是否可以在没有UIView的情况下显示CALayer？

Question

As far as I can tell, I need an UIView (or subclass of UIView) to display an CALayer on screen, right?

Then, what's the point of using CALayer for saving memory? The only point I see is when I would add several sublayers to a CALayer. Then those sublayers would not get copied 3 times for all the different tree types like presentation tree, render tree and so on. Is that right?

Answer 1

You can add CALayer s as sublayers of another CALayer . Each individual layer does not have to be backed by a view, but the root layer in the hierarchy must be backed by a UIView .

The point is not to avoid having copies of the CALayer s, which are quite lightweight, but to avoid having copies of UIViews or, more specifically, the graphics contexts that back UIView s. Those take up considerably more memory.