Я могу предложить вам создать собственный подкласс UICollectionViewFlowLayout, который будет генерировать необходимый макет. Вот простая схема потока, которую вы можете использовать. Вы можете настроить его под свои нужды, если я что-то пропустил.
public protocol CollectionViewFlowLayoutDelegate: class {
func numberOfColumns() -> Int
func height(at indexPath: IndexPath) -> CGFloat
}
public class CollectionViewFlowLayout: UICollectionViewFlowLayout {
private var cache: [IndexPath : UICollectionViewLayoutAttributes] = [:]
private var contentHeight: CGFloat = 0
private var contentWidth: CGFloat {
guard let collectionView = collectionView else {
return 0
}
let insets = collectionView.contentInset
return collectionView.bounds.width - (insets.left + insets.right)
}
public weak var flowDelegate: CollectionViewFlowLayoutDelegate?
public override var collectionViewContentSize: CGSize {
return CGSize(width: self.contentWidth, height: self.contentHeight)
}
public override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
var layoutAttributesArray = [UICollectionViewLayoutAttributes]()
if cache.isEmpty {
self.prepare()
}
for (_, layoutAttributes) in self.cache {
if rect.intersects(layoutAttributes.frame) {
layoutAttributesArray.append(layoutAttributes)
}
}
return layoutAttributesArray
}
public override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
return self.cache[indexPath]
}
public override func prepare() {
guard let collectionView = self.collectionView else {
return
}
let numberOfColumns = self.flowDelegate?.numberOfColumns() ?? 1
let cellPadding: CGFloat = 8
self.contentHeight = 0
let columnWidth = UIScreen.main.bounds.width / CGFloat(numberOfColumns)
var xOffset = [CGFloat]()
for column in 0 ..< numberOfColumns {
xOffset.append(CGFloat(column) * columnWidth)
}
var column = 0
var yOffset = [CGFloat](repeating: 0, count: numberOfColumns)
for item in 0 ..< collectionView.numberOfItems(inSection: 0) {
let indexPath = IndexPath(item: item, section: 0)
let photoHeight = self.flowDelegate?.height(at: indexPath) ?? 1
let height = cellPadding * 2 + photoHeight
let frame = CGRect(x: xOffset[column], y: yOffset[column], width: columnWidth, height: height)
let insetFrame = frame.insetBy(dx: cellPadding, dy: cellPadding)
let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)
attributes.frame = insetFrame
self.cache[indexPath] = attributes
self.contentHeight = max(self.contentHeight, frame.maxY)
yOffset[column] = yOffset[column] + height
column = column < (numberOfColumns - 1) ? (column + 1) : 0
}
}
}
Теперь в вашем UIViewController вы можете использовать его так:
override func viewDidLoad() {
super.viewDidLoad()
let flowLayout = CollectionViewFlowLayout()
flowLayout.flowDelegate = self
self.collectionView.collectionViewLayout = flowLayout
}
сделать недействительным collectionView макет после изменения ориентации
override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
guard let flowLayout = self.collectionView.collectionViewLayout as? CollectionViewFlowLayout else {
return
}
flowLayout.invalidateLayout()
}
и теперь заставьте ViewController соответствовать CollectionViewFlowLayoutDelegate
extension ViewController: CollectionViewFlowLayoutDelegate {
func height(at indexPath: IndexPath) -> CGFloat {
guard let cell = self.collectionView.cellForItem(at: indexPath) else {
return 1
}
cell.layoutIfNeeded()
//get calculated cell height
return cell.systemLayoutSizeFitting(UILayoutFittingCompressedSize).height
}
func numberOfColumns() -> Int {
//how much columns would be shown, depends on orientation
return UIDevice.current.orientation == .portrait ? 2 : 3
}
}