我一直在研究创建UIPickerView的各种方法,每次遇到同样的问题时:
我收到错误:
类型'timeselectviewController'不符合协议'UIPickerViewDataSource'
并且pickerView函数总是得到警告:
实例方法'pickerView(pickerView:titleForRow:forComponent :)'几乎匹配协议'UIPickerViewDelegate'的可选要求'pickerView(_:titleForRow:forComponent :)'
这是迄今为止的代码:
import UIKit
class timeselectviewController: 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]
}
}
UIPickerViewDataSource
委托方法:
您显然必须编写这些方法的代码,但它会准确地向您显示缺少哪些方法以及您必须执行的操作。
注意,它是numberOfComponents(in:)
,而不是numberOfComponentsInPickerView(pickerView:)
。您所拥有的似乎是旧的Swift 2语法。titleForRow
和didSelectRow
都缺少_
argument label作为第一个参数。他们分别是:
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? { ... }
和
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) { ... }`
请注意_
参数标签,就像你对numberOfRowsInComponent
一样。
每当您看到这样的警告时,请仔细查看相关协议的文档(本例中为UIPickerViewDelegate
)。
通常,如果您点击警告,它甚至会让您选择让Xcode为您修复方法签名。选择“......以满足此要求”的选项,而不是选择“...以消除此警告”:
最重要的是,每当您看到有关缺少协议要求和/或“几乎匹配”警告的警告时,请尝试编译器建议的修复和/或仔细检查协议文档。