向下/向上滚动时淡入/显示 UIButton

Question

我有一个表格视图。在视图中是 UIButton。我想要向下滚动按钮淡出和滚动停止或向上按钮显示时。

代码：

- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView{
NSLog(@"Start scroll");

//I assume the buttons are within your cells so you will have to enable them within your cells so you will probably have to handle this by sending a custom message to your cells or accessing them with properties.
CGRect frame = addCommentBtn.frame;
frame.origin.y = scrollView.contentOffset.y + self.newsTableView.frame.size.height  + 4;
addCommentBtn.frame = frame;

[self.view bringSubviewToFront:addCommentBtn];}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
NSLog(@"End scroll");

// do the same to enable them back
CGRect frame = addCommentBtn.frame;
frame.origin.y = scrollView.contentOffset.y + self.newsTableView.frame.size.height  + 4;
addCommentBtn.frame = frame;

[self.view bringSubviewToFront:addCommentBtn];}

但不能正常工作！ 谢谢

Answer 1

您使用了错误的方法。代替 scrollViewWillBeginDecelerating: 使用 scrollViewDidScroll: 并根据滚动视图的 contentOffset 更新按钮 alpha 和位置。