每个自定义单元格和自定义高度

Question

我通过 switch 函数输出 4 个自定义单元格，现在我需要为每个单元格输出动态高度值或固定高度值。我都喜欢，因为它们的高度始终是静态的。

我订阅了uiСollectionviewВelegateFlowLayout 协议并找到了如何更改所有单元格的高度

func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        sizeForItemAt indexPath: IndexPath) -> CGSize {
        let size = CGSize(width: 357, height: 600)
        return size

要覆盖单个单元格的高度，我使用该函数

cell.frame = CGRect(cell.frame.origin.x, cell.frame.origin.y, width: 100.0, height: 100.0)

但它不起作用，“表达式类型 '@lvalue CGRect' 在没有更多上下文的情况下是模棱两可的”

在这种情况下我该怎么办？用什么函数？

完整代码如下

// main protocols UICollectionView
extension ViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

    // width and height for cell in collectionView
    func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        sizeForItemAt indexPath: IndexPath) -> CGSize {
        let size = CGSize(width: 357, height: 600)
        return size
    }


    //margins for cell in collectionView
    func collectionView(_ collectionView: UICollectionView, layout
        collectionViewLayout: UICollectionViewLayout,
                        minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 40.0
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 4
    }

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


            var cell: UICollectionViewCell!

            switch indexPath.row {
            case 1:
                cell = collectionView.dequeueReusableCell(withReuseIdentifier: "secondCell", for: indexPath)
                    as? secondCollectionViewCell
                cell.frame = CGRect(cell.frame.origin.x, cell.frame.origin.y, width: 100.0, height: 100.0)

            case 2:
                cell = collectionView.dequeueReusableCell(withReuseIdentifier: "thirdCell", for: indexPath)
                    as? cellThirdCollectionViewCell

            case 3:
                cell = collectionView.dequeueReusableCell(withReuseIdentifier: "fourthCell", for: indexPath)
                    as? fourthCollectionViewCell

            default:
                cell = collectionView.dequeueReusableCell(withReuseIdentifier: "imageCell", for: indexPath)
                    as? imageModelCollectionViewCell
            }
            return cell
        }
    }

Answer 1

extension ViewController : UICollectionViewDelegateFlowLayout {
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        switch indexPath.row {
        case 1:
            return CGSize(width: 100, height: 200)
        case 2:
            return CGSize(width: 100, height: 300)
        case 3:
            return CGSize(width: 100, height: 400)
        default:
            return CGSize(width: 100, height: 100)
        }
    }
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        var cell: UICollectionViewCell!

        switch indexPath.row {
        case 1:
            cell = collectionView.dequeueReusableCell(withReuseIdentifier: "firstCell", for: indexPath)
                as? firstCollectionViewCell


        case 2:
            cell = collectionView.dequeueReusableCell(withReuseIdentifier: "secondCell", for: indexPath)
                as? secondCollectionViewCell

        case 3:
            cell = collectionView.dequeueReusableCell(withReuseIdentifier: "thirdCell", for: indexPath)
                as? thirdCollectionViewCell

        default:
            cell = collectionView.dequeueReusableCell(withReuseIdentifier: "imageCell", for: indexPath)
                as? imageModelCollectionViewCell
        }
        return cell
    }
}

彻底解决问题 别忘了加

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

附言如果您收到“collectionView.delegate = self”错误，可能是您在 viewController 而不是在 collectionViewController 中工作的原因

您需要添加IBOutlet

Answer 2

您是否尝试过将您的函数 func collectionView(_:layout:sizeForItemAt:) 更改为类似的内容？

let cellHeights = [ 90, 400, 100, 70 ]

// width and height for cell in collectionView
func collectionView( _ view: UICollectionView, 
                     layout collectionViewLayout: UICollectionViewLayout,
                     sizeForItemAt indexPath: IndexPath ) -> CGSize 
{
    return CGSize( 
        width: view.bounds.size.width, 
        height: cellHeights[indexPath.row] 
    )
}

此外，将collectionView.dequeueReusableCell(withReuseIdentifier:for:) 的结果转换为UICollectionViewCell 子类对您的代码没有影响...

我可能会将其更改为：

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell 
{
    // map row numbers to cell reuse identifiers...   
    let ids = [ 
        0: "secondCell", 
        1: "thirdCell", 
        2: "fourthCell" 
    ]

    // look up the reuse identifier for the row we want; if none found (subscript call returns `nil`), use `"imageCell"`
    let reuseID = ids[indexPath.row] ?? "imageCell"
    let cell = collectionView.dequeueReusableCell( withReuseIdentifier: reuseID, for: indexPath)

    return cell
}

Answer 3

您可以使用高度数组并根据 indexPath 检索单元格高度。

let heightArray = [90,400,100,70]

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

                return CGSize(width: 357, height: heightArray[indexPath.row])

        }