Comments on: UIScrollView Paging Hack

By: Theo

Theo — Thu, 21 Jul 2011 18:46:36 +0000

If you change scrollViewDidEndDragging to:

- (void)scrollViewDidEndDragging:(UIScrollView *)_scrollView willDecelerate:(BOOL)decelerate {
if(!decelerate)
[self snapToPosition:_scrollView];
}

It seems to be a lot cleaner. That way the scrollViewDidDecelerate deals with when the scroll view is flicked and the scrollViewDidEndDragging deals with when the user doesn’t flick.

Minor change to fix some unstable behaviour and conflict between the two methods that I thought might be useful to share. Really helpful otherwise. Thanks

By: Roland

Roland — Mon, 04 Jul 2011 02:37:55 +0000

Hi,

Thanks for the post. I found it extremely useful. The current design implies that the width of the view is twice that of the images or whatever uiview. In my case, I needed to make the center view large, hence making the left and right placeholders are smaller. Here’s the math that works: (monotouch C#)

float messageWidth = 550f, scrollerWidth = 1024f,
initialOffset = (1024f-550f)/2f;

svMessagesView.Scrolled += delegate(object sender, EventArgs e) {
UIScrollView s = (UIScrollView)sender;
float offset = s.ContentOffset.X/(scrollerWidth/initialOffset/2f);
CGAffineTransform transform = CGAffineTransform.MakeTranslation(offset, 0);
messageContainer.Transform = transform;
};

initialOffset – are the widths of the slices on the sides.

By: Mark

Mark — Sun, 06 Mar 2011 01:33:11 +0000

For me it works pretty well, but when the parameter “decelerate” is YES, it doesn’t snap.
The parameter “decelerate” is YES when you drag fast then release your finger to let the scrollView scroll alone with the inertial scrolling.
How do I miss to make it work in any case?

By: Praveen

Praveen — Fri, 04 Mar 2011 11:18:21 +0000

Can you please tell me how to implement paging with 8 uiviews per page and also having the ui being more responsible.

By: Peter

Peter — Thu, 09 Dec 2010 18:40:17 +0000

works flawlessly, with little modification you can set any paging size you want.

ludo: if u want your images in middle of screen u need to set right positions for images in contentView, considering your new paging size

By: ludo

ludo — Thu, 22 Apr 2010 12:53:55 +0000

Don’t need to approve my older post, its working now ^^

RickiG I use your method and divide my scrollView into 3 parts, everything is working fine.
Now what I want is everytime an image appear in the middle of the scrollView and stop, I will display some information related to that Image into my view.

But I don’t know how to do that. How can I know which image is in the middle of the scrollView?

Thanks

By: ludo

ludo — Thu, 22 Apr 2010 05:21:04 +0000

Hi,

Maybe someone can help me here. I have a scrollView with some pictures inside (10 pictures)
and the screen can display 3 pictures.
I want to be able to divide my scrollView in 3 parts, so when I scroll it will scroll part by part.

How can I do that? I can’t make any of your code really work.

Thank you

By: RickiG

RickiG — Sat, 05 Dec 2009 21:11:16 +0000

Hi
I just found this post and had to do something similar. My issue was that I would like to divide an entire page into X smaller pages but still have the snap effect. This works really well:

- (void)scrollViewDidEndDecelerating:(UIScrollView *)_scrollView {

[self snapToPosition:_scrollView];
}
- (void)scrollViewDidEndDragging:(UIScrollView *)_scrollView willDecelerate:(BOOL)decelerate {

[self snapToPosition:_scrollView];
}

- (void) snapToPosition:(UIScrollView *)_scrollView {

CGFloat itemWidth = 80.0f;
CGFloat position = [_scrollView contentOffset].x;
CGFloat newPosition = 0.0f;
CGFloat offSet = position / itemWidth;
NSUInteger target = (NSUInteger)(offSet + 0.5f);

newPosition = target * itemWidth;

[_scrollView setContentOffset:CGPointMake(newPosition, 0.0f) animated:YES];
}

itemWidth is the size of the smaller subviews I build the content of the scrollView from.

By: james

james — Thu, 23 Jul 2009 18:44:37 +0000

jochen: When using a scrollview, you generally need to add some subviews that contain the actual content to be scrolled. Instead of putting those subviews in the scrollview directly, you should add them to what I’m calling a container view, and then add the container view to the scrollview. If you’re still confused, I’d recommend checking out Apple’s documentation on using scrollviews and make sure you’re comfortable with their normal use before you try this technique.

By: jochen

jochen — Thu, 23 Jul 2009 16:14:56 +0000

can you please explain, how “contentView” in your example is created/used? It would be perfect, if you could provide a complete controller-code for this example…!

best regards & thanks