Smooth animation on CALayer shadowPath animation

Question

In my application, I have a UIView that uses CALayer to achieve the shadow:

 @implementation MyUIView - (instancetype) initWithFrame:(CGRect)frame { self = [super initWithFrame:frame]; if(!self) return self; self.layer.shadowColor = [UIColor colorWithWhite:0 alpha:.2].CGColor; self.layer.shadowOffset = CGSizeMake(0, 2); self.layer.shadowOpacity = 1; self.layer.shadowRadius = 1; return self; } @end 

If I need anything closer to reasonable performance, I have to define a CALayer shadowPath :

 @implementation MyUIView - (void) setFrame:(CGRect)frame { [super setFrame:frame]; self.layer.shadowPath = CGPathCreateWithRect(self.bounds, NULL); } @end 

I noticed two things when I revive this UIView :

• If I don't , use shadowPath , the shadow animates well with rotations and frame resizing. The danger here is very slow animation and a general lack of performance.

• If I do , use shadowPath whenever the UIView animation is smooth and timely, however the shadow transition itself is much more blocky (and less smooth) than without shadowPath .

<strong> Examples:

• With shadowPath : https://gfycat.com/ColdBlissfulIndusriverdolphin (notice how the shadow behaves like a poorly transformed rectangle?)
• Without shadowPath (the slowness of the animation is more obvious on the device, but you get the idea): https://gfycat.com/ActiveRemorsefulBandicoot

Edit:

It is worth noting that these animations are implicit - I myself do not call them. They are the result of rotation of the UIViewController with the device orientation. The shadow is on a UIView that changes size during rotation.

Answer 1

I tried to reproduce the behavior shown in the two gifs you submitted, but to no avail (maybe you could change your question using animation code like UIView animateWithDuration:animations: .

However, somewhere deep down I remember that from time to time I came across a similar problem, and it turned out that I had to rasterize the view to make it smooth.

Therefore, I can not guarantee that it solves the problem for you, but try:

 self.layer.shouldRasterize = YES; self.layer.rasterizationScale = [[UIScreen mainScreen] scale];