Detect direction of UIScrollView scroll in scrollViewWillBeginDragging

Question

I did google enough, & I did check posts like these ( Finding the direction of scrolling in a UIScrollView? ) in stackoverflow before posting this. I have a dynamic numb

Answer 1

Building off of @Oscar's answer, you can do things like

scrollView.bounces = actualPosition.y < 0 if you want the scrollView to bounce when you scroll to the bottom but not when you scroll to the top

Answer 2

Swift 3 Solution

1- Add UIScrollViewDelegate

2- Add this code

func scrollViewWillBeginDecelerating(_ scrollView: UIScrollView) {
    let actualPosition = scrollView.panGestureRecognizer.translation(in: scrollView.superview)
    if (actualPosition.y > 0){
        // Dragging down
    }else{
        // Dragging up
    }
}

Answer 3

I had no issues determining direction in scrollViewWillBeginDragging when checking the scroll view's panGestureRecognizer:

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{ 
    CGPoint translation = [scrollView.panGestureRecognizer translationInView:scrollView.superview];

    if(translation.y > 0)
    {
        // react to dragging down
    } else
    {
        // react to dragging up
    }
}

I found it very useful in canceling out of a scroll at the very first drag move when the user is dragging in a forbidden direction.

Answer 4

There seem to be issues with detecting scroll direction based on the translation of the scrollView's pan recognizer in iOS 7+. This seems to be working pretty seamlessly for my purposes

func scrollViewDidScroll(scrollView: UIScrollView) {
    if !scrollDirectionDetermined {
        let translation = scrollView.panGestureRecognizer.translationInView(self.view)
        if translation.y > 0 {
            println("UP")
            scrollDirectionDetermined = true
        }
        else if translation.y < 0 {
            println("DOWN")
            scrollDirectionDetermined = true
        }
    }
}

func scrollViewWillBeginDragging(scrollView: UIScrollView) {
    scrollDirectionDetermined = false
}

func scrollViewDidEndDecelerating(scrollView: UIScrollView) {
    scrollDirectionDetermined = false
}

Answer 5

scrollView.panGestureRecognizer translationInView:scrollView doesn't report anything useful in scrollViewWillBeginDragging in iOS 7.

This does:

In the @interface

BOOL scrollDirectionDetermined;

and:

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    if (!scrollDirectionDetermined) {
        if ([scrollView.panGestureRecognizer translationInView:scrollView.superview].x > 0) {
            //scrolling rightwards
        } else {
             //scrolling leftwards
       }
    scrollDirectionDetermined = YES;
    }
}

and:

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    scrollDirectionDetermined = NO;
}

Answer 6

For swift 2.0+ & ios 8.0+

func scrollViewWillBeginDecelerating(scrollView: UIScrollView) {
    let actualPosition = scrollView.panGestureRecognizer.translationInView(scrollView.superview)
    if (actualPosition.y > 0){
        // Dragging down 
    }else{
        // Dragging up
    }
}