UICollectionView cells with round pictures plus rotation assist

Round cells inside a group view

Reaching the objective is comparatively simple, but when you do not know what is going on on within the background it may be more durable than you’ll suppose first. So let’s create a brand new challenge add a storyboard with a UICollectionViewController, drag a UIImageView contained in the cell, resize it, add some constraints, set the cell identifier.

It ought to look one thing just like the picture above. Nothing particular only a easy UI for our instance utility. Now seek for some random picture, add it to the challenge and let’s do some actual coding. First I will present you the little trick within the cell subclass.

class Cell: UICollectionViewCell {

    @IBOutlet weak var imageView: UIImageView!

    override var bounds: CGRect {
        didSet {
            layoutIfNeeded()
        }
    }

    override func awakeFromNib() {
        tremendous.awakeFromNib()

        imageView.layer.masksToBounds = true
    }

    override func layoutSubviews() {
        tremendous.layoutSubviews()

        setCircularImageView()
    }

    func setCircularImageView() {
        imageView.layer.cornerRadius = CGFloat(
            roundf(Float(imageView.body.measurement.width / 2.0))
        )
    }
}

Are you able to see it? Sure, you need to override the bounds property. As the subsequent step we’ve to write down the controller class with some fundamental information supply for the gathering view and with the correct assist for the rotation strategies. 🤓

class ViewController: UICollectionViewController {

    override func collectionView(
        _ collectionView: UICollectionView,
        numberOfItemsInSection part: Int
    ) -> Int {
        30
    }

    override func collectionView(
        _ collectionView: UICollectionView,
        cellForItemAt indexPath: IndexPath
    ) -> UICollectionViewCell {

        let cell = collectionView.dequeueReusableCell(
            withReuseIdentifier: "Cell", 
            for: indexPath
        ) as! Cell

        cell.imageView.picture = UIImage(named: "Instance.jpg")
        cell.imageView.backgroundColor = .lightGray

        return cell
    }

    override func traitCollectionDidChange(
        _ previousTraitCollection: UITraitCollection?
    ) {
        tremendous.traitCollectionDidChange(previousTraitCollection)

        guard
            let previousTraitCollection = previousTraitCollection,
            traitCollection.verticalSizeClass != previousTraitCollection.verticalSizeClass ||
            traitCollection.horizontalSizeClass != previousTraitCollection.horizontalSizeClass
        else {
            return
        }

        collectionView?.collectionViewLayout.invalidateLayout()
        collectionView?.reloadData()
    }

    override func viewWillTransition(
        to measurement: CGSize, 
        with coordinator: UIViewControllerTransitionCoordinator
    ) {
        tremendous.viewWillTransition(to: measurement, with: coordinator)

        collectionView?.collectionViewLayout.invalidateLayout()

        coordinator.animate(alongsideTransition: { context in

        }, completion: { context in
            collectionView?.collectionViewLayout.invalidateLayout()

            collectionView?.visibleCells.forEach { cell in
                guard let cell = cell as? Cell else {
                    return
                }
                cell.setCircularImageView()
            }
        })
    }
}

extension ViewController: UICollectionViewDelegateFlowLayout {

    func collectionView(
        _ collectionView: UICollectionView,
        structure collectionViewLayout: UICollectionViewLayout,
        sizeForItemAt indexPath: IndexPath
    ) -> CGSize {
        .init(
            width: collectionView.body.measurement.width/3.0 - 8,
            top: collectionView.body.measurement.width/3.0 - 8
        )
    }
}

In case you are accustomed to assortment views, you may ask why am I doing this tutorial? It is so easy. It simply works, proper? No, truly with out the overridden bounds property the instance would look one thing like this on the left aspect. 😢

Humorous, huh? The picture on the best aspect is the precise consequence with the overridden bounds, that is the anticipated conduct. Scrolling and rotation goes to be actually unusual should you do not override bounds and you do not reset the cornerRadius property for the seen views. You may ask: however why? 🤔

Layers, springs & struts and a few clarification

Apple nonetheless has “Springs & Struts” primarily based code within UIKit. Because of this body and certain calculations are taking place within the underlying system and the constraint system is making an attempt to work arduous as nicely to determine the correct measures.

“Springs & Struts” must die!

Whereas there may be an init(body:) technique, or a required init(coder:) these structure issues will suck as hell. I actually like Interface Builder, however till we can’t get a high-quality instrument to create nice consumer interfaces IB goes to be simply one other layer of potential bugs.

This concern will not even be there should you create the cell from code solely utilizing auto structure constraints or structure anchors! It is as a result of IB creates the cell primarily based on the body you gave in when you designed your prototype. However should you overlook init(body:) and also you simply create a brand new UIImageView occasion and let auto structure do the arduous work, the structure system will remedy the whole lot else. Test this.

class Cell: UICollectionViewCell {

    weak var imageView: UIImageView!

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

    override init(body: CGRect) {
        tremendous.init(body: body)

        translatesAutoresizingMaskIntoConstraints = false

        let imageView = UIImageView()
        imageView.translatesAutoresizingMaskIntoConstraints = false
        addSubview(imageView)
        imageView = imageView

        imageView.topAnchor.constraint(equalTo: topAnchor)
        imageView.bottomAnchor.constraint(equalTo: bottomAnchor)
        imageView.leadingAnchor.constraint(equalTo: leadingAnchor)
        imageView.trailingAnchor.constraint(equalTo: trailingAnchor)
    }

    override func layoutSubviews() {
        tremendous.layoutSubviews()

        imageView.layer.masksToBounds = true
        imageView.layer.cornerRadius = CGFloat(
            roundf(Float(imageView.body.measurement.width/2.0))
        )
    }
}

Clearly you need to write extra code, register your cell class manually contained in the controller class and also you additionally need to override the layoutSubviews technique contained in the cell, nevertheless it’ll work as it’s anticipated. 🙄

collectionView?.register(Cell.self, forCellWithReuseIdentifier: "Cell")

Anyway, after you register the programmatically created cell you may have a pleasant approach of displaying round pictures. Utilizing this method is sort of difficult, nevertheless it undoubtedly works in each case. You possibly can obtain the instance from The.Swift.Dev. tutorials on GitHub.