如何判断uiscrollview是向上滚动还是向下滚动

有时候我们需要检测当前UIScrollView的滑动方向来做出相应的处理,可以借助UIScrollView的delegate函数来实现,
下面的例子可以检测到UIScrollview当前是向上滑动还是向下滑动：
[cpp] view plaincopyprint?
int _lastPosition; //A variable define in headfile

- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
int currentPostion = scrollView.contentOffset.y;
if (currentPostion - _lastPosition > 25) {
_lastPosition = currentPostion;
NSLog(@"ScrollUp now");
}
else if (_lastPosition - currentPostion > 25)
{
_lastPosition = currentPostion;
NSLog(@"ScrollDown now");
}
}
25 可以是任意数字,可根据自己的需要来设定.