Question

我有一个带有集合视图的视图控制器，如下所示：

import UIKit

private let reuseIdentifier = "LightboxCollectionViewCell"

class LightboxViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

    var items: [Image]?

    @IBOutlet weak var collectionView: UICollectionView!

    override func viewDidLoad() {
        super.viewDidLoad()

        self.collectionView.delegate = self
        self.collectionView.dataSource = self

        let collectionViewCell = UINib(nibName: reuseIdentifier, bundle: nil)
        self.collectionView.register(collectionViewCell, forCellWithReuseIdentifier: reuseIdentifier)
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return items!.count
    }

    func collectionView(_ collectionView: UICollectionView, didEndDisplaying cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
        guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath as IndexPath) as? LightboxCollectionViewCell else {
            fatalError(String(format: "The dequeued cell is not an instance of %s.", reuseIdentifier))
        }

        // Reset the zoom
        cell.imageView.transform = CGAffineTransform.identity
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath as IndexPath) as? LightboxCollectionViewCell else {
            fatalError(String(format: "The dequeued cell is not an instance of %s.", reuseIdentifier))
        }

        if let item = items?[indexPath.row] {
            cell.initialize(media: item)
        }

        return cell
    }

}

这是单元格类：

import UIKit
import Kingfisher

class LightboxCollectionViewCell: UICollectionViewCell {

    var media: Image?

    // Sets the maximum zoom
    let maxZoom: CGFloat = 10

    @IBOutlet weak var background: UIView!
    @IBOutlet weak var imageView: UIImageView!

    func initialize(media: PostImage) {
        self.media = media

        if let thumbnailUrl = media.thumbnailUrl {
            imageView.kf.setImage(with: URL(string: thumbnailUrl))
        }
    }

    override func awakeFromNib() {
        super.awakeFromNib()

        // Create pinch gesture recognizer to handle zooming
        let pinch = UIPinchGestureRecognizer(target: self, action: #selector(self.pinchToZoom(sender:)))
        self.imageView.addGestureRecognizer(pinch)
    }

    /**
     Handles pinch zooming.
     */
    @objc func pinchToZoom(sender: UIPinchGestureRecognizer) {
        if sender.state == .began || sender.state == .changed {
            let currentScale = self.imageView.frame.size.width / self.imageView.bounds.size.width
            var newScale = currentScale * sender.scale

            if newScale < 1 {
                newScale = 1
            }

            if newScale > maxZoom {
                newScale = maxZoom
            }

            let transform = CGAffineTransform(scaleX: newScale, y: newScale)

            self.imageView.transform = transform
            sender.scale = 1
        }
    }

}

如您所见，在didEndDisplaying中，我试图重置单元格的图像视图缩放，因为我具有让用户放大图像的功能。但是由于某种原因，变焦没有被重置，我也不知道为什么。

Answer 1

您要使一个新的单元出队（仅与cellForItemAt相关），而不使用提供的单元。将您的代码更改为以下代码，您应该会很好：

func collectionView(_ collectionView: UICollectionView, didEndDisplaying cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
    guard let cell = cell as? LightboxCollectionViewCell else {
        fatalError("The cell is not an instance of \(reuseIdentifier).")
    }

    // Reset the zoom
    cell.imageView.transform = CGAffineTransform.identity
}

Answer 2

您可以在单元格的 prepareForReuse 中设置图像的变换值作为标识，而不必使用 didEndDisplaying 功能。

在LightboxCollectionViewCell文件中，只需添加此功能

var distinctValues = theList.Distinct().ToArray();

for(int i = 0; i < distinctValues.Length; i++)
{
  var cnt = theList.Count(e => e == distinctValues[i]);
  Console.WriteLine($"Element {distinctValues[i]}, count {cnt}");
}

并从LightboxViewController中删除 didEndDisplaying 函数。

集合视图单元格缩放未重置

2 个答案: