CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
    animation.fromValue = [NSNumber numberWithFloat:0.f];
    animation.toValue = [NSNumber numberWithFloat:M_PI * 2];
    animation.duration = 1;
    animation.autoreverses = NO;
    animation.fillMode = kCAFillModeForwards;
    animation.repeatCount = MAXFLOAT;
    animation.removedOnCompletion = NO;
    [self.loadingImageView.layer addAnimation:animation forKey:nil];

有时动画无效,下面的代码有效.

    animation.removedOnCompletion = NO;