Question

我想在我的UITextField中保留相同的占位符文本，即“位置”。触摸UITextField后，我想要显示UIPickerView的第一个值。现在用户必须向下滚动然后备份以便在UITextField中显示该值。我想要在UIPickerView打开后立即在UITextField中显示该值。 unselected, selected-UITextField still shows no value

override func viewDidLoad() {
    let thePicker = UIPickerView()
    thePicker.delegate = self
    location.inputView = thePicker
    thePicker.selectRow(1, inComponent: 0, animated: true)
}

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

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

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    return pickOptions[row]
}


func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    location.text = pickOptions[row]
}

Answer 1

实施textFieldDidBeginEditing文本字段委托方法，并设置文本字段的文本（如果它还没有值）。

func textFieldDidBeginEditing(_ textField: UITextField) {
    if textField.text!.isEmpty {
        // set the text as needed
    }
}

Answer 2

import UIKit

class ActivityPersonDetail : UIViewController,UITextFieldDelegate,UIPickerViewDataSource, UIPickerViewDelegate {


    let salutations = ["1", "2", "3","4","5","6","7","8","9","10","11","12"]

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

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

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return salutations[row]
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        pickerTF.text = salutations[row]
        picker.isHidden = true

    }

    func textFieldDidBeginEditing(_ textField: UITextField) {

        if textField == self.pickerTF {
            picker.isHidden = false
            textField.endEditing(true)
        }
    }


    lazy var picker: UIPickerView = {
        let pickerView = UIPickerView()
        pickerView.delegate = self
        pickerView.translatesAutoresizingMaskIntoConstraints = false
        pickerView.backgroundColor = .white

        pickerTF.inputView = pickerView
        return pickerView
    }()

    let  arrowImage: UIImageView = {

        let image = UIImageView()
        image.translatesAutoresizingMaskIntoConstraints = false
        image.image = #imageLiteral(resourceName: "down_arrow")
        image.contentMode = .scaleAspectFit
        return image
    } ()

    lazy var pickerTF: UITextField = {

        let tf = UITextField()
        tf.delegate = self
        tf.translatesAutoresizingMaskIntoConstraints = false
        tf.textColor = .black
        tf.font = .systemFont(ofSize: 24, weight: .medium)
        tf.placeholder = salutations[0]
        return tf
    }()



    //
    // MARK :- viewDidLoad ============================================================================
    //
    private var pickerView: UIPickerView!

    override func viewDidLoad() {

        super .viewDidLoad()
        view.backgroundColor = .white

        setupNavigationBar()
        setupViews()
        setupAutoLayout()

    }

    // ================ setupNavigationBar =============

    func setupNavigationBar(){

        title = ""
        hideBackTitle()
        navigationController?.navigationBar.barTintColor = .navBar

    }
    func hideBackTitle() {
        let backbarItem = UIBarButtonItem()
        backbarItem.title = ""
        navigationItem.backBarButtonItem = backbarItem
    }


    // ================ setupViews =============

    func setupViews(){

        view.addSubview(pickerTF)
        pickerTF.addSubview(arrowImage)
        view.addSubview(picker)
        picker.isHidden = true
    }


    // ================ setupAutoLayout =============

    func setupAutoLayout() {

        pickerTF.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 80).isActive = true
        pickerTF.topAnchor.constraint(equalTo: view.topAnchor, constant: 80).isActive = true
        pickerTF.heightAnchor.constraint(equalToConstant: 60).isActive = true
        pickerTF.widthAnchor.constraint(equalToConstant: 70).isActive = true

        arrowImage.rightAnchor.constraint(equalTo: pickerTF.rightAnchor, constant: -15).isActive = true
        arrowImage.topAnchor.constraint(equalTo: pickerTF.topAnchor, constant: 16).isActive = true
        arrowImage.widthAnchor.constraint(equalToConstant: 22).isActive = true
        arrowImage.heightAnchor.constraint(equalToConstant: 22).isActive = true

        picker.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        picker.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        picker.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
        picker.heightAnchor.constraint(equalToConstant: 100).isActive = true


    }

}

Answer 3

我将以rmaddy的答案为基础，并在评论中添加更多细微差别和对问题的答案。

主要答案在于第一个扩展名，其余代码概述了所有工作所需的类结构和组件。

class ViewController {
    private var selectedItem: String = ""
    private let pickerList = [
        "First item",
        "Second item",
        "Third item"
    ]
     override func viewDidLoad() {
        super.viewDidLoad()
        pickerTextField.delegate = self
        //...
        // Layout setup
        //...
    }
    private let pickerTextField: UITextField = {
        let textField = UITextField()
        textField.tintColor = .clear // hides cursor
        return textField
    }()
    //...
    // UI Elements including picker
    //...
}

extension ViewController: UITextFieldDelegate {
    internal func textFieldDidBeginEditing(_ textField: UITextField) {
        if textField == pickerTextField, let textFieldText = textField.text, textFieldText.isEmpty {
            pickerTextField.text = pickerList.first   // fills textfield before any selection is made
        }
    }
}

extension ViewController: UIPickerViewDelegate, UIPickerViewDataSource {
    //...
    // PickerView delegate methods
    //...
}

Answer 4

@IBOutlet weak var tF: UITextField!

override func viewDidLoad() {
    super.viewDidLoad()

    tF.delegate = self
}

func textFieldDidEndEditing(_ textField: UITextField) {
    textField.text = pickOptions[row]
}

触摸UITextField时设置UIPickerView的默认值

4 个答案: