Uicollectionview Header Dynamic Height Using Auto Layout

How to give a collection view section header dynamic height

None of the answers given so far are good practices since calculating the size manually or by rendering a label offscreen are both inefficient and violate the single source of truth principle.

Instances of UICollectionReusableView have the preferredLayoutAttributesFitting() method. When the cell becomes displayed, this method will be called. In this method, if you use Auto Layout, you ask the whole cell for its systemLayoutSizeFitting() and then modify the attributes. The layout will then be responsible to apply them via layout invalidation.

UICollectionView dynamic header size calculation

I finally solved the problem by constraining the width:

reusableView.translatesAutoresizingMaskIntoConstraints = true
reusableView.widthAnchor.constraint(equalToConstant: UIScreen.main.bounds.width).isActive = true

Might be that you also have to play around with content compression resistances.

UICollectionView, full width cells, allow autolayout dynamic height?

1. Solution for iOS 13+

With Swift 5.1 and iOS 13, you can use Compositional Layout objects in order to solve your problem.

The following complete sample code shows how to display multiline UILabel inside full-width UICollectionViewCell:

CollectionViewController.swift

import UIKit

class CollectionViewController: UICollectionViewController {

    let items = [
        [
            "Lorem ipsum dolor sit amet.",
            "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris. Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
            "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.",
        ],
        [
            "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt.",
            "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.",
        ],
        [
            "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt.",
            "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.",
            "Lorem ipsum. Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.",
        ]
    ]

    override func viewDidLoad() {
        super.viewDidLoad()

        let size = NSCollectionLayoutSize(
            widthDimension: NSCollectionLayoutDimension.fractionalWidth(1),
            heightDimension: NSCollectionLayoutDimension.estimated(44)
        )
        let item = NSCollectionLayoutItem(layoutSize: size)
        let group = NSCollectionLayoutGroup.horizontal(layoutSize: size, subitem: item, count: 1)

        let section = NSCollectionLayoutSection(group: group)
        section.contentInsets = NSDirectionalEdgeInsets(top: 10, leading: 10, bottom: 10, trailing: 10)
        section.interGroupSpacing = 10

        let headerFooterSize = NSCollectionLayoutSize(
            widthDimension: .fractionalWidth(1.0),
            heightDimension: .absolute(40)
        )
        let sectionHeader = NSCollectionLayoutBoundarySupplementaryItem(
            layoutSize: headerFooterSize,
            elementKind: "SectionHeaderElementKind",
            alignment: .top
        )
        section.boundarySupplementaryItems = [sectionHeader]

        let layout = UICollectionViewCompositionalLayout(section: section)
        collectionView.collectionViewLayout = layout
        collectionView.register(CustomCell.self, forCellWithReuseIdentifier: "CustomCell")
        collectionView.register(HeaderView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: "HeaderView")
    }

    override func numberOfSections(in collectionView: UICollectionView) -> Int {
        return items.count
    }

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return items[section].count
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CustomCell", for: indexPath) as! CustomCell
        cell.label.text = items[indexPath.section][indexPath.row]
        return cell
    }

    override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
        let headerView = collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: "HeaderView", for: indexPath) as! HeaderView
        headerView.label.text = "Header"
        return headerView
    }

    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        super.viewWillTransition(to: size, with: coordinator)
        coordinator.animate(alongsideTransition: { context in
            self.collectionView.collectionViewLayout.invalidateLayout()
        }, completion: nil)
    }

}

HeaderView.swift

import UIKit

class HeaderView: UICollectionReusableView {

    let label = UILabel()

    override init(frame: CGRect) {
        super.init(frame: frame)
        backgroundColor = .magenta

        addSubview(label)
        label.translatesAutoresizingMaskIntoConstraints = false
        label.centerXAnchor.constraint(equalTo: centerXAnchor).isActive = true
        label.centerYAnchor.constraint(equalTo: centerYAnchor).isActive = true
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

}

CustomCell.swift

import UIKit

class CustomCell: UICollectionViewCell {

    let label = UILabel()

    override init(frame: CGRect) {
        super.init(frame: frame)

        label.numberOfLines = 0
        backgroundColor = .orange
        contentView.addSubview(label)

        label.translatesAutoresizingMaskIntoConstraints = false
        label.topAnchor.constraint(equalTo: contentView.topAnchor).isActive = true
        label.leadingAnchor.constraint(equalTo: contentView.leadingAnchor).isActive = true
        label.trailingAnchor.constraint(equalTo: contentView.trailingAnchor).isActive = true
        label.bottomAnchor.constraint(equalTo: contentView.bottomAnchor).isActive = true
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

}

Expected display:

Sample Image

2. Solution for iOS 11+

With Swift 5.1 and iOS 11, you can subclass UICollectionViewFlowLayout and set its estimatedItemSize property to UICollectionViewFlowLayout.automaticSize (this tells the system that you want to deal with autoresizing UICollectionViewCells). You'll then have to override layoutAttributesForElements(in:) and layoutAttributesForItem(at:) in order to set cells width. Lastly, you'll have to override your cell's preferredLayoutAttributesFitting(_:) method and compute its height.

The following complete code shows how to display multiline UILabel inside full-width UIcollectionViewCell (constrained by UICollectionView's safe area and UICollectionViewFlowLayout's insets):