How can I detect the scroll direction from the UICollectionView? - ios

Question

I have a UICollectionView. I want to detect scroll direction. I have a two different animation style for scroll down and scroll up. So I must learn scroll direction.
CGPoint scrollVelocity = [self.collectionView.panGestureRecognizer
velocityInView:self.collectionView.superview];
if (scrollVelocity.y > 0.0f)
NSLog(#"scroll up");
else if(scrollVelocity.y < 0.0f)
NSLog(#"scroll down");
This is just work at finger touched. Not work for me

Answer 1

Try this:
Add this somewhere in you header:
#property (nonatomic) CGFloat lastContentOffset;
Then override the scrollViewDidScroll: method:
#pragma mark - UIScrollViewDelegate
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
if (self.lastContentOffset > scrollView.contentOffset.y)
{
NSLog(#"Scrolling Up");
}
else if (self.lastContentOffset < scrollView.contentOffset.y)
{
NSLog(#"Scrolling Down");
}
self.lastContentOffset = scrollView.contentOffset.y;
}
Found in Finding the direction of scrolling in a UIScrollView?

Answer 2

this is the best way to get scroll direction, hope this helps you
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset {
CGPoint targetPoint = *targetContentOffset;
CGPoint currentPoint = scrollView.contentOffset;
if (targetPoint.y > currentPoint.y) {
NSLog(#"up");
}
else {
NSLog(#"down");
}
}

Answer 3

Swift 4.2
private var lastContentOffset: CGFloat = 0
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if lastContentOffset > scrollView.contentOffset.y && lastContentOffset < scrollView.contentSize.height - scrollView.frame.height {
// move up
print("move up")
originalHeight ()
} else if lastContentOffset < scrollView.contentOffset.y && scrollView.contentOffset.y > 0 {
// move down
print("move down")
minimizeHeaderView()
}
// update the new position acquired
lastContentOffset = scrollView.contentOffset.y
}

Answer 4

I was trying to find a way to detect if the user is mostly trying to pull vertically or horizontally the scrollView. I give you my solution, I hope it can be useful to anyone :
CGPoint _lastContentOffset;
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
_lastContentOffset = scrollView.contentOffset;
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
if (ABS(_lastContentOffset.x - scrollView.contentOffset.x) < ABS(_lastContentOffset.y - scrollView.contentOffset.y)) {
NSLog(#"Scrolled Vertically");
} else {
NSLog(#"Scrolled Horizontally");
}
}
This work find for me and I use this to avoid the scrollView to move horizontally when scrolling vertically and opposite.