动画旋转

    CABasicAnimation* animation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];

    animation.fromValue = [NSNumber numberWithFloat:0.0f];

    animation.toValue = [NSNumber numberWithFloat:2 * M_PI];

    animation.duration = 2.0f;

    animation.repeatCount = HUGE_VALF;

    [circleImg.layer addAnimation:animation forKey:nil];