UIPickerView 最佳实践？

一个简短的问题：在注册过程中，我想要求用户从值列表中选择一个值。

使用视图控制器添加所有文本字段并为值添加选择器视图是正确的方法吗？由于选择器视图在文本字段区域之间需要如此多的空间，我想知道在这种情况下的最佳实践是什么？

到目前为止，这是我的代码：

class RegisterViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource{

@IBOutlet weak var gradeTextField: UITextField!
@IBOutlet weak var gradePicker: UIPickerView!

let gradePickerValues = ["5. Klasse", "6. Klasse", "7. Klasse"]

func numberOfComponentsInPickerView(pickerView: UIPickerView!) -> Int{
    return 1
}
func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int{
    return gradePickerValues.count
}
func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {
    return gradePickerValues[row]
}
func pickerView(pickerView: UIPickerView!, didSelectRow row: Int, inComponent component: Int){
    gradeTextField.text = gradePickerValues[row]
    self.view.endEditing(true)
}

override func viewDidLoad() {
    super.viewDidLoad()

    statusMessageLabel.hidden = true

    gradePicker.dataSource = self
    gradePicker.delegate = self
    gradePicker.hidden = true

    gradeTextField.inputView = UIPickerView()
    gradeTextField.text = gradePickerValues[0]

}

选择器视图在开始时隐藏，仅当我选择文本字段时才出现，到目前为止这很好......但是选择器视图是空的......

这取决于控制器的外观。如果每个屏幕只有一个选择操作，那么最好将Table View在其上，所选行将是当前选择。

如果屏幕有多个字段，用户应该使用它，那么，在我看来，最好把label + button在其上方，当用户按下此按钮时button你只是表明Picker View从屏幕底部。当用户选择任意行时Picker View您更改标签文本，但不要隐藏选择器本身，应该通过按“完成”来完成button你放在上面。

希望这可以帮助。

Update:

你的问题是因为你忘记设置dataSource的财产UIPickerView

做就是了：gradePicker.dataSource = self in viewDidLoad()

并且不要忘记在这里实现协议：class RegisterViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource

Update 2:

终于成功了。如果你添加UIPickerView在你的textFiled的inputView中，那么它不应该在IB中。因此，您可以将其从故事板（或 .xib，如果您使用它）中删除。

然后将代码更改为如下所示：

class RegisterViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {

    @IBOutlet weak var gradeTextField: UITextField!
    var gradePicker: UIPickerView!

    let gradePickerValues = ["5. Klasse", "6. Klasse", "7. Klasse"]

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

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

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

    func pickerView(pickerView: UIPickerView!, didSelectRow row: Int, inComponent component: Int){
        gradeTextField.text = gradePickerValues[row]
        self.view.endEditing(true)
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        gradePicker = UIPickerView()

        gradePicker.dataSource = self
        gradePicker.delegate = self

        gradeTextField.inputView = gradePicker
        gradeTextField.text = gradePickerValues[0]
    }
}