问题
I'm having problems with my UIView subclass' drawRect: function.
I use CGContextDrawRadialGradient() in it, and it.
When the user drags my UIView it struggled to keep up if I include the gradient.
Using Time Profiler I see that literally > 98% of my time is spent in my subclass' drawRect: method.
First: would using a static image of a gradient be faster?
Second: is there any way to speed this up? Can I cache the gradient somehow? it doesn't change much but paths around it and intersecting it do change as you drag the UIView.
If anybody knows of a general guide on how to make drawRect: methods not suck up all the cpu cycles, that would be awesome.
回答1:
I'm having the same problem. One solution is to draw a smaller gradient and scale it up. The results is not pixel perfect, but faster.
See also the ideas mentioned in this answer.
来源：https://stackoverflow.com/questions/4425635/drawrect-speed-and-cgcontextdrawradialgradient-super-slow