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iosobjective-canimationuiviewcalayer

SpringWithDamping for CALayer animations?

After playing around a lot with the UIView dynamic animations introduced in iOS 7, most notably: 

[UIView animateWithDuration: delay: usingSpringWithDamping: initialSpringVelocity: options: animations: completion:];

I was wondering if there is an equivalent to 'SpringWithDamping/Velocity' method that can be accessed directly when creating a CALayer animation? I.e. either through CATransaction, CABasicAnimation or otherwise...

Thanks

Solution

  • in iOS9 Apple finally made the CASpringAnimation class public.

    You can use it like that:

    let spring = CASpringAnimation(keyPath: "position.x")
spring.damping = 5
spring.fromValue = myLayer.position.x
spring.toValue = myLayer.position.x + 100.0
spring.duration = spring.settlingDuration
myLayer.addAnimation(spring, forKey: nil)

    Notice that you cannot set the animation duration - you need to ask the CASpringAnimation class for the settlingDuration (e.g. "How much time is going to take for the spring system to settle down") and then set it as the duration of your animation.

    Check the header files for CASpringAnimation - it exposes a number of spring system variables you can adjust - stiffness, mass, etc.