TableView 中的重新排序行将在数据刷新后重置为默认值

Question

我实现了一个表格视图，它显示了一个文档列表

我用这段代码实现了重新排序功能

var documents = [PDFDocument]()
override func tableView(_ tableView: UITableView, moveRowAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {

    let movedObject = self.documents[sourceIndexPath.row]

    let fileManager = FileManager.default

    documents.remove(at: sourceIndexPath.row)

    documents.insert(movedObject, at: destinationIndexPath.row)

    NSLog("%@", "\(sourceIndexPath.row) => \(destinationIndexPath.row) \(documents)")



    do {


        let document = documents[sourceIndexPath.row]
        let documentURL = document.documentURL?.absoluteString


        let document_Dest = documents[destinationIndexPath.row]
        let documentURL_Dest = document_Dest.documentURL?.absoluteString

        try fileManager.moveItem(atPath: documentURL!, toPath: documentURL_Dest!)
    }
    catch let error as NSError {
        print("Ooops! Something went wrong: \(error)")
    }




    // To check for correctness enable: self.tableView.reloadData()
   refreshData()

}


  private func refreshData() {
    let fileManager = FileManager.default
    let documentDirectory = fileManager.urls(for: .documentDirectory, in: .userDomainMask)[0]
    let contents = try! fileManager.contentsOfDirectory(at: documentDirectory, includingPropertiesForKeys: nil, options: .skipsHiddenFiles)
    documents = contents.flatMap { PDFDocument(url: $0) }

    tableView.reloadData()
}

它在重新排序时完全正常，但问题是当我关闭应用程序并重新启动它时（任何时候刷新数据功能运行），行都会回到它们的默认位置。而我需要在重新排序时保存更改。

Answer 1

tableView 中的重新排序仅特定于 tableView。这种重新排序不会影响原始数据源。关闭应用程序并再次运行重新加载数据的方法后，将从文档目录中获取原始数据。您需要在 tableView 中更改此顺序时更改此原始文件的顺序。

1. 从文档目录中获取数据。

   private func refreshData() 
   {
       let fileManager = FileManager.default
       let documentDirectory = fileManager.urls(for: .documentDirectory, in: .userDomainMask)[0]
       let contents = try! fileManager.contentsOfDirectory(at: documentDirectory, includingPropertiesForKeys: nil, options: .skipsHiddenFiles)
       documents = contents.flatMap { PDFDocument(url: $0) }
   }
   

2. 创建一个字典，键为文档目录文件或文件夹名称，值为索引。

   private func refreshData() 
   {
       let fileManager = FileManager.default
       let documentDirectory = fileManager.urls(for: .documentDirectory, in: .userDomainMask)[0]
       let contents = try! fileManager.contentsOfDirectory(at: documentDirectory, includingPropertiesForKeys: nil, options: .skipsHiddenFiles)
       documents = contents.flatMap { PDFDocument(url: $0) 
   
   
       let index = 0
       let documentDic = NSMutableDictionary()
       for element in documents
       {
            documentDic.setValue(index, forKey: element.documentURL?.absoluteString) 
            index = index + 1
       }  
   
   }
   

3. 将此保存在用户默认值中

   private func refreshData() 
   {
       let fileManager = FileManager.default
       let documentDirectory = fileManager.urls(for: .documentDirectory, in: .userDomainMask)[0]
       let contents = try! fileManager.contentsOfDirectory(at: documentDirectory, includingPropertiesForKeys: nil, options: .skipsHiddenFiles)
       documents = contents.flatMap { PDFDocument(url: $0) 
   
       let index = 0
       let documentDic = NSMutableDictionary()
       for element in documents
       {
            documentDic.setValue(index, forKey: element.documentURL?.absoluteString) 
            index = index + 1
       }  
   
   
       NSUserDefaults.standardUserDefaults().setObject(documentDic, forKey: "ReorderingFormat")
   }
   

4. 一旦用户重新排序，更改字典中与每个 url 对应的值。

   //Read data from User Defaults
   let dic = NSUserDefaults.standardUserDefaults().objectForKey("Reordering Format")
   for element in documents
   {
       //This way you get the order or index number for any directory.
       dic.objectForKey(element)
   }
   

5. 当用户再次进入应用程序时，根据存储在 nsuserdefaults 中的字典值管理您的数组。