ios - 如何修复 UITableView 类，该类在 Firebase 数据库上重复读取两次元素，并且在加载时表为空？

Question

我正在尝试从 Firebase 实时数据库读取一系列指令。

我的 Vehicles 节点上有未知数量的信息，因此我仅使用 nextObject 方法来获取函数需要迭代的次数。

问题是在开幕时，我的 table 是空的。当我单击搜索栏时，我的单元格内容确实出现了。我该如何解决这些问题？

这是我的 UITableView 文件:

import UIKit
import FirebaseDatabase
import Alamofire




class Vehicles: UITableViewController,
UISearchResultsUpdating, UISearchBarDelegate {

    //variables
    var model: NSMutableArray = []
    var numberOfVehicles: NSMutableArray = []
    var price: NSMutableArray = []
    var imagePathString: NSMutableArray = []
    var detailpage: NSMutableArray = []



    var populator: NSMutableArray = []
    var searching = false
    var matches = [Int]()
    let searchController = UISearchController(searchResultsController: nil)

    @IBOutlet weak var InfoTableView: UITableView!

    var InfoList: [String] = []

    override func viewDidLoad() {
        super.viewDidLoad()
        loadData()
        //this should reload but, it didn't.
        self.InfoTableView.reloadData()
        //then the searchbar that is good and don't have any problem.
        searchingField()
    }



    func loadData() {
        //read data from database
        let rootRef = Database.database().reference()
        let conditionalRef = rootRef.child("Vehicles")
        conditionalRef.observe(.value) {(snap: DataSnapshot) in
            // Get all the children from snapshot you got back from Firebase
            let snapshotChildren = snap.children
            // Loop over all children in Firebase
            while let child = snapshotChildren.nextObject() as? DataSnapshot {
                // Get code node key and save it to they array
                self.populator.add(child.key)
                if self.populator.contains("\(child.key)") {
                    let userRef = rootRef.child("Vehicles").child("\(child.key)")

                    userRef.observeSingleEvent(of: .value, with: { snapshot in
                        let userDict = snapshot.value as! [String: Any]

                            let model1 = userDict["Model"] as! String
                            self.model.add(model1)

                            let detail1 = userDict["Detail"] as! String
                            self.detailpage.add(detail1)

                            let numberOfVehicles1 = userDict["numberOfVehicles"] as! String
                            self.numberOfVehicles.add(numberOfVehicles1)

                            let Price1 = userDict["Price"]  as! String
                            self.price.add(Price1)

                            let imageURL1 = userDict["imageURL"]  as! String
                            self.imagePathString.add(imageURL1)
                    }) //end second observeSingleEvent

                }
              else {
                    let alert = UIAlertController(title: "Error", message: "No one vehicle found", preferredStyle: UIAlertController.Style.alert)
                    alert.addAction(UIAlertAction(title: "ok", style: UIAlertAction.Style.default, handler: nil))
                self.present(alert, animated: true, completion: nil)
                }

            } //end searching object in Vehicles node



            } //end first observeSingleEvent

      }//end func


    func searchingField() {
        //setup searchbar
        tableView.estimatedRowHeight = 50
        navigationController?.navigationBar.prefersLargeTitles = true

        searchController.searchBar.delegate = self
        searchController.searchResultsUpdater = self
        searchController.searchBar.backgroundColor = UIColor.white
        searchController.obscuresBackgroundDuringPresentation = false
        searchController.searchBar.placeholder = "Search"
        navigationItem.searchController = searchController
        definesPresentationContext = true
        let attributes = [
            NSAttributedString.Key.foregroundColor : UIColor.black,
            NSAttributedString.Key.font : UIFont.boldSystemFont(ofSize: 17)
        ]
        UIBarButtonItem.appearance(whenContainedInInstancesOf: [UISearchBar.self]).setTitleTextAttributes(attributes, for: .normal)
        UIBarButtonItem.appearance(whenContainedInInstancesOf: [UISearchBar.self]).title = "Dismiss"
        UIBarButtonItem.appearance(whenContainedInInstancesOf: [UISearchBar.self])
    }





    // MARK: Search Controller
    func updateSearchResults(for searchController: UISearchController) {
        var regArray = self.model as NSArray as! [String]
        if let searchText = searchController.searchBar.text,
            !searchText.isEmpty { 
            matches.removeAll()

            for index in 0..<model.count {
                if regArray[index].lowercased().contains(
                    searchText.lowercased()) {
                    matches.append(index)
                }
            }
            searching = true
        } else {
            searching = false
        }
        tableView.reloadData()
    }

    func searchBarCancelButtonClicked(_ searchBar: UISearchBar) {
        searching = false
        tableView.reloadData()
    }



    // MARK: - Table view data source

    override func numberOfSections(in tableView: UITableView) -> Int {
        return searching ? matches.count : model.count
    }

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

        return searching ? matches.count : model.count
    }


    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cellIdentifier = "TableCell"

        let cell = tableView.dequeueReusableCell(withIdentifier: cellIdentifier) as! Vehicles_cell



        let row = indexPath.row
        var regArray = self.model as NSArray as! [String]
        cell.Label.text = searching ? regArray[matches[row]] : model[row] as! String
        cell.Subtitle?.text = "N. Vehicles: \(self.numberOfVehicles[indexPath.row]) - Price: \(self.price[indexPath.row])$"


        Alamofire.request("\(self.imagePathString[indexPath.row])").response { response in
            guard let image = UIImage(data:response.data!) else {
                // Handle error
                return
            }
            let imageData = image.jpegData(compressionQuality: 1.0)
            cell.Image.contentMode = .scaleAspectFit
            cell.Image.image = UIImage(data : imageData!)
        }

        return cell
    }



    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "ShowrentDetails" {

            let myIndexPath = self.tableView.indexPathForSelectedRow!

            //save detail1 in UserDefault
            let SVDetail = self.detailpage[myIndexPath.row]
            let SVDetaildefaults = UserDefaults.standard
            SVDetaildefaults.set(SVDetail, forKey: "sv_detail")
            SVDetaildefaults.synchronize()
            _ = segue.destination
                as! Vehicles_Detail
        }
    }

    //IMPOSTA LE DIMENSIONI DELLE CELLE
    override func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        switch indexPath.row {
        default:
            return 100
        }
    }


}

我希望表格在打开时显示数据库中的所有数据，而实际上，除非我单击搜索栏，否则不会重复。并且该表不应重复两次。

---

编辑(重复的解决方案)

这太尴尬了。这个问题的答案很简单

在numberOfSections函数中，我使用address.count代替使用1个Section。所以，我看到的不是重复的单元格，而是 model.count

的新 block 部分

Answer 1

在 Firebase 观察期间获取数据后，您的表格 View 不会重新加载数据，而是在 updateSearchResults() 中重新加载数据。是否在 loadData() 中添加 self.InfoTableView.reloadData() ，位于车辆节点中的 //end Searching 对象 和 之间//endfirstobserveSingleEvent 右括号解决了这个问题吗？

编辑:重新加载表格 View 数据无法解决 viewDidLoad() 中的问题的原因是它在 loadData() 函数开始迭代之前被调用通过您的 Firebase 数据对象。通过在 Firebase 观察结束时执行此操作，您可以确保在调用重新加载之前已从 Firebase 加载所有数据。