SpriteKit API reproducing UIView's spring animations with SKAction

Alexis Taugeron

Last update: Dec 17, 2022

Related tags

Utility SpriteKit-Spring

Overview

SpriteKit-Spring

SpriteKit-Spring is a set of extensions to perform spring animations with SpriteKit.

Installation

iOS 7

If you need to support iOS 7, you can just drop SpriteKit-Spring.swift in your project.

iOS 8

If you support iOS 8 only, you can install SpriteKit-Spring as a framework with CocoaPods (version 0.36 or above) by adding the following lines to your Podfile:

use_frameworks!

pod 'SpriteKit-Spring'

You then need to import SpriteKit-Spring wherever you want to use it:

Swift:

import SpriteKit_Spring

Objective-C:

#import <SpriteKit_Spring/SpriteKit_Spring-Swift.h>

Usage

In iOS 7, Apple introduced spring animations in UIKit by adding a new animation method on UIView (see WWDC video and UIView documentation).

This library replicates this feature by adding a spring variant to most factory methods of SKAction. The parameters usingSpringWithDamping: and initialSpringVelocity: have the same meaning as their UIKit counterpart. See below for examples.

Examples

Move

let move = SKAction.moveByX(0, y: 200, 
  duration: 5, delay: 5,
  usingSpringWithDamping: 0.2, initialSpringVelocity: 0)
  
node.runAction(move)

Scale

let scale = SKAction.scaleXTo(2, y: 0.5,
  duration: 5, delay: 5,
  usingSpringWithDamping: 0.2, initialSpringVelocity: 0)
  
node.runAction(scale)

Rotate

let rotate = SKAction.rotateByAngle(CGFloat(M_PI/2),
  duration: 5, delay: 5,
  usingSpringWithDamping: 0.2, initialSpringVelocity: 0)
  
node.runAction(rotate)

Notes

Because they use customActionWithDuration:actionBlock:, none of these actions is reversible (the reverse action performs the same animation).
All these factory methods are based on the lower level animateKeyPath:byValue:duration:delay:usingSpringWithDamping:initialSpringVelocity: and animateKeyPath:toValue:duration:delay:usingSpringWithDamping:initialSpringVelocity: methods, which can animate any CGFloat key path. If you have a SKNode subclass with a fancy CGFloat property that you'd like to animate, feel free to use these methods!

Creator

Alexis Taugeron (@ataugeron)

License

SpriteKit-Spring is released under the Apache 2 license. See LICENSE for details.

Comments

var parameters are depreciated and will be removed in swift 3.

private class func animateKeyPath(keyPath: String, **var** byValue initialDistance: CGFloat!, **var** toValue finalValue: CGFloat!, duration: NSTimeInterval, delay: NSTimeInterval, usingSpringWithDamping dampingRatio: CGFloat, initialSpringVelocity velocity: CGFloat) -> SKAction {

var initialDistance = byValue var finalValue = toValue would it be ok to create local variables from the immutable ones that would be in the parameters, perhaps?

opened by dkliman 4
Objective-C Version?

Any way you could translate this to Objective-C? I really want to use Spring Animations, but my Swift knowledge is sparse, and would take a lot more time than I would want to figure out how to write it myself. If not, that's okay, but I thought I would ask as it would probably be helpful for others as well who still use Obj-C. Thanks!

opened by KjellConnelly 2
Error upon building: CGFloat cast issue

Thanks for the 'package'. I am getting an error when I tried building my project after adding this pod

SpriteKit-Spring/SpriteKit-Spring.swift:240:62: 'AnyObject?' is not convertible to 'CGFloat'; did you mean to use 'as!' to force downcast?

opened by wbashir 2
Add explicit @objc markers for Objective-C support in Swift 4

Swift 4 by default requires explicit @objc markers to work with Objective-C.

Because of the Generics it wasn't clear how to make the Damping Logic functions @objc compatible but if they're only used internally they shouldn't need to be exposed?

opened by warpling 0
Make types more explicit to reduce complie times

SpriteKit-Spring.swift was taking over 50 seconds to compile in Xcode 7.3.1 / Swift 2.2. This appears to be due to the type inference engine having to work very hard.

I have made a few changes to make the types more explicit and this has reduced compile times to a few hundred ms.

Fair warning! I haven't tested this change for anything other than the functions I am using in my project.

opened by elgordino 0
Calculate distance correctly for animations using byValue
Hey! Awesome library, thanks for building it. I noticed that there's a bug with animations that use byValue, e.g.:

SKAction.scale(by:duration:delay:usingSpringWithDamping:initialSpringVelocity:)

The distance isn't calculated correctly, so the behavior uses byValue as the distance.

For example, say there's a node with a current scale of 1.0 - if we tried to scale it by 1.2, SpriteKit-Spring will currently scale it to 1.0 + 1.2 instead of 1.0 * 1.2, which in this case would more than double the scale instead of scaling appropariately. I put up an example app at https://github.com/noahsark769/NGSpriteKitSpringTest to demonstrate this.

The fix is to calculate the initialDistance based on multiplying it by initialValue.

Let me know if I need to do anything else to fix this bug! Thanks!
opened by noahsark769 1
Cocoa Pods support for tvOS

Is it possible to provide cocoa pods support for tvOS?. The helper works flawlessly on tvOS but doesn't have cocoa pods support which makes it harder to manage when having a universal iOS and tvOS game.

Thanks for your great helper.

opened by crashoverride777 2