DrawRect causes slow scrolling, even if it is not called

Question

In my application, I have scrollView with about 20 subviews in it. Each of these subzones has a drawRect method, which currently looks like this:

- (void)drawRect:(CGRect)rect { NSLog(@"drawRect called"); } 

When additional objects are added, drawRect is called, however when scrolling it is very slow, although drawRect is not called again.

If I remove the implementation for drawRect, the scroll is completely normal. Even if I can't get rid of slow scrolling, is there an alternative to drawRect that I could use instead?

Answer 1

Why are you calling drawRect if it only registers that it was called? If this is just a goal for you, then just do not call it. In fact, I believe that when you first create a class that inherits from UIView, which has a drawRect method in it, it is commented on and above the commented drawRect method, it says something like strings "Do not call this method if it doesn’t makes no drawing on the screen since it takes up a significant amount of memory. " In principle, do not call it in your case.

Hope this helps.

Answer 2

You can try to assign pre-drawn CGImages to the contents of each custom CALayer view before the view first appears. This can be faster than using drawRect to customize the look.