Question

我正在尝试使用以下方式绘制圆圈：

func drawProgressCircle(with endAngle: CGFloat) {
    let progressBezierPath = UIBezierPath(arcCenter: CGPoint(x: self.frame.width / 2, y: self.frame.width / 2), radius: self.frame.width / 2.5, startAngle: -CGFloat(Double.pi / 2), endAngle: endAngle, clockwise: true)
    let progressShapeLayer = CAShapeLayer()
    progressShapeLayer.path = progressBezierPath.cgPath

    progressShapeLayer.strokeColor = UIColor.brown.cgColor
    progressShapeLayer.fillColor = UIColor.clear.cgColor
    progressShapeLayer.lineWidth = 15.0

    // Do not draw initially. Wait for animation
    progressShapeLayer.strokeEnd = 0.0

    // Make corners rounded
    progressShapeLayer.lineCap = kCALineCapRound

    self.layer.addSublayer(progressShapeLayer)
    self.animate(circleWith: progressShapeLayer, from: -CGFloat(Double.pi / 2), to: endAngle, with: 2.0)
}

并为其设置动画我称之为此功能：

func animate(circleWith shapeLayer: CAShapeLayer, from: CGFloat, to: CGFloat, with duration: TimeInterval) {
    // We want to animate the strokeEnd property of the circleLayer
    let animation = CABasicAnimation(keyPath: "strokeEnd")

    // Set the animation duration appropriately
    animation.duration = duration

    // Animate from start point to end point
    animation.fromValue = from
    animation.toValue = to

    // Do a linear animation (i.e. the speed of the animation stays the same)
    animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)

    // Set the circleLayer's strokeEnd property to 1.0 now so that it's the
    // right value when the animation ends.
    shapeLayer.strokeEnd = 1.0

    // Do the actual animation
    shapeLayer.add(animation, forKey: "animate")
}

但我不知道为什么它没有动画。画布是空的，在2秒内它就会出现在画布上。没有任何动画。

有什么问题？为什么它没有动画画？

Answer 1

替换动画formValue＆amp; toValue by：

// Animate from start point to end point
animation.fromValue = 0
animation.toValue = 1

基本上，keyPath CABasicAnimation的{{1}}并不知道您正在绘制一个圆圈，它只是从0到1的动画。如果你给stroke一个0.5的值，它只会动画到路径的一半。

它与keyPath toValue的{{1}}不同，后者将CGPoint用于CABasicAnimation和position。

动画在Swift中绘制圆圈的奇怪问题

1 个答案: