README.md

Core Animation

Core Animation is the graphics system that powers UIKit Views. It's fundamental class is the CALayer.

import QuartzCore

let newLayer = CALayer()
newLayer.frame = CGRectMake(0, 0, 100, 100)
newLayer.backgroundColor = UIColor.redColor().CGColor
newLayer.cornerRadius = 10

Everything you do in UIView is backed by a CALayer.

public class UIView {
   public var layer: CALayer { get }
}

While it provides the visual content, it is the UIView that provides the other things like layout, touch, and gesture recognizers.

Deeply integated with UIView

CALayer and UIView are tightly integrated. Many times, when interacting with a UIView, you are actually affecting the CALayer.

public class UIView {
   public var frame: CGRect {
      get {
         return self.layer.frame
}
      set {
         self.layer.frame = newValue
      }
  }
}

let newLayer = CALayer()
view.layer.addSublayer(newLayer)

Mapping Contents to CALayer

You can map a bitmap to a layer by access it's .contents.

let trySwiftLogo = self.trySwiftLogo() as UIImage

let trySwiftLayer = CALayer()
trySwiftLayer.contents = trySwiftLogo.CGImage

This is very similar to a UIIMageView.

Masking CALayer Objects

Here is how you can take a layer and set it as the mask property of another layer.

let myLayer = CALayer()
myLayer.contents = self.makeRedCircleImage().CGImage

let myMask = CALayer()
myMask.contents = self.makeMaskImage().CGImage

myLayer.mask = myMask

This is the affect you can use for onboarding and tutorials.

Adding Shadoes to CALayer

Whenever you are working with shadows in CA, you should always make sure to set the .shadowPath property. This will tell CA in advance what the shape of the shadow will be, reducing render time.

let myLayer = view.layer
 myLayer.shadowColor = UIColor.blackColor().CGColor
 myLayer.shadowOpacity = 0.75
 myLayer.shadowOffset = CGSizeMake(5, 10)
 myLayer.shadowRadius = 10

// IMPORTANT FOR PERFORMANCE
let myShadowPath = UIBezierPath(roundedRect:
                     view.bounds, cornerRadius: 10)

myLayer.shadowPath = myShadowPath.CGPath

Links that help

• Advanced Graphics with Core Animation - Tim Oliver