将当前日期更改为前一/后一 - Swift DatePicker

Question

我有一个日期选择器。 我想将显示的日期更改为使用手势控制之前或之后的日期。 即，当一个人向左滑动时，日期会晚一天，如果一个人向右滑动，日期会晚一天。 我不确定如何实现这一点，因为我尝试了以下方法，但我收到一条错误消息，指出“无法转换类型为 'UITextField?”的值？ 到预期的参数类型“日期”。 如果有人可以帮助我或指出我正确的方向，我将不胜感激！ 谢谢

查看 Controller：

    @IBOutlet weak var userDate: UITextField!
    private var datePicker: UIDatePicker?

    override func viewDidLoad() {
        super.viewDidLoad()

        datePicker = UIDatePicker()
        datePicker?.datePickerMode = .date
        datePicker?.addTarget(self, action: #selector(Test.dateChanged(datePicker:)), for: .valueChanged)

        userDate.inputView = datePicker
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "EEEE, MMM d, yyyy"
        let todayDate = dateFormatter.string(from: Date.init())
        self.userDate.text = todayDate
        
        let swipeLeft = UISwipeGestureRecognizer(target: self, action: #selector(self.handleGesture(gesture:)))
            swipeLeft.direction = .left
            self.view.addGestureRecognizer(swipeLeft)

        let swipeRight = UISwipeGestureRecognizer(target: self, action: #selector(self.handleGesture(gesture:)))
            swipeRight.direction = .right
            self.view.addGestureRecognizer(swipeRight)

    }
    
    @objc func handleGesture(gesture: UISwipeGestureRecognizer) -> Void {
        
        if gesture.direction == UISwipeGestureRecognizer.Direction.right {
               print("Swipe Right")
              view.backgroundColor = .black
                // WHERE I WOULD LIKE TO CHANGE THE DATE ONE DAY AFTER
        }
        else if gesture.direction == UISwipeGestureRecognizer.Direction.left {
               print("Swipe Left")
                view.backgroundColor = .yellow
                // WHERE I WOULD LIKE TO CHANGE THE DATE ONE DAY BEFORE
           }
    }

我尝试了这种方法，但这是我得到错误的地方：

Calendar.current.date(byAdding: .day, value: 1, to: userDate)!

Answer 1

function date(byAdding:value:to:options:)期望将日期类型作为参数传递。 您正在传递 UITextField 而不是日期类型。 我想你想做的是

Calendar.current.date(byAdding: .day, value: 1, to: datePicker.date)!

Answer 2

您正在尝试在该方法需要日期的地方设置一个 textField：

Calendar.current.date(byAdding: .day, value: 1, to: userDate)!

从您的问题来看，您似乎想从 textField 中显示的当前日期中添加或减去一天。 试试下面的代码来做到这一点。 这从 userDate.text 中获取日期，并根据将 userDate.text 设置为新值的滑动方向增加或减少一天。

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var userDate: UITextField!
    private var datePicker: UIDatePicker?
    private let dateFormatter = DateFormatter()


    override func viewDidLoad() {
        super.viewDidLoad()

        datePicker = UIDatePicker()
        datePicker?.datePickerMode = .date
        // datePicker?.addTarget(self, action: #selector(Test.dateChanged(datePicker:)), for: .valueChanged)

        userDate.inputView = datePicker
        dateFormatter.dateFormat = "EEEE, MMM d, yyyy"
        let todayDate = dateFormatter.string(from: Date.init())
        self.userDate.text = todayDate

        let swipeLeft = UISwipeGestureRecognizer(target: self, action: #selector(self.handleGesture(gesture:)))
        swipeLeft.direction = .left
        self.view.addGestureRecognizer(swipeLeft)

        let swipeRight = UISwipeGestureRecognizer(target: self, action: #selector(self.handleGesture(gesture:)))
        swipeRight.direction = .right
        self.view.addGestureRecognizer(swipeRight)

    }

    @objc func handleGesture(gesture: UISwipeGestureRecognizer) -> Void {

        if gesture.direction == UISwipeGestureRecognizer.Direction.right {
            print("Swipe Right")
            // WHERE I WOULD LIKE TO CHANGE THE DATE ONE DAY AFTER
            let date = dateFormatter.date (from: userDate.text ?? dateFormatter.string(from: Date()))!
            let plusDay = Calendar.current.date(byAdding: .day, value: 1, to: date)!
            userDate.text = dateFormatter.string(from: plusDay)
        }
        else if gesture.direction == UISwipeGestureRecognizer.Direction.left {
            print("Swipe Left")
            // WHERE I WOULD LIKE TO CHANGE THE DATE ONE DAY BEFORE
            let date = dateFormatter.date (from: userDate.text ?? dateFormatter.string(from: Date()))!
            let minusDay = Calendar.current.date(byAdding: .day, value: -1, to: date)!
            userDate.text = dateFormatter.string(from: minusDay)
        }
    }
}