uiview 永久旋转动画

- (void)startAnimation

{

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

    rotationAnimation.toValue = [NSNumber numberWithFloat: M_PI * 2.0 ];

    rotationAnimation.duration = 2;

    rotationAnimation.cumulative = YES;

    rotationAnimation.repeatCount = HUGE_VALF;

    [_cloudArrow.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];

}

- (void)stopAnimation

{

    [_cloudArrow.layer removeAllAnimations];

}