带有自动调整大小的单元格的UICollectionView(estimatedSize)和sectionHeadersPinToVisibleBounds就是精神上的

Question

考虑以下情况.我有一个UICollectionView(内部UICollectionViewController),看起来几乎一样UITableView(我不使用的原因UITalbeView是因为我在布局上有非数据视图,我不想管理和搞乱我IndexPath).为了实现我设置的自动调整单元estimatedItemSize,类似的东西:

layout.estimatedItemSize = CGSize(width: self.view.bounds.size.width, height: 72)

另外,在我的单元格中,我有布局属性:

override func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
    layoutAttributes.bounds.size.height = systemLayoutSizeFitting(UILayoutFittingCompressedSize).height
    return layoutAttributes
}

所以,通过这样做,我得到了UITableView与自动调整一样的精确布局.而且效果很好.

现在,我正在尝试添加标题并将其固定在滚动到该部分的顶部,如下所示:

layout.sectionHeadersPinToVisibleBounds = false

但布局进入了奇怪的状态,我到处都有毛刺,细胞相互重叠,标题有时不会粘住.

更新:

视图控制器和单元的代码:

class ViewController: UICollectionViewController {

override func viewDidLoad() {
    super.viewDidLoad()
    let layout = collectionView?.collectionViewLayout as! UICollectionViewFlowLayout
    layout.sectionHeadersPinToVisibleBounds = true
    layout.estimatedItemSize = CGSize(width: collectionView?.bounds.size.width ?? 0, height: 36) // enables dynamic height
}

override func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 10
}

override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 10
}

override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let cell =  collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CustomCell
    cell.heightConstraint.constant = CGFloat(indexPath.row * 10 % 100) + 10 // Random constraint to make dynamic height work

    return cell
}

override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
    return collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "Header", for: indexPath)
}

class CustomCell : UICollectionViewCell {
let identifier = "CustomCell"

@IBOutlet weak var rectangle: UIView!
@IBOutlet weak var heightConstraint: NSLayoutConstraint!

override func awakeFromNib() {
    translatesAutoresizingMaskIntoConstraints = false
}

override func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
    layoutAttributes.bounds.size.height = systemLayoutSizeFitting(UILayoutFittingCompressedSize).height
    return layoutAttributes
}

视频中滞后的详细信息:https://vimeo.com/203284395

Answer 1

WWDC 2017 更新：

我的同事在 WWDC 2017 上，他向一位 UIKit 工程师询问了这个问题。工程师确认此问题是苹果已知的错误，目前尚未修复。