从 UICollectionViewController 获取 indexPath 到 UICollectionViewCell 子类

Question

在我的视图控制器中，我正在加载带有子类的自定义 CollectionViewCell。根据单元格索引路径的位置，我想以不同的方式格式化文本标签。 IE。第一行只有一个文本较大的单元格，而第二行有两个文本较小的单元格。

如何从 UICollectionViewCell 子类中的 UICollectionView 访问索引路径？我尝试了一个委托协议，但这总是返回 nil。

下面的代码，非常感谢！

马库斯

UICollectionViewController：

import UIKit

protocol WorkoutDataViewControllerCVDataSource: AnyObject {

func workoutType(for workoutDataViewControllerCV: WorkoutDataViewControllerCV) -> WorkoutType
func workoutDistance(for workoutDataViewControllerCV: WorkoutDataViewControllerCV) -> Double
func workoutDuration(for workoutDataViewControllerCV: WorkoutDataViewControllerCV) -> Double
func workoutInstantVelocity(for workoutDataViewControllerCV: WorkoutDataViewControllerCV) -> Double
}

final class WorkoutDataViewControllerCV: UIViewController {

@IBOutlet weak var collectionView: UICollectionView!

weak var dataSource: WorkoutDataViewControllerCVDataSource!

private lazy var velocityFormatter = VelocityFormatter(dataSource: self, delegate: self)
private lazy var averageVelocityFormatter = VelocityFormatter(dataSource: self, delegate: self)

override func viewDidLoad() {
    super.viewDidLoad()
    self.collectionView.register(MeasurementCollectionViewCell.preferredNib, forCellWithReuseIdentifier: MeasurementCollectionViewCell.preferredReuseIdentifier)
}

 }

   // MARK: - Managing UICollectionView

 extension WorkoutDataViewControllerCV: UICollectionViewDataSource {

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

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Measurement Cell", for: indexPath)
    return cell
     }

    }

   extension WorkoutDataViewControllerCV: UICollectionViewDelegateFlowLayout {

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

    let availableWidth = self.view.frame.width

    switch indexPath.row {
    case 0: return CGSize(width: availableWidth, height: 150)
    case 1: return CGSize(width: availableWidth/2.1, height: 150)
    case 2: return CGSize(width: availableWidth/2.1, height: 150)
    case 3: return CGSize(width: availableWidth, height: 150)
    default:
        return CGSize(width: availableWidth/2.1, height: 150)
    }
}
}

   // MARK: - Managing VelocityFormatter

   extension WorkoutDataViewControllerCV: VelocityFormatterDataSource     {

func duration(for velocityFormatter: VelocityFormatter) -> Double {
    return dataSource.workoutDuration(for: self)
}

func distance(for velocityFormatter: VelocityFormatter) -> Double {
    return dataSource.workoutDistance(for: self)
}

func instantVelocity(for velocityFormatter: VelocityFormatter) -> Double {
    return dataSource.workoutInstantVelocity(for: self)
}
}

UICollectionViewCell.swift

    import UIKit

  final class MeasurementCollectionViewCell: UICollectionViewCell {

@IBOutlet private var measurementPropertyLabel: UILabel!
@IBOutlet private var measurementValueLabel: UILabel!
@IBOutlet private var measurementUnitLabel: UILabel!

static let preferredReuseIdentifier = "Measurement Cell"
static let preferredNib = UINib(nibName: "MeasurementCollectionViewCell", bundle: nil)

override func awakeFromNib() {
    super.awakeFromNib()
    updateMeasurement(property: "Speed", value: "100", unit: "km/h")

    //measurementValueLabel.font = measurementValueLabel.font.monospacedDigitFont
}

func updateMeasurement(property: String, value: String, unit: String?) {
    measurementPropertyLabel.text = property
    measurementValueLabel.text = value
    measurementUnitLabel.text = unit
       }

    }

Answer 1

相当直接的方法是将indexPath 存储到UICollectionViewCell 类的子类中。从cellForRow at: index path 返回时分配它。所以现在子类 collectionviewcell 可以访问它自己的 indexpath

Answer 2

在UICollectionView delegate方法collectionView(_, didSelectItemAt _)中获取cell的实例。

extension WorkoutDataViewControllerCV: UICollectionViewDelegate {

    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

        if let cell = collectionView.cellForItem(at: indexPath) as? MeasurementCollectionViewCell {
            cell.selectedIndexPath(indexPath)
        }
    }
}

indexPath 将作为参数在方法 selectedIndexPath 中从上述方法传递给 MeasurementCollectionViewCell。

class MeasurementCollectionViewCell: UICollectionViewCell {

    ......
    func selectedIndexPath(_ indexPath: IndexPath) {

        //Do your business here.
    }
}

Answer 3

您可以使用响应者链来获取单元格的集合视图，您可以使用该视图获取索引路径。只需将这些扩展名添加到一个名为 UICollectionViewCell+IndexPath.swift 的新文件中即可。

extension UIResponder {
    func next<T: UIResponder>(_ type: T.Type) -> T? {
        return next as? T ?? next?.next(type)
    }
}

extension UICollectionViewCell {
    var indexPath: IndexPath? {
        return next(UICollectionView.self)?.indexPath(for: self)
    }
}

现在在您的单元格中，您可以使用self.indexPath