swift - 更改数据和 popViewController 后 TableView 不会重新加载

Question

在我的应用程序中，我使用 NSFetchedResultsControllerDelegate 在添加新数据后重新加载 Tableview，但此解决方案仅在我第一次访问 View 时才有效。

如果我删除数据并再次添加，该信息不会出现在表格 View 中。为此，我需要离开 View 并再次访问它。

我尝试过使用 Delegates 和 CallBack 来重新加载 TableView ，但没有成功。

我发现在删除旧数据后添加新数据后不会调用 cellForRowAt 。尽管已经调用了 numberOfSections。

我迷路了。有人可以帮助我吗？

Here is the video with app behaviour

在这里我向您展示我的代码的一些部分:

我的 NSFetchedResultsControllerDelegate

extension MeasureController: NSFetchedResultsControllerDelegate {

func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange sectionInfo: NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) {
    switch type {
    case .insert:
        myTableView.insertSections(IndexSet(integer: sectionIndex), with: .fade)
    case .delete:
        myTableView.deleteSections(IndexSet(integer: sectionIndex), with: .fade)
    case .move:
        break
    case .update:
        myTableView.reloadSections(IndexSet(integer: sectionIndex), with: .fade)
    @unknown default:
        fatalError()
    }
}


func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
    myTableView.reloadData()
    myCollectionView.reloadData()
}

//Allow to show full section name in header.
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, sectionIndexTitleForSectionName sectionName: String) -> String? {
    return sectionName
}

}

我的 MeasureController 中具有表格 View 的 viewWillAppear

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    self.fillDataInTheView()
    self.allMeasures = CoreDataManager.shared.loadAllMeasuresByAthlete(athlete: athleteToShow)

    //Get the last recorded date that has measures records
    if let allMeasures = self.allMeasures, let selectedDay = CoreDataManager.shared.getLastDayWithMeasures(measure: allMeasures) {
        self.selectedDay = selectedDay
    }

    if selectedDay != nil {
        if let measureByAthleteAndDay = CoreDataManager.shared.loadAllMeasuresByAthleteAndDay(athlete: athleteToShow, day: selectedDay) {
            self.measureByAthleteAndDay = measureByAthleteAndDay
        }

        do {
            try fetchedRCAllMeasuresByDay.performFetch()
        } catch let fetchedError {
            print("Error fetching Measures by Day:", fetchedError)
        }
    }

    do {
        try fetchedRCDay.performFetch()
    } catch let err {
        print(err)
    }

    if let lastEvaluation = getRecentDate() {
        lbEvaluationDate.text = "Última Avaliação: \(lastEvaluation.mediumDate())"
    } else {
        lbEvaluationDate.text = "Sem Avaliação Registrada"
    }

    self.myTableView.reloadData()
}

这是我的日期数据 myCollectioView

extension MeasureController: UICollectionViewDelegate, UICollectionViewDataSource {

// MARK: - Collection View Data Source

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    guard let dates = fetchedRCDay.fetchedObjects else {return 0}
    return dates.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = myCollectionView.dequeueReusableCell(withReuseIdentifier: cellCollectionViewID, for: indexPath) as! DateCollectionCell
    let day = fetchedRCDay.object(at: indexPath)
    if let date = day.title {
        cell.setupCell(date: date)
    }

    if day == selectedDay {
        cell.isSelected = true
    } else {
        cell.isSelected = false
    }

    cell.delegate = self

    return cell
}

// MARK: - Collection View Delegate

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    self.selectedCell(true, indexPath: indexPath)
    let day = fetchedRCDay.object(at: indexPath)
    self.alertToCreateEvaluation(day: day)
    myCollectionView.reloadData()
}

func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
    self.selectedCell(false, indexPath: indexPath)
    let day = fetchedRCDay.object(at: indexPath)
    if let date = day.title {
        lbEvaluationDate.text = "Data da Avaliação: \(date.mediumDate())"
    }
}

func hasMeasures(cell: DateCollectionCell, day: Day) {

    if day.allMeasures == nil {
        cell.ivIndicator.isHidden = true
    } else {
        cell.ivIndicator.isHidden = false
    }
}

}

如果您需要更多代码来更好地理解它，请告诉我。

Answer 1

试试这个...根据 Apple 文档 NSFetchedResultControllerDelegate ...

添加新的实例方法:

func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {

    tableView.beginUpdates()
}

更改现有的 controllerDidChangeContent(_:) 实例方法:

func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {

    tableView.endUpdates()
}

省略对 .reloadData() 的调用 - 这些是“强力”便捷方法，可以重新加载整个表或 Collection View ，并使微妙的 FRC 委托(delegate)方法的使用变得多余。