Question

if I use layer.shadow like this:

self.layer.shadowOffset = CGSizeMake(0, 1.5);
self.layer.shadowColor = [UIColor grayColor].CGColor;
self.layer.shadowOpacity = 1;

and put some(not more than 10) of these views(without images) into a UIScrollView,
it makes the scrollView very slow when is scrolling.

if I remove any codes about shadow, scrolling become quite smooth again.

FYI, the un-smooth case happen when running the app on iOS device,
but smooth on iOS simulator.

Does any one know how to keep both shadow and smooth scrolling?

Answer 1

It will help if you set a shadow path and set the should rasterize flag on the layer.

Something like this:

UIBezierPath *path = [UIBezierPath bezierPathWithRect:self.bounds];
self.layer.shadowPath = [path CGPath];
self.layer.shouldRasterize = YES;