Horizontal Pan Inside Vertical Scrollview

Question

I have a scrollview that is limited to scrolling vertically. Inside of it I was wanting to have views that have a UIPanGestureRecognizer to only recognize horizontal pans.

As is the horizontal recognizers win and prevent the scrollview from scrolling at all.

I want the horizontal pan to win if it's detecting a mostly horizontal gesture, otherwise the vertical scroll should win. Very similar to how Mailbox works, or swiping in iOS8 Mail.app

I'm kind of shocked I haven't been able to find this after extensive searching. So apologies if it's already been answered. — Tal
In what cases do you want horizontal panning to win and in what cases do you want vertical? — Lyndsey Scott

Lyndsey Scott Lyndsey Scott · Accepted Answer · 2014-11-30T23:30:09

You could use one of the UIGestureRecognizerDelegate methods like gestureRecognizerShouldBegin: to specify which pan gesture is triggered in which situation.

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer {

    // If the gesture is a pan, determine whether it starts out more
    // horizontal than vertical than act accordingly
    if ([gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]]) {

        UIPanGestureRecognizer *panGestureRecognizer = (UIPanGestureRecognizer *)gestureRecognizer;
        CGPoint velocity = [panGestureRecognizer velocityInView:self.view];

        if (gestureRecognizer == self.scrollView.panGestureRecognizer) {
            // For the vertical scrollview, if it's more vertical than
            // horizontal, return true; else false
            return fabs(velocity.y) > fabs(velocity.x);
        } else {
            // For the horizontal pan view, if it's more horizontal than
            // vertical, return true; else false
            return fabs(velocity.y) < fabs(velocity.x);
        }
    }
    else
        return YES;
}

Horizontal Pan Inside Vertical Scrollview

1 Answers