滚动表格视图时单元格变为空白（swift）

Question

I have a strange problem where my cells in the tableview are not consistent. Sometimes they will show as a blank cell and other times they will load with the correct data. See the GIF below.

Notice the blank cell in section 1 changes each time.

I also have this problem when adding new cells to the tableview, but closing and reopening the app always fixes it. It just doesn't load correctly when getting added... but sometimes it does load correctly. See GIF Below.

I've been recommended to use the reloadData(), but that doesn't seem to help anything at all. I'm hoping someone will see this that will know what to do.

See Code Below

Table View Controller: (Swift)

import UIKit
import CoreData

class ListItemsTVC: UITableViewController, NSFetchedResultsControllerDelegate {

// MARK: - Constants and Variables

let moc = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
var frc: NSFetchedResultsController = NSFetchedResultsController()
//var sequeItem: createItem?

// MARK: - App loading Functions

override func viewDidLoad() {
    super.viewDidLoad()

    frc = getFCR()
    frc.delegate = self

    do {
        try frc.performFetch()
    } catch {
        print("Failed to perform inital fetch")
    }
    self.tableView.rowHeight = 62

}

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

    self.tableView.reloadData()

}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

// MARK: - Table view data source

override func numberOfSectionsInTableView(tableView: UITableView) -> Int {

    if let sections = frc.sections {
        return sections.count
    }

    return 0

}

override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    if let sections = frc.sections {
        let currentSection = sections[section]
        return currentSection.numberOfObjects
    }

    return 0

}

override func tableView(tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {

    return 28

}

override func tableView(tableView: UITableView, titleForHeaderInSection section: Int) -> String? {

    if let sections = frc.sections {
        let currentSection = sections[section]
        return currentSection.name
    }

    return nil

}

func controllerWillChangeContent(controller: NSFetchedResultsController) {

    tableView.beginUpdates()

}

func controllerDidChangeContent(controller: NSFetchedResultsController) {

    tableView.endUpdates()

}

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    let cell = tableView.dequeueReusableCellWithIdentifier("listContentCell", forIndexPath: indexPath) as! ListItemsTVCell
    let item = frc.objectAtIndexPath(indexPath) as! Items

    cell.separatorInset = UIEdgeInsets(top: 0, left: 78, bottom: 0, right: 0)
    cell.itemName.text = item.name
    cell.itemSection.text = item.section
    cell.itemQty.text = "Qty: \(item.qty!)"
    cell.itemSize.text = item.size
    cell.itemPrice.text = floatToCurrency(Float(item.price!))
    //cell.itemImage.image = UIImage(data: item.image!)
    cell.itemID.text = String(item.id!)

    return cell

}

override func tableView(tableView: UITableView, editActionsForRowAtIndexPath indexPath: NSIndexPath) -> [UITableViewRowAction]? {

    let delete = UITableViewRowAction(style: .Destructive, title: "Delete") { (action, indexPath) in

        let item = self.frc.objectAtIndexPath(indexPath) as! Items
        let id = item.id!
        let request = self.fetchRequest()
        let pred = NSPredicate(format: "%K == %@", "id",id)
        request.predicate = pred
        var fetchResults = [AnyObject]()

        do {
            fetchResults = try self.moc.executeFetchRequest(request)
        } catch {
            fatalError("Fetching Data to Delete Failed")
        }

        self.moc.deleteObject(fetchResults[0] as! NSManagedObject)
        fetchResults.removeAtIndex(0)

        do {
            try self.moc.save()
        } catch {
            fatalError("Failed to Save after Delete")
        }

    }

    return [delete]

}

func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {

    switch type {
    case NSFetchedResultsChangeType.Delete:
        self.tableView.deleteSections(NSIndexSet(index: sectionIndex), withRowAnimation: UITableViewRowAnimation.Automatic)
        break
    case NSFetchedResultsChangeType.Insert:
        self.tableView.insertSections(NSIndexSet(index: sectionIndex), withRowAnimation: UITableViewRowAnimation.Automatic)
        break
    /*case NSFetchedResultsChangeType.Update:
        tableView.reloadSections(NSIndexSet(index: sectionIndex), withRowAnimation: UITableViewRowAnimation.Automatic)
        break*/
    default:
        print("Default in didChangeSection was called")
        break
    }

}

func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {

    switch type {
    case NSFetchedResultsChangeType.Delete:
        self.tableView.deleteRowsAtIndexPaths([indexPath!], withRowAnimation: UITableViewRowAnimation.Automatic)
        break
    case NSFetchedResultsChangeType.Insert:
        self.tableView.insertRowsAtIndexPaths([newIndexPath!], withRowAnimation: UITableViewRowAnimation.Fade)
        break
    default:
        print("Default in didChangeObject was called")
        break
    }

}

// MARK: - Custom Functions

func fetchRequest() -> NSFetchRequest {

    let fetchRequest = NSFetchRequest(entityName: "Items")
    let sortDesc1 = NSSortDescriptor(key: "section", ascending: true)
    let sortDesc2 = NSSortDescriptor(key: "isChecked", ascending: true)
    let sortDesc3 = NSSortDescriptor(key: "name", ascending: true)
    fetchRequest.sortDescriptors = [sortDesc1, sortDesc2, sortDesc3]

    return fetchRequest

}

func getFCR() -> NSFetchedResultsController {

    frc = NSFetchedResultsController(fetchRequest: fetchRequest(), managedObjectContext: moc, sectionNameKeyPath: "section" , cacheName: nil)

    return frc

}

func floatToCurrency(flt: Float) -> String {

    let formatter = NSNumberFormatter()
    formatter.numberStyle = NSNumberFormatterStyle.CurrencyStyle
    return String(formatter.stringFromNumber(flt)!)

}

}

Add Button View Controller: (Swift)

import UIKit
import CoreData

class AddItemListVC: UIViewController, NSFetchedResultsControllerDelegate {

// MARK: - Constants and Variables

let moc = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
var sendItem: Items?

// MARK: - App loading Functions

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

// MARK: - Outlets and Actions

@IBAction func addItem(sender: AnyObject) {

    let entityDesc = NSEntityDescription.entityForName("Items", inManagedObjectContext: moc)
    let item = Items(entity: entityDesc!, insertIntoManagedObjectContext: moc)

    if (NSUserDefaults.standardUserDefaults().objectForKey("nextItemID") == nil) {
        NSUserDefaults.standardUserDefaults().setObject(1, forKey: "nextItemID")
        NSUserDefaults.standardUserDefaults().synchronize()
    }

    let id = NSUserDefaults.standardUserDefaults().integerForKey("nextItemID")

    item.id = id
    switch id {
    case 1..<10:
        item.name = "Item ID 00\(id)"
    case 10..<100:
        item.name = "Item ID 0\(id)"
    default:
        item.name = "Item ID \(id)"
    }
    item.brand = "Brand \(id)"
    item.qty = 1
    item.price = 0
    item.size = "Size \(id)"
    let sec: Int = Int(arc4random_uniform(UInt32(4 - 1))) + 1
    item.section = "Section \(sec)"
    item.isChecked = false

    do {
        try moc.save()
        NSUserDefaults.standardUserDefaults().setObject(id + 1, forKey: "nextItemID")
        NSUserDefaults.standardUserDefaults().synchronize()
    } catch {
        fatalError("New item save failed")
    }

    navigationController!.popViewControllerAnimated(true)

}
}

Answer 1

@Jason Brady, I have just downloaded your code.

There is no problem with you core data, array or table view.

When i run an app in iPhone 5 / iPhone 6 / iPhone 6 Plus with 8.1 it is working fine, none of cell or add button is getting hidden.

But with same devices with 9.2 there is a problem.

Solutions

(1) Custom cell with dequeueReusableCellWithIdentifier

let cell : ListItemsTVCell! = tableView.dequeueReusableCellWithIdentifier("listContentCell", forIndexPath: indexPath)  as! ListItemsTVCell

(2) DidselectedRowAtIndex - Here you will get information at cell selection, So data is going perfectly.

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath)
{
        print("Select")

        let myCell = tableView.cellForRowAtIndexPath(indexPath) as! ListItemsTVCell
        print(myCell.itemName.text)

}

(3) Problem is with AutoLayout, when i disabled it, all label went to -X positions, when i have aligned it properly using auto resizing, it is now working fine. ( See attached screen shot )

So you need to check with AutoLayout, why it is giving problem in iOS 9 and newer.

Refer link

I hope you can figure out and resolve further.

All the best.

Download

Answer 2

Instead of using

tableView.dequeueReusableCellWithIdentifier("listContentCell", forIndexPath: indexPath)

try using

tableView.dequeueReusableCellWithIdentifier("listContentCell")