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🎚Swift playground for building animations with UIViewPropertyAnimator
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README.md

Playground Animation Scrubber 🎚

There are a lot of frameworks and tools for making animations and animated transitions for your iOS projects.

If you're targeting iOS/tvOS 10.0+, then UIViewPropertyAnimator is probably powerful enough for your needs: It includes the standard easing curves, a nice implementation of spring physics, an easy way to define your own custom timing curve, and a scalable API that allows from simple single step interpolation, to chained, interruptible, and animations that can be modified on the fly.

ScrubContainerView

This project doesn't modify or build on top of UIViewPropertyAnimator, but instead provides ScrubContainerView, a simple UIView subclass, that makes it easier to create, explore, debug, and refine an animation in a playground.

  1. Start by making a playground and importing UIKit and PlaygroundSupport
import UIKit
import PlaygroundSupport
  1. Create a new ScrubContainerView and make that the playground's liveView (this presents the view in the playground's assistant editor panel.
let container = ScrubContainerView()
PlaygroundPage.current.liveView = container
  1. Next, go ahead an set up the objects to be animated, adding them to the stage view of ScrubContainerView and setting their initial positions.
let square = UIView()
container.stage.addSubview(square)
square.center = container.stage.center
square.transform = .identity
square.bounds.size = CGSize(width: 150, height: 50)
square.backgroundColor = .red
  1. Finally, assign animator with a closure that returns a UIViewPropertyAnimator. This defines the animations to perform.
container.animator = {

    // create the animator with the duration and timing curve
    // (in this case using a spring-physics)
    let animator = UIViewPropertyAnimator(duration: 2.0, dampingRatio: 0.5)

    // define the properties to animate
    animator.addAnimations {
        square.transform = CGAffineTransform(rotationAngle: CGFloat.pi/2)
        square.bounds.size = CGSize(width: 50, height: 150)
        square.backgroundColor = .blue
    }
    // return the animator
    return animator
}

ScrubContainerView adds a UISlider that lets you scrub through the animation and look at it at any intermediate step.

An option for step #3 is to wrap the expressions that define the stating state into the startState closure:

container.startState = {
    square.transform = .identity
    square.bounds.size = CGSize(width: 150, height: 50)
    square.backgroundColor = .red
}

If this property is defined ScrubContainerView will add a button button that lets you to watch the animation perform with it's defined duration and timing curve:

Initializers

A ScrubContainerView can be initialized multiple ways. The default initializer creates a stage width a 300x300 pixel size.

ScrubContainerView.init(width: Double, height: Double) allows a stage of any size.

Convenience initializers ScrubContainerView.init(device: Device) and ScrubContainerView.init(device: Device, orientation: Orientation) allow for stages to be created for Device.iPhoneSE, .iPhone, and .iPhonePlus and orientations .portrait or .landscape.

Examples

The playground includes the example above, as well as a slightly more complex example that includes a 4-step animation chained together using keyframes to show how more complex multi-step animations can be built, and a blank template ready to start writing a new animation from scratch.

Roadmap

  • UISlider to scrub animations
  • Button to play animation with default timing curve and duration
  • Initializers for different device sizes
  • Resume animation after scrubbing
  • Pause/resume animation
  • Scrub paused animation

Requirements

  • Swift 3.0
  • iOS/tvOS 10.0+

Author

Made with ❤️ by @permakittens

Contributing

Feedback, or contributions for bug fixing or improvements are welcome. Feel free to submit a pull request or open an issue.

License

MIT

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