Android 14 Samsung calendar like carousel collectionView (iOS 12, UIKit) video clip in first comment

CarouselFlowLayout.swift

class CarouselFlowLayout: UICollectionViewFlowLayout {
    
    let scaleFactor: CGFloat = 0.7 // Minimum scale for side cells
    
    override func prepare() {
        super.prepare()
        guard let collectionView else { return }
        scrollDirection = .horizontal
        // Define cell size
        itemSize = collectionView.bounds.inset(by: UIEdgeInsets(top: 20, left: 20, bottom: 20, right: 20)).size
        // Calculate left right spaces
        let leftRightInset = (collectionView.bounds.width - itemSize.width) / 2
        // Adjust the minimum line spacing dynamically based on the scale factor
        minimumLineSpacing = calculateMinimumLineSpacing(forScale: scaleFactor)
        // Center cells in the screen
        sectionInset = .init(top: .zero, left: leftRightInset, bottom: .zero, right: leftRightInset)
    }
    
    private func calculateMinimumLineSpacing(forScale scale: CGFloat) -> CGFloat {
        // Calculate the width reduction due to scaling
        let scaledWidth = itemSize.width * scale
        // Calculate the spacing so that the smaller cells appear snug next to each other
        let spacing = (itemSize.width - scaledWidth) / 2.2
        return -spacing // Negative spacing ensures tight alignment
    }

    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        guard let attributesArray = super.layoutAttributesForElements(in: rect) else { return nil }
        let centerX = collectionView!.contentOffset.x + collectionView!.frame.size.width / 2
        // Iterate over the copied attributes, not the originals
        let copiedAttributesArray = attributesArray.map { $0.copy() as! UICollectionViewLayoutAttributes }
        for attributes in copiedAttributesArray {
            let distance = abs(attributes.center.x - centerX)
            let normalizedDistance = distance / (collectionView!.frame.width / 2)
            let scale = 1 - (1 - scaleFactor) * min(1, normalizedDistance)

            attributes.transform = CGAffineTransform(scaleX: scale, y: scale)
            attributes.alpha = scale // Adjust opacity based on scale
        }

        return copiedAttributesArray
    }

    override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
        return true // Ensure the layout updates during scrolling
    }
}

CarouselViewController.swift

class CarouselViewController: UIViewController {
    
    private lazy var collectionView: UICollectionView = {
        let collectionView = UICollectionView(frame: .zero, collectionViewLayout: CarouselFlowLayout())
        collectionView.backgroundColor = .clear
        collectionView.showsVerticalScrollIndicator = false
        collectionView.showsHorizontalScrollIndicator = false
        collectionView.decelerationRate = .fast // Smooth scrolling effect
        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: String(describing: UICollectionViewCell.self))
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        return collectionView
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .blue
        configureCollectionView()
    }

    private func configureCollectionView() {
        view.addSubview(collectionView)
        NSLayoutConstraint.activate([
            collectionView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
            collectionView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor),
            collectionView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor),
            collectionView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor),
        ])
        
        collectionView.delegate = self
        collectionView.dataSource = self
    }

}

extension CarouselViewController: UICollectionViewDelegate, UICollectionViewDataSource {
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { 10 }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cellId = String(describing: UICollectionViewCell.self)
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath)
        cell.contentView.layer.cornerRadius = 30
        cell.contentView.backgroundColor = .white
        return cell
    }
}

extension CarouselViewController: UIScrollViewDelegate {
    // Snap item to center
    func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
        let layout = collectionView.collectionViewLayout as! UICollectionViewFlowLayout
        let cellWidthIncludingSpacing = layout.itemSize.width + layout.minimumLineSpacing
        
        let estimatedIndex = targetContentOffset.pointee.x / cellWidthIncludingSpacing
        let index: CGFloat

        if velocity.x > 0 { index = ceil(estimatedIndex)
        } else if velocity.x < 0 { index = floor(estimatedIndex)
        } else { index = round(estimatedIndex)
        }

        targetContentOffset.pointee = CGPoint(x: index * cellWidthIncludingSpacing, y: 0)
    }
}

Simulator.Screen.Recording.-.iPhone.12.Pro.-.2024-10-23.at.23.18.29.mp4

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