UIView shadow not working

问题

This is my code.

listView.layer.masksToBounds = NO;
listView.layer.shadowOffset = CGSizeMake(-3, 3);
listView.layer.shadowColor=[[UIColor blackColor] CGColor];
listView.layer.shadowRadius = 4;
listView.layer.shadowOpacity = 1.0;
[listView.layer setShouldRasterize:YES];

It works good with shadow effect.

While changing

listView.layer.masksToBounds = YES;

I didnt get shadow effect.

回答1:

The shadow is actually drawn below the UIView. If you set maskToBounds to YES, this clips any drawing outside of the UIView frame. Here is a SO link that describes this in more detail.

回答2:

The shadow is drawn outside of the layer's bounds. You have to set listView.layer.masksToBounds = NO to see the shadow

if you set listView.layer.masksToBounds = YES you can't draw anything out side of bounds so you can not get shadow

回答3:

If you have to use masksToBounds = YES; check out this SO post. It tells you how to use both shadows and rounded corners (in this particular case) on a view by using two nested views: the outer view casts the shadow and does not mask to bounds while the inner view has rounded corners and masks to bounds.

来源：https://stackoverflow.com/questions/10384207/uiview-shadow-not-working