iOS icon jiggle algorithm

Question

I am writing an iPad app that presents user documents similar to the way Pages presents them (as large icons of the actual document). I also want to mimic the jiggling beha

Answer 1

@mientus Original Apple Jiggle code in Swift 4, with optional parameters to adjust the duration (i.e. speed), displacement (i.e. position change) and degrees (i.e. rotation amount).

private func degreesToRadians(_ x: CGFloat) -> CGFloat {
    return .pi * x / 180.0
}

func startWiggle(
    duration: Double = 0.25,
    displacement: CGFloat = 1.0,
    degreesRotation: CGFloat = 2.0
    ) {
    let negativeDisplacement = -1.0 * displacement
    let position = CAKeyframeAnimation.init(keyPath: "position")
    position.beginTime = 0.8
    position.duration = duration
    position.values = [
        NSValue(cgPoint: CGPoint(x: negativeDisplacement, y: negativeDisplacement)),
        NSValue(cgPoint: CGPoint(x: 0, y: 0)),
        NSValue(cgPoint: CGPoint(x: negativeDisplacement, y: 0)),
        NSValue(cgPoint: CGPoint(x: 0, y: negativeDisplacement)),
        NSValue(cgPoint: CGPoint(x: negativeDisplacement, y: negativeDisplacement))
    ]
    position.calculationMode = "linear"
    position.isRemovedOnCompletion = false
    position.repeatCount = Float.greatestFiniteMagnitude
    position.beginTime = CFTimeInterval(Float(arc4random()).truncatingRemainder(dividingBy: Float(25)) / Float(100))
    position.isAdditive = true

    let transform = CAKeyframeAnimation.init(keyPath: "transform")
    transform.beginTime = 2.6
    transform.duration = duration
    transform.valueFunction = CAValueFunction(name: kCAValueFunctionRotateZ)
    transform.values = [
        degreesToRadians(-1.0 * degreesRotation),
        degreesToRadians(degreesRotation),
        degreesToRadians(-1.0 * degreesRotation)
    ]
    transform.calculationMode = "linear"
    transform.isRemovedOnCompletion = false
    transform.repeatCount = Float.greatestFiniteMagnitude
    transform.isAdditive = true
    transform.beginTime = CFTimeInterval(Float(arc4random()).truncatingRemainder(dividingBy: Float(25)) / Float(100))

    self.layer.add(position, forKey: nil)
    self.layer.add(transform, forKey: nil)
}