ios - UIPanGestureRecognizer - Only vertical or horizontal

Question

I have a view that has a UIPanGestureRecognizer to drag the view vertically. So in the recognizer callback, I only update the y-coordinate to move it. The superview of this view, has a UIPanGestureRecognizer that will drag the view horizontally, just updating the x-coordinate.

The problem is that the first UIPanGestureRecognizer is taking the event to move the view vertically, so I can not use the superview gesture.

I have tried

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
 shouldRecognizeSimultaneouslyWithGestureRecognizer:
                            (UIGestureRecognizer *)otherGestureRecognizer;

and both will work, but I don't want that. I want the horizontally to be detected only if the movement is clearly horizontal. So it would be great if the UIPanGestureRecognizer had a direction property.

How can I achieve this behavior? I find the docs very confusing, so maybe someone can explain it better here.

Answer 1

Just do this for the vertical pan gesture recognizer, it works for me:

- (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)panGestureRecognizer {
    CGPoint velocity = [panGestureRecognizer velocityInView:someView];
    return fabs(velocity.y) > fabs(velocity.x);
}

And for Swift:

func gestureRecognizerShouldBegin(_ gestureRecognizer: UIPanGestureRecognizer) -> Bool {
    let velocity = gestureRecognizer.velocity(in: someView)
    return abs(velocity.x) > abs(velocity.y)
}