// 创建layer并设置属性
CAShapeLayer *layer = [CAShapeLayer layer];
layer.fillColor = [UIColor clearColor].CGColor;
layer.lineWidth = 2.0f;
layer.lineCap = kCALineCapRound;
layer.lineJoin = kCALineJoinRound;
layer.strokeColor = [UIColor redColor].CGColor;
[self.view.layer addSublayer:layer];
// 创建贝塞尔路径~
UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:CGPointMake(10, 100)];
[path addLineToPoint:CGPointMake(100, 200)];
[path addLineToPoint:CGPointMake(200, 50)];
[path addLineToPoint:CGPointMake(240, 150)];
[path addLineToPoint:CGPointMake(300, 120)];
// 关联layer和贝塞尔路径~
layer.path = path.CGPath;
// 创建Animation
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
animation.fromValue = @(0.0);
animation.toValue = @(1.0);
layer.autoreverses = NO;
animation.duration = 2.0;
// 设置layer的animation
[layer addAnimation:animation forKey:nil];
// 第一种设置动画完成,不移除结果的方法
// animation.fillMode = kCAFillModeForwards;
// animation.removedOnCompletion = NO;
// 第二种
layer.strokeEnd = 1;