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iosswiftanimationcore-graphics

Rotation animation with spring effect

I want to make rotation of CAShapeLayer with spring effect (like in UIView.animateWithDuration(_:delay:usingSpringWithDamping:initialSpringVelocity:options:animations:completion:)) but on layer not on a view.

When the button is tapped its sublayer of main layer should rotate to 3*PI/4 and spring should bounce to 2*PI/3. Then, when button is tapped again, layer rotation should be done in reversed order than before: first bounce to 2*PI/3, then rotation to the initial position (before first rotation).

How I could do that? I cannot achieve it by UIView.animateWithDuration(_:delay:usingSpringWithDamping:initialSpringVelocity:options:animations:completion:) because layer's transform property is animatable by default.

I've tried changing CATransaction but it rotates only by one angle (without taking into consideration other rotation):

let rotation1 = CGAffineTransformRotate(CGAffineTransformIdentity, angle1)
let rotation2 = CGAffineTransformRotate(CGAffineTransformIdentity, angle2)
let transform = CGAffineTransformConcat(rotation1, rotation2)
CATransaction.begin()
CATransaction.setAnimationDuration(0.6)
self.plusLayer.setAffineTransform(transform)
CATransaction.commit()

Update

According to Duncan C post I try to use CASpringAnimation and I achive animation in one direction:

myLayer.setAffineTransform(CGAffineTransformMakeRotation(angle))
let spring = CASpringAnimation(keyPath: "transform.rotation")
spring.damping = 12.0
spring.fromValue = 2.0 * CGFloat(M_PI)
spring.toValue = 3.0 * CGFloat(M_PI_4)
spring.duration = 0.5
myLayer.addAnimation(spring, forKey: "rotation")

But how to reverse that animation on button tapped?

Thanks in advance for your help.

Solution

  • UIView block animation is for animating view properties. You could animate the button's transform (of type CGAffineTransform, a 2D transform) using UIView.animateWithDuration(_:delay:usingSpringWithDamping:initialSpringVelocity:options:animations:completion:

    If you need to animate layer properties, though, you'll need to use Core Animation.

    It seems Apple added (or made public) a spring CAAnimation in iOS 9. It doesn't seem to be in the Xcode docs however.

    Check out this thread:

    SpringWithDamping for CALayer animations?