ios - 如何为CGPath的绘图部分制作动画

Question

我想处理以下情况:



如果我使用CGBezierPath和CAShapeLayer绘制矩形，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];

而且我想添加动画，例如附加的图像，该空白区域会在矩形路径周围不断移动，从而使矩形的视觉效果不断出现。 [旧蛇游戏中的蛇运动]

我尝试使用CABasicAnimation制作动画，但实际上我什么都做不了，谢谢。

Answer 1

尝试使用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"];

此代码用于绘制带有动画的矩形。