调整 UIAlertView 内 UIPickerView 的大小

我想放一个UIPickerView in a UIAlertView但我似乎无法正确调整它的大小。这是我得到的：

这是我的代码：

    let alertView = UIAlertController(title: "Select item from list", message: "", preferredStyle: UIAlertControllerStyle.alert)

    let pickerView = UIPickerView(frame: CGRect(x: 0, y: 0, width: 250, height: 60))
    pickerView.dataSource = self
    pickerView.delegate = self

    alertView.view.addSubview(pickerView)

    let action = UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil)

    alertView.addAction(action)
    parent.present(alertView, animated: true, completion: nil)

诀窍是：

• 使用多行消息来为新视图留出空间

• 出现警报视图时调整新视图的大小

  let alertView = UIAlertController(
      title: "Select item from list",
      message: "\n\n\n\n\n\n\n\n\n",
      preferredStyle: .alert)
  
  let pickerView = UIPickerView(frame:
      CGRect(x: 0, y: 50, width: 260, height: 162))
  pickerView.dataSource = self
  pickerView.delegate = self
  
  // comment this line to use white color
  pickerView.backgroundColor = UIColor.lightGray.withAlphaComponent(0.2)
  
  alertView.view.addSubview(pickerView)
  
  let action = UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: nil)
  
  alertView.addAction(action)
  present(alertView, animated: true, completion: { _ in
      pickerView.frame.size.width = alertView.view.frame.size.width
  })