UICollectionView: One Row or Column

Question

I want to use UICollectionView to display a horizontal scrollable list of thumbnails, however, I want this to be a single row. On another view, I'm displaying the thumbnails in a UICollectionView but this one scrolls vertically and it's in a single column.

Currently, the way I'm doing this is by changing the size of the collection view to only be big enough for one item so it autowraps and works, but now I'm dealing with variable sized items so it doesn't work anymore.

How do you make a UICollectionView display one row or column?

Answer 1

I am guessing you are using the built in Flow Layout. However, for your case, you should make a custom UICollectionView Layout. Make it subclass of UICollectionViewFlowLayout and add this code in the init method:

- (id)init {
    if ((self = [super init])) {
        self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
        self.minimumLineSpacing = 10000.0f;
    }
    return self; 
}

The minimumLineSpacing is the key to making it have one line here.

I hope this helps!

Answer 2

I found that setting the minimumLineSpacing just made my scroll area really big and that setting the minimumInteritemSpacing=big accomplished keeping the items in one scrolling row or column, centered in the middle of the collectionview.

Answer 3

There isn't a real reason to subclass if you can trust the type cast.

((UICollectionViewFlowLayout *)self.collectionView.collectionViewLayout).minimumLineSpacing = 1000.0f;

If you have your collectionView loaded from a nib you could also play around with the parameters in the Attributes and Size Inspectors.

Same goes for scroll direction.

Answer 4

In iOS 13, thanks to UICollectionViewCompositionalLayout, this is trivial, because you can specify the number of cells per column in a horizontal layout, or the number of cells per row in a vertical layout. Here's a simple example for a single horizontally scrolling, vertically centered row of cells:

func layout() -> UICollectionViewCompositionalLayout {
    let itemSize = NSCollectionLayoutSize(
        widthDimension: .fractionalWidth(1),
        heightDimension: .fractionalHeight(1))
    let item = NSCollectionLayoutItem(layoutSize: itemSize)
    let groupSize = NSCollectionLayoutSize(
        widthDimension: .absolute(75),
        heightDimension: .absolute(75))
    let group = NSCollectionLayoutGroup.vertical(
        layoutSize: groupSize, subitem: item, count: 1) // *
    group.edgeSpacing = NSCollectionLayoutEdgeSpacing(
        leading: nil, top: .flexible(0),
        trailing: nil, bottom: .flexible(0))
    let section = NSCollectionLayoutSection(group: group)
    section.interGroupSpacing = 65
    let config = UICollectionViewCompositionalLayoutConfiguration()
    config.scrollDirection = .horizontal
    let layout = UICollectionViewCompositionalLayout(
        section: section, configuration:config)
    return layout
}

Set your collection view's collectionViewLayout to the output of that function call and you're all set.

Answer 5

When you init your UICollectionView pass the following UICollectionViewFlowLayout in the init parameter.

Note: You do not need to create a subclass of UICollectionViewFlowLayout

var collectionViewFlowControl = UICollectionViewFlowLayout()
collectionViewFlowControl.scrollDirection = UICollectionViewScrollDirection.Horizontal

For 0 px Cell Spacing:

collectionViewFlowControl.minimumInteritemSpacing = 0;
collectionViewFlowControl.minimumLineSpacing = 0;

collectionView = UICollectionView(frame: CGRectMake(0, 0, self.view.frame.size.width, 120), collectionViewLayout: collectionViewFlowControl)

Answer 6

For Swift 3

let flowLayout = UICollectionViewFlowLayout()
flowLayout.itemSize = CGSize(width: UIScreen.main.bounds.width/2-10, height: 190)
flowLayout.sectionInset = UIEdgeInsetsMake(0, 5, 0, 5)
flowLayout.scrollDirection = UICollectionViewScrollDirection.horizontal
flowLayout.minimumInteritemSpacing = 0.0
self.gCollectionView.collectionViewLayout = flowLayout

Answer 7

I wanted one column, left aligned and the other answers didn't help me.

So here is my very simple solution for one column, left aligned:

class GCOneColumnLeftAlignedFlowLayout: UICollectionViewFlowLayout {
    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        let attributes = super.layoutAttributesForElements(in: rect)

        var y: CGFloat = sectionInset.top
        attributes?.forEach { layoutAttribute in
            layoutAttribute.frame.origin.x = sectionInset.left
            layoutAttribute.frame.origin.y = y
            y = y + layoutAttribute.frame.height + minimumLineSpacing
        }

        return attributes
    }
}

you also should set something like

estimatedItemSize = CGSize(width: 120, height: 40)

Don't forget to remove the line

minimumLineSpacing = big number

From the other solutions.

Hope this is helpful because it's a completely different approach compared to the other answers.

Answer 8

This worked for me to get a single row of cells regardless of the height of the CollectionView. Set the Min spacing for cells to 1000

Answer 9

I think the documentation is the best :

minimumLineSpacingForSectionAt:

For a vertically scrolling grid, this value represents the minimum spacing between successive rows. For a horizontally scrolling grid, this value represents the minimum spacing between successive columns. This spacing is not applied to the space between the header and the first line or between the last line and the footer.

minimumInteritemSpacingForSectionAt:

For a vertically scrolling grid, this value represents the minimum spacing between items in the same row. For a horizontally scrolling grid, this value represents the minimum spacing between items in the same column. This spacing is used to compute how many items can fit in a single line, but after the number of items is determined, the actual spacing may possibly be adjusted upward.

So if your scrollDirection is horizontal, you need to set minimumInteritemSpacingForSectionAt to CGFloat.greatestFiniteMagnitude and if your scrollDirection is vertical, you need to set minimumLineSpacingForSectionAt to CGFloat.greatestFiniteMagnitude for getting one row collectionView

Answer 10

 UICollectionViewFlowLayout *layout=[[UICollectionViewFlowLayout alloc] init];
 [layout setScrollDirection:UICollectionViewScrollDirectionHorizontal];

 layout.minimumInteritemSpacing = 0;
 layout.minimumLineSpacing = 0;


 blendEffectCollectionView=[[UICollectionView alloc] initWithFrame:CGRectMake(0, 95, 320, 60) collectionViewLayout:layout];
 [blendEffectCollectionView setDataSource:self];
 [blendEffectCollectionView setDelegate:self];
 [blendEffectCollectionView registerClass:[BlendModeCell class] forCellWithReuseIdentifier:@"cellIdentifier"];
 [blendEffectCollectionView setBackgroundColor:[UIColor clearColor]];

 [bottomActivityView addSubview:blendEffectCollectionView];

Answer 11

2022, for anyone using TVOS

Thanks to the great answer from @matt we know how to do this now.

I found two insurmountable problems in TVOS project.

1. There's basically a bug where it inserts a large left content inset for some reason. The only way to get rid of it is to override safeAreaInsets.

2. Separate issue: Strangely if you just set the layout "inline" in the view controller as in the accepted answer from @matt, there's a bug or misbehaviour where the scroll does not start properly on the left, but in a random central position. (Even worse if you have many of the collection views on the screen, they all behave erraticlly.) Miraculously if you subclass instead, for some reason that fixes it (I guess due to the bringup order somehow).

Hence

class TightCollectionView: UICollectionView {
    override var safeAreaInsets: UIEdgeInsets {
        get {
            return UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0)
        }
        set {
        }
    }
    

and then ...

    func layout() -> UICollectionViewCompositionalLayout {
        let itemSize = NSCollectionLayoutSize(widthDimension: .absolute(500), heightDimension: .absolute(300))
        let item = NSCollectionLayoutItem(layoutSize: itemSize)
        
        let groupSize = NSCollectionLayoutSize(widthDimension: .absolute(500), heightDimension: .absolute(300))
        let group = NSCollectionLayoutGroup.vertical(layoutSize: groupSize, subitem: item, count: 1) // one count for single row
        
        group.edgeSpacing = NSCollectionLayoutEdgeSpacing(leading: .fixed(0), top: .fixed(0), trailing: .fixed(0), bottom: .fixed(0))
        
        let section = NSCollectionLayoutSection(group: group)
        section.interGroupSpacing = 20
        
        let config = UICollectionViewCompositionalLayoutConfiguration()
        config.scrollDirection = .horizontal
        
        let layout = UICollectionViewCompositionalLayout(section: section, configuration:config)
        return layout
    }
    

and thus ...

    var bringup: Bool = true // I hate doing this but there's no really solid alternative in UIKit, thanks Apple
    
    override func layoutSubviews() {
        if bringup {
            collectionViewLayout = layout()
            bringup = false
        }
        super.layoutSubviews()
    }
}

Footnote - note that code like this:

        // section.contentInsetsReference = .none
        // config.contentInsetsReference = .none

Seemingly does nothing at all on TVOS. I fiddled with it for hours.

Footnote

.absolute(500)

I could really only get solid results on all gen. of TVOS by just setting everything absolutely in the compositional layout. For now (2022!) it just seems too flakey otherwise.