如何动画CGPath的绘图部分

Question

我想接近以下情况：

如果我使用CGBezierPath和CAShapeLayer绘制一个矩形，如下所示：

    CAShapeLayer *layerX = [CAShapeLayer layer];
    layerX.path = path.CGPath;

    layerX.lineWidth   = 3;
    layerX.strokeColor = [[UIColor whiteColor] CGColor];
    layerX.fillColor   = [[UIColor clearColor] CGColor];

    [self.view.layer addSublayer: layerX];

我想添加动画，就像我附加的图像一样，这个被清除的区域一直在矩形路径上移动，因此它提供了一遍又一遍地绘制的矩形的视觉效果。 [老蛇游戏中的蛇运动]

我尝试使用CABasicAnimation制作动画，但事实上我无法实现任何目标。

Answer 1

尝试此代码可能会有所帮助。

    UIBezierPath *drawablePath = [UIBezierPath bezierPathWithRect:CGRectMake(100.0, 100.0, 150.0, 100.0)];
    CAShapeLayer *squareLayer = [[CAShapeLayer alloc] init];
    squareLayer.path = drawablePath.CGPath;
    squareLayer.strokeColor = [UIColor redColor].CGColor;
    squareLayer.lineWidth = 5.f;
    squareLayer.fillColor = [UIColor clearColor].CGColor;
    squareLayer.strokeEnd = 1.f;
    //squareLayer.strokeEnd = 0.9; // this line use draw half line but some animation issue.
    [self.view.layer addSublayer:squareLayer];

    CABasicAnimation *drawAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    drawAnimation.fromValue = (id)[NSNumber numberWithFloat:0.10];
    drawAnimation.toValue = (id)[NSNumber numberWithFloat:1.f];
    drawAnimation.duration = 5.f;
    drawAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    [squareLayer addAnimation:drawAnimation forKey:@"drawRectStroke"];

此代码用于绘制带动画的矩形。

Answer 2

您必须为：strokeStart和strokeEnd设置动画，并使用CAAnimationGroup使它们同时发生。

我发现这个link做了类似但快速的事情。我认为这可能会有所帮助。

如果你不能这样做，我会尝试实施它。但我现在不能。

快乐的编码。

Answer 3

    let drawablePath = UIBezierPath(rect: CGRect(x: 100, y: 100, width: 150, height: 150))
    let squareLayer = CAShapeLayer()
    squareLayer.path = drawablePath.cgPath;
    squareLayer.strokeColor = UIColor.red.cgColor;
    squareLayer.lineWidth = 5;
    squareLayer.fillColor = UIColor.clear.cgColor;
    squareLayer.strokeEnd = 1;
    //squareLayer.strokeEnd = 0.9; // this line use draw half line but some animation issue.
    flowerView.layer.addSublayer(squareLayer)

    let drawAnimation = CABasicAnimation(keyPath: "strokeEnd")
    drawAnimation.fromValue = 0.1
    drawAnimation.toValue = 1.0
    drawAnimation.duration = 5
    drawAnimation.timingFunction = CAMediaTimingFunction(name:.linear)
    squareLayer.add(drawAnimation, forKey:"drawRectStroke")

这并不是对原始问题的真正答案，但这是Dixit Akabari的答案的Swift 5版本，它本身很有用，因为它演示了如何通过对strokeEnd进行动画来绘制UIBezierPath动画。