UICollectionView cells with round photographs plus rotation assist

Round cells inside a set view

Reaching the purpose is comparatively simple, but when you do not know what is going on on within the background it should be more durable than you’ll assume first. So let’s create a brand new mission 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 software. Now seek for some random picture, add it to the mission and let’s do some actual coding. First I am going to 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.dimension.width / 2.0))
        )
    }
}

Are you able to see it? Sure, you need to override the bounds property. As the subsequent step we now have to write down the controller class with some primary information supply for the gathering view and with the right 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 dimension: CGSize, 
        with coordinator: UIViewControllerTransitionCoordinator
    ) {
        tremendous.viewWillTransition(to: dimension, 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,
        format collectionViewLayout: UICollectionViewLayout,
        sizeForItemAt indexPath: IndexPath
    ) -> CGSize {
        .init(
            width: collectionView.body.dimension.width/3.0 - 8,
            peak: collectionView.body.dimension.width/3.0 - 8
        )
    }
}

If you’re aware of assortment views, you would possibly ask why am I doing this tutorial? It is so easy. It simply works, proper? No, really with out the overridden bounds property the instance would look one thing like this on the left aspect. 😢

Humorous, huh? The picture on the fitting aspect is the precise consequence with the overridden bounds, that is the anticipated habits. 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 would possibly ask: however why? 🤔

Layers, springs & struts and a few clarification

Apple nonetheless has “Springs & Struts” based mostly code within UIKit. Which means that body and certain calculations are occurring within the underlying system and the constraint system is attempting to work onerous as nicely to determine the right measures.

“Springs & Struts” must die!

Whereas there’s an init(body:) technique, or a required init(coder:) these format issues will suck as hell. I actually like Interface Builder, however till we can’t get a tremendous device to create nice consumer interfaces IB goes to be simply one other layer of doable bugs.

This problem will not even be there should you create the cell from code solely utilizing auto format constraints or format anchors! It is as a result of IB creates the cell based mostly 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 format do the onerous work, the format system will resolve every part else. Examine 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.dimension.width/2.0))
        )
    }
}

Clearly it’s important to write extra code, register your cell class manually contained in the controller class and also you additionally must 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 method of displaying round photographs. Utilizing this method is sort of difficult, nevertheless it positively works in each case. You’ll be able to obtain the instance from The.Swift.Dev. tutorials on GitHub.