Basically I just add a simple rotate animation on an imageView which is a subview of UICollectionViewCell, the animation works fine, but when I scroll the collection view and scroll back, the animation just stoped. How to solve this problem?
This is what I added to the imageView.
let rotationAnimation = CABasicAnimation(keyPath: "transform.rotation")
rotationAnimation.fromValue = 0.0
rotationAnimation.toValue = Double.pi
rotationAnimation.duration = 2.0
rotationAnimation.repeatCount = .infinity
view.layer.add(rotationAnimation, forKey: nil)
To avoid scrolling's influence, need to use Runloop and its commonModes, making animation with CADisplayLink can do it:
private var _displayLinkForRotation:CADisplayLink?
var displayLinkForRotation:CADisplayLink {
get{
if _displayLinkForRotation == nil {
_displayLinkForRotation = CADisplayLink(target: self, selector: #selector(excuteAnimations))
_displayLinkForRotation?.add(to: RunLoop.current, forMode: RunLoopMode.commonModes)
}
return _displayLinkForRotation!
}
}
func excuteAnimations() {
//This function will be called 60 times per second.
//According to your question, you have 2 seconds to rotate the view to 180 angle. So we rotate 90 angle per second here.
//self.view could be replaced by another view you want to rotate.
self.view.transform = self.view.transform.rotated(by: 90.0 / 60.0 / 180.0 * CGFloat.pi)
let angle = atan2(self.view.transform.b, self.view.transform.a) * (45.0/atan(1.0))
if (round(angle) >= 180.0) { //Stop when rotated 180 angle
self.displayLinkForRotation.isPaused = true
}
}
To start animation:
self.displayLinkForRotation.isPaused = false
To destroy it:
self.displayLinkForRotation.invalidate()
_displayLinkForRotation = nil
Because you have not added key for animation, which you used when initialising rotationAnimation
change line
view.layer.add(rotationAnimation, forKey: nil)
to
view.layer.add(rotationAnimation, forKey: "transform.rotation")
Hope it helps
Related
I created a function with Core Animation that animate the layer height from 0 to N and it's delayable.
extension CALayer {
func animate(to height: CGFloat, duration: Double, delay: Double) {
let animation: CABasicAnimation = .init(keyPath: "bounds.size.height")
animation.fromValue = 0
animation.toValue = height
animation.beginTime = CACurrentMediaTime() + delay
animation.duration: duration
animation.timingFunction = .init(name: kCAMediaTimingFunctionEaseInEaseOut)
// I want to improvement this part.
//
// self.isHidden = true
//
// DispatchQueue.main.asyncAfter(deadline: .now() + delay) {
// self.isHidden = false
// }
self.bounds.size.height = height
self.add(animation, forKey: "bounds.size.height")
}
}
And the layer does transform well during animation, but it returns to original height before begin time and after finish. So I had to set isHidden of layer according to time to delay.
But I don't think it's a safe way. So I want to improvement that code.
What do you usually do in this case?
Try setting animation.fillMode = .backwards. I think that will make the animation will apply its fromValue to the layer until the animation's beginTime is reached.
I am making an async call whenever a button is clicked now I want an image which is like a refresh icon to be rotating or spinning until I get a response from my server. What i have now only rotates pi that's 180 and when the response arrives too the image doesn't reset. Have pasted my sample code below:
//When the update button is clicked
#objc func updateHome(){
UIView.animate(withDuration: 1) {
self.updateIcon.transform = CGAffineTransform(rotationAngle: .pi)
}
getBalances()
}
//Inside getBalances function
DispatchQueue.main.async {
if responseCode == 0 {
let today = self.getTodayString()
print("Time: \(today)")
UIView.animate(withDuration: 1) {
self.updateIcon.transform = CGAffineTransform(rotationAngle: .pi)
}
}
This code rotates your UIImageView indefinitely using CABasicAnimation:
let rotateAnimation = CABasicAnimation(keyPath: "transform.rotation")
rotateAnimation.fromValue = 0.0
rotateAnimation.toValue = CGFloat(.pi * 2.0)
rotateAnimation.duration = 1.0 // Change this to change how many seconds a rotation takes
rotateAnimation.repeatCount = Float.greatestFiniteMagnitude
updateIcon.layer.add(rotateAnimation, forKey: "rotate")
And when you get your signal from your server you can call
updateIcon.layer.removeAnimation(forKey: "rotate")
to stop the animation
For continuous rotation, you can use CAKeyframeAnimation too like below.
#objc func updateHome() {
let animation = CAKeyframeAnimation(keyPath: "transform.rotation.z")
animation.duration = 1.0
animation.fillMode = kCAFillModeForwards
animation.repeatCount = .infinity
animation.values = [0, Double.pi/2, Double.pi, Double.pi*3/2, Double.pi*2]
let moments = [NSNumber(value: 0.0), NSNumber(value: 0.1),
NSNumber(value: 0.3), NSNumber(value: 0.8), NSNumber(value: 1.0)]
animation.keyTimes = moments
self.updateIcon.layer.add(animation, forKey: "rotate")
getBalances()
}
In your Async method (inside)DispatchQueue.main.async, you can stop like below. This will keep you to the original position of the image.
self.updateIcon.layer.removeAllAnimations()
One way you can handle this is to add an instance variable that tracks when the work is completed:
var finished: Bool = false
Then write a function that rotates the image and uses the completion handler to call itself to continue rotating:
func rotateImage() {
UIView.animate(withDuration: 1,
delay: 0.0,
options: .curveLinear
animations: {
self.updateIcon.transform = CGAffineTransform(rotationAngle: .pi)
},
completion: { completed in
if !self.finished {
self.rotateImage()
}
}
}
}
If you want to stop the animation instantly, you should set finished = true and call updateIcon.layer.removeAllAnimations()
I have an image which is a square and I know how to make it spin. But not sure how to make it spin exactly like this animation here:
Notice how it spins... then stops a little... then spins again... and so on.
What I have just is a basic spin but doesn't look like the gif above:
extension UIView {
func rotate360Degrees(duration: CFTimeInterval = 3) {
let rotateAnimation = CABasicAnimation(keyPath: "transform.rotation")
rotateAnimation.fromValue = 0.0
rotateAnimation.toValue = CGFloat(M_PI * 2)
rotateAnimation.isRemovedOnCompletion = false
rotateAnimation.duration = duration
rotateAnimation.repeatCount=Float.infinity
self.layer.add(rotateAnimation, forKey: nil)
}
}
Any thoughts on how this is done?
You need to use a timing function that accelerates and decelerates, also known as an ease-in-ease-out timing function.
I've modified your function to use Core Animation's standard ease-in-ease-out timing function:
extension UIView {
func rotate360Degrees(duration: CFTimeInterval = 0.8) {
let rotateAnimation = CABasicAnimation(keyPath: "transform.rotation")
rotateAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
let radians = CGFloat.pi / 4
rotateAnimation.fromValue = radians
rotateAnimation.toValue = radians + .pi
rotateAnimation.isRemovedOnCompletion = false
rotateAnimation.duration = duration
rotateAnimation.repeatCount=Float.infinity
self.layer.add(rotateAnimation, forKey: nil)
}
}
Result:
Note that in your image, it looks like the box pauses every 180 degrees, so I've changed the function to rotate by only 180 degrees. Since the box has 90 degree radial symmetry, it still looks like it goes all the way around, with pauses at 180 and 360 degrees.
If you need to animate an image without any radial symmetry, you'll need to use a CAKeyframeAnimation to achieve the ease-in-ease-out at both 180 and 360 degrees.
Similar effect can also be achieved with a repeated animation with a delay.
UIView.animate(withDuration: 1,
delay: 0.2,
options: [.repeat],
animations: { imageView.transform = imageView.transform.rotated(by: CGFloat.pi) },
completion: nil)
Using this code:
func rotateTheView(_ aView: UIView, inClockwiseDirection isClockwise: Bool) {
let multiplier = (isClockwise ? 1 : -1)
let key = (isClockwise ? "Spin" : "Rotate")
var rotation: CABasicAnimation?
rotation = CABasicAnimation(keyPath: "transform.rotation")
rotation!.fromValue = Int(0)
let multiplicand = multiplier * 2
rotation!.toValue = Int(Double(multiplicand) * .pi)
rotation!.duration = 30 // Speed
rotation!.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)
rotation!.repeatCount = HUGE //HUGE_VALF Repeat forever.
aView.layer.add(rotation!, forKey: key)
}
I get the animation I want. (Either a wheel spins, or a cell rotates fast enough in the opposite direction to always remain exactly right side up).
However, when the 30 seconds (duration) is up, there is a flicker as the view jumps back to how it looked before the animation.
I understand it is supposed to work this way.
How do I apply the rotation to the "before" image so that when the duration expires I don't see any cells jump?
Increasing the duration of the animation slows the wheel's spin, so that is not an appropriate solution.
If #22521690 applies, I don't understand how - I do not have an explicit CATransaction.
Try
rotation!.toValue = Double(multiplicand) * .pi
instead of
rotation!.toValue = Int(Double(multiplicand) * .pi)
The issue is with the radian precision which is lost due to Int conversion.
On the next line after applying the animation to the layer, set the property you're animating to its ending value.
Because an animation is "in-flight", the normal display of the layer is covered the presentation layer, a special animation layer.
Once the animation is complete, the presentation layer is hidden/removed, and the actual layer is exposed. If it is a the same state as the presentation layer at the end of the animation then there's no jump.
That code might look like this:
func rotateTheView(_ aView: UIView, inClockwiseDirection isClockwise: Bool) {
let multiplier = (isClockwise ? 1 : -1)
let key = (isClockwise ? "Spin" : "Rotate")
var rotation: CABasicAnimation?
rotation = CABasicAnimation(keyPath: "transform.rotation")
rotation!.fromValue = 0.0
let multiplicand = multiplier * 2
let finalAngle = Double(multiplicand) * .pi
rotation!.toValue = finalAngle
rotation!.duration = 30 // Speed
rotation!.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear)
rotation!.repeatCount = HUGE //HUGE_VALF Repeat forever.
aView.layer.add(rotation!, forKey: key)
//-------------------
//Set the final transform on the layer to the final rotation,
//but without animation
CATransaction.begin()
CATransaction.setDisableActions(true)
let finalTransform = CATransform3DMakeRotation(CGFloat(finalAngle), 0.0, 0.0, 1.0)
aView.layer.transform = finalTransform
CATransaction.commit()
//-------------------
}
I am having a hard time trying to pause and continue from the current state of the rotation any UIView rotation technique.
Tried:
CGAffineTransformRotate
CGAffineTransformMakeRotation
CATransform3DMakeRotation
CABasicAnimation
Basically, if i call view.layer.removeAllAnimations() or, layer.speed = 0 , they all reset current rotation degree.
Also tried snapshotting the view for using the image instead the true rotation, but with no luck, since the snapshot ignored rotation.
Finally got it, with more than one answer on SO, many in objective-c, put them all together in an UIView extension, and even documented:
extension UIView {
/**
Will rotate `self` for ever.
- Parameter duration: The duration in seconds of a complete rotation (360ยบ).
- Parameter clockwise: If false, will rotate counter-clockwise.
*/
func startRotating(duration duration: Double, clockwise: Bool) {
let kAnimationKey = "rotation"
var currentState = CGFloat(0)
// Get current state
if let presentationLayer = layer.presentationLayer(), zValue = presentationLayer.valueForKeyPath("transform.rotation.z"){
currentState = CGFloat(zValue.floatValue)
}
if self.layer.animationForKey(kAnimationKey) == nil {
let animate = CABasicAnimation(keyPath: "transform.rotation")
animate.duration = duration
animate.repeatCount = Float.infinity
animate.fromValue = currentState //Should the value be nil, will start from 0 a.k.a. "the beginning".
animate.byValue = clockwise ? Float(M_PI * 2.0) : -Float(M_PI * 2.0)
self.layer.addAnimation(animate, forKey: kAnimationKey)
}
}
/// Will stop a `startRotating(duration: _, clockwise: _)` instance.
func stopRotating() {
let kAnimationKey = "rotation"
var currentState = CGFloat(0)
// Get current state
if let presentationLayer = layer.presentationLayer(), zValue = presentationLayer.valueForKeyPath("transform.rotation.z"){
currentState = CGFloat(zValue.floatValue)
}
if self.layer.animationForKey(kAnimationKey) != nil {
self.layer.removeAnimationForKey(kAnimationKey)
}
// Leave self as it was when stopped.
layer.transform = CATransform3DMakeRotation(currentState, 0, 0, 1)
}
}
Use it like yourView.startRotating(duration: 1, clockwise: true), later to stop do yourView.stopRotating().