Detect touch position on UiScrollView

Question

I need to get the touch position from a UIScrollView. But when I create a subclass for my scrollview :

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
  NSArray *touchesArray = [touches allObjects];
  UITouch *touch = (UITouch *)[touchesArray objectAtIndex:0];
  CGPoint point = [touch locationInView:self];
  self.position = point;}

The function touchesBegan isn't always called. If I swipe fast, touchesBegan is never called, but scrollViewDidScroll gets directly called instead.

I can't use UIGesture (UITapGestureRecognizer, ... ) because users don't tap or swipe.

Are there others methods to get the position from UIScrollView ?

EDIT :

Thanks ThXou : https://stackoverflow.com/a/15763450/1752843

UIScrollView subclass :

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event{
    self.position = point;
    return self;
}

iVenky · Accepted Answer · 2013-04-02 11:30:50Z

7

To detect the touch location inside scrollview, try this code

UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(singleTapGestureCaptured:)];
[scrollView addGestureRecognizer:singleTap]; 

- (void)singleTapGestureCaptured:(UITapGestureRecognizer *)gesture
 { 
   CGPoint touchPoint=[gesture locationInView:scrollView];
 }

edited Apr 2, 2013 at 11:30

answered Apr 2, 2013 at 11:13

iVenky

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4 Comments

VivienCormier Over a year ago

But the function "touchesBegan" or "touchesMoved" are never called when my scrollview is scrolled. And I want to get the touch when my scrollview is used.

VivienCormier Over a year ago

Even though "touchesBegan" is empty, her are never called.

iVenky Over a year ago

Sorry try the above code. other method is yu need to call the sub classes . For further details, check out this link iosdevelopertips.com/user-interface/…

bob Over a year ago

To detect touchesBegan and touchesMoved, sub-classing is NOT required. You can add the UIScrollViewDelegate to the "h" file and applicable functions to detect touches based on user intention. See stackoverflow.com/questions/993280/…

rounak · Accepted Answer · 2014-02-21 12:15:43Z

3

You could alternatively use scrollview.panGestureRecognizer's locationInView method to get the coordinates of a touch in your view. This could be in any of scrollView's delegate method depending on your requirements.

answered Feb 21, 2014 at 12:15

rounak

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Comments

Community · Accepted Answer · 2017-05-23 12:06:40Z

2

I saw an answer in SO that I think that it can solve you problem. It seems that the SDK doesn't pass the touch handling methods to the UIScrollView subclasses anymore. So, you should to perform a hitTest: to pass the touches to your subclass.

See the answer for more information.

edited May 23, 2017 at 12:06

CommunityBot

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answered Apr 2, 2013 at 11:54

thxou

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1 Comment

VivienCormier Over a year ago

Thx! My code : '- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event{ self.position = point; return self; }'

Łukasz Gierałtowski · Accepted Answer · 2017-09-13 11:12:23Z

1

scrollView.delaysContentTouches = NO;

It will makes that touchesBegan and other touch events will be triggered before scrollViewDidScroll.

The hitTest is a hack and should not be preferred solution.

edited Sep 13, 2017 at 11:12

answered Sep 12, 2017 at 9:18

Łukasz Gierałtowski

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