UIKit Swift：上下文菜单关闭后阴影延迟显示问题求助

我有一个带阴影的CollectionView单元格，给它添加了上下文菜单。关闭菜单后，单元格及其内部元素的阴影会有大约0.5秒的延迟才显示出来，不清楚问题出在哪里。相关代码如下：

func collectionView(_ collectionView: UICollectionView, contextMenuConfigurationForItemAt indexPath: IndexPath, point: CGPoint) -> UIContextMenuConfiguration? {
    
    if collectionView == foodOnTheShelf {
        
        let config = UIContextMenuConfiguration(identifier: nil, previewProvider: nil) { _ in

            let edit = UIAction(title: "Изменить", image: UIImage(systemName: "pencil"), identifier: nil, discoverabilityTitle: nil, state: .off) { _ in
                self.alert.showAlert(viewController: self,
                                     image:  UIImage(named: test[indexPath.row].name)!,
                                     food: test[indexPath.row],
                                     picker: self.picker,
                                     consumePicker: self.consumePicker,
                                     unit: self.unit,
                                     currentWeigt: test[indexPath.row].weight,
                                     currentProductDate: test[indexPath.row].productionDate,
                                     currentExperationDate: test[indexPath.row].expirationDate,
                                     searchController: nil)
            }
            
            let delete = UIAction(title: "Удалить", image: UIImage(systemName: "trash"), attributes: .destructive) { _ in
                test.remove(at: indexPath.row)
                self.viewDidAppear(true)
            }
            return UIMenu(title: "", image: nil, identifier: nil, options: UIMenu.Options.displayInline , children: [edit, delete])
        }
        return config
    }
 return nil
}

这个延迟问题大概率和上下文菜单关闭后的动画冲突，或是单元格阴影的渲染未及时触发更新，可从以下几个方向修复：

• 禁止手动调用生命周期方法
  你在删除操作里直接调用viewDidAppear(true)，这是错误的用法——生命周期方法不应手动触发。正确的做法是用CollectionView的专用更新方法，避免干扰视图渲染流程：

  let delete = UIAction(title: "Удалить", image: UIImage(systemName: "trash"), attributes: .destructive) { _ in
      test.remove(at: indexPath.row)
      self.foodOnTheShelf.deleteItems(at: [indexPath])
  }
  

• 监听菜单关闭事件，强制刷新单元格
  通过UIContextMenuInteractionDelegate的方法监听菜单关闭，然后触发对应单元格的图层重绘，确保阴影及时显示：

  func contextMenuInteractionDidEnd(_ interaction: UIContextMenuInteraction) {
      guard let indexPath = foodOnTheShelf.indexPathsForSelectedItems?.first else { return }
      if let cell = foodOnTheShelf.cellForItem(at: indexPath) {
          cell.layer.setNeedsDisplay()
          cell.layoutIfNeeded()
      }
  }
  

• 检查单元格阴影的设置逻辑
  确保阴影设置在单元格的主图层而非contentView上，同时可开启光栅化优化渲染性能，避免层级导致的延迟：

  // 在单元格初始化方法中配置阴影
  override init(frame: CGRect) {
      super.init(frame: frame)
      setupShadow()
  }
  
  private func setupShadow() {
      layer.shadowColor = UIColor.black.cgColor
      layer.shadowOpacity = 0.2
      layer.shadowOffset = CGSize(width: 0, height: 2)
      layer.shadowRadius = 4
      layer.masksToBounds = false
      // 可选：开启光栅化提升重复渲染性能
      layer.shouldRasterize = true
      layer.rasterizationScale = UIScreen.main.scale
  }
  

• 菜单关闭后立即触发布局刷新
  如果以上方法无效，可以在菜单创建时，通过异步队列触发CollectionView的布局失效，强制更新视图：

  let config = UIContextMenuConfiguration(identifier: nil, previewProvider: nil) { [weak self] _ in
      // ... 菜单操作定义
      let menu = UIMenu(title: "", image: nil, identifier: nil, options: .displayInline , children: [edit, delete])
      DispatchQueue.main.async {
          self?.foodOnTheShelf.collectionViewLayout.invalidateLayout()
      }
      return menu
  }
  

内容的提问来源于stack exchange，提问作者himynameisartem