/**核心代码 */

CABasicAnimation* rotationAnimation;

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

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

rotationAnimation.duration = duration;

rotationAnimation.cumulative = YES;

rotationAnimation.repeatCount = repeat;

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