scrollView.frame.size.height)) {
    //reach bottom
}

if (scrollView.contentOffset.y < 0){
    //reach top
}

if (scrollView.contentOffset.y >= 0 && scrollView.contentOffset.y < (scrollView.contentSize.height - scrollView.frame.size.height)){
    //not top and not bottom
}}

卡洛斯的回答更好。
对于Swift 4.x，您必须更改方法名称：

func scrollViewDidScroll(_ scrollView: UIScrollView) {
        if (scrollView.contentOffset.y + 1) >= (scrollView.contentSize.height - scrollView.frame.size.height) {
            //bottom reached
        }
    }

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView 
{
    float bottomEdge = scrollView.contentOffset.y + scrollView.frame.size.height;
    if (bottomEdge >= scrollView.contentSize.height) 
    {
        // we are at the end
    }
}

有时候你必须在条件中使用+1，因为contentSize.height会多给你几位小数，所以如果你使用这个，你就避免了...

override func scrollViewDidScroll(scrollView: UIScrollView) {

   if (scrollView.contentOffset.y + 1) >= (scrollView.contentSize.height - scrollView.frame.size.height) {
       //bottom reached
   }
}

你有没有想过添加一个布尔值。当方法第一次被调用时更新它，或者当用户向上滚动时更新它。

我使用了一种混合的方法，让我解释一下：
虽然您的演算是正确的，但是您所监听的委托是多余的，因为scrollViewDidScroll被调用了很多次，这可能会导致性能问题。您应该（像我一样）使用scrollViewDidEndDragging和scrollViewDidEndDecelerating，它们只在每个事件结束时被调用一次。

func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
    // Scrolling acceleration didn't continue after the finger was lifted
    if !decelerate {
        executeActionAtTheEnd(of: scrollView)
    }
}

func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
    executeActionAtTheEnd(of: scrollView)
}

private func executeActionAtTheEnd(of scrollView: UIScrollView) {
    if scrollView.contentOffset.y + 1 >= (scrollView.contentSize.height - scrollView.frame.size.height) {
        // Do here whatever you want when end of scrolling is reached
    }
}

对于Swift 4.5：

func scrollViewDidScroll(_ scrollView: UIScrollView) 
{    
   let scrollViewHeight = scrollView.frame.size.height
    let scrollContentSizeHeight = scrollView.contentSize.height
     let scrollOffset = scrollView.contentOffset.y

    if (scrollOffset == 0)
    {
        // then we are at the top
        print("then we are at the top")
    }
    else if (scrollOffset + scrollViewHeight == scrollContentSizeHeight)
    {
        print("then we are at the end")
        // then we are at the end
    }      
}

实现scrollViewDidScroll:并在中检查contentOffset，以达到终点

func scrollViewDidEndDecelerating(scrollView: UIScrollView) {

if (scrollView.contentOffset.y >= (scrollView.contentSize.height - scrollView.frame.size.height)) {
    //reach bottom
}

if (scrollView.contentOffset.y <= 0){
    //reach top
}

if (scrollView.contentOffset.y >= 0 && scrollView.contentOffset.y < (scrollView.contentSize.height - scrollView.frame.size.height)){
    //not top and not bottom
}}

确保视图实现了UIScrollViewDelegate

MyView: UITableViewDelegate,UIScrollViewDelegate