swift - 如何在 UICollectionView 拖/放过程中删除 'ghost' 单元格，并使移动单元格不透明？

Question

我正在尝试在我的 UICollectionView 中实现拖放机制，这与在快捷方式应用程序中重新排序快捷方式的组件非常相似。

截至目前，行为是当您开始拖动时，会留下一个透明的单元格 View ，而另一个透明的单元格 View 会随手指移动。

我想摆脱“幽灵”单元格，并使移动的单元格完全不透明。

这是我的拖放行为(主要取自 this post )

func collectionView(_ collectionView: UICollectionView, itemsForBeginning session: UIDragSession, at indexPath: IndexPath) -> [UIDragItem] {
    let item = itemData[indexPath.item]
    let itemProvider = NSItemProvider(object: item.title as NSString)
    let dragItem = UIDragItem(itemProvider: itemProvider)
    dragItem.localObject = item


    return [dragItem]
}

func collectionView(_ collectionView: UICollectionView, dropSessionDidUpdate session: UIDropSession, withDestinationIndexPath destinationIndexPath: IndexPath?) -> UICollectionViewDropProposal {

    if collectionView.hasActiveDrag {
        return UICollectionViewDropProposal(operation: .move, intent: .insertAtDestinationIndexPath)
    }

    return UICollectionViewDropProposal(operation: .forbidden)
}

func collectionView(_ collectionView: UICollectionView, performDropWith coordinator: UICollectionViewDropCoordinator) {

    var destinationIndexPath: IndexPath
    if let indexPath = coordinator.destinationIndexPath {
        destinationIndexPath = indexPath
    }
    else {
        let row = collectionView.numberOfItems(inSection: 0)
        destinationIndexPath = IndexPath(row: row - 1, section: 0)
    }

    reorderItems(coordinator: coordinator, destinationIndexPath: destinationIndexPath, collectionView: collectionView)

}

fileprivate func reorderItems(coordinator: UICollectionViewDropCoordinator,
                              destinationIndexPath: IndexPath,
                              collectionView: UICollectionView) {

    if let item = coordinator.items.first,
        let sourceIndexPath = item.sourceIndexPath {

        collectionView.performBatchUpdates({
            self.itemData.remove(at: sourceIndexPath.item)
            self.itemData.insert(item.dragItem.localObject as! PlanItem, at: destinationIndexPath.item)

            collectionView.deleteItems(at: [sourceIndexPath])
            collectionView.insertItems(at: [destinationIndexPath])
        }, completion: nil)

        coordinator.drop(item.dragItem, toItemAt: destinationIndexPath)
    }
}

Answer 1

不确定问题是否仍然存在，但如果是:以下是处理单元格拖动状态的方法:

Is there a method to check the UICollectionView item drag cancellation if the item wasn't moved?

只需通过 DispatchQueue.main.async 在拖动时隐藏它{}

并在 .none 状态下再次可见。对我有用:)