- (void)viewDidLoad {
 [super viewDidLoad];
 // Do any additional setup after loading the view, typically from a nib.

 CALayer *layer = [CALayer layer];
 layer.backgroundColor = [UIColor redColor].CGColor; //圆环底色
 layer.frame = CGRectMake(100, 100, 110, 110);


 //创建一个圆环
 UIBezierPath *bezierPath = [UIBezierPath bezierPathWithArcCenter:CGPointMake(55, 55) radius:50 startAngle:0 endAngle:M_PI*2 clockwise:YES];

 //圆环遮罩
 CAShapeLayer *shapeLayer = [CAShapeLayer layer];
 shapeLayer.fillColor = [UIColor clearColor].CGColor;
 shapeLayer.strokeColor = [UIColor redColor].CGColor;
 shapeLayer.lineWidth = 5;
 shapeLayer.strokeStart = 0;
 shapeLayer.strokeEnd = 0.8;
 shapeLayer.lineCap = @"round";
 shapeLayer.lineDashPhase = 0.8;
 shapeLayer.path = bezierPath.CGPath;

 //颜色渐变
 NSMutableArray *colors = [NSMutableArray arrayWithObjects:(id)[UIColor redColor].CGColor,(id)[UIColor whiteColor].CGColor, nil];
 CAGradientLayer *gradientLayer = [CAGradientLayer layer];
 gradientLayer.shadowPath = bezierPath.CGPath;
 gradientLayer.frame = CGRectMake(50, 50, 60, 60);
 gradientLayer.startPoint = CGPointMake(0, 1);
 gradientLayer.endPoint = CGPointMake(1, 0);
 [gradientLayer setColors:[NSArray arrayWithArray:colors]];
 [layer addSublayer:gradientLayer]; //设置颜色渐变
 [layer setMask:shapeLayer]; //设置圆环遮罩
 [self.view.layer addSublayer:layer];

 //动画
 CABasicAnimation *scaleAnimation1 = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
 scaleAnimation1.fromValue = [NSNumber numberWithFloat:1.0];
 scaleAnimation1.toValue = [NSNumber numberWithFloat:1.5];
 scaleAnimation1.autoreverses = YES;
// scaleAnimation1.fillMode = kCAFillModeForwards;
 scaleAnimation1.duration = 0.8;

 CABasicAnimation *rotationAnimation2 = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
 rotationAnimation2.fromValue = [NSNumber numberWithFloat:0];
 rotationAnimation2.toValue = [NSNumber numberWithFloat:6.0*M_PI];
 rotationAnimation2.autoreverses = YES;
// scaleAnimation.fillMode = kCAFillModeForwards;
 rotationAnimation2.repeatCount = MAXFLOAT;
 rotationAnimation2.beginTime = 0.8; //延时执行，注释掉动画会同时进行
 rotationAnimation2.duration = 2;


 //组合动画
 CAAnimationGroup *groupAnnimation = [CAAnimationGroup animation];
 groupAnnimation.duration = 4;
 groupAnnimation.autoreverses = YES;
 groupAnnimation.animations = @[scaleAnimation1, rotationAnimation2];
 groupAnnimation.repeatCount = MAXFLOAT;
 [layer addAnimation:groupAnnimation forKey:@"groupAnnimation"];

}

- (void)didReceiveMemoryWarning {
 [super didReceiveMemoryWarning];
 // Dispose of any resources that can be recreated.
}
@end