滚动方向

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

 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。

floatlastContentOffset;

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{

    lastContentOffset = scrollView.contentOffset.y;

}

 

- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView{

    if(lastContentOffset < scrollView.contentOffset.y) {

        NSLog(@"向上滚动");

    }else{

        NSLog(@"向下滚动");

    }

}