检测UIScrollview底部到达

Question

我有一个带图像的UIScrollView,当用户滚动到scrollview的末尾时,我想更新内容.这是我的代码,用于检测何时到达scrollview的底部:

以下代码在scrollViewDidScroll:委托中实现

CGFloat scrollViewHeight = imagesScrollView.bounds.size.height;
CGFloat scrollContentSizeHeight = imagesScrollView.contentSize.height;
CGFloat bottomInset = imagesScrollView.contentInset.bottom;
CGFloat scrollViewBottomOffset = scrollContentSizeHeight + bottomInset - scrollViewHeight;

if(imagesScrollView.contentOffset.y > scrollViewBottomOffset){


    [imagesView addSubview:imagesBottomLoadingView];

    [self downloadImages];

}

我的问题是,当用户滚动到底部时,我的函数被多次调用,但我想只调用一次.我尝试使用imagesScrollView.contentOffset.y == scrollViewBottomOffset但它不起作用并且不调用该函数

Answer 1

如果你想在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
}}

Answer 2

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
        }
    }

Answer 3

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

Answer 4

你有没有想过添加一个布尔值。当第一次调用该方法时或者当用户向后滚动时更新它。