当我在应用程序上按editButton并尝试删除collectionView中的单元格时，会收到以下错误消息：
'无效更新：第0部分中的项目数无效。 更新（3）之后现有部分中包含的项目必须是 等于该节之前该部分中包含的项目数 更新（3），加上或减去从中插入或删除的项目数 该部分（插入了0个，删除了1个），加上或减去 项目移入或移出了该部分（移入了0个，移出了0个）。'
通读other similar posts之后，我仍然不确定如何为该问题应用解决方案。我确实看到文件已从FileManager中删除，因为我已经在Finder中打开了目录，但是我对如何使collectionView与FileManager中的文件数量保持同步感到困惑。
import UIKit
import AVFoundation
class ViewController: UIViewController, AVAudioRecorderDelegate, UICollectionViewDelegate, UICollectionViewDataSource {
var audioRecorder: AVAudioRecorder!
var audioPlayer: AVAudioPlayer!
var numberOfRecordings = 0
@IBOutlet weak var recordButton: UIButton!
@IBOutlet weak var editButton: UIButton!
@IBOutlet weak var myCollectionView: UICollectionView!
override func viewDidLoad() {
super.viewDidLoad()
recordButton.layer.cornerRadius = 10
editButton.layer.cornerRadius = 10
// Set the numberOfRecordings to be exactly the number of files stored in the File Manager so that they're in sync.
let fileManager = FileManager.default
let documentsURL = fileManager.urls(for: .documentDirectory, in: .userDomainMask)[0]
do {
let fileURLs = try fileManager.contentsOfDirectory(at: documentsURL, includingPropertiesForKeys: nil, options: .skipsHiddenFiles)
numberOfRecordings = fileURLs.count
} catch {
print("Error while enumerating files \(documentsURL.path): \(error.localizedDescription)")
}
}
// Let's get the directory where we're going to store the recordings
func getDirectory() -> URL {
let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
let documentDirectory = paths[0]
return documentDirectory
}
// Let's create a genearl alert to display error messages
func displayAlert(title: String, message: String) {
let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Dismiss", style: .default, handler: nil))
present(alert, animated: true, completion: nil)
}
//MARK: - Record Button Methods
@IBAction func record(_ sender: Any) {
if audioRecorder == nil {
numberOfRecordings += 1
let fileURL = getDirectory().appendingPathComponent("\(numberOfRecordings).m4a")
let settings = [
AVFormatIDKey: Int(kAudioFormatMPEG4AAC),
AVSampleRateKey: 12000,
AVNumberOfChannelsKey: 1,
AVEncoderAudioQualityKey: AVAudioQuality.high.rawValue
]
do {
audioRecorder = try AVAudioRecorder(url: fileURL, settings: settings)
audioRecorder.delegate = self
audioRecorder.record()
recordButton.setTitle("Stop Recording", for: .normal)
} catch {
displayAlert(title: "Oops!", message: "Recording Failed")
}
} else {
audioRecorder.stop()
audioRecorder = nil
UserDefaults.standard.set(numberOfRecordings, forKey: "numberOfRecordings")
recordButton.setTitle("Start Recording", for: .normal)
myCollectionView.reloadData()
}
}
//MARK: - Collection View Setup
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return numberOfRecordings
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! RecordingCollectionViewCell
cell.recordingLabel.text = String(indexPath.row + 1)
cell.layer.cornerRadius = 10
cell.delegate = self as RecordingCellDelegate
return cell
}
//MARK: - Audio Player
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let path = getDirectory().appendingPathComponent("\(indexPath.row + 1).m4a")
do {
audioPlayer = try AVAudioPlayer(contentsOf: path)
audioPlayer.volume = 1.0
audioPlayer.prepareToPlay()
audioPlayer.play()
} catch let error {
print("Error: \(error.localizedDescription)")
}
}
//MARK: - Edit Button Methods
@IBAction func editButtonTapped(_ sender: Any) {
if editButton.titleLabel?.text == "Edit" {
recordButton.isEnabled = isEditing
editButton.setTitle("Stop Editing", for: .normal)
if let indexPaths = myCollectionView?.indexPathsForVisibleItems {
for indexPath in indexPaths {
if let cell = myCollectionView?.cellForItem(at: indexPath) as? RecordingCollectionViewCell {
cell.isEditing = !isEditing
}
}
}
} else {
editButton.setTitle("Edit", for: .normal)
if let indexPaths = myCollectionView?.indexPathsForVisibleItems {
for indexPath in indexPaths {
if let cell = myCollectionView?.cellForItem(at: indexPath) as? RecordingCollectionViewCell {
cell.isEditing = isEditing
}
}
}
}
}
}
extension ViewController: RecordingCellDelegate {
func delete(cell: RecordingCollectionViewCell) {
if let indexPath = myCollectionView?.indexPath(for: cell) {
// 1. Delete the recording from the File Manager
let fileManager = FileManager.default
let fileURL = getDirectory().appendingPathComponent("\(indexPath.row + 1).m4a")
do {
try fileManager.removeItem(at: fileURL)
} catch let error {
print("File not found: \(error.localizedDescription)")
displayAlert(title: "Oops!", message: "File not found: \(error.localizedDescription)")
}
// 2. Delete it in the collectionView
myCollectionView.deleteItems(at: [indexPath])
}
}
}
答案 0 :(得分：0)
您永远不会更新数据模型。除了删除文件并告诉集合视图某个项目已被删除之外，您还需要更新集合视图使用的模型。这意味着您需要更新numberOfRecordings（在调用myCollectionView.deleteItems(at: [indexPath])之前。
答案 1 :(得分：0)
错误明确指出，要添加新行或删除现有行，您还需要对相应的数组进行相同的更改，即 numberOfRecordings 。
像，如果您要删除1行，则需要对数组进行相同的更改（例如，之前有3行（数组也有3项），并且现在您要删除1行，因此您需要从相应的array（numberOfRecordings）中删除相同数量的项（即1）。
同样也适用于添加。
在对数组进行任何更改之前，执行对数组的添加或删除操作 带有
tableView.deleteRows()的表视图或tableView.insertRows()