cellForItemAtIndexPath not called but numberOfItemsInSection does

Question

This could be a duplicate post but I haven't found the solution.

I'm setting my UICollectionView as:

UINib *nib = [UINib nibWithNibName:@"CollectionViewCell"
                           bundle:[NSBundle mainBundle]];
[_collectionView registerNib: nib forCellWithReuseIdentifier:@"bCell"];

(I've tried to set a delegate, without delegate, etcetera).

But then, only the

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section gets called while

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath doesn't.

I've checked the numberOfItemsInSection I return, and it's always > 0 (it's exactly 17).

I've checked to call [_collectionView reloadData]; and nothing happens either.

I've tried different things but I can't make it work.

Furthermore, my UICollectionView should be here but it's not:

enter image description here

Does anyone have a clue? Thank you.

have you added "numberofsectionsincollectionview" method..? Please put delegate and datasource methods by this we can help you more. — V.J., Jun 12 '15 at 14:15
`collectionView:cellForItemAtIndexPath:` will be called only if item exists (i.e. item present for indexPath) and are visible. For instance, what's the size of the cells? Did you put some "space" between them, etc. DO you call `reloadData` in main thread? — Larme, Jun 12 '15 at 14:22

score 59 · Accepted Answer · answered Jun 12 '15 at 14:25

59

Ok I think this could be useful for future problems with this...

It was because of constraints on the StoryBoard. I don't really understand why that happens, because I just had fixed an horizontal space. I removed the horizontal space as constraint for that View and everything works fine.

Well, let's life flow.

answered Jun 12 '15 at 14:25

Rafael Ruiz Muñoz

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I was missing a height constraint. Thanks for the hint. Saved me some time for sure. :) – Robert Gummesson Apr 04 '16 at 21:17
Ok, I know I need to find a constraint that causes this issue but I can't figure out which constraint to change. Can somebody explain how to look for? – Murat Yasar Jul 30 '16 at 11:13
1

look for the specific constraints of collectionView. In my case, the top constraint was trying to set distance with an removed element.. – Eva Madrazo Oct 05 '16 at 09:53
2

It's bizarre that this still works. :) I literally was pulling my hairs of trying to figure out what the issue was and then after I saw this, just created a height constraint and it started working. – AnBisw Jul 10 '17 at 22:29
1

Thanks you so much! I think it's kinda stupid for apple to have this issue. Maybe I don't want constraints!! – Arnaldo Capo Sep 16 '17 at 21:47
1

After days of debugging, THIS was the issue! Thanks Rafael! – Noam May 24 '18 at 03:40

score 24 · Answer 2 · answered Sep 02 '16 at 15:16

24

I also face same issue and finally got to know that i have passed wrong class object for collectionViewLayout , i change to UICollectionViewFlowLayout instead of UICollectionViewLayout while creating object for UICollectionView like below its stared calling all delegate method.

 collectionView = UICollectionView(frame: CGRectMake(5, 0, 400, 40) , collectionViewLayout: UICollectionViewFlowLayout())

answered Sep 02 '16 at 15:16

Narayana

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I just spent around 2 hours to -finally- find this mistake, I wish I could read this answer before! – Dot Freelancer Feb 01 '18 at 17:48
Wow I wish I read this before as well. Thank you. FYI for anyone else who might have created their `UICollectionView ` programmatically – Sami Jul 02 '18 at 00:17
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Thank you! Two hours of searching and found this! – Teng L Nov 30 '19 at 04:53

Vijay-Apple-Dev.blogspot.com · Answer 3 · 2015-06-12T14:35:05.160

1. cellForItemAtIndexPath will be called when you return More than 0 Items on numberOfItemsInSection method.

2. Check that your UICollectionViewFlowLayout is correct or your own. UICollectionViewLayout is abstract class you can't use it directly

3. Check the size of the collection view cell & Collection view.

4. Try to set your collectionview size by in code. [yourCollectionViewFlowLayout setItemSize:CGSizeMake(200, 200)];

5.If any of them NOT works, then kill the XCode & restart . Sometimes it will fix the issue.

Apple says

The UICollectionViewLayout class is an abstract base class that you subclass and use to generate layout information for a collection view. The job of a layout object is to determine the placement of cells, supplementary views, and decoration views inside the collection view’s bounds and to report that information to the collection view when asked. The collection view then applies the provided layout information to the corresponding views so that they can be presented onscreen.

You must subclass UICollectionViewLayout in order to use it. Before you consider subclassing, though, you should look at the UICollectionViewFlowLayout class to see if it can be adapted to your layout needs.

I didn't explain it very well, but this is what's regarding with the number: ** I've checked the count I return, and it's always > 0 (it's exactly 17). ** — Rafael Ruiz Muñoz, Jun 12 '15 at 14:07
`collectionViewContentSize` cannot be `.zero`, or else `cellForItemAt` will not be called. — DawnSong, Aug 16 '17 at 10:49

score 19 · Answer 4 · edited Mar 18 '18 at 10:45

19

I meet this problem too. I checked all the possible issues, everything looks ok. Then I tried to changed the reload methods.

[self.colView reloadData] -> [self.collectionView reloadSections:[NSIndexSet indexSetWithIndex:x]];

Then all things worked. However I still don't understand how.

edited Mar 18 '18 at 10:45

Silviu St

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answered Oct 17 '16 at 08:13

frank

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What a bug! >:( Thank you for the solution. – Thomás Pereira Feb 21 '19 at 17:34
What is the reason for it? Only this worked for me also. – e.ozmen Mar 06 '20 at 06:39
@frank What is x hear? – Muju May 28 '20 at 09:40

score 19 · Answer 5 · answered Nov 06 '16 at 10:42

19

Add this to viewDidLoad:

self.automaticallyAdjustsScrollViewInsets = NO;

answered Nov 06 '16 at 10:42

reza_khalafi

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The best answer, it wasted me a day. – Zou Nov 10 '17 at 08:37
while iOS13 fix this bug. – leo.tan Jul 13 '20 at 11:25

score 9 · Answer 6 · answered Dec 05 '16 at 18:07

9

I just found that NONE of cellForItemAtIndexPath gets called (in iOS 10) as long as at least ONE cell has a height of zero.

Disclaimer: sorry if this should have been a comment - not enough reputation.

answered Dec 05 '16 at 18:07

KiRviz

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It looks like `sizeForItemAtIndexPath` can't return zero if there is postitive `numberOfItemsInSection` for the same section – akaDuality May 04 '18 at 20:01

score 7 · Answer 7 · answered Jul 25 '18 at 07:26

For me the cellForItemAtIndexPath not called for the first time after i set the constraint of the collectionView to 0 and then again setting it to its Actual Size.

 @IBOutlet weak var collectionVwHeightContraint: NSLayoutConstraint!
 if attachments.count > 0 {

     collectionVwHeightContraint.constant = 100
 }else {

     collectionVwHeightContraint.constant = 0
 }
 // collectionVwHeightContraint is my collectionView height Contraint outlet

I solved this by calling:

self.view.layoutIfNeeded()

Hope it will help someone :)

score 3 · Answer 8 · answered Sep 24 '19 at 20:26

Might help somebody else, it could be 2 things:

Height of the cell is not calculated properly, so need to check the constraints of the cell.

To fix this, I implemented UICollectionViewLayout's method: extension TableViewCellActionItemPageControl: UICollectionViewDelegateFlowLayout {

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    return CGSize(width: 414, height: 213) 
}

Other possibility is: the size of the collection view cell returned is more that the collection view itself. Make sure the height of your cell is smaller than the height of your collective.

score 2 · Answer 9 · answered Oct 28 '15 at 01:52

2

What helped me was to set the correct itemSize. My cellForItemAtIndexPath was not being called because of the wrong height.

So I set the size at:

[self.myCollectionViewFlowLayout setItemSize:CGSizeMake(170, 300)];

answered Oct 28 '15 at 01:52

Luiz Dias

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score 1 · Answer 10 · answered Jul 05 '16 at 23:30

For me the issue was that I was creating my Collection View programmatically but I had given it CGRectZero as its frame. I was laying it out using Auto Layout after viewDidLoad. If I lay out the collection view while the view controller is loading, it ends up calling cellForItemAtIndexPath: correctly.

score 1 · Answer 11 · answered Nov 11 '17 at 22:46

1

For me it was that my collectionView's container didn't have translatesAutoresizingMaskIntoConstraints = false

answered Nov 11 '17 at 22:46

Jeremy Kelleher

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vilas deshmukh · Answer 12 · 2020-09-21T06:19:46.670

1

In my case, it was working alternatively. then I run reloadData() on the main thread and the issue fixed. But later after certain changes again the same issue arose. Finally, I made it like below. Now no issues, I feel self.view.layoutIfNeeded() plays a key role

DispatchQueue.main.async {
                self.view.layoutIfNeeded()
                self.collectionView.reloadData()
            }

edited Sep 21 '20 at 06:19

answered Sep 11 '20 at 12:14

vilas deshmukh

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score 0 · Answer 13 · answered May 31 '17 at 10:19

I had same problem with collection view outlet on a storyboard with "standard" constraints (bottom, top, leading, trailing fixed to inner view).

I solved in this way:

let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
layout.itemSize = self.collectionView.frame.size

score 0 · Answer 14 · answered Jan 24 '18 at 07:29

0

I had faced a similar problem. The issue was with the numberOfItems in section. Your cellForRowAtIndexPath might not be called if either your number of sections or number of rows in section is below zero.

answered Jan 24 '18 at 07:29

iPhoneDeveloper

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score 0 · Answer 15 · answered Mar 27 '19 at 17:23

0

In my case, I messed up with my custom cell label constraints. Verify your constraints once again.

answered Mar 27 '19 at 17:23

Madhurya Gandi

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score 0 · Answer 16 · answered Sep 19 '19 at 13:10

0

reza_khalafi answer worked for me, i am using Xcode 11 and swift 4.2. swift 4.2 version of reza's answer.

add this on viewDidLoad

self.automaticallyAdjustsScrollViewInsets = false

answered Sep 19 '19 at 13:10

Faris Muhammed

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score 0 · Answer 17 · answered Dec 04 '19 at 07:29

0

In my case, collectionViewCell's height was greater than CollectionView height.

answered Dec 04 '19 at 07:29

Niki

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score 0 · Answer 18 · answered Oct 05 '20 at 08:36

To complete @frank answer: (swifty answer)

extension UICollectionView {
   func reloadFirstSection() {
        let indexPath = IndexPath(item: 0, section: 0)
        reloadSections(IndexSet(integer: indexPath.section) )
    }
}

and then instead of collectionView.reloadData() call collectionView.reloadFirstSection()

cellForItemAtIndexPath not called but numberOfItemsInSection does

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