UICollectionReusableView method not being called

Question

I want my sections in the UICollectionView to have a header with an image.

I have followed these steps:

at the storyboard, assigned a header as an accessory for my UICollectionView
gave it an identifier
created a subclass of UICollectionReusableView for it
assigned the custom class to the class at the storyboard.
put an ImageView at the header accessory
made an outlet for the ImageView at the custom class in the .h file
Implemented the following at viewDidLoad:

[self.collectionView registerClass:[ScheduleHeaderView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:headerIdentifier];

-(UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
    UICollectionReusableView *reusableview = nil;

    if (kind == UICollectionElementKindSectionHeader)
    {
        ScheduleHeaderView *headerView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:headerIdentifier forIndexPath:indexPath];

        headerView.headerImageView.image = [UIImage imageNamed:@"blah.png"];

        reusableview = headerView;
    }

    return reusableview;
}

I know that the datasource and delegate methods are working because I can see all the cells and its sections. However, I don't have my headers. I put in a breakpoint at the method above and it's never being called.

What am i doing wrong?

Note that you compare the string pointers `kind == UICollectionElementKindSectionHeader` instead of the strings contents, you probably want to use `[kind isEqualToString: UICollectionElementKindSectionHeader]` instead. — Mac_Cain13, Apr 03 '14 at 11:31

score 207 · Accepted Answer · edited Sep 05 '20 at 09:59

207

It seems that you have to give your header a non-zero size or collectionView:viewForSupplementaryElementOfKind:atIndexPath isn't called. So either set the headerReferenceSize property of the flow layout like so:

flowLayout.headerReferenceSize = CGSizeMake(self.collectionView.frame.size.width, 100.f);

Swift 5+

flowLayout.headerReferenceSize = CGSize(CGSize(width: self.collectionView.frame.size.width, height: 100))

or, implement collectionView:layout:referenceSizeForHeaderInSection if you want to vary the size by section.

edited Sep 05 '20 at 09:59

Naveed Ahmad

6,199
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answered Aug 11 '13 at 16:41

rdelmar

102,832
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1

in collection view, can i do for dynamic height by autolayout instead of defining headerReference size? – Khant Thu Linn Dec 01 '16 at 08:21
is it possible to set headerReferenceSize in Storyboard on flowLayout? – Radek Wilczak Jul 18 '17 at 09:13
1

Yes It Worked ! layout.headerReferenceSize = CGSize(width: (self.collectionView?.frame.width)!, height: 50); for swift4 – Antony Ouseph Mar 04 '18 at 03:46
`headerReferenceSize` works but I need different sizes for different sections. And the method you specified isn't called at all – Vyachaslav Gerchicov Jun 25 '20 at 10:01

score 33 · Answer 2 · edited Jun 11 '15 at 07:28

You answered the question, but in words I understand better:

To make the method being called, add these methods:

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section {
    return CGSizeMake(60.0f, 30.0f);
}

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section {
    return CGSizeMake(60.0f, 30.0f);
}

...and go from there.

score 32 · Answer 3 · answered Oct 12 '17 at 21:44

32

Swift 4 Xcode 9.1 Beta 2

Add @objc

@objc func collectionView(_ collectionView: UICollectionView, layout  collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize{
    let size = CGSize(width: 400, height: 50)
    return size
}

Credits: https://medium.com/@zonble/your-delegation-methods-might-not-be-called-in-swift-3-c6065ed7b4cd

answered Oct 12 '17 at 21:44

cwilliamsz

686
9
20

Thank you! Saved my butt. Btw, I noticed this function doesn't show up in the auto-complete list for collectionViewDelegate. I don't know why, so weird. Also weird that we need the @objc tag in front of it. – C0D3 Dec 13 '17 at 19:16
3

Only adding @objc to the function in Swift 4 worked for me. Ridiculous. – Louis Cremen Jan 25 '18 at 06:36
7

Conforming to UICollectionViewDelegateFlowLayout instead of UICollectionViewDelegate also fixes this without @objc if you're using UICollectionViewFlowLayout. – nemissm Apr 10 '18 at 12:16
it is a lot better if you use the collectionView bounds to set the with of your section header/footer: let size = CGSize(collectionView.bounds.width, height: 50) – omaestra Mar 20 '19 at 15:17

score 18 · Answer 4 · edited Aug 06 '19 at 08:53

18

Did you add UICollectionViewDelegateFlowLayout in current interface? This worked for me.

@interface MyViewController () <UICollectionViewDelegateFlowLayout>

Swift:

class MyViewController: UICollectionViewDelegateFlowLayout {

edited Aug 06 '19 at 08:53

Kerberos

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answered Jan 17 '15 at 04:13

CheshireKat

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Ahh! so this is it...`UICollectionViewDelegateFlowLayout` – Ayan Sengupta Jul 20 '16 at 07:19

score 9 · Answer 5 · edited Aug 06 '19 at 08:53

9

Swift 3.0 (xcode 8.2.1)

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
    return CGSize(width:collectionView.frame.size.width, height:30.0)
}

edited Aug 06 '19 at 08:53

Kerberos

3,656
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answered Jan 17 '17 at 18:54

Zeeshan

3,886
25
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score 5 · Answer 6 · answered Aug 15 '16 at 12:57

There is the swift version :

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
    let size = CGSize(width: 400, height: 50)
    return size
}

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize {
    let size = CGSize(width: 400, height: 50)
    return size
}

XCode (version 7.3.1 ) does not propose these methods in autocomplete !

If you just want a header, just keep the header method.

score 3 · Answer 7 · answered Apr 20 '20 at 11:19

    @objc (collectionView:viewForSupplementaryElementOfKind:atIndexPath:)
    func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView { }

The above code worked for me

score 2 · Answer 8 · answered Feb 18 '17 at 16:38

2

My problem was that in swift 3, the name of the viewForSupplementaryElementOfKind function has changed slightly from any posts that were on stack overflow. Hence, it was never getting called. Make sure that, if you're in swift 3, you're delegate function matches:

func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {}

answered Feb 18 '17 at 16:38

Daniel Jones

882
7
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Mine too. For me there was a missing "_", "atIndexPath" instead of "at" and "NSIndexPath" instead of "IndexPath"; as I have copied the method from somewhere and IDE didn't give me an error. – Ashkan Sarlak Jan 01 '18 at 12:59

score 1 · Answer 9 · edited Aug 06 '19 at 08:54

1

I have the same issue. I have added referenceSizeForFooterInSection but then also viewForSupplementaryElementOfKind not getting called. I have added this code in viewDidLoad() and it worked for me:

if let flowLayout = self.collectionView.collectionViewLayout as? UICollectionViewFlowLayout {
    flowLayout.sectionFootersPinToVisibleBounds = true   
}

edited Aug 06 '19 at 08:54

Kerberos

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answered Jan 31 '19 at 13:17

Twinkle

21
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score 1 · Answer 10 · answered Feb 13 '21 at 15:24

Swift 5 Smooth and easy way

only these two line are missing in your code and you will done

use these line any where

let layout = self.colv.collectionViewLayout as! UICollectionViewFlowLayout
layout.headerReferenceSize = CGSize(width: self.colv.frame.size.width, height: 100)

I am using these lines in

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    let CellCount = CGFloat(3.0)
    let width = CGFloat(collectionView.frame.size.width/CellCount)
    //let height = CGFloat(collectionView.frame.size.height)

    
    let layout = self.colv.collectionViewLayout as! UICollectionViewFlowLayout

    layout.headerReferenceSize = CGSize(width: self.colv.frame.size.width, height: 100)
    
    return CGSize(width: width, height: width+10)
}

score 0 · Answer 11 · answered May 07 '19 at 12:38

For me, in Swift 4.2, func collectionView(collectionView:kind:indexPath:) -> UICollectionReusableView was never being called. This was for a collection view in a UIViewController. I noticed the existing collection view functions were qualified with @objc, and that the UICollectionView had not adopted the UICollectionViewDataSource and UICollectionViewDelegate protocols. As soon as I adopted the protocols, I got errors that the collection view functions did not match the protocol. I corrected the function syntax, removed the qualifiers, and the section headers started working.

score 0 · Answer 12 · answered Oct 31 '20 at 22:06

If you've got a generic subclass then you must take care to specify ObjC delegate method name if it's different then Swift name (https://bugs.swift.org/browse/SR-2817).

@objc (collectionView:viewForSupplementaryElementOfKind:atIndexPath:)
func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
...

UICollectionReusableView method not being called

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