表加载时预选单元格

Question

我想在表加载时预选单元格。我已遵循此答案，但无法正常工作。它并不总是预先选择正确的单元格。https://stackoverflow.com/a/19296095/12114641它仅选择最后一个单元格。如何使其正常工作？

Tableview设置为单一选择。

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    guard let cell = tableView.dequeueReusableCell(withIdentifier: "TableViewCell", for: indexPath) as? TableViewCell else {
        fatalError("Can't find cell")
    }

    cell.title = dataSource[indexPath.row]        

    if globalCheckedArray[indexPath.row].checked {
        self.tableView.selectRow(at: indexPath, animated: false, scrollPosition: .none)
    } else {
        self.tableView.deselectRow(at: indexPath, animated: false)
    }

    return cell
}

func tableView(_ tableView: UITableView, willSelectRowAt indexPath: IndexPath) -> IndexPath? {

    globalCheckedArray[indexPath.row].checked = true

    if tableView.indexPathsForSelectedRows?.contains(indexPath) ?? false {
        tableView.deselectRow(at: indexPath, animated: true)
        return nil
    }

    return indexPath
}

func tableView(_ tableView: UITableView, willDeselectRowAt indexPath: IndexPath) -> IndexPath? {
    return nil
}

Answer 1

您需要做几件事...

• 使用数据结构-可能是自定义对象的数组-跟踪“选定”状态
• 为.accessoryType中的单元格设置cellForRowAt
• 将选定行（选定对象）的数组传递给下一个视图控制器

这里是一个非常简单的例子。在您的情节提要中，添加一个UITableViewController，将其自定义类设置为TestTableViewController，然后将其嵌入到UINavigationController中。

[运行时，您可以选择-即添加复选标记-多行。

当您点击导航栏中的“测试”按钮时，它将被推至SampleViewController，它将在标签中显示所选的行标题。

当您“返回”时，您的数据将被保留，正确的行将带有复选标记。

struct MyDataStruct {
    var title: String = ""
    var isSelected: Bool = false
}

class TestTableViewController: UITableViewController {

    var myData: [MyDataStruct] = [
        MyDataStruct(title: "One", isSelected: false),
        MyDataStruct(title: "Two", isSelected: false),
        MyDataStruct(title: "Three", isSelected: false),
        MyDataStruct(title: "Four", isSelected: false),
        MyDataStruct(title: "Five", isSelected: false),
        MyDataStruct(title: "Six", isSelected: false),
        MyDataStruct(title: "Seven", isSelected: false),
        MyDataStruct(title: "Eight", isSelected: false),
        MyDataStruct(title: "Nine", isSelected: false),
        MyDataStruct(title: "Ten", isSelected: false),
        MyDataStruct(title: "Eleven", isSelected: false),
        MyDataStruct(title: "Twelve", isSelected: false),
        MyDataStruct(title: "Thirteen", isSelected: false),
        MyDataStruct(title: "Fourteen", isSelected: false),
        MyDataStruct(title: "Fifteen", isSelected: false),
        MyDataStruct(title: "Sixteen", isSelected: false),
        MyDataStruct(title: "Seventeen", isSelected: false),
        MyDataStruct(title: "Eighteen", isSelected: false),
        MyDataStruct(title: "Nineteen", isSelected: false),
        MyDataStruct(title: "Twenty", isSelected: false),
    ]

    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "TableViewCell")

        let b = UIBarButtonItem(title: "Test", style: .plain, target: self, action: #selector(barButtonTapped(_:)))
        self.navigationItem.rightBarButtonItem = b
    }

    @objc func barButtonTapped(_ sender: Any?) -> Void {

        // instantiate the next view controller
        let vc = SampleViewController()

        // filter myData to only the elements with isSelected = true
        let selectedItems = myData.filter{ $0.isSelected == true }

        // set the next VC's property (i.e. pass the data to it)
        vc.theSelectedRows = selectedItems

        // push to the next VC
        self.navigationController?.pushViewController(vc, animated: true)

    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return myData.count
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "TableViewCell", for: indexPath)
        let dataElement: MyDataStruct = myData[indexPath.row]
        cell.textLabel?.text = dataElement.title
        cell.accessoryType = dataElement.isSelected ? .checkmark : .none
        return cell
    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        // toggle selected state in data
        myData[indexPath.row].isSelected = !myData[indexPath.row].isSelected
        tableView.reloadRows(at: [indexPath], with: .automatic)
    }

}

class SampleViewController: UIViewController {

    var theSelectedRows: [MyDataStruct] = [MyDataStruct]()

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white

        let resultLabel: UILabel = UILabel()
        view.addSubview(resultLabel)
        resultLabel.translatesAutoresizingMaskIntoConstraints = false
        resultLabel.numberOfLines = 0
        var s = ""
        theSelectedRows.forEach { d in
            s += d.title + "\n"
        }
        resultLabel.text = s
        resultLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        resultLabel.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
    }

}

输出：