UICollectionView Imposta il numero di colonne

Ho appena iniziato a conoscere UICollectionViews. Mi chiedo se qualcuno sappia come specificare il numero di colonne in una collectionview. L'impostazione predefinita è 3 (iPhone / ritratto). Ho esaminato la documentazione e non riesco a trovare una risposta concisa.

CollectionViews sono molto potenti e hanno un prezzo. Molte e molte opzioni. Come ha detto omz:

ci sono molti modi per cambiare il numero di colonne

Suggerirei di implementare il <UICollectionViewDelegateFlowLayout>protocollo, dandoti accesso ai seguenti metodi in cui puoi avere un maggiore controllo sul layout del tuo UICollectionView, senza la necessità di sottoclassarlo:

• collectionView:layout:insetForSectionAtIndex:
• collectionView:layout:minimumInteritemSpacingForSectionAtIndex:
• collectionView:layout:minimumLineSpacingForSectionAtIndex:
• collectionView:layout:referenceSizeForFooterInSection:
• collectionView:layout:referenceSizeForHeaderInSection:
• collectionView:layout:sizeForItemAtIndexPath:

Inoltre, l'implementazione del seguente metodo costringerà il tuo UICollectionView ad aggiornare il suo layout su un cambio di orientamento: (supponi di voler ridimensionare le celle per il paesaggio e farle allungare)

-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
                               duration:(NSTimeInterval)duration{

    [self.myCollectionView.collectionViewLayout invalidateLayout];
}

Inoltre, ecco 2 tutorial davvero validi su UICollectionViews:

http://www.raywenderlich.com/22324/beginning-uicollectionview-in-ios-6-part-12

http://skeuo.com/uicollectionview-custom-layout-tutorial

Con Swift 5 e iOS 12.3, puoi utilizzare una delle 4 seguenti implementazioni per impostare il numero di elementi per riga UICollectionViewdurante la gestione degli inserti e delle modifiche alle dimensioni (inclusa la rotazione).

# 1. Creazione di sottoclassi UICollectionViewFlowLayoute utilizzo UICollectionViewFlowLayoutdella itemSizeproprietà di

ColumnFlowLayout.swift:

import UIKit

class ColumnFlowLayout: UICollectionViewFlowLayout {

    let cellsPerRow: Int

    init(cellsPerRow: Int, minimumInteritemSpacing: CGFloat = 0, minimumLineSpacing: CGFloat = 0, sectionInset: UIEdgeInsets = .zero) {
        self.cellsPerRow = cellsPerRow
        super.init()

        self.minimumInteritemSpacing = minimumInteritemSpacing
        self.minimumLineSpacing = minimumLineSpacing
        self.sectionInset = sectionInset
    }

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

    override func prepare() {
        super.prepare()

        guard let collectionView = collectionView else { return }
        let marginsAndInsets = sectionInset.left + sectionInset.right + collectionView.safeAreaInsets.left + collectionView.safeAreaInsets.right + minimumInteritemSpacing * CGFloat(cellsPerRow - 1)
        let itemWidth = ((collectionView.bounds.size.width - marginsAndInsets) / CGFloat(cellsPerRow)).rounded(.down)
        itemSize = CGSize(width: itemWidth, height: itemWidth)
    }

    override func invalidationContext(forBoundsChange newBounds: CGRect) -> UICollectionViewLayoutInvalidationContext {
        let context = super.invalidationContext(forBoundsChange: newBounds) as! UICollectionViewFlowLayoutInvalidationContext
        context.invalidateFlowLayoutDelegateMetrics = newBounds.size != collectionView?.bounds.size
        return context
    }

}

CollectionViewController.swift:

import UIKit

class CollectionViewController: UICollectionViewController {

    let columnLayout = ColumnFlowLayout(
        cellsPerRow: 5,
        minimumInteritemSpacing: 10,
        minimumLineSpacing: 10,
        sectionInset: UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10)
    )

    override func viewDidLoad() {
        super.viewDidLoad()

        collectionView?.collectionViewLayout = columnLayout
        collectionView?.contentInsetAdjustmentBehavior = .always
        collectionView?.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
    }

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 59
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
        cell.backgroundColor = UIColor.orange
        return cell
    }

}

# 2. Utilizzando UICollectionViewFlowLayoutil itemSizemetodo di

import UIKit

class CollectionViewController: UICollectionViewController {

    let margin: CGFloat = 10
    let cellsPerRow = 5

    override func viewDidLoad() {
        super.viewDidLoad()

        guard let collectionView = collectionView, let flowLayout = collectionViewLayout as? UICollectionViewFlowLayout else { return }

        flowLayout.minimumInteritemSpacing = margin
        flowLayout.minimumLineSpacing = margin
        flowLayout.sectionInset = UIEdgeInsets(top: margin, left: margin, bottom: margin, right: margin)

        collectionView.contentInsetAdjustmentBehavior = .always
        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
    }

    override func viewWillLayoutSubviews() {
        guard let collectionView = collectionView, let flowLayout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout else { return }
        let marginsAndInsets = flowLayout.sectionInset.left + flowLayout.sectionInset.right + collectionView.safeAreaInsets.left + collectionView.safeAreaInsets.right + flowLayout.minimumInteritemSpacing * CGFloat(cellsPerRow - 1)
        let itemWidth = ((collectionView.bounds.size.width - marginsAndInsets) / CGFloat(cellsPerRow)).rounded(.down)
        flowLayout.itemSize =  CGSize(width: itemWidth, height: itemWidth)
    }

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 59
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
        cell.backgroundColor = UIColor.orange
        return cell
    }

    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        collectionView?.collectionViewLayout.invalidateLayout()
        super.viewWillTransition(to: size, with: coordinator)
    }

}

# 3. Utilizzando UICollectionViewDelegateFlowLayoutil collectionView(_:layout:sizeForItemAt:)metodo di

import UIKit

class CollectionViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {

    let inset: CGFloat = 10
    let minimumLineSpacing: CGFloat = 10
    let minimumInteritemSpacing: CGFloat = 10
    let cellsPerRow = 5

    override func viewDidLoad() {
        super.viewDidLoad()

        collectionView?.contentInsetAdjustmentBehavior = .always
        collectionView?.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: inset, left: inset, bottom: inset, right: inset)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return minimumLineSpacing
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return minimumInteritemSpacing
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let marginsAndInsets = inset * 2 + collectionView.safeAreaInsets.left + collectionView.safeAreaInsets.right + minimumInteritemSpacing * CGFloat(cellsPerRow - 1)
        let itemWidth = ((collectionView.bounds.size.width - marginsAndInsets) / CGFloat(cellsPerRow)).rounded(.down)
        return CGSize(width: itemWidth, height: itemWidth)
    }

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 59
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
        cell.backgroundColor = UIColor.orange
        return cell
    }

    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        collectionView?.collectionViewLayout.invalidateLayout()
        super.viewWillTransition(to: size, with: coordinator)
    }

}

# 4. Creazione di sottoclassi UICollectionViewFlowLayoute utilizzo UICollectionViewFlowLayoutdella estimatedItemSizeproprietà di

CollectionViewController.swift:

import UIKit

class CollectionViewController: UICollectionViewController {

    let items = [
        "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "Lorem ipsum dolor sit amet, consectetur.",
        "Lorem ipsum dolor sit amet.",
        "Lorem ipsum dolor sit amet, consectetur.",
        "Lorem ipsum dolor sit amet, consectetur adipiscing.",
        "Lorem ipsum.",
        "Lorem ipsum dolor sit amet.",
        "Lorem ipsum dolor sit.",
        "Lorem ipsum dolor sit amet, consectetur adipiscing.",
        "Lorem ipsum dolor sit amet, consectetur adipiscing elit.",
        "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor.",
        "Lorem ipsum dolor sit amet, consectetur."
    ]

    let columnLayout = FlowLayout(
        cellsPerRow: 3,
        minimumInteritemSpacing: 10,
        minimumLineSpacing: 10,
        sectionInset: UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10)
    )

    override func viewDidLoad() {
        super.viewDidLoad()

        collectionView?.collectionViewLayout = columnLayout
        collectionView?.contentInsetAdjustmentBehavior = .always
        collectionView?.register(Cell.self, forCellWithReuseIdentifier: "Cell")
    }

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

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

    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        collectionView?.collectionViewLayout.invalidateLayout()
        super.viewWillTransition(to: size, with: coordinator)
    }

}

FlowLayout.swift:

import UIKit

class FlowLayout: UICollectionViewFlowLayout {

    let cellsPerRow: Int

    required init(cellsPerRow: Int = 1, minimumInteritemSpacing: CGFloat = 0, minimumLineSpacing: CGFloat = 0, sectionInset: UIEdgeInsets = .zero) {
        self.cellsPerRow = cellsPerRow

        super.init()

        self.minimumInteritemSpacing = minimumInteritemSpacing
        self.minimumLineSpacing = minimumLineSpacing
        self.sectionInset = sectionInset
        estimatedItemSize = UICollectionViewFlowLayout.automaticSize
    }

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

    override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        guard let layoutAttributes = super.layoutAttributesForItem(at: indexPath) else { return nil }
        guard let collectionView = collectionView else { return layoutAttributes }

        let marginsAndInsets = collectionView.safeAreaInsets.left + collectionView.safeAreaInsets.right + sectionInset.left + sectionInset.right + minimumInteritemSpacing * CGFloat(cellsPerRow - 1)
        layoutAttributes.bounds.size.width = ((collectionView.bounds.width - marginsAndInsets) / CGFloat(cellsPerRow)).rounded(.down)

        return layoutAttributes
    }

    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        let superLayoutAttributes = super.layoutAttributesForElements(in: rect)!.map { $0.copy() as! UICollectionViewLayoutAttributes }
        guard scrollDirection == .vertical else { return superLayoutAttributes }

        let layoutAttributes = superLayoutAttributes.compactMap { layoutAttribute in
            return layoutAttribute.representedElementCategory == .cell ? layoutAttributesForItem(at: layoutAttribute.indexPath) : layoutAttribute
        }

        // (optional) Uncomment to top align cells that are on the same line
        /*
        let cellAttributes = layoutAttributes.filter({ $0.representedElementCategory == .cell })
        for (_, attributes) in Dictionary(grouping: cellAttributes, by: { ($0.center.y / 10).rounded(.up) * 10 }) {
            guard let max = attributes.max(by: { $0.size.height < $1.size.height }) else { continue }
            for attribute in attributes where attribute.size.height != max.size.height {
                attribute.frame.origin.y = max.frame.origin.y
            }
        }
         */

        // (optional) Uncomment to bottom align cells that are on the same line
        /*
        let cellAttributes = layoutAttributes.filter({ $0.representedElementCategory == .cell })
        for (_, attributes) in Dictionary(grouping: cellAttributes, by: { ($0.center.y / 10).rounded(.up) * 10 }) {
            guard let max = attributes.max(by: { $0.size.height < $1.size.height }) else { continue }
            for attribute in attributes where attribute.size.height != max.size.height {
                attribute.frame.origin.y += max.frame.maxY - attribute.frame.maxY
            }
        }
         */

        return layoutAttributes
    }

}

Cell.swift:

import UIKit

class Cell: 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.layoutMarginsGuide.topAnchor).isActive = true
        label.leadingAnchor.constraint(equalTo: contentView.layoutMarginsGuide.leadingAnchor).isActive = true
        label.trailingAnchor.constraint(equalTo: contentView.layoutMarginsGuide.trailingAnchor).isActive = true
        label.bottomAnchor.constraint(equalTo: contentView.layoutMarginsGuide.bottomAnchor).isActive = true
    }

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

    override func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
        layoutIfNeeded()
        label.preferredMaxLayoutWidth = label.bounds.size.width
        layoutAttributes.bounds.size.height = contentView.systemLayoutSizeFitting(UIView.layoutFittingCompressedSize).height
        return layoutAttributes
    }

    // Alternative implementation
    /*
    override func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
        label.preferredMaxLayoutWidth = layoutAttributes.size.width - contentView.layoutMargins.left - contentView.layoutMargins.right
        layoutAttributes.bounds.size.height = contentView.systemLayoutSizeFitting(UIView.layoutFittingCompressedSize).height
        return layoutAttributes
    }
    */

}

Ho implementato UICollectionViewDelegateFlowLayoutsul mio UICollectionViewControllere sovrascrivo il metodo responsabile della determinazione della dimensione della cella. Ho quindi preso la larghezza dello schermo e l'ho divisa con il mio requisito di colonna. Ad esempio, volevo avere 3 colonne su ogni dimensione dello schermo. Quindi ecco come appare il mio codice:

- (CGSize)collectionView:(UICollectionView *)collectionView
                  layout:(UICollectionViewLayout *)collectionViewLayout
  sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    CGRect screenRect = [[UIScreen mainScreen] bounds];
    CGFloat screenWidth = screenRect.size.width;
    float cellWidth = screenWidth / 3.0; //Replace the divisor with the column count requirement. Make sure to have it in float.
    CGSize size = CGSizeMake(cellWidth, cellWidth);

    return size;
}

Espandendo la risposta di noob:

func collectionView(collectionView: UICollectionView,
    layout collectionViewLayout: UICollectionViewLayout,
    sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {

        let flowLayout = collectionViewLayout as! UICollectionViewFlowLayout
        let totalSpace = flowLayout.sectionInset.left
            + flowLayout.sectionInset.right
            + (flowLayout.minimumInteritemSpacing * CGFloat(numberOfItemsPerRow - 1))
        let size = Int((collectionView.bounds.width - totalSpace) / CGFloat(numberOfItemsPerRow))
        return CGSize(width: size, height: size)
}

Ciò consente qualsiasi spaziatura tra le celle. Si presuppone una Intvariabile membro chiamata numberOfItemsPerRowe anche che tutte le celle siano quadrate e della stessa dimensione. Come notato nella risposta di jhilgert00, dobbiamo anche reagire ai cambiamenti di orientamento, ma ora utilizzando viewWillTransitionToSizeas willRotateToInterfaceOrientationè deprezzato.

Ecco il codice funzionante per Swift 3, per avere un layout a due colonne:

func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    sizeForItemAt indexPath: IndexPath) -> CGSize {

    let nbCol = 2

    let flowLayout = collectionViewLayout as! UICollectionViewFlowLayout
    let totalSpace = flowLayout.sectionInset.left
        + flowLayout.sectionInset.right
        + (flowLayout.minimumInteritemSpacing * CGFloat(nbCol - 1))
    let size = Int((collectionView.bounds.width - totalSpace) / CGFloat(nbCol))
    return CGSize(width: size, height: size)
}

Sentiti libero di cambiare "nbCol" con il numero di colonne desiderato.

Se sei pigro usando delegate.

extension UICollectionView {
    func setItemsInRow(items: Int) {
        if let layout = self.collectionViewLayout as? UICollectionViewFlowLayout {
            let contentInset = self.contentInset
            let itemsInRow: CGFloat = CGFloat(items);
            let innerSpace = layout.minimumInteritemSpacing * (itemsInRow - 1.0)
            let insetSpace = contentInset.left + contentInset.right + layout.sectionInset.left + layout.sectionInset.right
            let width = floor((CGRectGetWidth(frame) - insetSpace - innerSpace) / itemsInRow);
            layout.itemSize = CGSizeMake(width, width)
        }
    }
}

PS: dovrebbe essere chiamato anche dopo la rotazione

Aggiornato a Swift 3:

Invece del layout di flusso, preferisco utilizzare il layout personalizzato per il numero di colonna e il numero di riga specifici. Perché:

1. Può essere trascinato orizzontalmente se il numero di colonna è molto grande.
2. È logicamente più accettabile a causa dell'utilizzo di colonne e righe.

Cella normale e cella di intestazione: (Aggiungi UILabel come IBOutlet al tuo xib):

class CollectionViewCell: UICollectionViewCell {

@IBOutlet weak var label: UILabel!

override func awakeFromNib() {
    super.awakeFromNib()
    // Initialization code
    self.backgroundColor = UIColor.black
    label.textColor = UIColor.white
}
}

class CollectionViewHeadCell: UICollectionViewCell {

@IBOutlet weak var label: UILabel!

override func awakeFromNib() {
    super.awakeFromNib()
    // Initialization code
    self.backgroundColor = UIColor.darkGray
    label.textColor = UIColor.white
}
}

Layout personalizzato:

let cellHeight: CGFloat = 100
let cellWidth: CGFloat = 100

class CustomCollectionViewLayout: UICollectionViewLayout {
    private var numberOfColumns: Int!
    private var numberOfRows: Int!

    // It is two dimension array of itemAttributes
    private var itemAttributes = [[UICollectionViewLayoutAttributes]]()
    // It is one dimension of itemAttributes
    private var cache = [UICollectionViewLayoutAttributes]()

override func prepare() {
    if self.cache.isEmpty {

        self.numberOfColumns = self.collectionView?.numberOfItems(inSection: 0)
        self.numberOfRows = self.collectionView?.numberOfSections

        // Dynamically change cellWidth if total cell width is smaller than whole bounds
        /* if (self.collectionView?.bounds.size.width)!/CGFloat(self.numberOfColumns) > cellWidth {
         self.cellWidth = (self.collectionView?.bounds.size.width)!/CGFloat(self.numberOfColumns)
         }
         */
        for row in 0..<self.numberOfRows {
            var row_temp = [UICollectionViewLayoutAttributes]()
            for column in 0..<self.numberOfColumns {

                let indexPath = NSIndexPath(item: column, section: row)

                let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath as IndexPath)
                attributes.frame = CGRect(x: cellWidth*CGFloat(column), y: cellHeight*CGFloat(row), width: cellWidth, height: cellHeight)

                row_temp.append(attributes)

                self.cache.append(attributes)
            }
            self.itemAttributes.append(row_temp)
        }
    }
}
override var collectionViewContentSize: CGSize {
    return CGSize(width: CGFloat(self.numberOfColumns)*cellWidth, height: CGFloat(self.numberOfRows)*cellHeight)
}

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

    var layoutAttributes = [UICollectionViewLayoutAttributes]()

    for attributes in cache {
        if attributes.frame.intersects(rect) {
            layoutAttributes.append(attributes)
        }
    }
    return layoutAttributes
}
}

CollectionView:

let CellIdentifier = "CellIdentifier"
let HeadCellIdentifier = "HeadCellIdentifier"

class CollectionView: UICollectionView, UICollectionViewDelegate, UICollectionViewDataSource {

init() {
    let layout = CustomCollectionViewLayout()

    super.init(frame: CGRect.zero, collectionViewLayout: layout)

    self.register(UINib(nibName: "CollectionViewCell", bundle: nil), forCellWithReuseIdentifier: CellIdentifier)
    self.register(UINib(nibName: "CollectionViewHeadCell", bundle: nil), forCellWithReuseIdentifier: HeadCellIdentifier)

    self.isDirectionalLockEnabled = true
    self.dataSource = self
    self.delegate = self
}

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

func updateCollectionView() {
    DispatchQueue.main.async {
        self.reloadData()
    }
}

// MARK: CollectionView datasource
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 20
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 20
}
override func numberOfItems(inSection section: Int) -> Int {
    return 20
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let column = (indexPath as NSIndexPath).row
    let row = (indexPath as NSIndexPath).section

    if column == 0 {
        let cell : CollectionViewHeadCell = collectionView.dequeueReusableCell(withReuseIdentifier: HeadCellIdentifier, for: indexPath) as! CollectionViewHeadCell

        cell.label.text = "\(row)"

        return cell
    }
    else if row == 0 {
        let cell : CollectionViewHeadCell = collectionView.dequeueReusableCell(withReuseIdentifier: HeadCellIdentifier, for: indexPath) as! CollectionViewHeadCell

        cell.label.text = "\(column)"

        return cell
    }
    else {
        let cell : CollectionViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: CellIdentifier, for: indexPath) as! CollectionViewCell

        cell.label.text = String(format: "%d", arguments: [indexPath.section*indexPath.row])

        return cell
    }
}

// MARK: CollectionView delegate
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

    let column = (indexPath as NSIndexPath).row
    let row = (indexPath as NSIndexPath).section

    print("\(column)  \(row)")
}
}

Usa CollectionView da ViewController:

class ViewController: UIViewController {
let collectionView = CollectionView()

override func viewDidLoad() {
    collectionView.translatesAutoresizingMaskIntoConstraints = false
    self.view.addSubview(collectionView)
    self.view.backgroundColor = UIColor.red

    self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|[collectionView]|", options: [], metrics: nil, views: ["collectionView": collectionView]))
    self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[collectionView]|", options: [], metrics: nil, views: ["collectionView": collectionView]))
}

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    collectionView.updateCollectionView()
}
}

Finalmente puoi avere la fantasia CollectionView!

Perché UICollectionView è così flessibile, esistono diversi modi per modificare il numero di colonne, a seconda del tipo di layout utilizzato.

L' UICollectionViewFlowLayout(che è probabilmente quello che si sta lavorando con) non specifica un numero di colonne direttamente (perché dipende dalla vista dimensioni / orientamento). Il modo più semplice per cambiarlo sarebbe impostare la itemSizeproprietà e / o minimumInteritemSpacing/ minimumLineSpacing.

Swift 3.0. Funziona per le direzioni di scorrimento orizzontale e verticale e per la spaziatura variabile

Specifica il numero di colonne

let numberOfColumns: CGFloat = 3

Configura per flowLayouteseguire il rendering specificatonumberOfColumns

if let flowLayout = collectionView?.collectionViewLayout as? UICollectionViewFlowLayout {
    let horizontalSpacing = flowLayout.scrollDirection == .vertical ? flowLayout.minimumInteritemSpacing : flowLayout.minimumLineSpacing
    let cellWidth = (collectionView.frame.width - max(0, numberOfColumns - 1)*horizontalSpacing)/numberOfColumns
    flowLayout.itemSize = CGSize(width: cellWidth, height: cellWidth)
}

Aggiornato a Swift 5+ iOS 13

La dimensione della stima di Collectionview deve essere nessuna

Dichiara margine per cella

let margin: CGFloat = 10

In viewDidLoad configure minimumInteritemSpacing, minimumLineSpacing,sectionInset

 guard let collectionView = docsColl, let flowLayout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout else { return }

    flowLayout.minimumInteritemSpacing = margin
    flowLayout.minimumLineSpacing = margin
    flowLayout.sectionInset = UIEdgeInsets(top: margin, left: margin, bottom: margin, right: margin)

UICollectionViewDataSource metodosizeForItemAt

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

    let noOfCellsInRow = 2   //number of column you want
    let flowLayout = collectionViewLayout as! UICollectionViewFlowLayout
    let totalSpace = flowLayout.sectionInset.left
        + flowLayout.sectionInset.right
        + (flowLayout.minimumInteritemSpacing * CGFloat(noOfCellsInRow - 1))

    let size = Int((collectionView.bounds.width - totalSpace) / CGFloat(noOfCellsInRow))
    return CGSize(width: size, height: size)
}

È tutta una questione di layout che vuoi disegnare. È possibile creare una classe personalizzata che eredita da UICollectionViewFlowLayout. Attualmente non esiste alcun metodo diretto per impostare le colonne. Se vuoi ottenere questo tipo di funzionalità devi farlo manualmente. È necessario gestirlo nella classe di layout del flusso personalizzato.

Ora sorgerà la domanda su come lo farai? Se non vuoi disturbare il frame della cella puoi regolare

 collectionView:layout:minimumInteritemSpacingForSectionAtIndex:
 collectionView:layout:minimumLineSpacingForSectionAtIndex:

Un altro modo è fornire le proprie posizioni delle celle. Sovrascrivendo i seguenti due metodi, che verranno chiamati durante la formazione del layout.

  - (NSArray*)layoutAttributesForElementsInRect:(CGRect)rect
  - (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)path

UICollectionViewLayoutAttributes è una classe che si occuperà della posizione della cella, del frame, di Zindex ecc

Questa risposta è per swift 3.0 ->

prima conformi al protocollo:

 UICollectionViewDelegateFlowLayout

quindi aggiungi questi metodi:

    //this method is for the size of items      
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let width = collectionView.frame.width/3
        let height : CGFloat = 160.0
        return CGSize(width: width, height: height)
    }
    //these methods are to configure the spacing between items

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsetsMake(0,0,0,0)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }

Volevo solo aggiungere alla risposta n. 2 di Imanou Petit. Per garantire che i margini siano esatti indipendentemente dalla larghezza dello schermo, utilizzo un risolutore iterativo con un margine desiderato e il numero di colonne come input. Ho anche aggiunto una bandiera direzionale su dove i loro margini finali saranno confrontati con il loro obiettivo.

Il risolutore iterativo è mostrato di seguito e restituisce cellWidth e margin.

private func iterativeCellSpacing(targetMargins : CGFloat,
                                  cellsPerRow : Int,
                                  isMinTarget : Bool) -> (CGFloat, CGFloat)
{
    var w : CGFloat = 0
    var m : CGFloat = targetMargins
    let cols : CGFloat = CGFloat(cellsPerRow)

    let numMargins : CGFloat = cols + 1.0
    let screenWidth : CGFloat = collectionView!.bounds.size.width


    var delta = CGFloat.greatestFiniteMagnitude
    while abs(delta) > 0.001
    {
        let totalMarginSpacing = numMargins * m
        let totalCellSpacing = screenWidth - totalMarginSpacing

        if (isMinTarget)
        {
            w = floor(totalCellSpacing / cols)
            m = ceil((screenWidth - cols * w) / numMargins)
        }
        else
        {
            w = ceil(totalCellSpacing / cols)
            m = floor((screenWidth - cols * w) / numMargins)
        }

        delta = screenWidth - w * CGFloat(cellsPerRow) - m * numMargins
    }

    return (w, m)
}

Lo chiamo come tale:

fileprivate var margin: CGFloat = 20
fileprivate var cellWidth : CGFloat = 80
fileprivate let cellsPerRow = 4

override func viewDidLoad()
{
    super.viewDidLoad()

    (cellWidth, margin) = iterativeCellSpacing(targetMargins: margin, cellsPerRow: 4, isMinTarget: true)
    ...
}

Quindi applico i valori cellWidth e margin al layout di flusso come tale:

extension MyCollectionController : UICollectionViewDelegateFlowLayout

{func collectionView (_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {return CGSize (width: cellWidth, height: cellWidth)}

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    collectionView?.collectionViewLayout.invalidateLayout()
    super.viewWillTransition(to: size, with: coordinator)
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets
{
    return UIEdgeInsetsMake(margin, margin, margin, margin)
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat
{
    return margin
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat
{
    return margin
}

}

Spero che questo ti aiuti. Probabilmente esiste un modo più semplice per garantire che i margini siano esatti, ma questo è un metodo. Inoltre, questo codice non è stato testato per i dispositivi che consentono la rotazione delle visualizzazioni di raccolta.

Grazie,

la soluzione perfetta è usare UICollectionViewDelegateFlowLayout ma puoi facilmente calcolare la larghezza della cella e dividerla sul numero di colonne desiderato

il difficile è creare la larghezza senza frazione

(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath

{
 CGFloat screenWidth = self.view.frame.size.width;
   CGFloat marginWidth = (screenWidth - collectionView.frame.size.width);


   CGFloat cellWith = (collectionView.frame.size.width - marginWidth )/3;
   cellWith= floorf(cellWith);




  CGSize retval = CGSizeMake(cellWith,cellWith);


  return retval;}

Ho realizzato un layout di raccolta.

Per rendere visibile il separatore, imposta il colore di sfondo della vista raccolta su grigio. Una riga per sezione.

Utilizzo:

let layout = GridCollectionViewLayout()
layout.cellHeight = 50 // if not set, cellHeight = Collection.height/numberOfSections
layout.cellWidth = 50  // if not set, cellWidth = Collection.width/numberOfItems(inSection)
collectionView.collectionViewLayout = layout

Disposizione:

import UIKit

class GridCollectionViewLayout: UICollectionViewLayout {


var cellWidth : CGFloat = 0
var cellHeight : CGFloat = 0
var seperator: CGFloat = 1

private var cache = [UICollectionViewLayoutAttributes]()



override func prepare() {

    guard let collectionView = self.collectionView else {
        return
    }

    self.cache.removeAll()



        let numberOfSections = collectionView.numberOfSections

        if cellHeight <= 0
        {
            cellHeight = (collectionView.bounds.height - seperator*CGFloat(numberOfSections-1))/CGFloat(numberOfSections)
        }

        for section in 0..<collectionView.numberOfSections {

            let numberOfItems = collectionView.numberOfItems(inSection: section)

            let cellWidth2 : CGFloat
            if cellWidth <= 0
            {
                cellWidth2 = (collectionView.bounds.width - seperator*CGFloat(numberOfItems-1))/CGFloat(numberOfItems)
            }
            else
            {
                cellWidth2 = cellWidth
            }


            for row in 0..<numberOfItems {


                let indexPath = NSIndexPath(row: row, section: section)

                let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath as IndexPath)
                attributes.frame = CGRect(x: (cellWidth2+seperator)*CGFloat(row),
                                          y: (cellHeight+seperator)*CGFloat(section),
                                          width: cellWidth2,
                                          height: cellHeight)

                //row_temp.append(attributes)

                self.cache.append(attributes)
            }
            //self.itemAttributes.append(row_temp)
        }

}

override var collectionViewContentSize: CGSize {

    guard let collectionView = collectionView else
    {
        return CGSize.zero
    }

    if (collectionView.numberOfSections <= 0)
    {
        return collectionView.bounds.size
    }

    let width:CGFloat
    if cellWidth <= 0
    {
        width = collectionView.bounds.width
    }
    else
    {
        width = cellWidth*CGFloat(collectionView.numberOfItems(inSection: 0))
    }

    let numberOfSections = CGFloat(collectionView.numberOfSections)
    var height:CGFloat = 0
    height += numberOfSections * cellHeight
    height += (numberOfSections - 1) * seperator



    return CGSize(width: width, height: height)
}

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

    var layoutAttributes = [UICollectionViewLayoutAttributes]()

    for attributes in cache {
        if attributes.frame.intersects(rect) {
            layoutAttributes.append(attributes)
        }
    }
    return layoutAttributes
}

override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
    return cache[indexPath.item]
}
}

Prova questo, funziona perfettamente per me,

Segui i passaggi seguenti:

1. Definire i valori nel file .h.

     #define kNoOfColumsForCollection 3
     #define kNoOfRowsForCollection 4
     #define kcellSpace 5
     #define kCollectionViewCellWidth (self.view.frame.size.width - kcellSpace*kNoOfColumsForCollection)/kNoOfColumsForCollection
     #define kCollectionViewCellHieght (self.view.frame.size.height-40- kcellSpace*kNoOfRowsForCollection)/kNoOfRowsForCollection

O

  #define kNoOfColumsForCollection 3
  #define kCollectionViewCellWidthHieght (self.view.frame.size.width - 6*kNoOfColumsForCollection)/kNoOfColumsForCollection

2.Aggiungi il codice nella raccolta Visualizza i metodi dell'origine dati del layout come di seguito,

 #pragma mark Collection View Layout data source methods
// collection view with autolayout

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
return 4;
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
 {
 return 1;
}

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
return UIEdgeInsetsMake(4, 4, 4, 4);
}
- (CGSize)collectionView:(UICollectionView *)collectionView
              layout:(UICollectionViewLayout *)collectionViewLayout
   sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
 return 
 CGSizeMake(kCollectionViewCellWidth,kCollectionViewCellHieght);
 // CGSizeMake (kCollectionViewCellWidthHieght,kCollectionViewCellWidthHieght);
}

Spero che questo possa essere d'aiuto per qualcuno.

Per prima cosa aggiungi UICollectionViewDelegateFlowLayout come protocollo.

Poi:

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
{
        var columnCount = 3
        let width  = (view.frame.width - 20) / columnCount
        return CGSize(width: width, height: width)
}