如何获取UIPicker的更改值以用于标签？ -斯威夫特3

Question

I have declared table cells and each cell I have added a label and a UIPicker. Once the UIPicker Value is changed, I would like to show the value in the label of the corresponding label.

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, UIPickerViewDelegate, UIPickerViewDataSource {

    @IBOutlet weak var myTable: UITableView!


    override func viewDidLoad() {
        super.viewDidLoad()
    }


    public func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int{
        return 2
    }


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

        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)

        let picker = UIPickerView()
        let y = 200 * indexPath.row
        picker.frame = CGRect(x: 200, y: y, width: 100, height: 150)
        picker.delegate = self
        picker.dataSource = self
        picker.tag = indexPath.row
        view.addSubview(picker)

        let myLbl = UILabel()
        myLbl.frame = CGRect(x: 100, y: y, width: 80, height: 100)
        myLbl.backgroundColor = UIColor.gray
        myLbl.textColor = UIColor.white
        myLbl.textAlignment = .center
        myLbl.tag = indexPath.row
        myLbl.text = "hi" // I would like to show the value of the UI picker
        view.addSubview(myLbl)

        return cell
    }

    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        return 200
    }


    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        print(indexPath.row)
        NotificationCenter.default.addObserver(self, selector: #selector(pickerChangeAction), name: NSNotification.Name("pickerChange"), object: self)
    }

    public func numberOfComponents(in pickerView: UIPickerView) -> Int{
        return 1
    }


    public func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int{
        return myData.count
    }

     public func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String?{

        return myData[row]

}

     public func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int){

       NotificationCenter.default.post(name: NSNotification.Name("pickerChange"), object: self)
        print("Hello2")
    }

    func pickerChangeAction(){
        print("Hello1")
    }
}

Answer 1

Simple solution using a custom cell and a callback closure:

• Create a custom cell in Interface Builder, add an UILabel and an UIPickerView .

• Create a custom class PickerViewCell , which contains the outlets, the picker data source and a callback closure.

   class PickerViewCell: UITableViewCell { var pickerDataSource = ["Alpha", "Beta", "Gamma", "Delta"] var callback : ((String) -> ())? @IBOutlet var picker : UIPickerView! @IBOutlet var selectedText : UILabel! } extension PickerViewCell : UIPickerViewDataSource, UIPickerViewDelegate { func numberOfComponents(in pickerView: UIPickerView) -> Int { return 1 } func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int { return pickerDataSource.count } func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? { return pickerDataSource[row] } func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) { callback?(pickerDataSource[row]) } } 

• In Interface Builder

  • Set the class of the custom cell to PickerViewCell and the identifier to PickerCell .
  • Connect the UI elements to the outlets.
  • Connect delegate and datasource of the picker to the custom cell.

• Implement cellForRow this way, the callback is used to update the label text and to be able to update the data model and do other things after the user picks a value.

   override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCell(withIdentifier: "PickerCell", for: indexPath) as! PickerViewCell cell.callback = { (value) in cell.selectedText.text = value // update the data model } return cell } 

If the picker instances are supposed to have different data source arrays, declare the arrays in the view controller and set the data source in cellForRow respectively.

Answer 2

1. Create a custom UITableViewCell.
2. Add a UILabel and UIPickerView to it.
3. Set the custom cell as the delegate for the picker view and move the pickers methods to the custom cell.
4. In the didSelectRow function update the cells corresponding UILabel

Have a look at the following link if you need help creating a custom UITableViewCell: https://www.ralfebert.de/tutorials/ios-swift-uitableviewcontroller/custom-cells/