如何在iOS工具栏中显示标准的向上/向下控件

import UIKit

class ViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {
    
    let toolbar = UIToolbar()
    let pickerView = UIPickerView()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        pickerView.delegate = self
        pickerView.dataSource = self
        
        let flexibleSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
        let doneButton = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(doneButtonTapped))
        
        toolbar.items = [flexibleSpace, doneButton]
        
        textField.inputView = pickerView
        textField.inputAccessoryView = toolbar
    }
    
    // UIPickerViewDataSource methods
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }
    
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return 10
    }
    
    // UIPickerViewDelegate methods
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return "Option \(row)"
    }
    
    @objc func doneButtonTapped() {
        // Handle done button tap event
        textField.resignFirstResponder()
    }
}