相关疑难解决方法(0)

我很难理解为什么动画不能像预期的那样工作.我在做什么是这样的:

1. UIBezierPath使用圆弧创建一个沿此路径移动Label并为路径描边设置动画.

   //Start Point is -.pi /2 to let the Arc start at the top.
   //self.progress = Value between 0.0 and 1.0
   let path : UIBezierPath = UIBezierPath.init(arcCenter: CGPoint.init(x: self.bounds.width * 0.5, y: self.bounds.height * 0.5), 
   radius: self.bounds.width * 0.5, startAngle: -.pi / 2, endAngle: (2 * self.progress * .pi) - (.pi / 2), clockwise: true)
   return path
   

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2. 将此路径添加到 CAShapeLayer

   circlePathLayer.frame = bounds
   circlePathLayer.path = self.path.cgPath
   circlePathLayer.strokeStart = 0
   circlePathLayer.strokeEnd = 1
   

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3. 使用a为strokeEnd属性设置动画 CABasicAnimation

   let animation = CABasicAnimation(keyPath: "strokeEnd") …

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