Question

我正在创建一个事件应用程序，其中从API提取的参与者列表在UITableView中列出。当用户轻按checkInOutbutton时，事件check in和register或事件后check out。用户从事件签入或签出的每一次之后，用户都应pull to refresh更新表中的数据。我使用下面的代码来更新数据。

var refresher: UIRefreshControl!

 override func viewDidLoad() {
    super.viewDidLoad()

  refresher = UIRefreshControl()
    refresher.attributedTitle = NSAttributedString(string: "Pull to refresh")
    refresher.addTarget(self, action: #selector(ParticipantsViewController.refresh), for: UIControlEvents.valueChanged)
    ParticipantTableView.addSubview(refresher)


}

//MARK: FUNCTIONS

@objc func refresh() {

    refresher.endRefreshing()
    getParticipants()
    ParticipantTableView.reloadData()
     _ = SCLAlertView(appearance: Appearance).showSuccess("Success", subTitle: "Participants Updated!")
}

使用pull to refresh后，我成功更新了表。问题是，当我轻按back button进入我的dashboard并轻按该按钮返回我的UItableview的VC时，该UItableview是participantViewController, the data is not updated. It goes back to its original data. How can I retain the updated data even if I tapped the back button and goes back to the个参与者or注册参与者的VC ？希望你能帮助我。

原始数据，灰色bgcolor和未注册标签（签入和签出按钮位于折叠单元格内

。

数据，一旦用户点击“签到”按钮，背景颜色变为绿色并且标签已注册

点击后退按钮时的仪表板

点击后退按钮

 @IBAction func backbutton(_ sender: UIButton) {
     self.dismiss(animated: true, completion: nil)
}

ParticipantViewController

import UIKit
import FoldingCell
import SCLAlertView
import AASquaresLoading

class ParticipantsViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

@IBOutlet weak var ParticipantTableView: UITableView!
@IBOutlet weak var titleLabel: UILabel!
@IBOutlet weak var countLabel: UILabel!
@IBOutlet weak var notifImageView: UIImageView!

var refresher: UIRefreshControl!

var validPincode: String!
var titleString: String!

var participants: [Attendee]!
var filteredParticipants = [Attendee]()


let kCloseCellHeight: CGFloat = 122
let kOpenCellHeight: CGFloat = 475

var cellHeights = [CGFloat]()

let searchController = UISearchController(searchResultsController: nil)


override func viewDidLoad() {
    super.viewDidLoad()

    createCellHeightsArray()
    configureSearchBar()
    configureAALoading()
    countNotif()

    titleLabel.text = self.titleString

    refresher = UIRefreshControl()
    refresher.attributedTitle = NSAttributedString(string: "Pull to refresh")
    refresher.addTarget(self, action: #selector(ParticipantsViewController.refresh), for: UIControlEvents.valueChanged)
    ParticipantTableView.addSubview(refresher)


}

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


override func viewDidAppear(_ animated: Bool) {
    self.ParticipantTableView.reloadData()
}



@IBAction func backbutton(_ sender: UIButton) {
     self.dismiss(animated: true, completion: nil)
}



//MARK: FUNCTIONS

@objc func refresh() {

    refresher.endRefreshing()
    getParticipants()
    ParticipantTableView.reloadData()
     _ = SCLAlertView(appearance: Appearance).showSuccess("Success", subTitle: "Participants Updated!")


}


func configureAALoading() {
    self.view.squareLoading.color = UIColor(red: 80/255.0, green: 187/255.0, blue: 113/255.0, alpha: 1.0)
    self.view.squareLoading.backgroundColor = UIColor(red: 0/255.0, green: 0/255.0, blue: 0/255.0, alpha: 0.7)
}

func getParticipants() {

    var participantType: ParticipantType!

    if self.titleString == "PARTICIPANTS" {
        participantType = .all
    }else {
        participantType = .active
    }

    self.view.squareLoading.start(0.0)

    let api = APIService()

    api.getParticipants(enteredPincode: validPincode, participantType: participantType, successBlock: { (attendees) in

         self.participants = attendees
        self.view.squareLoading.stop(0.0)

        if self.searchController.isActive && self.searchController.searchBar.text != "" {
            self.filterContentForSearchText(searchText: self.searchController.searchBar.text!)
        }else {
            self.ParticipantTableView.reloadData()
        }



    }) { (error) in
        // Hide loading view
        self.view.squareLoading.stop(0.0)
        _ = SCLAlertView(appearance: Appearance).showError("Network Error", subTitle: "\(error)")

    }


}



func countNotif(){

    if participants.count == 0 {
        countLabel.isHidden = true
        notifImageView.isHidden = true

    }else {
        countLabel.text = "\(participants.count)"
        notifImageView.image = #imageLiteral(resourceName: "participant_notif")
    }
}


  func createCellHeightsArray() {

    cellHeights.removeAll()

    if searchController.isActive && searchController.searchBar.text != "" {
        for _ in 0...filteredParticipants.count {
            cellHeights.append(kCloseCellHeight)
        }
    }else {
        for _ in 0...participants.count {
            cellHeights.append(kCloseCellHeight)
        }
    }
}


    func filterContentForSearchText(searchText: String, scope: String = "All") {
        filteredParticipants = participants.filter { participants in
            return participants.displayName.lowercased().contains(searchText.lowercased()) || (participants.department.lowercased().contains(searchText.lowercased()))
            //                || (participants.employeeNumber?.contains(searchText))! ||
        }

        createCellHeightsArray()
        ParticipantTableView.reloadData()

    }

func configureSearchBar() {

    searchController.searchResultsUpdater = self
    searchController.dimsBackgroundDuringPresentation = false
    definesPresentationContext = true

    searchController.searchBar.textColor = UIColor.white
    searchController.searchBar.placeholder = "Search by name, department, and employee number"
    searchController.searchBar.searchBarStyle = .minimal
    searchController.searchBar.barTintColor = UIColor(red: 26/255.0, green: 99/255, blue: 42/255, alpha: 1.0)
    searchController.searchBar.tintColor = UIColor.white
    searchController.searchBar.backgroundColor = UIColor(red: 26/255.0, green: 99/255, blue: 42/255, alpha: 1.0)

    searchController.searchBar.isTranslucent = false

    self.ParticipantTableView.tableHeaderView = searchController.searchBar
}



// MARK: TABLE VIEW DATA SOURCE



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

    if searchController.isActive && searchController.searchBar.text != "" {
        return filteredParticipants.count
    }
    //print(participants.count)
    return (participants.count)
}

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

func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {

    guard case let cell as ParticipantCell = cell else {
        return
    }

    cell.backgroundColor = UIColor.clear

    if searchController.isActive && searchController.searchBar.text != "" {
        cell.participant = filteredParticipants[indexPath.row]
    }else {
        cell.participant = participants[indexPath.row]
    }

    if cellHeights[(indexPath as NSIndexPath).row] == kCloseCellHeight {
        cell.unfold(false, animated: false, completion: nil)
    } else {
        cell.unfold(true, animated: false, completion: nil)
    }
}

func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    return cellHeights[(indexPath as NSIndexPath).row]
}

// MARK: TABLE VIEW DELEGATE

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

    let cell = tableView.cellForRow(at: indexPath) as! FoldingCell

    if cell.isAnimating() {
        return
    }

    var duration = 0.0

    if cellHeights[(indexPath as NSIndexPath).row] == kCloseCellHeight { // open cell
        cellHeights[(indexPath as NSIndexPath).row] = kOpenCellHeight
        cell.unfold(true, animated: true, completion: nil)
        duration = 0.3
    } else {// close cell
        cellHeights[(indexPath as NSIndexPath).row] = kCloseCellHeight
        cell.unfold(false, animated: true, completion: nil)
        duration = 0.5
    }

    UIView.animate(withDuration: duration, delay: 0, options: .curveEaseOut, animations: { () -> Void in
        tableView.beginUpdates()
        tableView.endUpdates()
    }, completion: nil)

    }

}

extension ParticipantsViewController: UISearchResultsUpdating {
func updateSearchResults(for searchController: UISearchController) {
    filterContentForSearchText(searchText: searchController.searchBar.text!)
    }
}

extension UISearchBar {

var textColor: UIColor? {
    get {
        if let textField = self.value(forKey: "searchField") as? UITextField {
            return textField.textColor
        }else {
            return nil
        }
    }

    set (newValue) {
        if let textField = self.value(forKey: "searchField") as? UITextField {
            textField.textColor = newValue
            textField.font = UIFont(name: "HelveticaNeue", size: 20.0)
            }
        }
    }
}

Answer 1

您对问题的解释让我有些困惑，但我想我理解您的意思。我的解释：您提供一个tableView的视图控制器，并使用一些新数据刷新该表视图。然后，当您关闭视图控制器并返回到它时，新数据消失了，您只看到了旧数据。

如果这是您的问题，那么解决方案非常简单。当您返回视图控制器时，您可能只是在创建一个全新的viewController并将其呈现出来……这将不会具有从网络中获取的新数据。

在这种情况下，您必须将原始的viewController实例存储在变量中并显示THAT，而不是创建一个全新的实例。

编辑：

在仪表板代码中的某处，您可能有此行

self.present(ParticipantsViewController(), animated: false)

...或其他形式。代替这个，做一些...

class DashboardViewController: UIViewController{

 var participantsViewController = ParticipantsViewController()

    func responseToSomeUserAction(){
        self.present(self.participantsViewController, animated: true)
    }

}

在上面的代码中，每次用户想要显示表视图时，都会显示相同的viewController实例，因此所有数据仍将存在。

点击后退按钮时如何在UITableView中保留更新的数据

1 个答案: