I have a circular CAShapeLayer where I'd like to on tap, change the stroke and fill colors. To do so, I added a CABasicAnimation, but to my confusion, the animation doesn't end to the set toValue. Instead, the animation, resets back to the original color.
I tried using the animationDidStop delegate method in setting the stroke and fill colors to the desired end color, which worked, but a flashing glitch of the original colors appeared.
Any guidance would be appreciated.
func createCircleShapeLayer() {
let layer = CAShapeLayer()
let circularPath = UIBezierPath(arcCenter: view.center, radius: 50, startAngle: 0, endAngle: 2 * CGFloat.pi, clockwise: true)
layer.path = circularPath.cgPath
layer.strokeColor = UIColor.red.cgColor
layer.lineWidth = 10
layer.fillColor = UIColor.clear.cgColor
layer.lineCap = CAShapeLayerLineCap.round
layer.frame = view.bounds
view.layer.addSublayer(layer)
}
func animateLayerOnTap() {
let strokeAnim = CABasicAnimation(keyPath: "strokeColor")
strokeAnim.toValue = UIColor.red.cgColor
strokeAnim.duration = 0.8
strokeAnim.repeatCount = 0
strokeAnim.autoreverses = false
let fillAnim = CABasicAnimation(keyPath: "fillColor")
fillAnim.toValue = UIColor.lightGray.cgColor
fillAnim.duration = 0.8
fillAnim.repeatCount = 0
fillAnim.autoreverses = false
layer.add(fillAnim, forKey: "fillColor")
layer.add(strokeAnim, forKey: "strokeColor")
}
UIView animation is pretty clean and simple to use. When you submit a block-based UIView animation, the system creates an animation that animates your view's properties to their end values, and they stay there. (Under the covers UIView animation adds one or more CAAnimations to the view's layer, and manages updating the view's properties to the final values once the animation is complete, but you don't need to care about those details.)
None of that is true with Core Animation. It's confusing, non-intuitive, and poorly documented. With Core animation, the animation adds a temporary "presentation layer" on top of your layer that creates the illusion that your properties are animating from their start to the their end state, but it is only an illusion.
By default, the presentation layer is removed once the animation is complete, and your layer seems to snap back to it's pre-animation state, as you've found. There are settings you can apply that cause the animation layer to stick around in it's final state once the animation is complete, but resist the urge to do that.
Instead, what you want to do is to set your layer's properties to their end state explicitly right after the animation starts. Making that more complicated, though, is the fact that a fair number of layer properties are "implicitly animated", meaning that if you change them, the system creates an animation that makes that change for you. (In that case, the change "sticks" once the implicit animation is complete.)
You are animating strokeColor and FillColor, which are both animatable. It would be easier to take advantage of the implicit animation of those layer properties. The tricky part there is that if you want to change any of the default values (like duration) for implicit animations, you have to enclose your changes to animatable properties between a call to CATransaction.begin() and CATransaction.commit(), and use calls to CATransaction to change those values.
Here is what your code to animate your layer's strokeColor and fillColor might look like using implicit animation and a CATransaction:
CATransaction.begin()
CATransaction.setAnimationDuration(0.8)
layer.strokeColor = UIColor.red.cgColor // Your strokeColor was already red?
layer.fillColor = UIColor.lightGray.cgColor
CATransaction.commit()
I would like to animate lineCap property of a CAShapeLayer.
Here is my code:
func animate() {
let animation = CABasicAnimation(keyPath: "lineCap")
animation.toValue = CAShapeLayerLineCap.round
animation.duration = 0.3
//var progressLayer: CAShapeLayer?
progressLayer?.add(animation, forKey: "AnimationKey")
}
Nothing happens. Probably the error is in keyPath, but a can't find proper value
Line cap is not animatable according to the documentation.
https://developer.apple.com/documentation/quartzcore/cashapelayer
Take a look at the documentation:
https://developer.apple.com/documentation/quartzcore/cashapelayer/1521905-linecap
Search for the word "animatable". You won't find it (at least, not with respect to this property). So your expectation that you can animate this property is wrong.
I'm trying to make very basic animation for UIButton. The goal is rotate layer 180 degrees. Here is my animation code which is called from beginTrackingWithTouch:
private func rotateButton() {
let rotationAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
rotationAnimation.timingFunction = CAMediaTimingFunction(name: "easeIn")
rotationAnimation.toValue = M_PI
rotationAnimation.duration = CollapseButton.kCollapseButtonAnimationDuration
rotationAnimation.repeatCount = 1
rotationAnimation.cumulative = true
layer.addAnimation(rotationAnimation, forKey: "rotationAnimation")
}
Now I'd like to add collapsing view animation when tapping this button. In my VC:
__weak __typeof(self) weakSelf = self;
[UIView animateWithDuration:CollapseButton.kCollapseButtonAnimationDuration animations:^{
CGRect currentFrame = weakSelf.frame;
currentFrame.size.height = 20;
weakSelf.frame = currentFrame;
}];
I have 2 questions:
After button finishes its animation it resets layer position. So, if arrow were showing top, it animated to showing down and finally resets to top. How can I preserve layer orientation?
As you can see animation duration and timing functions are the same. For the reason I cannot understand UIView animates much slower. Any ideas?
Core animation is strange. The animation creates a "presentation layer" that generates the appearance of the change you are animating, but does not actually change the property in question.
In order to get your animation to finish with the object at the end state, you should set both a fromValue (at the starting setting) and a toValue, and then set the property to it's ending value after submitting the animation:
private func rotateButton() {
let rotationAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
rotationAnimation.timingFunction = CAMediaTimingFunction(name: "easeIn")
rotationAnimation.fromValue = 0.0 //<<--- NEW CODE
rotationAnimation.toValue = M_PI
rotationAnimation.duration = CollapseButton.kCollapseButtonAnimationDuration
rotationAnimation.repeatCount = 1
rotationAnimation.cumulative = true
layer.addAnimation(rotationAnimation, forKey: "rotationAnimation")
layer.transform = CATransformMakeRotation(M_PI) //<<--- NEW CODE
}
You can also set the animation's removeWhenFinished property to true, but that has other complications.
BTW, you should not try to manipulate the frame of a view that has a non-identity transform. Instead, set the scale on the view's transform.
I'm not sure why the 2 animations are taking different amounts of time. I do notice that you are setting the CAAnimation's timing function to easeIn, but leaving the UIView's timing function as the default (ease-in, ease-out.) That will create animations that don't look the same. You should probably set your view animation to use easeIn timing as well. (To do that you'll need to use the longer form animateWithDuration:delay:options:animations:completion:)
Before this code, my movie pic alpha is set to 0,
CABasicAnimation* fadein= [CABasicAnimation animationWithKeyPath:#"alpha"];
[fadein setToValue:[NSNumber numberWithFloat:1.0]];
[fadein setDuration:0.5];
[[moviepic layer]addAnimation:fadein forKey:#"alpha"];
Nothing happened, if I set alpha to 0.5 beforehand instead, the alpha remains at 0.5 and not animating to 1.
I've seen a code using UIView beginAnimations: around, but I'm teaching core animation so I wondered why CABasicAnimation can't do simple task like this?
[CABasicAnimation animationWithKeyPath:#"opacity"];
UIView exposes this as alpha where as CALayer exposes this as opacity.
For Swift:
let opacity = CABasicAnimation(keyPath: "opacity")
opacity.fromValue = fromValue
opacity.toValue = toValue
opacity.duration = duration
opacity.beginTime = CACurrentMediaTime() + beginTime //If a delay is needed
view.layer.add(opacity, forKey: nil)
If you want to keep the final alpha value, you have to set the current view controller as the delegate of the opacity animation:
opacity.delegate = self
And, in the delegate function animationDidStop, you should do:
extension ViewController: CAAnimationDelegate {
func animationDidStop(_ anim: CAAnimation, finished flag: Bool) {
view.alpha = toValue
}
}
#ohho answers the posted question. Mine will be a bit more generic. For a list what can and how be animated with CABasicAnimation please refer to Apple's documentation
I am rotating a CALayer and trying to stop it at its final position after animation is completed.
But after animation completes it resets to its initial position.
(xcode docs explicitly say that the animation will not update the value of the property.)
any suggestions how to achieve this.
Here's the answer, it's a combination of my answer and Krishnan's.
cabasicanimation.fillMode = kCAFillModeForwards;
cabasicanimation.removedOnCompletion = NO;
The default value is kCAFillModeRemoved. (Which is the reset behavior you're seeing.)
The problem with removedOnCompletion is the UI element does not allow user interaction.
I technique is to set the FROM value in the animation and the TO value on the object.
The animation will auto fill the TO value before it starts, and when it's removed will leave the object at it's correct state.
// fade in
CABasicAnimation *alphaAnimation = [CABasicAnimation animationWithKeyPath: #"opacity"];
alphaAnimation.fillMode = kCAFillModeForwards;
alphaAnimation.fromValue = NUM_FLOAT(0);
self.view.layer.opacity = 1;
[self.view.layer addAnimation: alphaAnimation forKey: #"fade"];
Core animation maintains two layer hierarchies: the model layer and the presentation layer. When the animation is in progress, the model layer is actually intact and keeps it initial value. By default, the animation is removed once the it's completed. Then the presentation layer falls back to the value of the model layer.
Simply setting removedOnCompletion to NO means the animation won't be removed and wastes memory. In addition, the model layer and the presentation layer won't be synchronous any more, which may lead to potential bugs.
So it would be a better solution to update the property directly on the model layer to the final value.
self.view.layer.opacity = 1;
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:#"opacity"];
animation.fromValue = 0;
animation.toValue = 1;
[self.view.layer addAnimation:animation forKey:nil];
If there's any implicit animation caused by the first line of above code, try to turn if off:
[CATransaction begin];
[CATransaction setDisableActions:YES];
self.view.layer.opacity = 1;
[CATransaction commit];
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:#"opacity"];
animation.fromValue = 0;
animation.toValue = 1;
[self.view.layer addAnimation:animation forKey:nil];
Reference:
Animations Explained by objc.io.
"iOS 7 Programming Pushing the Limits" by Rob Napier and Mugunth Kumar.
Set the following property:
animationObject.removedOnCompletion = NO;
You can simply set the key of CABasicAnimation to position when you add it to the layer. By doing this, it will override implicit animation done on the position for the current pass in the run loop.
CGFloat yOffset = 30;
CGPoint endPosition = CGPointMake(someLayer.position.x,someLayer.position.y + yOffset);
someLayer.position = endPosition; // Implicit animation for position
CABasicAnimation * animation =[CABasicAnimation animationWithKeyPath:#"position.y"];
animation.fromValue = #(someLayer.position.y);
animation.toValue = #(someLayer.position.y + yOffset);
[someLayer addAnimation:animation forKey:#"position"]; // The explicit animation 'animation' override implicit animation
You can have more information on 2011 Apple WWDC Video Session 421 - Core Animation Essentials (middle of the video)
just put it inside your code
CAAnimationGroup *theGroup = [CAAnimationGroup animation];
theGroup.fillMode = kCAFillModeForwards;
theGroup.removedOnCompletion = NO;
A CALayer has a model layer and a presentation layer. During an animation, the presentation layer updates independently of the model. When the animation is complete, the presentation layer is updated with the value from the model. If you want to avoid a jarring jump after the animation ends, the key is to keep the two layers in sync.
If you know the end value, you can just set the model directly.
self.view.layer.opacity = 1;
But if you have an animation where you don't know the end position (e.g. a slow fade that the user can pause and then reverse), then you can query the presentation layer directly to find the current value, and then update the model.
NSNumber *opacity = [self.layer.presentationLayer valueForKeyPath:#"opacity"];
[self.layer setValue:opacity forKeyPath:#"opacity"];
Pulling the value from the presentation layer is also particularly useful for scaling or rotation keypaths. (e.g. transform.scale, transform.rotation)
So my problem was that I was trying to rotate an object on pan gesture and so I had multiple identical animations on each move. I had both fillMode = kCAFillModeForwards and isRemovedOnCompletion = false but it didn't help. In my case, I had to make sure that the animation key is different each time I add a new animation:
let angle = // here is my computed angle
let rotate = CABasicAnimation(keyPath: "transform.rotation.z")
rotate.toValue = angle
rotate.duration = 0.1
rotate.isRemovedOnCompletion = false
rotate.fillMode = CAMediaTimingFillMode.forwards
head.layer.add(rotate, forKey: "rotate\(angle)")
This works:
let animation = CABasicAnimation(keyPath: "opacity")
animation.fromValue = 0
animation.toValue = 1
animation.duration = 0.3
someLayer.opacity = 1 // important, this is the state you want visible after the animation finishes.
someLayer.addAnimation(animation, forKey: "myAnimation")
Core animation shows a 'presentation layer' atop your normal layer during the animation. So set the opacity (or whatever) to what you want to be seen when the animation finishes and the presentation layer goes away. Do this on the line before you add the animation to avoid a flicker when it completes.
If you want to have a delay, do the following:
let animation = CABasicAnimation(keyPath: "opacity")
animation.fromValue = 0
animation.toValue = 1
animation.duration = 0.3
animation.beginTime = someLayer.convertTime(CACurrentMediaTime(), fromLayer: nil) + 1
animation.fillMode = kCAFillModeBackwards // So the opacity is 0 while the animation waits to start.
someLayer.opacity = 1 // <- important, this is the state you want visible after the animation finishes.
someLayer.addAnimation(animation, forKey: "myAnimation")
Finally, if you use 'removedOnCompletion = false' it'll leak CAAnimations until the layer is eventually disposed - avoid.
Without using the removedOnCompletion
You can try this technique:
self.animateOnX(item: shapeLayer)
func animateOnX(item:CAShapeLayer)
{
let endPostion = CGPoint(x: 200, y: 0)
let pathAnimation = CABasicAnimation(keyPath: "position")
//
pathAnimation.duration = 20
pathAnimation.fromValue = CGPoint(x: 0, y: 0)//comment this line and notice the difference
pathAnimation.toValue = endPostion
pathAnimation.fillMode = kCAFillModeBoth
item.position = endPostion//prevent the CABasicAnimation from resetting item's position when the animation finishes
item.add(pathAnimation, forKey: nil)
}
Simply setting fillMode and removedOnCompletion didn't work for me. I solved the problem by setting all of the properties below to the CABasicAnimation object:
CABasicAnimation* ba = [CABasicAnimation animationWithKeyPath:#"transform"];
ba.duration = 0.38f;
ba.fillMode = kCAFillModeForwards;
ba.removedOnCompletion = NO;
ba.autoreverses = NO;
ba.repeatCount = 0;
ba.toValue = [NSValue valueWithCATransform3D:CATransform3DMakeScale(0.85f, 0.85f, 1.0f)];
[myView.layer addAnimation:ba forKey:nil];
This code transforms myView to 85% of its size (3rd dimension unaltered).
#Leslie Godwin's answer is not really good, "self.view.layer.opacity = 1;" is done immediately (it takes about one second), please fix alphaAnimation.duration to 10.0, if you have doubts.
You have to remove this line.
So, when you fix fillMode to kCAFillModeForwards and removedOnCompletion to NO, you let the animation remains in the layer. If you fix the animation delegate and try something like:
- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag
{
[theLayer removeAllAnimations];
}
...the layer restores immediately at the moment you execute this line. It's what we wanted to avoid.
You must fix the layer property before remove the animation from it. Try this:
- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag
{
if([anim isKindOfClass:[CABasicAnimation class] ]) // check, because of the cast
{
CALayer *theLayer = 0;
if(anim==[_b1 animationForKey:#"opacity"])
theLayer = _b1; // I have two layers
else
if(anim==[_b2 animationForKey:#"opacity"])
theLayer = _b2;
if(theLayer)
{
CGFloat toValue = [((CABasicAnimation*)anim).toValue floatValue];
[theLayer setOpacity:toValue];
[theLayer removeAllAnimations];
}
}
}
The easiest solution is to use implicit animations. This will handle all of that trouble for you:
self.layer?.backgroundColor = NSColor.red.cgColor;
If you want to customize e.g. the duration, you can use NSAnimationContext:
NSAnimationContext.beginGrouping();
NSAnimationContext.current.duration = 0.5;
self.layer?.backgroundColor = NSColor.red.cgColor;
NSAnimationContext.endGrouping();
Note: This is only tested on macOS.
I initially did not see any animation when doing this. The problem is that the layer of a view-backed layer does not implicit animate. To solve this, make sure you add a layer yourself (before setting the view to layer-backed).
An example how to do this would be:
override func awakeFromNib() {
self.layer = CALayer();
//self.wantsLayer = true;
}
Using self.wantsLayer did not make any difference in my testing, but it could have some side effects that I do not know of.
It seems that removedOnCompletion flag set to false and fillMode set to kCAFillModeForwards doesn't work for me either.
After I apply new animation on a layer, an animating object resets to its initial state and then animates from that state.
What has to be done additionally is to set the model layer's desired property according to its presentation layer's property before setting new animation like so:
someLayer.path = ((CAShapeLayer *)[someLayer presentationLayer]).path;
[someLayer addAnimation:someAnimation forKey:#"someAnimation"];
Here is a sample from playground:
import PlaygroundSupport
import UIKit
let resultRotation = CGFloat.pi / 2
let view = UIView(frame: CGRect(x: 0.0, y: 0.0, width: 200.0, height: 300.0))
view.backgroundColor = .red
//--------------------------------------------------------------------------------
let rotate = CABasicAnimation(keyPath: "transform.rotation.z") // 1
rotate.fromValue = CGFloat.pi / 3 // 2
rotate.toValue = resultRotation // 3
rotate.duration = 5.0 // 4
rotate.beginTime = CACurrentMediaTime() + 1.0 // 5
// rotate.isRemovedOnCompletion = false // 6
rotate.fillMode = .backwards // 7
view.layer.add(rotate, forKey: nil) // 8
view.layer.setAffineTransform(CGAffineTransform(rotationAngle: resultRotation)) // 9
//--------------------------------------------------------------------------------
PlaygroundPage.current.liveView = view
Create an animation model
Set start position of the animation (could be skipped, it depends on your current layer layout)
Set end position of the animation
Set animation duration
Delay animation for a second
Do not set false to isRemovedOnCompletion - let Core Animation clean after the animation is finished
Here is the first part of the trick - you say to Core Animation to place your animation to the start position (you set in step #2) before the animation has even been started - extend it backwards in time
Copy prepared animation object, add it to the layer and start the animation after the delay (you set in step #5)
The second part is to set correct end position of the layer - after the animation is deleted your layer will be shown at the correct place