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如何获得更均匀的单元格垂直距离?

uicollectionviewcell autolayout layout swift

Mozahler · 技术社区 · 7 年前

我已经使用自动布局(没有故事板或XIB)动态创建了单元格,但布局管理器似乎是将细胞配对,这样一个短的和一个高的细胞并排组成一行。

我想要的是让单元格之间的距离均匀(垂直堆叠),而不是大的空白。因此,左边连续的三个短单元格在高度和位置上可能与右边的一个大单元格相等。换言之:所有单元格之间的垂直均匀距离。

  /// Everything is a side effect.  Configure the cell passed in
    ///
    /// - Parameters:
    ///   - cell: cell to format
    ///   - indexPath: index of cell
    func formatAutolayoutCell(cell: AutoResizingTextCell, at indexPath: IndexPath) {
        let event = eventsSource[indexPath.row]
        cell.layer.borderColor = event.calendar.cgColor
        cell.contentView.backgroundColor =  UIColor(cgColor: event.calendar.cgColor).withAlphaComponent(0.1)

        cell.titleLabel.text = event.title

        cell.contentView.addSubview(cell.titleLabel)
        cell.titleLabel.topAnchor.constraint(equalTo: cell.contentView.topAnchor).isActive = true
        cell.titleLabel.widthAnchor.constraint(equalToConstant: cellWidth).isActive = true
        cell.titleLabel.textColor = UIColor(cgColor: event.calendar.cgColor)
        cell.titleLabel.textAlignment = .center

        cell.contentView.addSubview(cell.bodyLabel)
        cell.bodyLabel.text = event.notes ?? ""
        cell.bodyLabel.widthAnchor.constraint(equalToConstant: cellWidth).isActive = true
        cell.bodyLabel.bottomAnchor.constraint(equalTo: cell.contentView.bottomAnchor).isActive = true
        cell.titleLabel.bottomAnchor.constraint(equalTo: cell.bodyLabel.topAnchor).isActive = true
    }

编辑:

使用 Galo Torres Sevilla 我的建议是 UICollectionViewLayout . 它让我更接近我的目标,但是看起来单元格的数量是按列平均分配的,所以如果最左边的列有短的单元格,它会“早”用完单元格,并且左侧底部有很多空间。我可能需要按大小对单元格进行排序,以获得更好的分布。

1 回复 | 直到 7 年前

Galo Torres Sevilla 7 年前

遵循代码 https://www.raywenderlich.com/392-uicollectionview-custom-layout-tutorial-pinterest

您可以将uiCollectionViewFlowLayout子类化,以获得所需的内容。

这是它的主要代码。 注:代码来自上述网站

import UIKit

protocol PinterestLayoutDelegate: class {
  // 1. Method to ask the delegate for the height of the image
  func collectionView(_ collectionView:UICollectionView, heightForPhotoAtIndexPath indexPath:IndexPath) -> CGFloat
}

class PinterestLayout: UICollectionViewLayout {
  //1. Pinterest Layout Delegate
  weak var delegate: PinterestLayoutDelegate!

  //2. Configurable properties
  fileprivate var numberOfColumns = 2
  fileprivate var cellPadding: CGFloat = 6

  //3. Array to keep a cache of attributes.
  fileprivate var cache = [UICollectionViewLayoutAttributes]()

  //4. Content height and size
  fileprivate var contentHeight: CGFloat = 0

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

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

  override func prepare() {
    // 1. Only calculate once
    guard cache.isEmpty == true, let collectionView = collectionView else {
      return
    }
    // 2. Pre-Calculates the X Offset for every column and adds an array to increment the currently max Y Offset for each column
    let columnWidth = contentWidth / 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)

    // 3. Iterates through the list of items in the first section
    for item in 0 ..< collectionView.numberOfItems(inSection: 0) {

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

      // 4. Asks the delegate for the height of the picture and the annotation and calculates the cell frame.
      let photoHeight = delegate.collectionView(collectionView, heightForPhotoAtIndexPath: indexPath)
      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)

      // 5. Creates an UICollectionViewLayoutItem with the frame and add it to the cache
      let attributes = UICollectionViewLayoutAttributes(forCellWith: indexPath)
      attributes.frame = insetFrame
      cache.append(attributes)

      // 6. Updates the collection view content height
      contentHeight = max(contentHeight, frame.maxY)
      yOffset[column] = yOffset[column] + height

      column = column < (numberOfColumns - 1) ? (column + 1) : 0
    }
  }

  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]
  }

}