ios - 开始使用 UIDatePicker 时的 Action

Question

我想在用户开始更改 UIDatePicker 的值时立即触发一个操作。我的第一直觉是使用 datePickerEditingDidBegin 方法，但似乎没有完成这项工作。

Answer 1

直接来自文档:

UIDatePicker: Responding to User Interaction

Date pickers use the Target-Action design pattern to notify your appwhen the user changes the selected date. To be notified when the datepicker’s value changes, register your action method with thevalueChanged event. At runtime the date picker calls your methods inresponse to the user selecting a date or time.

You connect a datepicker to your action method using the addTarget(_:action:for:) methodor by creating a connection in Interface Builder. The signature of anaction method takes one of three forms, which are listed in Listing 1.Choose the form that provides the information that you need to respondto the value change in the date picker.

Listing 1 Action methods for date pickers

@IBAction func doSomething()
@IBAction func doSomething(sender: UIDatePicker)
@IBAction func doSomething(sender: UIDatePicker, forEvent event: UIEvent)

连接您的日期选择器 valueChanged 将事件发送到您的 IBAction

编辑:

根据文档，UIDatePicker 没有任何委托(delegate)方法，因此像 datePickerEditingDidBegin 这样的东西没有任何意义。

您必须使用 UIControlEvent。如果 valueChanged 不符合您的需求，我可能会建议您使用 touchDragInside。

An event where a finger is dragged inside the bounds of the control.

其他UIControlEvent描述位于here in the docs .