Question

我找不到任何针对这种粘性问题的地方。我的问题是当用户开始滚动时我需要更改alpha值。滚动alpha值的开始应为1，然后在滚动alpha值的中间应该是0.5，最后它必须是0.这是我需要做的。我用谷歌搜索找不到。帮帮我PLZ

Answer 1

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    /* This is the offset at the bottom of the scroll view. */
    CGFloat totalScroll = scrollView.contentSize.height - scrollView.bounds.size.height;

    /* This is the current offset. */
    CGFloat offset = - scrollView.contentOffset.y;

    /* This is the percentage of the current offset / bottom offset. */
    CGFloat percentage = offset / totalScroll;

    /* When percentage = 0, the alpha should be 1 so we should flip the percentage. */
    scrollView.alpha = (1.f - percentage);
}

Answer 2

这是如何在 Swift 中执行此操作，我的控制器中有 2 个 UILabel，我需要增加第一个 UILabel 的 alpha 并减少第一个 func scrollViewDidScroll(_ scrollView: UIScrollView) { if (scrollView.contentOffset.y >= (scrollView.contentSize.height - scrollView.frame.size.height)) { // Bottom } if (scrollView.contentOffset.y < 0){ // Top lblTitleHeader.alpha = 0 lblTitleBody.alpha = 1 } if (scrollView.contentOffset.y >= 0 && scrollView.contentOffset.y < (scrollView.contentSize.height - scrollView.frame.size.height)){ // Middle let percentage: CGFloat = (scrollView.contentOffset.y) / 20 // This label loses alpha when you scroll down (or slide up) lblTitleHeader.alpha = (percentage) // This label gets more alpha when you scroll up (or slide down) lblTitleBody.alpha = (1 - percentage) } } 的 alpha第二个：

{"assembly":"45","Lot Number":"2021 109 M 21 - 1","Expiry date":"12/05/2023","Quantity":"682"}

如何更改alpha值以及滚动

2 个答案: