如何从显示时间的文本字段中减去分钟

Question

我一直在研究如何执行此操作，但没有成功，我仍然不太了解 NSdate 和执行操作的方式。

我有一个应用程序，其中按下 timeText(UITextField) 会弹出 UIDatPicker，用户可以 select 使用滚轮所需的时间。然后，一旦按下 doneBTN（从工具栏），它就会填充该文本字段上所需的时间。

我要找的是分别在Tminus3（UILabel）、Tminus10（UILabel）、Tminus20（UILabel）上显示timeText（select来自用户的结果）减去3分钟（ Tminus3), 负10分钟(Tminus10), 负20分钟(Tminus20) 分别在每个标签上。

即用户按下时间文本和 select 时间，比方说 11:30。当我按 updateBTN 我想获得 Tminus3.text = 11:27, Tminus10.text = 11:20, Tminus20.text = 11:10.[= 的值11=]

这是初始代码。

提前致谢

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var timeText: UITextField!
    let timePicker = UIDatePicker()
    
    @IBOutlet weak var Tminus3: UILabel!
    @IBOutlet weak var Tminus10: UILabel!
    @IBOutlet weak var Tminus20: UILabel!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        createTimeP()
    }
    func creteToolB() -> UIToolbar {
        let toolbar = UIToolbar()
        toolbar.sizeToFit()
        
        let doneBTN = UIBarButtonItem(barButtonSystemItem: .done, target: nil, action: #selector(donePressed))
        toolbar.setItems([doneBTN], animated: true)
     
        return toolbar
    }
    func createTimeP() {
        timePicker.preferredDatePickerStyle = .wheels
        timePicker.datePickerMode = .time
        timePicker.locale = NSLocale(localeIdentifier: "UTC") as Locale
        timePicker.minuteInterval = 5
        timeText.inputView = timePicker
        timeText.inputAccessoryView = creteToolB()
        
    }
    
    @objc func donePressed() {
        let timeFormatter = DateFormatter()
        timeFormatter.dateStyle = .none
        timeFormatter.timeStyle = .short
        timeFormatter.dateFormat = "HH:mm"
        self.timeText.text = timeFormatter.string(from: timePicker.date)
        self.view.endEditing(true)
        
    }
    
    @IBAction func **updateBTN**(_ sender: Any) {
    
        
    // from the timeText.text = "HH:mm" get the value —> minus3.text(label) minutes, minus10.text()label minutes, minus20.text(label) minutes.
      
        
    }
    
}

Answer 1

试试这个：

import UIKit

class tViewController: UIViewController {

    @IBOutlet weak var timeText: UITextField!
    let timePicker = UIDatePicker()
    
    @IBOutlet weak var Tminus3: UILabel!
    @IBOutlet weak var Tminus10: UILabel!
    @IBOutlet weak var Tminus20: UILabel!

    var selectedDate: Date? = nil
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        createTimeP()
    }
    func creteToolB() -> UIToolbar {
        let toolbar = UIToolbar()
        toolbar.sizeToFit()
        
        let doneBTN = UIBarButtonItem(barButtonSystemItem: .done, target: nil, action: #selector(donePressed))
        toolbar.setItems([doneBTN], animated: true)
     
        return toolbar
    }
    func createTimeP() {
        timePicker.preferredDatePickerStyle = .wheels
        timePicker.datePickerMode = .time
        timePicker.locale = NSLocale(localeIdentifier: "UTC") as Locale
        timePicker.minuteInterval = 5
        timeText.inputView = timePicker
        timeText.inputAccessoryView = creteToolB()
        
    }
    
    @objc func donePressed() {
        let timeFormatter = DateFormatter()
        timeFormatter.dateStyle = .none
        timeFormatter.timeStyle = .short
        timeFormatter.dateFormat = "HH:mm"
        self.timeText.text = timeFormatter.string(from: timePicker.date)
        self.selectedDate = timePicker.date
        self.view.endEditing(true)
        
    }
    
    func getTime(date: Date) -> String {
        let timeFormatter = DateFormatter()
        timeFormatter.dateStyle = .none
        timeFormatter.timeStyle = .short
        timeFormatter.dateFormat = "HH:mm"
        return timeFormatter.string(from: date)
    }
    
    @IBAction func updateBTN(_ sender: Any) {
    
        if let selectedDate = self.selectedDate {
            let tminus3Date = Calendar.current.date(byAdding: .minute, value: -3, to: selectedDate)!
            let tminus10Date = Calendar.current.date(byAdding: .minute, value: -10, to: selectedDate)!
            let tminus20Date = Calendar.current.date(byAdding: .minute, value: -20, to: selectedDate)!
            
            self.Tminus3.text = getTime(date: tminus3Date)
            self.Tminus10.text = getTime(date: tminus10Date)
            self.Tminus20.text = getTime(date: tminus20Date)
        }
        
    }
    
}

如何从显示时间的文本字段中减去分钟

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ios