如何获取 UICollectionView Header 的 IndexPath？

Question

视图：页眉视图

class HeaderCell: UICollectionViewCell {
    //MARK: - Properties

....

    lazy var clearButton: UIButton = {
        let bt = UIButton(type: .custom)
        bt.backgroundColor = .clear
        bt.addTarget(self, action: #selector(handleClearButton(button:)), for: .touchUpInside)
        return bt
    }()

    weak var delegate: HeaderCellDelegate?

   //MARK: - Init
   required init?(coder aDecoder: NSCoder) {
        return nil
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        configureCell()
        addViews()
        setConstraints()
    }

....

    //MARK: - Handlers
    @objc func handleClearButton(button: UIButton) {
        delegate?.expandSelectedHeader(self)
    }

协议：HeaderCellDelegate

protocol HeaderCellDelegate: class {
    func expandSelectedHeader(_ header: UICollectionViewCell)
}

控制器：SomeController

func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
        switch kind {
        case UICollectionView.elementKindSectionHeader:
            let header = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: reuseIdentifierForHeader, for: indexPath) as! HeaderCell
            header.toMenuControllerDelegate = self
            return header

        case UICollectionView.elementKindSectionFooter:
            let footer = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: reuseIdentifierForFooter, for: indexPath) as! MenuFooterCell
            return footer
        default:
            return UICollectionReusableView()
        }
    }


extension SomeController:HeaderCellDelegate {
    func expandSelectedHeader(_ header: UICollectionViewCell) {
        let indexPath = collectionView.indexPath(for: header)
        print(indexPath)
    }
}

我正在尝试在 headerView 中使用 clearButton，当点击按钮时，它会将自身（UIcollectionViewCell）发送到控制器。因此，一旦控制器接收到有关单元格的信息，我就可以使用collectionView.indexPath(for cell:UICollectionViewCell) 来获取点击按钮的标题的 indexPath。但是使用上面的代码，我只能得到nil 和print(indexPath)。

我该如何解决这个问题？？？ 我提前感谢您的帮助。

Answer 1

您的委托函数expandSelectedHeader() 不知道它的indexPath，除非您将它传递给它。一种解决方法是在 HeaderCell 类中声明一个索引路径属性，并在创建补充视图时传递该值：

class HeaderCell: UICollectionViewCell {
    //MARK: - Properties
    var indexPath: IndexPath?
   // rest of the code
}

//MARK: - Handlers
    @objc func handleClearButton(button: UIButton) {
        delegate?.expandSelectedHeader(self, indexPath: self.indexPath)
    }

还要稍微修改一下协议：

protocol HeaderCellDelegate: class {
    func expandSelectedHeader(_ header: UICollectionViewCell, indexPath: IndexPath?)
}

在创建视图时分配索引路径：

// ...
let header = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: reuseIdentifierForHeader, for: indexPath) as! HeaderCell
// I'd suggest do not force down case the view as HeaderCell, use if..let
header.toMenuControllerDelegate = self
header.indexPath = indexPath
// ...

最后：

extension SomeController:HeaderCellDelegate {
    func expandSelectedHeader(_ header: UICollectionViewCell, indexPath: IndexPath) {
        print(indexPath)
    }
}

Answer 2

而不是发送整个单元格然后获取索引路径。在协议中发送 IndexPath 并从中获取标头是一个好方法

override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
  switch kind {
    case UICollectionElementKindSectionHeader:
        let headerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: "header", for: indexPath) as! HeaderCollectionReusableView
        let gestureRecognizer: UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(didSelectSection(gesture:)))
        headerView.addGestureRecognizer(gestureRecognizer)
        return headerView
    }
}

现在在 didSelectSection 中：

@objc func didSelectSection(_ gestureRecognizer: UITapGestureRecognizer) {
    let indexPaths = self.collectionView?.indexPathsForVisibleSupplementaryElements(ofKind: UICollectionElementKindSectionHeader)
    for indexPath in indexPaths! {
        if (gestureRecognizer.view as! HeaderCollectionReusableView) == collectionView?.supplementaryView(forElementKind: UICollectionElementKindSectionHeader, at: indexPath){
            print("found at : \(indexPath)")
            break
        }
    }
}