在《CALayer 自定义属性绘制动画》中讲解通过CALayer 自定义动画属性绘制圆，使用CABasicAnimation添加绘制动画，下面通过CGPath绘制圆使用CAKeyframeAnimation添加绘制动画

 

UIBezierPath *path = [UIBezierPathbezierPathWithArcCenter:CGPointMake(20, 20) radius:20 startAngle:0 endAngle:2*M_PIclockwise:0];

   

CAKeyframeAnimation *animation = [CAKeyframeAnimationanimationWithKeyPath:@"strokeEnd"];

animation.values = @[@(0.0f),@(1.0f)];

animation.duration = 10.0f;

animation.repeatCount = MAXFLOAT;

   

CAShapeLayer *layer = [CAShapeLayer layer];

layer.frame = CGRectMake(10, 100, 40, 40);

layer.path = path.CGPath;

layer.lineWidth = 3.0f;

layer.fillColor = [UIColorwhiteColor].CGColor;

layer.strokeColor = [UIColorredColor].CGColor;

[layer addAnimation:animation forKey:@"angle_key"];