ios - 防止 UICollectionViewCell 阴影转换到其他单元格上

Question

我希望有人能有一个聪明的解决方案来解决这个问题，因为目前我很困惑。我有一个 collectionView，其单元格都在其后面的区域上转换了相当大的阴影。问题是，由于它们距离很近，每个单元格也会将阴影转换到紧邻的前一个单元格上。所有这些单元格在其layoutAttributes中都具有相同的zIndex，但Apple似乎将具有较高indexPath值的单元格放置在较高的zIndex处。有没有好的方法来防止这些细胞将阴影转换到其他细胞上？

细胞通过以下方式设置阴影:

    cell.layer.shadowOpacity = 1
    cell.layer.shadowRadius = 54
    cell.layer.shadowOffset = CGSize(width: 0, height: 12)
    cell.layer.shadowColor = UIColor.black.withAlphaComponent(0.5).cgColor

谢谢!

Answer 1

设置 Collection View 图层的阴影属性，而不是在每个单元格上设置它们。确保 Collection View 没有 backgroundView 并且它的 backgroundColor 为零。还要确保 Collection View 的某些祖先 View 确实具有背景颜色或其他填充。

结果:

源代码:

import UIKit

class ViewController: UIViewController, UICollectionViewDataSource {

    var cellIdentifier: String { return "cell" }

    override func loadView() {
        let view = UIView(frame: CGRect(x: 0, y: 0, width: 300, height: 300))
        view.backgroundColor = .white

        let layout = UICollectionViewFlowLayout()
        layout.itemSize = CGSize(width: 50, height: 50)
        layout.minimumInteritemSpacing = 4
        layout.minimumLineSpacing = 4
        layout.scrollDirection = .vertical
        layout.sectionInset = UIEdgeInsets(top: 4, left: 4, bottom: 4, right: 4)

        let collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
        collectionView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        collectionView.backgroundColor = nil
        collectionView.dataSource = self
        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: cellIdentifier)

        collectionView.layer.shadowColor = UIColor.black.cgColor
        collectionView.layer.shadowRadius = 8
        collectionView.layer.shadowOpacity = 1

        view.addSubview(collectionView)

        self.view = view
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 100
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellIdentifier, for: indexPath)
        let layer = cell.contentView.layer
        layer.backgroundColor = #colorLiteral(red: 1.0, green: 1.0, blue: 1.0, alpha: 1.0)
        layer.borderColor = #colorLiteral(red: 0.4392156899, green: 0.01176470611, blue: 0.1921568662, alpha: 1)
        layer.borderWidth = 2
        layer.cornerRadius = 8
        layer.masksToBounds = true
        return cell
    }

}