Cannot convert string to date for datePicker

问题

I try to get string from textfield, then convert it to date and put this value in datepicker. But for some reason it fails everytime and I get: "There is issue in dateformatter. Not able to convert string to Date".

I don't understand what I'm doing wrong and how I get this works.

My code:

import UIKit

class ViewController: UIViewController {

@IBOutlet weak var DOBTextField: UITextField!

override func viewDidLoad() {
    super.viewDidLoad()

    DOBTextField.addInputViewDatePicker(target: self, selector: #selector(doneButtonPressed), textFieldText: DOBTextField.text)
}

@objc func doneButtonPressed() {
    if let  datePicker = self.DOBTextField.inputView as? UIDatePicker {
        let dateFormatter = DateFormatter()
        dateFormatter.dateStyle = .long
        dateFormatter.timeStyle = .none
        self.DOBTextField.text = dateFormatter.string(from: datePicker.date)
    }
    self.DOBTextField.resignFirstResponder()
 }
}


 extension UITextField {

   func addInputViewDatePicker(target: Any, selector: Selector , textFieldText: String?) {


    let screenWidth = UIScreen.main.bounds.width

    let datePicker = UIDatePicker(frame: CGRect(x: 0, y: 0, width: screenWidth, height: 216))
    datePicker.datePickerMode = .date
    self.inputView = datePicker

    let dateFormatter = DateFormatter()
    dateFormatter.dateStyle = .long
    dateFormatter.timeStyle = .none

    if textFieldText != nil {
        if let date = dateFormatter.date(from: textFieldText!) {
            datePicker.date = date
        } else {
        print("There is issue in dateformatter. Not able to convert string to Date ")
        }
      }
     else {
      datePicker.date = Date()
    }


    //Add Tool Bar as input AccessoryView
    let toolBar = UIToolbar(frame: CGRect(x: 0, y: 0, width: screenWidth, height: 44))
    let flexibleSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
    let cancelBarButton = UIBarButtonItem(title: "Cancel", style: .plain, target: self, action: #selector(cancelPressed))
    let doneBarButton = UIBarButtonItem(title: "Done", style: .plain, target: target, action: selector)
    toolBar.setItems([cancelBarButton, flexibleSpace, doneBarButton], animated: false)

    self.inputAccessoryView = toolBar
 }

   @objc func cancelPressed() {
     self.resignFirstResponder()
   }
}

I don't understand what I'm doing wrong and why this code doesn't work. May be someone can help me resolve this issue?

回答1:

As I see when you call addInputViewDatePicker on viewDidLoad, the value of textFieldText is "" that's why you see your print from start

you can try use this code (but, I guess, you can optimize it):

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var DOBTextField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()

        prepareDOBTextField()

        DOBTextField.addInputViewDatePicker(target: self, selector: #selector(doneButtonPressed), textFieldText: DOBTextField.text)
    }

    @objc func doneButtonPressed() {
        if let  datePicker = self.DOBTextField.inputView as? UIDatePicker {
            let dateFormatter = DateFormatter()
            dateFormatter.dateStyle = .long
            dateFormatter.timeStyle = .none
            self.DOBTextField.text = dateFormatter.string(from: datePicker.date)
        }
        self.DOBTextField.resignFirstResponder()
    }

    func prepareDOBTextField() {
        let date = Date()
        let formatter = DateFormatter()
        formatter.dateStyle = .long
        formatter.timeStyle = .none
        let result = formatter.string(from: date)

        self.DOBTextField.text = result
    }
}


extension UITextField {

    func addInputViewDatePicker(target: Any, selector: Selector , textFieldText: String?) {


        let screenWidth = UIScreen.main.bounds.width

        let datePicker = UIDatePicker(frame: CGRect(x: 0, y: 0, width: screenWidth, height: 216))
        datePicker.datePickerMode = .date
        self.inputView = datePicker

        let dateFormatter = DateFormatter()
        dateFormatter.dateStyle = .long
        dateFormatter.timeStyle = .none

        if textFieldText != nil && textFieldText != "" {
              if let date = dateFormatter.date(from: textFieldText!) {
                  datePicker.date = date
              } else {
                  print("There is issue in dateformatter. Not able to convert string to Date ")
              }
          }
          else {
              datePicker.date = Date()
          }

        //Add Tool Bar as input AccessoryView
        let toolBar = UIToolbar(frame: CGRect(x: 0, y: 0, width: screenWidth, height: 44))
        let flexibleSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
        let cancelBarButton = UIBarButtonItem(title: "Cancel", style: .plain, target: self, action: #selector(cancelPressed))
        let doneBarButton = UIBarButtonItem(title: "Done", style: .plain, target: target, action: selector)
        toolBar.setItems([cancelBarButton, flexibleSpace, doneBarButton], animated: false)

        self.inputAccessoryView = toolBar
    }

    @objc func cancelPressed() {
        self.resignFirstResponder()
    }
}

回答2:

You can do this by follow my code below.

@objc func doneButtonPressed() {
   //Converting string to date
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd HH:mm"
    let date = dateFormatter.date(from: DOBTextField.text!)

    //Sets the date in the date picker
    datepicker.setDate(date!, animated: true)
}

So first you're converting your textfield (DOBTextField.text) into Date.

Right after you're setting the datePicker to be the correct date.

In this case you will have to enter exactly like this in the textfield: "2019-12-18 14:50"

回答3:

Solved this question. I get rid of extenstion and write code for datepicker in ViewController.

import UIKit

class ViewController: UIViewController {

    @IBOutlet var textField: UITextField!

    let datePicker = UIDatePicker()

    override func viewDidLoad() {
        super.viewDidLoad()

        createDatePicker()
    }


    func createDatePicker() {
        textField.inputView = datePicker

        datePicker.datePickerMode = .date
        datePicker.maximumDate = Date()

        let toolbar = UIToolbar()
        toolbar.sizeToFit()

        let doneButton = UIBarButtonItem(barButtonSystemItem: .done, target: nil, action: #selector(doneClicked))
        let flexibleSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)

        toolbar.setItems([flexibleSpace, doneButton], animated: true)

        textField.inputAccessoryView = toolbar
    }

    @objc func doneClicked() {
        let dateFormatter = DateFormatter()
        dateFormatter.dateStyle = .long
        dateFormatter.timeStyle = .none

        textField.text = dateFormatter.string(from: datePicker.date)
        self.view.endEditing(true)

    }

}

After I added to viewWillAppear actual values of datepicker:

   override func viewWillAppear(_ animated: Bool) {

                let dateFormatter = DateFormatter()
                dateFormatter.dateStyle = .long
                dateFormatter.timeStyle = .none
                datePicker.date = dateFormatter.date(from: textfield.text!)!
    }

来源：https://stackoverflow.com/questions/59392923/cannot-convert-string-to-date-for-datepicker