This issue has been encountered by someone else, but I've not seen any solutions - see ( http://openradar.appspot.com/6941930 ).
I have a UIScrollView whose content view's layer contains two CATiledLayers. One tiled layer draws content quite fast (but long enough to make drawInRect: too slow!), the other draws them slowly.
The quicker CATiledLayer doesn't Zoom has has default LOD settings, with a large tile size.
The slower CATiledLayer is zoomable.
Using just one of the CATiledLayers behaves as expected.
The problem is adding both layers to the visible screen causes one or the other to behave slowly. Annoyingly, it seems to make the content that draws normally fast, much slower.
I've not seen a way yet to reliably know when one CATiledLayer has completed its draw.
I think the solution would be to queue the Tiled Layers, so draw the slower tiled layer when the quicker one has finished. But the documentation on CATiledLayer is pretty bad.
I've tried to use a NSTimer, and set it for a 3 second wait before drawing the 2nd Tiled Layer. This however does not seem to solve the problem! I'm lost!
