Question

我试图在屏幕上每秒创建一个新的动画线。每一秒我都会得到一条新线，但它会覆盖旧线。我不知道为什么，但它可能是我忽略的愚蠢行为。这是我的代码：

func repeatThis() {
    for x in 1...10 {
        let time = dispatch_time(dispatch_time_t(DISPATCH_TIME_NOW), Int64(x) * Int64(NSEC_PER_SEC))
        dispatch_after(time, dispatch_get_main_queue()) {
            var topLinePatha: UIBezierPath {
                return UIBezierPath(rect: CGRect(x: 0, y: 0 + (x * 10), width: 1, height: 10))
            }

            var topLinePathb: UIBezierPath {
                return UIBezierPath(rect: CGRect(x: 0, y: 0 + (x * 10), width: Int(UIScreen.mainScreen().bounds.width), height: 10))
            }

            let expAnimation: CABasicAnimation = CABasicAnimation(keyPath: "path")
            expAnimation.fromValue = topLinePatha.CGPath
            expAnimation.toValue = topLinePathb.CGPath
            expAnimation.duration = self.animationTime
            expAnimation.fillMode = kCAFillModeForwards
            expAnimation.removedOnCompletion = false
            self.addAnimation(expAnimation, forKey: nil)
            print(x)
        }
    }
}

感谢您的帮助

编辑1：

这是我在动画时机中遇到的问题，基本上动画会互相覆盖：

func repeatThis() {
    var runningPath = UIBezierPath()

    for x in 0...10 {
        delay(Double(x) / 10) {
            let topLineStartPath = UIBezierPath(rect: CGRect(x: 0, y: x * 10, width: 1, height: 10))
            let topLineEndPath = UIBezierPath(rect: CGRect(x: 0, y: x * 10, width: Int(self.bounds.width), height: 10))

            let fullStartPath = runningPath.copy() as! UIBezierPath
            fullStartPath.appendPath(topLineStartPath)
            let fullEndPath = runningPath.copy() as! UIBezierPath
            fullEndPath.appendPath(topLineEndPath)

            let expAnimation: CABasicAnimation = CABasicAnimation(keyPath: "path")
            expAnimation.fromValue = fullStartPath.CGPath
            expAnimation.toValue = fullEndPath.CGPath
            expAnimation.duration = self.animationTime
            expAnimation.fillMode = kCAFillModeForwards
            expAnimation.removedOnCompletion = false
            self.addAnimation(expAnimation, forKey: nil)
            print(x)

            runningPath = fullEndPath
        }
    }
}

func delay(delay:Double, closure:()->()) {
    dispatch_after(
        dispatch_time(
            DISPATCH_TIME_NOW,
            Int64(delay * Double(NSEC_PER_SEC))
        ),
        dispatch_get_main_queue(), closure)
}

Answer 1

每次动画时，您的代码都会替换CAShapeLayer的路径，因此对于您设置动画的每个“线”，都会丢失过去的行。

要显示多行，您可以：

使用方法UIBezierPath.appendPath为CAShapeLayer的路径添加多个子路径，每个路径一个。
使用多个CAShapeLayer s，每行一个。

这是备选方案＃1，与您当前的代码相比变化较小。这是一个自包含的示例，您可以在名为ViewController的视图控制器中添加到新的iOS项目中。

import UIKit

class MyShapeLayer: CAShapeLayer {
    var animationTime: NSTimeInterval = 0.75

    func repeatThis() {
        // Keep track of the path so far
        var runningPath = UIBezierPath()

        for x in 1...10 {
            let time = dispatch_time(dispatch_time_t(DISPATCH_TIME_NOW), Int64(x) * Int64(NSEC_PER_SEC))
            dispatch_after(time, dispatch_get_main_queue()) {
                // We will add a rectangular subpath onto runningPath.
                // It will be animated starting with:
                let topLineStartPath = UIBezierPath(rect: CGRect(x: 0, y: x * 10, width: 1, height: 10))
                // and ending with:
                let topLineEndPath = UIBezierPath(rect: CGRect(x: 0, y: x * 10, width: Int(self.bounds.width), height: 10))

                // Copy the running path, and add the starting and ending subpaths onto it
                let fullStartPath = runningPath.copy() as! UIBezierPath
                fullStartPath.appendPath(topLineStartPath)
                let fullEndPath = runningPath.copy() as! UIBezierPath
                fullEndPath.appendPath(topLineEndPath)

                // Animate from fullStartPath to fullEndPath
                let expAnimation: CABasicAnimation = CABasicAnimation(keyPath: "path")
                expAnimation.fromValue = fullStartPath.CGPath
                expAnimation.toValue = fullEndPath.CGPath
                expAnimation.duration = self.animationTime
                expAnimation.fillMode = kCAFillModeForwards
                expAnimation.removedOnCompletion = false
                self.addAnimation(expAnimation, forKey: nil)
                print(x)

                // The next time through the loop, add on to this iteration's ending path
                runningPath = fullEndPath
            }
        }
    }
}

class MyView: UIView {
    override class func layerClass() -> AnyClass {
        return MyShapeLayer.self
    }
}

class ViewController: UIViewController {
    override func loadView() {
        self.view = MyView()
        self.view.backgroundColor = UIColor.whiteColor()
    }

    override func viewDidLoad() {
        if let myShapeLayer = self.view.layer as? MyShapeLayer {
            myShapeLayer.repeatThis()
        }
    }
}

结果：

这是一种替代＃2的方法。我使animationTime更长，所以你可以看到每行的动画可以重叠。

class LineAtATimeView: UIView {
    var animationTime = 1.25    // longer duration so line animations overlap

    func repeatAddingLines() {
        for x in 1...10 {
            let time = dispatch_time(dispatch_time_t(DISPATCH_TIME_NOW), Int64(x) * Int64(NSEC_PER_SEC))
            dispatch_after(time, dispatch_get_main_queue()) {
                let newLayer = CAShapeLayer()
                newLayer.frame = self.bounds
                self.layer.addSublayer(newLayer)

                let topLineStartPath = UIBezierPath(rect: CGRect(x: 0, y: x * 10, width: 1, height: 10))
                let topLineEndPath = UIBezierPath(rect: CGRect(x: 0, y: x * 10, width: Int(self.bounds.width), height: 10))

                let expAnimation: CABasicAnimation = CABasicAnimation(keyPath: "path")
                expAnimation.fromValue = topLineStartPath.CGPath
                expAnimation.toValue = topLineEndPath.CGPath
                expAnimation.duration = self.animationTime
                expAnimation.fillMode = kCAFillModeForwards
                expAnimation.removedOnCompletion = false
                newLayer.addAnimation(expAnimation, forKey: nil)
            }
        }
    }
}

class ViewController2: UIViewController {
    override func loadView() {
        self.view = LineAtATimeView()
        self.view.backgroundColor = UIColor.whiteColor()
    }

    override func viewDidLoad() {
        if let v = self.view as? LineAtATimeView {
            v.repeatAddingLines()
        }
    }
}

对于循环覆盖动画

1 个答案: