ios - 如何使用 NSFetchedResultsController 更新 tableview 内容

Question

我正在更新 coredata 的某些部分，并且我希望 NSFetchedResultsController 自动重新加载包含所有动画的表格 View 。我正在更改用于对 TableView 进行排序的 coredata 元素。我通过在单元格上向右滑动，然后将该特定 tableviewcell 的priorityNumber更改为零来完成此操作，以便任务转到底部和其他一些事情。我希望表格重新加载但带有动画。现在我只是在做 tableView.reload() 但它不能正常工作。

我想看到单元格移动到设备底部的动画。任何帮助将不胜感激!

代码如下:我对 coreData 所做的更改:

func tableView(_ tableView: UITableView,
               leadingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration?
{
    let closeAction = UIContextualAction(style: .normal, title:  "✓", handler: { (ac:UIContextualAction, view:UIView, success:(Bool) -> Void) in

        //???

        self.fetchedResultsController.object(at: indexPath).sTaskCompleted = !(self.fetchedResultsController.object(at: indexPath).sTaskCompleted)

        if ( self.fetchedResultsController.object(at: indexPath).sTaskCompleted)
        {
            print("Completed")
            //Change priority number to 0 after saving their current priority number in previousPN
            //Change priority circle color
            //Change background of the cell to something else




            self.fetchedResultsController.object(at: indexPath).sPreviousPN = self.fetchedResultsController.object(at: indexPath).sPriorityNumber
            self.fetchedResultsController.object(at: indexPath).sPriorityNumber = 0
            self.fetchedResultsController.object(at: indexPath).cellbackgroundColor = UIColor(red:0.93, green:0.91, blue:0.91, alpha:1.0)
            self.fetchedResultsController.object(at: indexPath).previousPriorityColor = self.fetchedResultsController.object(at: indexPath).sPriorityColor
            self.fetchedResultsController.object(at: indexPath).sPriorityColor = .clear

            var error: NSError?


            do {
                // Save The object

                try self.moContext.save()
                print("SAVED")
            } catch let error1 as NSError {
                error = error1
            }


            DispatchQueue.main.asyncAfter(deadline: .now() + 0.3, execute: {
                UIView.transition(with: tableView,
                                  duration: 0.15,
                                  options: .transitionCrossDissolve,
                                  animations: { self.tableView.reloadData() })
            })

        } else {
            print("InCompleted")


            self.fetchedResultsController.object(at: indexPath).sPriorityNumber =  self.fetchedResultsController.object(at: indexPath).sPreviousPN

            self.fetchedResultsController.object(at: indexPath).cellbackgroundColor = .white
            self.fetchedResultsController.object(at: indexPath).sPriorityColor = self.fetchedResultsController.object(at: indexPath).previousPriorityColor

            var error: NSError?


            do {
                // Save The object

                try self.moContext.save()
                print("SAVED")
            } catch let error1 as NSError {
                error = error1
            }
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.3, execute: {
                UIView.transition(with: tableView,
                                  duration: 0.15,
                                  options: .transitionCrossDissolve,
                                  animations: { self.tableView.reloadData() })
            })

        }

        success(true)

    })

    closeAction.backgroundColor = UIColor(red:0.18, green:0.87, blue:0.65, alpha:1.0)

    return UISwipeActionsConfiguration(actions: [closeAction])

}

现在如何使用 FRC 委托(delegate)方法 (.update) 用适当的动画刷新 tableView。

Answer 1

TableView Controller 需要符合 NSFetchedResultsControllerDelegate 并实现其委托(delegate)方法。如果配置正确，获取的结果 Controller 将监视托管对象上下文的更改，并调用适当的委托(delegate)方法以使用动画更新 TableView 。

class TaskTableViewController: UITableViewController, NSFetchedResultsControllerDelegate {

    var fetchedResultsController: NSFetchedResultsController<Task>!

    override func viewDidLoad() {
        super.viewDidLoad()
        configureFetchedResultsController()
    }

    func configureFetchedResultsController() {

        if fetchedResultsController == nil {

            // 1. Get fetch request
            let fetchRequest: NSFetchRequest<Task> = Task.fetchRequest()

            // 2. Add sort descriptors
            fetchRequest.sortDescriptors = [NSSortDescriptor(key: "sPriorityNumber", ascending: false)]

            // 3. Configure the FRC
            fetchedResultsController = NSFetchedResultsController<Task>(fetchRequest: fetchRequest, managedObjectContext: CoreDataStack.context, sectionNameKeyPath: nil, cacheName: nil)

            // 4. Set the FRC delegate as self
            fetchedResultsController.delegate = self
        }

        // 5. Tell the FRC to start watching the MOC for changes
        do {
            try fetchedResultsController.performFetch()
        } catch {
            NSLog("Error starting fetched results controller  \(error)")
        }
    }

    // FRC delegate methods

    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>,
                    didChange anObject: Any,
                    at indexPath: IndexPath?,
                    for type: NSFetchedResultsChangeType,
                    newIndexPath: IndexPath?) {
        switch type {
        case .insert:
            guard let newIndexPath = newIndexPath else { return }
            tableView.insertRows(at: [newIndexPath], with: .automatic)
        case .delete:
            guard let indexPath = indexPath else { return }
            tableView.deleteRows(at: [indexPath], with: .fade)
        case .move:
            tableView.reloadData()
        case .update:
            guard let indexPath = indexPath else { return }
            tableView.reloadRows(at: [indexPath], with: .automatic)
        }
    }

    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>,
                    didChange sectionInfo: NSFetchedResultsSectionInfo,
                    atSectionIndex sectionIndex: Int,
                    for type: NSFetchedResultsChangeType) {
        switch type {
        case .delete:
            tableView.deleteSections(IndexSet(integer: sectionIndex), with: .automatic)
        case .insert:
            tableView.insertSections(IndexSet(integer: sectionIndex), with: .automatic)
        default:
            break
        }
    }
}