[英]CALayer animation beginTime
我正在为iOS开发一个关键帧动画编辑器,该编辑器允许用户创建简单的动画并查看它们,并根据时间线进行绘制。 用户可以拖动时间线以更改当前时间。
这意味着我需要能够在用户指定的时间开始动画。
尽管可以实现此功能,但每次将动画重新添加到图层时,我也会遇到烦人的故障。 该故障会导致动画的第一帧在CoreAnimation遵守开始时间之前快速闪烁。 通过在刷新前将layer.alpha设置为0,在刷新后将layer.alpha设置为1,可以稍微减轻这种效果,但是这仍然会导致讨厌的单帧闪光!
我已经重新创建了一个示例视图控制器,该示例控制器演示了“更改正在运行的动画的时间”所需的代码,但是由于该项目是如此简单,因此您看不到冲洗的负面影响: https://gist.github .com / chrisbirch / 5cafca50804cf9d778ccd0fdc9e68d56
该代码的基本思想如下:
每次用户更改当前时间时,我都会重新启动动画,并使用CALayer计时属性进行调整(addStoppedAnimation:line 215):
ani = createGroup()
animatableLayer.speed = 0
animatableLayer.add(ani, forKey: "an animation key")
let time = CFTimeInterval(slider.value)
animatableLayer.timeOffset = 0
animatableLayer.beginTime = animatableLayer.superlayer!.convertTime(CACurrentMediaTime(), from: nil) - time
CATransaction.flush()
animatableLayer.timeOffset = time// offset
print("Time changed \(time)")
故障是由于我必须在设置timeOffset之前立即调用CATransaction.flush引起的。 未能调用此刷新会导致开始时间被忽略。
我觉得我已经搜寻了整个互联网,以寻求解决此问题的方法,但是Im,我认为我陷入了困境。
我的问题是这样的:
任何人都可以阐明为什么我需要调用CATransaction.flush才能使我设置的beginTime值生效吗? 查看苹果代码,我从来没有见过为此目的使用冲洗功能,所以也许我遇到了明显的错误!
提前谢谢了
克里斯
使用您的要旨中的测试代码,我已经对其进行了更新以检查动画,从而无需阅读它。 您可以使用唯一的ID来跟踪所有动画并将其存储在具有视图属性的字典中。 我没有实现这部分,但这就是我将要做的。 希望我足够了解您的问题。 另外,我使用Xcode 9,但不确定代码是否相同。 我更改了一些逻辑部分,所以让我知道是否可以解决问题。
UUID().uuidString //for unique string in implementation
//from your code just slightly altered.
//
// ViewController.swift
// CATest
//
// CATestViewController.swift
// SimpleCALayerTest
import UIKit
class CATestViewController: UIViewController, CAAnimationDelegate{
var slider : UISlider!
var animatableLayer : CALayer!
var animationContainerView : UIView!
var centerY : CGFloat!
var startTranslationX : CGFloat!
var endTranslationX : CGFloat!
let duration = 10.0
///boring nibless view setup code
override func loadView() {
let marginX = CGFloat(10)
let marginY = CGFloat(10)
let view = UIView(frame: CGRect(x: 0, y: 0, width: 400, height: 400))
view.backgroundColor = .lightGray
slider = UISlider(frame: CGRect(x: marginX, y: 0, width: 200, height: 50))
slider.maximumValue = Float(duration)
slider.addTarget(self, action: #selector(sliderChanged(_:)), for: .valueChanged)
slider.addTarget(self, action: #selector(sliderDragStart(_:)), for: .touchDown)
slider.addTarget(self, action: #selector(sliderDragEnd(_:)), for: .touchUpInside)
//A view to house an animated sublayer
animationContainerView = UIView(frame: CGRect(x: marginX, y: 50, width: 200, height: 70))
//add a play button that will allow the animation to be played without hindrance from the slider
let playButton = UIButton(frame: CGRect(x: marginX, y: animationContainerView.frame.maxY + marginY, width: 200, height: 50))
playButton.setTitle("Change Frame", for: .normal)
playButton.addTarget(self, action: #selector(playAnimation), for: .touchUpInside)
view.addSubview(playButton)
//add a stopped ani button that will allow the animation to be played using slider
let addStoppedAniButton = UIButton(frame: CGRect(x: playButton.frame.origin.x, y: playButton.frame.maxY + marginY, width: playButton.frame.width, height: playButton.frame.size.height))
addStoppedAniButton.setTitle("Pause", for: .normal)
addStoppedAniButton.addTarget(self, action: #selector(cmPauseTapped(_:)), for: .touchUpInside)
view.addSubview(addStoppedAniButton)
let animatableLayerWidth = animationContainerView.bounds.width / CGFloat(4)
centerY = animationContainerView.bounds.midY
startTranslationX = animatableLayerWidth / CGFloat(2)
endTranslationX = animationContainerView.bounds.width - animatableLayerWidth / CGFloat(2)
animationContainerView.backgroundColor = .white
animationContainerView.layer.borderColor = UIColor.black.withAlphaComponent(0.5).cgColor
animationContainerView.layer.borderWidth = 1
view.addSubview(slider)
view.addSubview(animationContainerView)
//Now add a layer to animate to the container
animatableLayer = CALayer()
animatableLayer.backgroundColor = UIColor.yellow.cgColor
animatableLayer.borderWidth = 1
animatableLayer.borderColor = UIColor.black.withAlphaComponent(0.5).cgColor
var r = animationContainerView.bounds.insetBy(dx: 0, dy: 4)
r.size.width = animatableLayerWidth
animatableLayer.frame = r
animationContainerView.layer.addSublayer(animatableLayer)
self.view = view
}
@objc func cmPauseTapped(_ sender : UIButton){
if animatableLayer.speed == 0{
resume()
}else{
pause()
}
}
@objc func sliderChanged(_ sender: UISlider){
if animatableLayer.speed == 0{
let time = CFTimeInterval(sender.value)
animatableLayer.speed = 0
animatableLayer.timeOffset = time// offset
print("Time changed \(time)")
}
}
var animations = [CAAnimation]()
func addAnimations(){
let ani = CAAnimation()
animations.append(ani)
}
@objc func sliderDragStart(_ sender: UISlider)
{
if animatableLayer.speed > 0{
animatableLayer.speed = 0
}
addStoppedAnimation()
}
func pause(){
//just updating slider
if slider.value != Float(animatableLayer.timeOffset){
UIView.animate(withDuration: 0.3, animations: {
self.slider.setValue(Float(self.animatableLayer.timeOffset), animated: true)
})
}
animatableLayer.timeOffset = animatableLayer.convertTime(CACurrentMediaTime(), from: nil)
animatableLayer.speed = 0
}
func resume(){
if let _ = animatableLayer.animationKeys()?.contains("an animation key"){
animatableLayer.speed = 1.0;
let pausedTime = animatableLayer.timeOffset
animatableLayer.beginTime = 0.0;
let timeSincePause = animatableLayer.convertTime(CACurrentMediaTime(), from: nil) - pausedTime
animatableLayer.beginTime = timeSincePause;
return
}
print("Drag End with need to readd animation")
ani = createGroup()
animatableLayer.speed = 1
animatableLayer.add(ani, forKey: "an animation key")
let time = CFTimeInterval(slider.value)
animatableLayer.timeOffset = time
animatableLayer.beginTime = CACurrentMediaTime()
}
@objc func sliderDragEnd(_ sender: UISlider){
resume()
}
//Animations
var ani : CAAnimationGroup!
func createGroup() -> CAAnimationGroup
{
let ani = CAAnimationGroup()
ani.isRemovedOnCompletion = false
ani.duration = 10
ani.delegate = self
ani.animations = [createTranslationAnimation(),createColourAnimation()]
return ani
}
func createTranslationAnimation() -> CAKeyframeAnimation
{
let ani = CAKeyframeAnimation(keyPath: "position")
ani.delegate = self
ani.isRemovedOnCompletion = false
ani.duration = 10
ani.values = [CGPoint(x:0,y:centerY),CGPoint(x:endTranslationX,y:centerY)]
ani.keyTimes = [0,1]
return ani
}
func createColourAnimation() -> CAKeyframeAnimation
{
let ani = CAKeyframeAnimation(keyPath: "backgroundColor")
ani.delegate = self
ani.isRemovedOnCompletion = false
ani.duration = 10
ani.values = [UIColor.red.cgColor,UIColor.blue.cgColor]
ani.keyTimes = [0,1]
return ani
}
func animationDidStop(_ anim: CAAnimation, finished flag: Bool) {
print("Animation Stopped")
}
func animationDidStart(_ anim: CAAnimation) {
print("Animation started")
}
func addStoppedAnimation()
{
if let _ = animatableLayer.animationKeys()?.contains("an animation key"){
slider.value += 0.5
sliderChanged(slider)
return
//we do not want to readd it
}
ani = createGroup()
animatableLayer.speed = 0
animatableLayer.add(ani, forKey: "an animation key")
let time = CFTimeInterval(slider.value)
animatableLayer.timeOffset = time
animatableLayer.beginTime = CACurrentMediaTime()
}
@objc func playAnimation(){
addStoppedAnimation()
}
}
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