当我点击返回时如何重新加载集合视图？

Question

当我从列表重新排序的 tableview 中点击返回时，我的 collectionview 没有重新加载。

我已经阅读了一些主题，但我不知道出了什么问题。有人能找到吗？

我可以将代码的一部分放在一个单独的 swift 文件中并包含这个 ViewController。所以是的，怎么做？因为我在更多的 ViewControllers 中使用它。

下面是我的代码。

非常感谢。

import UIKit
import AVFoundation

class CollectionViewController: UICollectionViewController {

    @IBOutlet var soundBoard: UICollectionView!

    var list = ["January","February","March","April","May","June", "July","August","September","October","November", "December"]
    var bgColor = [""]

    var buttonOn: Bool = true

    override func viewDidLoad() {
        super.viewDidLoad()

        let blockItems = UserDefaults.standard.object(forKey:"soundboard")

        if(blockItems != nil) {
            list = blockItems as! [String]
        }

        let itemSize = UIScreen.main.bounds.width/2 - 2
        let itemHeight = itemSize / 2
        let layout = UICollectionViewFlowLayout()
        layout.sectionInset = UIEdgeInsetsMake(3, 0, 3, 0)
        layout.itemSize = CGSize(width: itemSize, height: itemHeight)

        layout.minimumInteritemSpacing = 3
        layout.minimumLineSpacing = 3

        soundBoard.collectionViewLayout = layout
    }

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

        self.collectionView!.reloadData()
    }

    // MARK: - Collection View

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        // #warning Incomplete implementation, return the number of items

        return list.count
    }


    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> MyCollectionViewCell {

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! MyCollectionViewCell

        cell.cellTitle.text = list[indexPath.row]

        return cell
    }

    override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

        Speak(currentTitle: list[indexPath.row])
    }


    // MARK: - Speak function


    let synth = AVSpeechSynthesizer()
    var myUtterance = AVSpeechUtterance(string: "")

    func Speak(currentTitle: String) {

        if !synth.isSpeaking {
            // Controleert volume
            let volume = AVAudioSession.sharedInstance().outputVolume

            if volume < 0.5 {
                MuteButton()
            }

            // Spreekt de tekst uit
            let myUtterance = AVSpeechUtterance(string: currentTitle)
            myUtterance.rate = 0.4
            myUtterance.volume = 1

            if let theVoice = UserDefaults.standard.object(forKey:"voice") {
                myUtterance.voice = AVSpeechSynthesisVoice(language: theVoice as? String)
            }

            synth.speak(myUtterance)
        }
    }


    func MuteButton() {

        let alertController = UIAlertController(title: "Check your volume", message:
            "Please check your volume or mute button.", preferredStyle: UIAlertControllerStyle.alert)
        alertController.addAction(UIAlertAction(title: "Close", style: UIAlertActionStyle.default,handler: nil))

        self.present(alertController, animated: true, completion: nil)
    }

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

    // MARK: -- Save UserDefaults 

    func save() {
        UserDefaults.standard.set(self.list, forKey:"soundboard")
        UserDefaults.standard.synchronize()

        self.collectionView?.reloadData()
    }


    // MARK: -- Add new sound item

    @IBAction func addNew(_ sender: Any) {

        let alertController = UIAlertController(title: "Create a new sound", message: "", preferredStyle: UIAlertControllerStyle.alert)

            alertController.addTextField { (textField: UITextField) in
                textField.keyboardAppearance = .dark
                textField.keyboardType = .default
                textField.autocorrectionType = .default
                textField.placeholder = "Type something here"
                textField.clearButtonMode = .whileEditing
            }


        alertController.addAction(UIAlertAction(title: "Create", style: .default) { [weak alertController] _ in
            if let alertController = alertController {
                let loginTextField = alertController.textFields![0] as UITextField

                self.list.append( loginTextField.text!)

                self.save()
            }
        })


        alertController.addAction(UIAlertAction(title: "Cancel", style: UIAlertActionStyle.default,handler: nil))

        self.present(alertController, animated: true, completion: nil)
    }
}

Answer 1

这里发生了两件事。首先，您似乎在CollectionViewController 中有两个不同的集合视图； collectionView 继承自超类和您声明的 soundboard。在viewWillAppear 中，您告诉collectionView 重新加载。如果这不是连接到 IB 中的那个，那什么都行不通。

第二个问题是，在 soundboardTableViewController 中，您使用正确的数据更新用户默认值，而在 CollectionViewController 中加载视图后，您从未读取过它。

你应该移动这个：

let blockItems = UserDefaults.standard.object(forKey:"soundboard")
if(blockItems != nil) {
   list = blockItems as! [String]
}

在您调用重新加载集合视图之前进入viewWillAppear，然后验证您正在告诉正确的集合视图重新加载。

Answer 2

我在这里看到了一些可能出错的地方。但是，在另一个视图控制器中查看代码会有所帮助。

首先，您确定您正在正确地重新排序模型数组吗？请记住，数组是一种值类型。这意味着如果您将数组传递给另一个视图，则您传递的是该数组的副本，而不是集合视图控制器中的数组。将模型数组包装在可以传递引用的对象中可能是一个更好的主意。更多关于 here.

此外，最好将重新加载与模型中的更改联系起来，而不是与视图生命周期联系起来。要使用您当前的代码执行此操作，您可以执行以下操作：

var list = ["January","February","March","April","May","June", "July","August","September","October","November", "December"] {
   didSet {
      self.collectionView?.reloadData()
      // or
      self.soundBoard.reloadData()
      // I'm confused about which collection view you're using/trying to reload. 
   }
}

如果您有任何问题，请告诉我。我会留意，如果需要可以编辑我的答案。

Answer 3

这是另一个 ViewController 的代码，您可以在其中重新排序行并可以点击

import UIKit

class soundboardTableViewController: UITableViewController {

    var list = ["January","February","March","April","May","June", "July","August","September","October","November", "December"]



    override func viewDidLoad() {
        super.viewDidLoad()


        self.navigationItem.rightBarButtonItem = self.editButtonItem

        let blockItems = UserDefaults.standard.object(forKey:"soundboard")

        if(blockItems != nil) {
            list = blockItems as! [String]
        }
    }


    // MARK: - Table view data source

    override func numberOfSections(in tableView: UITableView) -> Int {
        // #warning Incomplete implementation, return the number of sections
        return 1
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        // #warning Incomplete implementation, return the number of rows
        return list.count
    }


    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)

        cell.textLabel?.text = list[indexPath.row]

        return cell
    }


    // Override to support conditional editing of the table view.
    override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
        // Return false if you do not want the specified item to be editable.
        return true
    }


    /* Override to support editing the table view.*/
    override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
        if editingStyle == .delete {
            list.remove(at: indexPath.row)

            UserDefaults.standard.set(self.list, forKey:"soundboard")
            UserDefaults.standard.synchronize()

            tableView.reloadData()
        }
    }

    // Override to support rearranging the table view.
    override func tableView(_ tableView: UITableView, moveRowAt indexPath: IndexPath, to: IndexPath) {
        /*let itemToMove = list[indexPath.row]
        list.remove(at: indexPath.row)
        list.insert(itemToMove, at: indexPath.row)

        UserDefaults.standard.set(self.list, forKey:"soundboard")
        UserDefaults.standard.synchronize()*/

        let itemToMove = list[indexPath.row]
        list.remove(at: indexPath.row)
        list.insert(itemToMove, at: to.row)

        UserDefaults.standard.set(self.list, forKey:"soundboard")
    }

    override func setEditing(_ editing: Bool, animated: Bool) {
        super.setEditing(editing, animated: animated)

        if(self.isEditing) {

        }
    }


    // Override to support conditional rearranging of the table view.
    override func tableView(_ tableView: UITableView, canMoveRowAt indexPath: IndexPath) -> Bool {
        // Return false if you do not want the item to be re-orderable.
        return true
    }



    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.
    }


}