如何在 SwiftUI 上的 DatePicker 中设置 countDownTimer 模式？

Question

使用 UIKit，UIDatePicker 允许将模式设置为 UIDatePicker.Mode.countDownTimer，我们可以设置持续时间。

使用 SwiftUI，我看不到任何解决此问题的本地方法。唯一的方法是与 UIKit 进行交互？

[更新]
仅找到解决方案

DurationPickerView.swift

import SwiftUI
import UIKit

struct DurationPickerView: UIViewRepresentable {
    @Binding var time: Time

    func makeCoordinator() -> DurationPickerView.Coordinator {
        Coordinator(self)
    }

    func makeUIView(context: Context) -> UIDatePicker {
        let datePicker = UIDatePicker()
        datePicker.datePickerMode = .countDownTimer
        datePicker.addTarget(context.coordinator, action: #selector(Coordinator.onDateChanged), for: .valueChanged)
        return datePicker
    }

    func updateUIView(_ datePicker: UIDatePicker, context: Context) {
        let date = Calendar.current.date(bySettingHour: time.hour, minute: time.minute, second: time.second, of: datePicker.date)!
        datePicker.setDate(date, animated: true)
    }

    class Coordinator: NSObject {
        var durationPicker: DurationPickerView

        init(_ durationPicker: DurationPickerView) {
            self.durationPicker = durationPicker
        }

        @objc func onDateChanged(sender: UIDatePicker) {
            print(sender.date)
            let calendar = Calendar.current
            let date = sender.date
            durationPicker.time = Time(hour: calendar.component(.hour, from: date), minute: calendar.component(.minute, from: date), second: calendar.component(.second, from: date))
        }
    }
}

Time.swift

import Foundation

struct Time {
    var hour: Int
    var minute: Int
    var second: Int = 0
}

Answer 1

现在获得倒计时行为的唯一方法是将 UIDatePicker 包装在自定义视图中。

这是使用 countDownDuration 的代码的简化版本。

import SwiftUI

struct DurationPicker: UIViewRepresentable {
    @Binding var duration: TimeInterval

    func makeUIView(context: Context) -> UIDatePicker {
        let datePicker = UIDatePicker()
        datePicker.datePickerMode = .countDownTimer
        datePicker.addTarget(context.coordinator, action: #selector(Coordinator.updateDuration), for: .valueChanged)
        return datePicker
    }

    func updateUIView(_ datePicker: UIDatePicker, context: Context) {
        datePicker.countDownDuration = duration
    }

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    class Coordinator: NSObject {
        let parent: DurationPicker

        init(_ parent: DurationPicker) {
            self.parent = parent
        }

        @objc func updateDuration(datePicker: UIDatePicker) {
            parent.duration = datePicker.countDownDuration
        }
    }
}

Answer 2

这是另一个解决方案。它只是将两个选择器并排放置，所以看起来不太好。但它确实避免了另一个答案中的错误，即它不会在第一次更新选择器中选择的值。

import SwiftUI

struct CountDownPicker: View {
    
    var hours = Array(0...23)
    var min = Array(0...59)
    
    @Binding var selectedHours: Int
    @Binding var selectedMins: Int
    
    var body: some View {
        GeometryReader { geometry in
            HStack {
                Picker(selection: $selectedHours, label: Text("hrs")) {
                    ForEach(0..<self.hours.count) {
                        Text("\(self.hours[[=10=]]) hrs")
                            .bold()
                    }
                }
                .frame(maxWidth: geometry.size.width / 2)
                .clipped()
                .pickerStyle(.wheel)
                
                Picker(selection: self.$selectedMins, label: Text("mins")) {
                    ForEach(0..<self.min.count) {
                        Text("\(self.min[[=10=]]) mins")
                            .bold()
                    }
                }
                .frame(maxWidth: geometry.size.width / 2)
                .clipped()
                .pickerStyle(.wheel)
            }
        }
        .offset(y: -100)
        .padding()
        .frame(width: .infinity, height: 140, alignment: .center)
        
    }
}

如何在 SwiftUI 上的 DatePicker 中设置 countDownTimer 模式？

How can I set countDownTimer mode in DatePicker on SwiftUI?

swift

swiftui

uidatepicker