How to know in which way UITableView is being scrolled - iphone

Question

Is there any way in which we can know if a UITableView is being scrolled in upward direction or downward direction?

Answer 1

-(void) scrollViewDidScroll:(UIScrollView *)scrollView
{
CGPoint currentOffset = scrollView.contentOffset;
if (currentOffset.y > self.lastContentOffset.y)
{
// Downward
}
else
{
// Upward
}
self.lastContentOffset = currentOffset;
}

Answer 2

-(void)scrollViewWillEndDragging:(UIScrollView *)scrollView
withVelocity:(CGPoint)velocity
targetContentOffset:(inout CGPoint *)targetContentOffset{
if (velocity.y > 0){
NSLog(#"up");
}
if (velocity.y < 0){
NSLog(#"down");
}
}

Answer 3

Could we do like this?
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
if ([scrollView.panGestureRecognizer translationInView:scrollView].y > 0) {
// down
} else {
// up
}
}

Answer 4

UITableView is a UIScrollView subclass, thus you can set yourself as the UIScrollViewDelegate and get scroll view delegate callbacks.
The argument for one of these delegate methods (-scrollViewDidScroll:) is the scroll view that did scroll, you can compare it to your table views to know which one it was that scrolled.
Sorry, I misread your question. I thought you wanted to know which table view is being scrolled (I missed the "way").
To know the direction you can keep the previous offset in a variable and see if the delta (current.y - previous.y) is positive (scrolling down) or negative (scrolling up).

Answer 5

You can track the difference in content offset. Keep the old one in a member/static variable and check against the current. If the old value it's lower then the scrolling was directed downwards and vice versa.

Answer 6

override func scrollViewWillEndDragging(scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
if targetContentOffset.memory.y < scrollView.contentOffset.y {
//println("Going up!")
} else {
// println("Going down!")
}
}

Answer 7

You can do this by implementing UIScrollView's delegate method in this way, it's graceful.
PS: lastOffset and scrollingUpward is property of ViewController.
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
CGPoint currentOffset = scrollView.contentOffset;
self.scrollingUpward = currentOffset.y > self.lastOffset.y;
self.lastOffset = currentOffset;
}

Answer 8

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
if (yourTableView.isDragging || yourTableView.isDecelerating)
{
// your tableview is scrolled.
// Add your code here
}
}
Here you have to replace your tableview name instead of "yourTableView".
yourTableView.isDragging - It returns YES if user has started scrolling. this may require some time and or distance to move to initiate.
yourTableView.isDecelerating - It returns YES if user isn't dragging (touch up) but scroll view is still moving.