Question

我已经以编程方式创建了一个表视图，下面是代码，当我尝试使用完成处理程序更新标签时，该值不会显示在表视图单元格中。

有人可以建议我如何在tableview中的 languagesSpokenCell 中更新textLabel吗？我花了几个小时试图解决这个问题，但我仍然无法解决。

这是在用户选择他所说的语言后调用的完成处理程序。

func showLanguagesSpoken(_ languagesSpoken: [String]?){
        languagesSpokenString = (languagesSpoken?.joined(separator: ", "))!
        languagesSpokenCell.textLabel?.text = languagesSpokenString
       //*** In the below print statement the value is printed correctly but the text label is not updated in the cell. 
        print("languagesSpokenCell.textLabel?.text: \(languagesSpokenCell.textLabel?.text)") 
            self.tableView.reloadData()
        }

这里我以编程方式创建表格视图单元格

// FOR TABLE VIEW - Tableview cells
    var tableView: UITableView  =   UITableView()

    var firstNameCell: UITableViewCell = UITableViewCell()
    var lastNameCell: UITableViewCell = UITableViewCell()
    var languagesSpokenCell: UITableViewCell = UITableViewCell()
    
    
    // FOR TABLE VIEW - Textfields
    var firstName: UITextField = UITextField()
    var lastName: UITextField = UITextField()



override func loadView() {
        super.loadView()
        
        // construct first name cell, section 0, row 0
        self.firstNameCell.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 0.5)
        self.firstName = UITextField(frame: self.firstNameCell.contentView.bounds.insetBy(dx: 15, dy: 0))
        self.firstName.placeholder = "First Name"
        self.firstNameCell.addSubview(self.firstName)
        
        // construct last name cell, section 0, row 1
        self.lastNameCell.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 0.5)
        self.lastName = UITextField(frame: self.lastNameCell.contentView.bounds.insetBy(dx: 15, dy: 0))
        self.lastName.placeholder = "Last Name"
        self.lastNameCell.addSubview(self.lastName)
        
        self.languagesSpokenCell.textLabel?.text = "Languages Spoken"
        self.languagesSpokenCell.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 0.5)
        self.languagesSpokenCell.accessoryType = UITableViewCellAccessoryType.disclosureIndicator
  
    }

以下是表格视图方法

func numberOfSections(in tableView: UITableView) -> Int {
        return 2
    }

    // Return the number of rows for each section in your static table
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        switch(section) {
        case 0: return 2    // section 0 has 2 rows
        case 1: return 1    // section 1 has 1 row
        default: fatalError("Unknown number of sections")
        }
    }

    // Return the row for the corresponding section and row

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        switch(indexPath.section) {
        case 0:
            switch(indexPath.row) {
            case 0: return self.firstNameCell   // section 0, row 0 is the first name
            case 1: return self.lastNameCell    // section 0, row 1 is the last name
            default: fatalError("Unknown row in section 0")
            }
        case 1:
            switch(indexPath.row) {
            case 0: return self.languagesSpokenCell
            }
        default: fatalError("Unknown section")
        }
    }

    // Customize the section headings for each section
    func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        switch(section) {
        case 0: return "Profile"
        case 1: return "Languages Spoken"
        default: fatalError("Unknown section")
        }
    }

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let row     = indexPath.row
        let section = indexPath.section

        let currentCell = tableView.cellForRow(at: indexPath) as! UITableViewCell


       if section == 4 && row == 0 {
            // The user has clicked on languages spoken cell
            self.performSegue(withIdentifier: "showLanguageSelectionTVC", sender: self)
        }

        print("Printing celll text label: \(currentCell.textLabel!.text)")

    }

以下是我在ViewDidLoad()方法中设置的约束。

    tableView = UITableView(frame: CGRect.zero, style: UITableViewStyle.grouped)
    tableView.delegate      =   self
    tableView.dataSource    =   self
    tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
    self.view.addSubview(self.tableView)

    // Disabling automatic constraints

    tableView.translatesAutoresizingMaskIntoConstraints                     = false

    // Do any additional setup after loading the view.

    let viewDict = [
        "tableView"                 : tableView
    ]


    // Setting Constraints for the table view
    self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[tableView]|", options: [], metrics: nil, views: viewDict))
    self.view.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|[tableView]|", options: [], metrics: nil, views: viewDict))

Answer 1

要更新tableview中的任何单元格，您需要重新加载它。您可以为每个单元格或特定单元格或整个tableview重新加载它。在重新加载tableview之前，请确保更新数据源。

在这个showLanguagesSpoken方法中，您尝试更改单元格的文本而不更新tableView。

另请确保始终更改cellForRowAtIndexpath

中的数据

Answer 2

从以下方法中删除reloadData。

func showLanguagesSpoken(_ languagesSpoken: [String]?){
        languagesSpokenString = (languagesSpoken?.joined(separator: ", "))!
        languagesSpokenCell.textLabel?.text = languagesSpokenString
       //*** In the below print statement the value is printed correctly but the text label is not updated in the cell. 
        print("languagesSpokenCell.textLabel?.text: \(languagesSpokenCell.textLabel?.text)") 
        }

Answer 3

标签languagesSpokenCell.textLabel文字更新流程应位于主线程。

func showLanguagesSpoken(_ languagesSpoken: [String]?) {

    DispatchQueue.main.async {

        languagesSpokenString = (languagesSpoken?.joined(separator: ", "))!

        languagesSpokenCell.textLabel?.text = languagesSpokenString

        print("languagesSpokenCell.textLabel?.text: \(languagesSpokenCell.textLabel?.text)")
    }
}

如何更新tableview单元格中的textLabel iOS Swift

3 个答案: