ios - CollectionView Flowlayout自定义

Question

我正在像 tinder 编辑个人资料图片一样制作个人资料图片 Collection View 。我想要第一个单元格比其他单元格大，除了第一个单元格还有 2、3 个单元格，其他单元格应该像 3、4、5。有什么建议吗？

extension ViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        if indexPath.item == 0 {
        return CGSize(width: 213.34, height: 213.34)
        } else {
            return CGSize(width: 101.66, height:101.66 )
        }

    }


    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 6
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)
        let lbl = cell.viewWithTag(1) as! UILabel
        lbl.text = String(format: "%d", indexPath.row + 1)
        return cell
    }


}

Answer 1

你需要实现一个UICollectionViewLayout，我称之为FillingLayout，注意你可以调整列数和大单元格的大小，使用委托(delegate)方法

Explanation

您需要添加一个数组来跟踪您的列高度并查看最短的列是 private var columsHeights : [CGFloat] = [] 并且您还需要一个 数组(Int,Float) 元组来保留哪些空间可以被填充，我还在委托(delegate)中添加了一个方法来获取 Collection View 中我们想要的列数，以及一个方法来知道一个单元格是否可以被填充根据他们的大小添加或不在一个位置。

然后，如果我们想添加一个单元格，我们检查是否可以添加，如果不能，因为第一列已填充，我们在 avaiableSpaces 数组中添加对应于 column2 的空间，当我们首先添加下一个单元格时，我们检查是否可以在任何可用空间中添加，如果可以添加，我们会添加和删除可用空间。

这里是完整的代码

import UIKit

protocol FillingLayoutDelegate: class {
    func collectionView(_ collectionView:UICollectionView, sizeForViewAtIndexPath indexPath:IndexPath) -> Int
    //  Returns the amount of columns that have to display at that moment
    func numberOfColumnsInCollectionView(collectionView:UICollectionView) ->Int
}

class FillingLayout: UICollectionViewLayout {
    weak var delegate: FillingLayoutDelegate!

    fileprivate var cellPadding: CGFloat = 10

    fileprivate var cache = [UICollectionViewLayoutAttributes]()

    fileprivate var contentHeight: CGFloat = 0
    private var columsHeights : [CGFloat] = []
    private var avaiableSpaces : [(Int,CGFloat)] = []

    fileprivate var contentWidth: CGFloat {
        guard let collectionView = collectionView else {
            return 0
        }
        let insets = collectionView.contentInset
        return collectionView.bounds.width - (insets.left + insets.right)
    }

    var columnsQuantity : Int{
        get{
            if(self.delegate != nil)
            {
                return (self.delegate?.numberOfColumnsInCollectionView(collectionView: self.collectionView!))!
            }
            return 0
        }
    }

    //MARK: PRIVATE METHODS
    private func shortestColumnIndex() -> Int{
        var retVal : Int = 0
        var shortestValue = MAXFLOAT

        var i = 0
        for columnHeight in columsHeights {
            //debugPrint("Column Height: \(columnHeight) index: \(i)")
            if(Float(columnHeight) < shortestValue)
            {
                shortestValue = Float(columnHeight)
                retVal = i
            }
            i += 1
        }
        //debugPrint("shortest Column index: \(retVal)")
        return retVal
    }

    //MARK: PRIVATE METHODS
    private func largestColumnIndex() -> Int{
        var retVal : Int = 0
        var largestValue : Float = 0.0

        var i = 0
        for columnHeight in columsHeights {
            //debugPrint("Column Height: \(columnHeight) index: \(i)")
            if(Float(columnHeight) > largestValue)
            {
                largestValue = Float(columnHeight)
                retVal = i
            }
            i += 1
        }
        //debugPrint("shortest Column index: \(retVal)")
        return retVal
    }

    private func canUseBigColumnOnIndex(columnIndex:Int,size:Int) ->Bool
    {
        if(columnIndex < self.columnsQuantity - (size-1))
        {
            let firstColumnHeight = columsHeights[columnIndex]
            for i in columnIndex..<columnIndex + size{
                if(firstColumnHeight != columsHeights[i]) {
                    return false
                }
            }
            return true
        }

        return false
    }

    override var collectionViewContentSize: CGSize {
        return CGSize(width: contentWidth, height: contentHeight)
    }

    override func prepare() {
        // Check if cache is empty
        guard cache.isEmpty == true, let collectionView = collectionView else {
            return
        }

        //  Set all column heights to 0
        self.columsHeights = []
        for _ in 0..<self.columnsQuantity {
            self.columsHeights.append(0)
        }

        for item in 0 ..< collectionView.numberOfItems(inSection: 0) {

            let indexPath = IndexPath(item: item, section: 0)

            let viewSize: Int = delegate.collectionView(collectionView, sizeForViewAtIndexPath: indexPath)
            let blockWidth = (contentWidth/CGFloat(columnsQuantity))
            let width = blockWidth * CGFloat(viewSize)
            let height = width

            var columIndex = self.shortestColumnIndex()
            var xOffset = (contentWidth/CGFloat(columnsQuantity)) * CGFloat(columIndex)
            var yOffset = self.columsHeights[columIndex]

            if(viewSize > 1){//Big Cell
                if(!self.canUseBigColumnOnIndex(columnIndex: columIndex,size: viewSize)){
                    //  Set column height
                    for i in columIndex..<columIndex + viewSize{
                        if(i < columnsQuantity){
                            self.avaiableSpaces.append((i,yOffset))
                            self.columsHeights[i] += blockWidth
                        }
                    }
                    //  Set column height
                    yOffset = columsHeights[largestColumnIndex()]
                    xOffset = 0
                    columIndex = 0
                }

                for i in columIndex..<columIndex + viewSize{
                    if(i < columnsQuantity){
                        //current height
                        let currValue = self.columsHeights[i]
                        //new column height with the update
                        let newValue = yOffset + height
                        //space that will remaing in blank, this must be 0 if its ok
                        let remainder = (newValue - currValue) - CGFloat(viewSize) * blockWidth
                        if(remainder > 0) {
                            debugPrint("Its bigger remainder is \(remainder)")
                            //number of spaces to fill
                            let spacesTofillInColumn = Int(remainder/blockWidth)
                            //we need to add those spaces as avaiableSpaces
                            for j in 0..<spacesTofillInColumn {
                                self.avaiableSpaces.append((i,currValue + (CGFloat(j)*blockWidth)))
                            }
                        }
                        self.columsHeights[i] = yOffset + height
                    }
                }
            }else{
                //if there is not avaiable space
                if(self.avaiableSpaces.count == 0)
                {
                    //  Set column height
                    self.columsHeights[columIndex] += height
                }else{//if there is some avaiable space
                    yOffset = self.avaiableSpaces.first!.1
                    xOffset = CGFloat(self.avaiableSpaces.first!.0) * width
                    self.avaiableSpaces.remove(at: 0)
                }
            }

            print(width)

            let frame = CGRect(x: xOffset, y: yOffset, width: width, height: height)
            let insetFrame = frame.insetBy(dx: cellPadding, dy: cellPadding)

            let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)
            attributes.frame = insetFrame
            cache.append(attributes)

            contentHeight = max(contentHeight, frame.maxY)
        }
    }

    func getNextCellSize(currentCell: Int, collectionView: UICollectionView) -> Int {
        var nextViewSize = 0
        if currentCell < (collectionView.numberOfItems(inSection: 0) - 1) {
            nextViewSize = delegate.collectionView(collectionView, sizeForViewAtIndexPath: IndexPath(item: currentCell + 1, section: 0))
        }
        return nextViewSize
    }

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

        var visibleLayoutAttributes = [UICollectionViewLayoutAttributes]()

        // Loop through the cache and look for items in the rect
        for attributes in cache {
            if attributes.frame.intersects(rect) {
                visibleLayoutAttributes.append(attributes)
            }
        }
        return visibleLayoutAttributes
    }

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

已更新

您需要将 viewController 设置为 FillingLayoutDelegate

override func viewDidLoad() {
    super.viewDidLoad()

    collectionView.delegate = self
    collectionView.dataSource = self

    // Do any additional setup after loading the view.
    if let layout = self.collectionView.collectionViewLayout as? FillingLayout
    {
        layout.delegate = self
    }

}

ViewController 中的 FillingLayoutDelegate 实现

extension ViewController: FillingLayoutDelegate{
func collectionView(_ collectionView:UICollectionView,sizeForViewAtIndexPath indexPath:IndexPath) ->Int{
        if(indexPath.row == 0 || indexPath.row == 4)
        {
            return 2
        }

        if(indexPath.row == 5)
        {
            return 3
        }

        return 1
    }

    func numberOfColumnsInCollectionView(collectionView:UICollectionView) ->Int{
        return 3
    }
}

屏幕截图有效