理解UIView，UICollectionView，UITableView，UIScrollView的bounds属性时出现困惑

Question

I have been seeing negative value in UICollectionView bounds "Y" value and its keep on reducing it when scrolls down and increasing to positive value when scroll up.

How does bounds values work in UICollectionView?

as far as I know, bounds in UIView has constant X and Y values. Am I thinking in a wrong way?

Could someone explain how bounds works in UIView, UITableView and UICollectionView and UIScrollView ?

Answer 1

For most UIView s, the bounds origin will always be (0,0). However, UITableView and UICollectionView are both subclasses of UIScrollView . UIScrollView achieves its scrolling effect by changing the x and y values of the origin of its bounds. Here's a nice article explaining in more depth: http://oleb.net/blog/2014/04/understanding-uiscrollview/ .