UITableView 以级联动画的方式进行行的删除和插入

Question

我有兴趣使用动画tableView.deleteRows(at: [singleIndexPath], with: .automatic) 从UITableView 中删除一批行。然而，我的目标是级联删除动画，以便它们以级联动画的方式发生，这样，动画将显示它们一个接一个地被删除，而不是整批被删除。

我发现了一个有用的 UITableView 扩展，在动画完成后我会得到一个完成块，例如：

extension UITableView {

    /// Perform a series of method calls that insert, delete, or select rows and sections of the table view.
    /// This is equivalent to a beginUpdates() / endUpdates() sequence,
    /// with a completion closure when the animation is finished.
    /// Parameter update: the update operation to perform on the tableView.
    /// Parameter completion: the completion closure to be executed when the animation is completed.

    func performUpdate(_ update: ()->Void, completion: (()->Void)?) {

        CATransaction.begin()
        CATransaction.setCompletionBlock(completion)

        // Table View update on row / section
        beginUpdates()
        update()
        endUpdates()

        CATransaction.commit()
    }

}

我的问题是弄清楚如何利用块自动化行删除（以及后来的行插入）的动画。现在，下面两行 IndexPaths 的示例代码仍然同时出现动画，这不是我的目标。

    let singleIndexPath = IndexPath(row: 0, section: 0)
    let anotherIndexPath = IndexPath(row: 1, section: 0)

    self.tableView.performUpdate({

        self.tableView.deleteRows(at: [singleIndexPath, anotherIndexPath], with: .automatic)
        self.tableView.insertRows(at: [singleIndexPath, anotherIndexPath], with: .left)
        //Happening at the same time, which is not what I want
    }, completion: {

    })

非常感谢任何提示。

Answer 1

级联表视图行删除

用法：

let indexPathsToDelete = [IndexPath(row: 1, section: 0), IndexPath(row: 4, section: 0), IndexPath(row: 6, section: 0)]
 deleteRowsAt(indexPaths: indexPathsToDelete, in: tableView)

代码：

func deleteRowsAt(indexPaths: [IndexPath], in tableView: UITableView) {
    var state = (0 ..< tableView.numberOfSections).map {
        Array(0 ..< tableView.numberOfRows(inSection: $0))
    }

    func cascadeDeleteAt(indexPath indexPathToDelete: IndexPath) {

        // Get the current row for the index path we wish to delete.
        // It could be diffrent to its original index path if other rows have been deleted.
        guard let currentRow = state[indexPathToDelete.section].index(of: indexPathToDelete.row) else { return }

        let currentIndexPath = IndexPath(row: currentRow, section: indexPathToDelete.section)
        print(currentIndexPath)

        // --- IMPLEMENT THE DELETION FROM YOUR DATA SOURCE ---
        source.remove(at: currentIndexPath.row)


        state[indexPathToDelete.section].remove(at: currentIndexPath.row)

        tableView.performUpdate({
            tableView.deleteRows(at: [currentIndexPath], with: .left)
        }, completion: {
            guard var idx = indexPaths.index(of: indexPathToDelete) else { return }
            idx += 1
            if idx < indexPaths.count {
                let nextIndexPathToDelete = indexPaths[idx]
                cascadeDeleteAt(indexPath: nextIndexPathToDelete)
            }
        })
    }

    if let indexPath = indexPaths.first {
        cascadeDeleteAt(indexPath: indexPath)
    }
}

当以级联方式删除行（即一次删除一行而不是一次删除所有行）时，棘手的部分是：

1. 删除一行后，其他索引（索引路径以及数据源的索引）不再指向它们原来的位置。
2. 需要从递归函数中调用函数performUpdate，以允许仅在删除当前行后删除下一行。