如何使用 UIDatePicker 输入管理带有两个 UITextField 的 firstResponder

Question

我有一个 ViewController，其中两个 UITextFields 使用 UIDatePicker(s) 作为输入。一个是 "From" 日期，另一个是 "To" 日期，所以这似乎是一个相当常见的场景。

问题是，当一个字段的 DatePicker 处于活动状态时，用户可能会点击屏幕上的另一个字段。活动的 DatePicker 仍然与第一个字段相关联，因此 UI 会让用户感到困惑，因为光标在另一个字段中闪烁，但输入不在那里。

我认为正确的 UI 解决方案是防止用户在关闭 DatePicker 之前点击任何其他字段。但是我无法找到一种方法来检测 firstResponder 正在更改或暂时禁用对其他字段的编辑。

这是我当前的代码，它没有做我需要它做的事情：

class AddTripLocationVC: UIViewController, UITextFieldDelegate {

@IBOutlet private weak var tripLocFromDateInput: UITextField!
@IBOutlet private weak var tripLocToDateInput: UITextField!

override func viewDidLoad() {
    super.viewDidLoad()

    //set up datepickers for text field inputs
    createDatePicker(forDateField: tripLocFromDateInput)
    createDatePicker(forDateField: tripLocToDateInput)

}

//automatically update the label fields when the date vairables are updated by the UIDatePicker
var locFromDate: Date? {
    didSet {
        guard locFromDate != nil else { return }
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "dd MMM yyyy"
        tripLocFromDateInput.text = dateFormatter.string(from: locFromDate!)
    }
}

var locToDate: Date? {
    didSet {
        guard locToDate != nil else { return }
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "dd MMM yyyy"
        tripLocFromDateInput.text = dateFormatter.string(from: locToDate!)
        //Comment after solution found...The problem was the line above
        //It should be:
        tripLocToDateInput.text = dateFormatter.string(from: locToDate!)
    }
}

func createDatePicker(forDateField dateField: UITextField) {

    let datePickerView = UIDatePicker()
    datePickerView.datePickerMode = .date
    dateField.inputView = datePickerView
    datePickerView.addTarget(self, action: #selector(handleDatePicker(sender:)), for: .valueChanged)

    let doneButton = UIBarButtonItem.init(title: "Done", style: .done, target: self, action: #selector(self.datePickerDone))
    let toolBar = UIToolbar.init(frame: CGRect(x: 0, y: 0, width: view.bounds.size.width, height: 44))
    toolBar.setItems([UIBarButtonItem(barButtonSystemItem: UIBarButtonItem.SystemItem.flexibleSpace, target: nil, action: nil), doneButton],
                     animated: true)
    dateField.inputAccessoryView = toolBar
}

@objc
func handleDatePicker(sender: UIDatePicker) {

    if tripLocFromDateInput.isFirstResponder {
        locFromDate = sender.date
    } else {
        if tripLocToDateInput.isFirstResponder {
            locToDate = sender.date
        } else {
            print("Error: Can't find first responder field.")
        }
    }
}

@objc
func datePickerDone(dateField: UITextView) {

    if tripLocFromDateInput.isFirstResponder {
        tripLocFromDateInput.resignFirstResponder()
    } else {
        if tripLocToDateInput.isFirstResponder {
            tripLocToDateInput.resignFirstResponder()
        } else {
            print("Error: Can't find first responder field.")
        }
    }
}

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    self.view.endEditing(true)
}

func textFieldDidEndEditing(_ textField: UITextField) {
    textField.becomeFirstResponder()
}
}

对于 iOS 中的此类 'From' 和 'To' 日期字段，UI 是否有 'standard' 方法？

Answer 1

您可以注册一个 UITextField 委托，其中包含您特别感兴趣的两个方法，特别是：

textFieldDidBeginEditing(:)
textFieldDidEndEditing(:)

要获取更多信息，请访问：https://developer.apple.com/documentation/uikit/uitextfielddelegate

请注意，您还可以在任何 UITextField 上使用 becomeFirstResponder() 来激活它。激活的那个应该有闪烁的光标。

编辑：根据您更新的代码：

//
//  ViewController.swift
//  datepickers
//
//  Created by Dave Poirier on 2019-06-13.
//

import UIKit

class ViewController: UIViewController,  UITextFieldDelegate {

    @IBOutlet private weak var tripLocFromDateInput: UITextField!
    @IBOutlet private weak var tripLocToDateInput: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()

        //set up datepickers for text field inputs
        createDatePicker(forDateField: tripLocFromDateInput)
        createDatePicker(forDateField: tripLocToDateInput)

        //set text field delegates to be notified when focus changes
        tripLocFromDateInput.delegate = self
        tripLocToDateInput.delegate = self
    }


    func createDatePicker(forDateField dateField: UITextField) {

        let datePickerView = UIDatePicker()
        datePickerView.datePickerMode = .date
        dateField.inputView = datePickerView
        datePickerView.addTarget(self, action: #selector(handleDatePicker(sender:)), for: .valueChanged)

        let doneButton = UIBarButtonItem.init(title: "Done", style: .done, target: self, action: #selector(self.datePickerDone))
        let toolBar = UIToolbar.init(frame: CGRect(x: 0, y: 0, width: view.bounds.size.width, height: 44))
        toolBar.setItems([UIBarButtonItem(barButtonSystemItem: UIBarButtonItem.SystemItem.flexibleSpace, target: nil, action: nil), doneButton],
                         animated: true)
        dateField.inputAccessoryView = toolBar
    }

    @objc
    func handleDatePicker(sender: UIDatePicker) {

        if tripLocFromDateInput.isFirstResponder {
            let locFromDate = sender.date
            tripLocFromDateInput.text = "FROM: \(locFromDate)"
        } else {
            if tripLocToDateInput.isFirstResponder {
                let locToDate = sender.date
                tripLocToDateInput.text = "TO: \(locToDate)"
            } else {
                print("Error: Can't find first responder field.")
            }
        }
    }

    @objc
    func datePickerDone(dateField: UITextView) {

        if tripLocFromDateInput.isFirstResponder {
            tripLocFromDateInput.resignFirstResponder()
        } else {
            if tripLocToDateInput.isFirstResponder {
                tripLocToDateInput.resignFirstResponder()
            } else {
                print("Error: Can't find first responder field.")
            }
        }
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesBegan(touches, with: event)
        self.view.endEditing(true)
    }
}

}

上面的代码在一个全新的项目中为我工作，创建了两个输入字段并连接了 IBOutlets

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