swift CollectionViewCell的Autolayout

Posted 2021-05-19

let v = UIView(frame: .zero)

    let l1 = UILabel(frame: .zero)
        l1.translatesAutoresizingMaskIntoConstraints = false
        l1.font = .systemFont(ofSize: 27.0)
        l1.text = "asdlas"

    v.addSubview(l1)
    NSLayoutConstraint.activate([
      l1.topAnchor.constraint(equalTo: v.topAnchor),
      l1.leadingAnchor.constraint(equalTo: v.leadingAnchor),
    ])
    l1.setContentHuggingPriority(.required, for: .vertical)
    l1.setContentCompressionResistancePriority(.required, for: .vertical)

    let trailing = l1.trailingAnchor.constraint(equalTo: v.trailingAnchor)
        trailing.priority = .defaultHigh
    NSLayoutConstraint.activate([
      trailing
    ])

    let l2 = UILabel(frame: .zero)
        l2.translatesAutoresizingMaskIntoConstraints = false
        l2.font = .systemFont(ofSize: 17.0)
        l2.text = ""

    v.addSubview(l2)
    NSLayoutConstraint.activate([
      l2.topAnchor.constraint(equalTo: l1.bottomAnchor),
      l2.leadingAnchor.constraint(equalTo: v.leadingAnchor),
    ])
    l2.setContentHuggingPriority(.required, for: .vertical)
    l2.setContentCompressionResistancePriority(.required, for: .vertical)

    let trailing_ = l2.trailingAnchor.constraint(equalTo: v.trailingAnchor)
        trailing_.priority = .defaultHigh
    let bottom = l2.bottomAnchor.constraint(equalTo: v.bottomAnchor)
        bottom.priority = .defaultHigh
    NSLayoutConstraint.activate([
      trailing_,
      bottom
    ])


    let s = v.systemLayoutSizeFitting(UIView.layoutFittingCompressedSize)

    view.addSubview(v)
    v.frame.size = s
    v.center = view.center
    v.layer.borderColor = UIColor.red.cgColor
    v.layer.borderWidth = 1.0
    
    
    //---------------------------

    func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes
  {
    let layoutAttributes = super.preferredLayoutAttributesFitting(layoutAttributes)

    let fittingSize = UIView.layoutFittingCompressedSize

    layoutAttributes.frame.size = systemLayoutSizeFitting(
      fittingSize,
      withHorizontalFittingPriority: .fittingSizeLevel,
      verticalFittingPriority: .fittingSizeLevel
    )

    return layoutAttributes
  }