WWDC 2014 Session 221: Creating Custom iOS User Interfaces

Spring Animations

• -[UIView animateWithDuration:delay:usingSpringWithDamping: initialSpringVelocity:options:animation:completion]
  • Can be applied to any animatable property.

Vibrancy and Blur

• Continue using -[UIView drawViewHierarchyInRect:afterScreenUpdates:] for static blurs.
• UIVisualEffectView is a new API for creating live blurs and vibrancy effects.
  • Vibrancy is used to make content visible when the background is blurred.
  • Blurs can be tinted by setting the backgroundColor of the contentView
  • Changing the alpha will result in the blur being dropped.
  • Can not be placed in a view hierarchy that contains masks.
• UIBlurEffect
  • Has 3 styles: dark, light, extra light
  • Not just a simple Gaussian blur. Three steps:
    1. Downsample
    2. Modify colors
    3. Compute the blur
  • Rendered offscreen.
• UIVibrancyEffect
  • Used as a subview of or layered on top of a UIVisualEffectView that uses a UIBlurEffect to make content (e.g. text) more vivid and legible.
  • Also rendered offscreen, takes even more time than blur.

Shape Layers

• CAShapeLayer is used to create animatable bezier paths.
  • Rasterizes shape layer on CPU and sends the rasterized layer to the render server
  • Expensive in CPU time, be cautious about frequent changes.

Dynamic Core Animation Behaviours

• Actions can be used to implement dynamic animation behaviour based on the context.
  • -actionForLayer:forKey: is called on the CALayerDelegate when an animatable property is set.
    • Return an object that conforms to the CAAction protocol to run custom animations.