删除每个uiCollectionViewCell之间的间距并将其移到uiCollectionView的外部单元格

这可以通过自定义布局实现,子类来自 UICollectionViewFlowLayout . 这是一个布局和演示集合视图/单元实现。

更新 视图控制器.swift

class ViewController: UIViewController {

    private var collectionView: UICollectionView!
    private let demoLabel = UILabel()
    private let minCellSpacing: CGFloat = 16.0
    private var maxCellWidth: CGFloat!

    var data: [String] = ["Tech", "Design", "Humor", "Travel", "Music", "Writing", "Social Media", "Life", "Education", "Edtech", "Education Reform", "Photography", "Startup", "Poetry", "Women In Tech", "Female Founders", "Business", "Fiction", "Love", "Food", "Sports", "Autos", "Cleaning", "Technology", "Business", "Sports", "Childcare", "Airsoft", "Cycling", "Fitness", "Baseball", "Basketball", "Bird Watching", "Bodybuilding", "Camping", "Dowsing", "Driving", "Fishing", "Flying", "Flying Disc", "Foraging", "Freestyle Football", "Gardeing", "Geocaching", "Ghost hunting", "Grafitti", "Handball", "High-power rocketry", "Hooping", "Horseback riding", "Hunting"]

    override func viewDidLoad() {
        super.viewDidLoad()

        self.maxCellWidth = UIScreen.main.bounds.width - (minCellSpacing * 2)

        self.view.backgroundColor = .white
        self.demoLabel.font = CollectionViewCell().label.font

        let layout = FlowLayout()
        layout.sectionInset = UIEdgeInsets(top: self.minCellSpacing, left: 2.0, bottom: self.minCellSpacing, right: 2.0)
        layout.minimumInteritemSpacing = self.minCellSpacing
        layout.minimumLineSpacing = 16.0

        collectionView = UICollectionView(frame: self.view.bounds, collectionViewLayout: layout)
        collectionView.backgroundColor = .clear
        collectionView.delegate = self
        collectionView.dataSource = self
        collectionView.register(CollectionViewCell.self, forCellWithReuseIdentifier: "cellId")
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        self.view.addSubview(collectionView)
        collectionView.topAnchor.constraint(equalTo: self.view.layoutMarginsGuide.topAnchor).isActive = true
        collectionView.bottomAnchor.constraint(equalTo: self.view.layoutMarginsGuide.bottomAnchor).isActive = true

        // Leading/Trailing gutter CellSpacing+ShadowWidth
        collectionView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: minCellSpacing + layout.sectionInset.left).isActive = true
        collectionView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -(minCellSpacing + layout.sectionInset.right)).isActive = true
    }
}

extension ViewController: UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return self.data.count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! CollectionViewCell
        cell.label.text = self.data[indexPath.item]
        return cell
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        self.demoLabel.text = self.data[indexPath.item]
        self.demoLabel.sizeToFit()
        return CGSize(width: min(self.demoLabel.frame.width + 16, self.maxCellWidth), height: 36.0)
    }

}

流程布局.swift

class FlowLayout: UICollectionViewFlowLayout {

    private var attribs = [IndexPath: UICollectionViewLayoutAttributes]()

    override func prepare() {
        self.attribs.removeAll()
    }

    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        var updatedAttributes = [UICollectionViewLayoutAttributes]()

        let sections = self.collectionView?.numberOfSections ?? 0
        var indexPath = IndexPath(item: 0, section: 0)
        while (indexPath.section < sections) {
            guard let items = self.collectionView?.numberOfItems(inSection: indexPath.section) else { continue }

            while (indexPath.item < items) {
                if let attributes = layoutAttributesForItem(at: indexPath), attributes.frame.intersects(rect) {
                    updatedAttributes.append(attributes)
                }

                let headerKind = UICollectionElementKindSectionHeader
                if let headerAttributes = layoutAttributesForSupplementaryView(ofKind: headerKind, at: indexPath) {
                    updatedAttributes.append(headerAttributes)
                }

                let footerKind = UICollectionElementKindSectionFooter
                if let footerAttributes = layoutAttributesForSupplementaryView(ofKind: footerKind, at: indexPath) {
                    updatedAttributes.append(footerAttributes)
                }
                indexPath.item += 1
            }
            indexPath = IndexPath(item: 0, section: indexPath.section + 1)
        }

        return updatedAttributes
    }

    override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        if let attributes = attribs[indexPath] {
            return attributes
        }

        var rowCells = [UICollectionViewLayoutAttributes]()
        var collectionViewWidth: CGFloat = 0
        if let collectionView = collectionView {
            collectionViewWidth = collectionView.bounds.width - collectionView.contentInset.left
                - collectionView.contentInset.right
        }

        var rowTestFrame: CGRect = super.layoutAttributesForItem(at: indexPath)?.frame ?? .zero
        rowTestFrame.origin.x = 0
        rowTestFrame.size.width = collectionViewWidth

        let totalRows = self.collectionView?.numberOfItems(inSection: indexPath.section) ?? 0

        // From this item, work backwards to find the first item in the row
        // Decrement the row index until a) we get to 0, b) we reach a previous row
        var startIndex = indexPath.row
        while true {
            let lastIndex = startIndex - 1

            if lastIndex < 0 {
                break
            }

            let prevPath = IndexPath(row: lastIndex, section: indexPath.section)
            let prevFrame: CGRect = super.layoutAttributesForItem(at: prevPath)?.frame ?? .zero

            // If the item intersects the test frame, it's in the same row
            if prevFrame.intersects(rowTestFrame) {
                startIndex = lastIndex
            } else {
                // Found previous row, escape!
                break
            }
        }

        // Now, work back UP to find the last item in the row
        // For each item in the row, add it's attributes to rowCells
        var cellIndex = startIndex
        while cellIndex < totalRows {
            let cellPath = IndexPath(row: cellIndex, section: indexPath.section)

            if let cellAttributes = super.layoutAttributesForItem(at: cellPath),
                cellAttributes.frame.intersects(rowTestFrame),
                let cellAttributesCopy = cellAttributes.copy() as? UICollectionViewLayoutAttributes {
                rowCells.append(cellAttributesCopy)
                cellIndex += 1
            } else {
                break
            }
        }

        let flowDelegate = self.collectionView?.delegate as? UICollectionViewDelegateFlowLayout
        let selector = #selector(UICollectionViewDelegateFlowLayout.collectionView(_:layout:minimumInteritemSpacingForSectionAt:))
        let delegateSupportsInteritemSpacing = flowDelegate?.responds(to: selector) ?? false

        var interitemSpacing = minimumInteritemSpacing

        // Check for minimumInteritemSpacingForSectionAtIndex support
        if let collectionView = collectionView, delegateSupportsInteritemSpacing && rowCells.count > 0 {
            interitemSpacing = flowDelegate?.collectionView?(collectionView,
                                                             layout: self,
                                                             minimumInteritemSpacingForSectionAt: indexPath.section) ?? 0
        }

        let aggregateInteritemSpacing = interitemSpacing * CGFloat(rowCells.count - 1)

        var aggregateItemWidths: CGFloat = 0
        for itemAttributes in rowCells {
            aggregateItemWidths += itemAttributes.frame.width
        }

        let alignmentWidth = aggregateItemWidths + aggregateInteritemSpacing
        let alignmentXOffset: CGFloat = (collectionViewWidth - alignmentWidth) / 2

        var previousFrame: CGRect = .zero
        for itemAttributes in rowCells {
            var itemFrame = itemAttributes.frame

            if previousFrame.equalTo(.zero) {
                itemFrame.origin.x = alignmentXOffset
            } else {
                itemFrame.origin.x = previousFrame.maxX + interitemSpacing
            }

            itemAttributes.frame = itemFrame
            previousFrame = itemFrame

            attribs[itemAttributes.indexPath] = itemAttributes
        }

        return attribs[indexPath]
    }
}

集合视图单元格.swift

class CollectionViewCell: UICollectionViewCell {

    let label = UILabel()

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

        self.label.translatesAutoresizingMaskIntoConstraints = false
        self.contentView.addSubview(label)
        self.contentView.addConstraints([
            NSLayoutConstraint(item: label, attribute: .leading, relatedBy: .equal, toItem: contentView,
                               attribute: .leading, multiplier: 1.0, constant: 8.0),
            NSLayoutConstraint(item: label, attribute: .top, relatedBy: .equal, toItem: contentView,
                               attribute: .top, multiplier: 1.0, constant: 8.0),
            NSLayoutConstraint(item: contentView, attribute: .trailing, relatedBy: .equal, toItem: label,
                               attribute: .trailing, multiplier: 1.0, constant: 8.0),
            NSLayoutConstraint(item: contentView, attribute: .bottom, relatedBy: .equal, toItem: label,
                               attribute: .bottom, multiplier: 1.0, constant: 8.0)])

        self.backgroundColor = .white
        self.label.textColor = UIColor(red: 0.1, green: 0.1, blue: 0.1, alpha: 1)
        self.layer.cornerRadius = 3.0
        self.layer.shadowColor = UIColor.darkGray.cgColor
        self.layer.shadowOffset = CGSize(width: 0.1, height: 0.2)
        self.layer.shadowOpacity = 0.28
    }

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

这是最后的用户界面