ios - UICollectionView 边到边布局

Question

目标:在所有尺寸的 iPhone 上具有 2 个单元格的边到边 UICollectionView。

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {

   let screenSize = collectionView.bounds
    let screenWidth = screenSize.width
    print("Zhenya: \(screenWidth)") // prints correct 375, which is half of iPhone 6
    let cellEdgeLength: CGFloat = screenWidth / 2.0

    return CGSize(width: cellEdgeLength, height: cellEdgeLength)
}

还有

override func viewDidLoad() {
    super.viewDidLoad()
    collectionView.delegate = self
    collectionView.dataSource = self

    let flow = UICollectionViewFlowLayout()
    flow.scrollDirection = UICollectionViewScrollDirection.vertical
    flow.minimumInteritemSpacing = 0
    flow.minimumLineSpacing = 0
    collectionView.collectionViewLayout = flow
}

但是在 iPhone 6 上:

集合单元格属性:

Collection View 属性:

更新: func 的渐变，实际上得到了正确的宽度: (位于自定义 UICollectionViewCell 类)

  func addGradient () {

    let gradient = CAGradientLayer()
    gradient.frame = gradientView.bounds
    let topColor = UIColor(red:0.07, green:0.07, blue:0.07, alpha:1)
    let botomColor = UIColor.clear
    gradient.colors = [topColor.cgColor, botomColor.cgColor]

    if gradientWasRemoved == false {
    gradientView.layer.insertSublayer(gradient, at: 0)
    } else if gradientWasRemoved == true {
        self.addSubview(gradientView)
    }

更新 2: 注意:在 iPhone 7 Plus 上测试。 我发现 UICollectionViewFlowLayout 覆盖 sizeForItemAtIndexPath: 中创建的单元格大小(看起来像) 使用此代码:

    let flow = UICollectionViewFlowLayout()
    let screenSize = collectionView.bounds
    let screenWidth = screenSize.width
    let cellEdgeLength: CGFloat = screenWidth / 2.0

    flow.itemSize =  CGSize(width: cellEdgeLength, height: cellEdgeLength)

    flow.scrollDirection = UICollectionViewScrollDirection.vertical
    flow.minimumInteritemSpacing = 0
    flow.minimumLineSpacing = 0
    collectionView.collectionViewLayout = flow

我有这个:

然后我决定手动指定单元格边缘长度(iPhone7Plust 宽度的一半 = 207):

 let cellSide: CGFloat = 207
 flow.itemSize =  CGSize(width: cellSide, height: cellSide)

 flow.scrollDirection = UICollectionViewScrollDirection.vertical
 flow.minimumInteritemSpacing = 0
 flow.minimumLineSpacing = 0
 collectionView.collectionViewLayout = flow

我明白了:

Answer 1

找到了解决方案。 问题出在内部 imageView 自动布局设置中。我没有具体说明它们。 我不知道为什么那一小段废话会妨碍我的 flow.itemSize。 对我来说更奇怪的是，为什么当在第二次更新中手动将 cellEdgeLength 指定为 207 时，突然之间，它确实覆盖了 imageView 约束的缺乏。