主要是红色区域会随着下面列表的滚动而隐藏显示，这功能如何实现？界面如何布局？
In the delegate of scrollview, decide whether to hide or display based on the current scrolling direction and the position of the current red view.
UICollectionView
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In the delegate of scrollview, decide whether to hide or display based on the current scrolling direction and the position of the current red view.
UICollectionView