ios 下滑 转动图片

if(!_flag){
_firstY = scrollView.contentOffset.y*-1;
_flag = YES;
}else {
_currentY = (scrollView.contentOffset.y*-1 -64);

}

YLLog(@"%f",_currentY);

int x = _currentY /100 * 180;//arc4random() % 360;
// 计算秒针转多少度
//CGFloat secondA = x * perSecondA;
_secondLayer.transform = CGAffineTransformMakeRotation(x *M_PI / 180.0);