[英]How can I change toValue/fromValue of CABasicAnimation while the animation is on
我正在嘗試更改動畫為heartBeatAnimation
的CABasicAnimation的toValue / fromValue的值
let heartBeatAnimation = CABasicAnimation(keyPath: "transform.scale.xy")
heartBeatAnimation.duration = 0.75
heartBeatAnimation.repeatCount = Float.infinity
heartBeatAnimation.autoreverses = true
heartBeatAnimation.fromValue = 1.0
heartBeatAnimation.toValue = 1.15
當動畫打開時,我在動畫期間通過以下命令獲取transform.scale
的當前值:
let currentValue = someView.layer.presentation()?.value(forKeyPath: "transform.scale")
heartBeatAnimation.fromValue = currentValue
heartBeatAnimation.toValue = currentValue
更改值后, heartBeatAnimation
不會更改其toValue/fromValue
直到我刪除動畫然后再次添加!
有沒有辦法在動畫播放時實時進行這些更改?
您可以通過將模型層的當前比例更新為表示層的比例,然后通過對beginTime屬性進行更新來讀取動畫來使它實時顯示,從而使動畫看起來從未停止過。 這是一個例子。
import UIKit
class ViewController: UIViewController {
var scale : CGFloat = 1.2
var shapeLayer : CAShapeLayer!
var button : UIButton!
override func viewDidLoad() {
super.viewDidLoad()
//add a shapelayer
shapeLayer = CAShapeLayer()
shapeLayer.frame = CGRect(x: 0, y: 0, width: self.view.bounds.width/4, height: self.view.bounds.width/4)
shapeLayer.position = self.view.center
shapeLayer.path = drawStarPath(frame: shapeLayer.bounds).cgPath
let color = UIColor(red: 0.989, green: 1.000, blue: 0.000, alpha: 1.000)
shapeLayer.fillColor = color.cgColor
self.view.layer.addSublayer(shapeLayer)
//button for action
button = UIButton(frame: CGRect(x: 0, y: 0, width: self.view.bounds.width - 20, height: 50))
button.center = self.view.center
button.center.y = self.view.bounds.height - 70
button.addTarget(self, action: #selector(ViewController.pressed(sender:)), for: .touchUpInside)
button.setTitle("Animate", for: .normal)
button.setTitleColor(.blue, for: .normal)
self.view.addSubview(button)
}
@objc func pressed(sender:UIButton) {
var isInterupted = false
if let presentation = shapeLayer.presentation(){
if let animScale = presentation.value(forKeyPath: "transform.scale.xy"){
if let value = animScale as? CGFloat{
//set current animation spot
shapeLayer.transform = CATransform3DScale(CATransform3DIdentity, value, value, 1)
shapeLayer.removeAllAnimations()
scale += 0.2
isInterupted = true
print("The current toValue is \(scale)")
}
}
}
button.setTitle("Animating...", for: .normal)
let heartBeatAnimation = CABasicAnimation(keyPath: "transform.scale.xy")
heartBeatAnimation.duration = 0.5
let beginTimeNeeded = (1/scale) * CGFloat(heartBeatAnimation.duration)
heartBeatAnimation.repeatCount = .greatestFiniteMagnitude
heartBeatAnimation.autoreverses = true
heartBeatAnimation.fromValue = 1.0
heartBeatAnimation.toValue = scale
if isInterupted == true{
heartBeatAnimation.beginTime = CFTimeInterval(beginTimeNeeded)
}
heartBeatAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
shapeLayer.add(heartBeatAnimation, forKey: "beatAnimation")
}
func drawStarPath(frame: CGRect = CGRect(x: 0, y: 0, width: 140, height: 140)) ->UIBezierPath{
//// Star Drawing
let starPath = UIBezierPath()
starPath.move(to: CGPoint(x: frame.minX + 0.50000 * frame.width, y: frame.minY + 0.21071 * frame.height))
starPath.addLine(to: CGPoint(x: frame.minX + 0.60202 * frame.width, y: frame.minY + 0.35958 * frame.height))
starPath.addLine(to: CGPoint(x: frame.minX + 0.77513 * frame.width, y: frame.minY + 0.41061 * frame.height))
starPath.addLine(to: CGPoint(x: frame.minX + 0.66508 * frame.width, y: frame.minY + 0.55364 * frame.height))
starPath.addLine(to: CGPoint(x: frame.minX + 0.67004 * frame.width, y: frame.minY + 0.73404 * frame.height))
starPath.addLine(to: CGPoint(x: frame.minX + 0.50000 * frame.width, y: frame.minY + 0.67357 * frame.height))
starPath.addLine(to: CGPoint(x: frame.minX + 0.32996 * frame.width, y: frame.minY + 0.73404 * frame.height))
starPath.addLine(to: CGPoint(x: frame.minX + 0.33492 * frame.width, y: frame.minY + 0.55364 * frame.height))
starPath.addLine(to: CGPoint(x: frame.minX + 0.22487 * frame.width, y: frame.minY + 0.41061 * frame.height))
starPath.addLine(to: CGPoint(x: frame.minX + 0.39798 * frame.width, y: frame.minY + 0.35958 * frame.height))
return starPath
}
}
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