UIScrollView velocity 0 while decelerating

Question

I need to detect the user scroll direction to prevent wrong swipe. I use this following code

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

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


            if (fabs(velocity.y) * 2 < fabs(velocity.x))
            {
                //scroll LEFT or RIGHT 
                return NO;
            }
            else
            {
                //scroll UP or DOWN 
            }


         return YES;
}

it works in most case, except if the user scroll while the scrollview is decelerating, then the velocity factor is null, and i can't calculate the scroll direction.

EDIT 1

similar problem : link

set the contentsize to width of screen and it won't scroll to left to right — Ahmad Ishfaq, May 18 '16 at 19:50
i use a vertical collectionView inside an horizontal pageViewController. When the user scroll up/down the collectionView, i need to prevent ambigus left/right swipe. it works except when the collectionView is decelerating. — Julie Bsd, May 18 '16 at 20:05

score 1 · Answer 1 · edited May 23 '17 at 10:28

1

I think the simplest solution will be to detect the scroll direction directly on the UIScrollViewDelegate. Have a look at this answer

edited May 23 '17 at 10:28

Community

1
1

answered May 18 '16 at 20:01

Julien Quere

2,407
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i need to know the direction inside the `- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer` method to block any wrong gestures – Julie Bsd May 19 '16 at 16:46

UIScrollView velocity 0 while decelerating

1 Answers1