PickerView只顯示'？'

Question

這是我的源代碼，我所做的是讓storyBoard上的選取器視圖。通過控制+拖動在該控制器中製作IBOutlet。

然而，它可以被編譯，只有'？'出現在選取器視圖中。

問題在哪裏？

import UIKit 

class SelectViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate{ 
    var songNames = ["test1","test2","test3"] 

    @IBOutlet weak var songPicker: UIPickerView! 

    override func viewDidLoad(){ 
     songPicker.delegate = self 
     songPicker.dataSource = self 

    } 

    func numberOfComponents(in pickerView: UIPickerView) -> Int { 
     return 1 
    } 

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int { 
     return songNames.count 
    } 

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int) -> String? { 
     return songNames[row] 
    } 
} 

Answer 1

您錯過了dataSource方法中的forComponent參數。在titleForRow功能添加這樣的：

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? { 
    return songNames[row] 
} 

這應該可以解決您所遇到的問題。