另一个类中的 WPF 事件处理程序

本文关键字：事件处理 程序 WPF 另一个 | 更新日期: 2023-09-27 18:36:10

我已经为一些自定义 WPF 控件构建了一系列事件处理程序。 事件句柄根据所包含的数据类型（电话号码、邮政编码、货币值等）设置用户输入或离开文本框时显示的文本的格式。

现在，我将 C# 代码中的所有事件本地直接附加到 xaml。 因为我开发了一个可以控件，这意味着逻辑重复了很多，如果我想更改程序范围的功能，我必须在事件代码所在的任何地方进行更改。

我相信有一种方法可以将我的所有事件处理程序放在一个类中。 谁能帮我指出正确的方向？

我看到了这篇文章：事件处理程序位于与 MainWindow 不同的类中，但我不确定它是否与我正在做的事情直接相关。 我宁愿对现有逻辑进行小的更改，因为它有效，然后将所有内容重写为命令。

如果可能的话，我基本上想这样的事情：

LostFocus="ExpandedTextBoxEvents.TextBox_LostFocus"

做这样的事情很容易： 

private void TextBoxCurrencyGotFocus(object sender, RoutedEventArgs e)
{
    ExpandedTextBoxEvents.TextBoxCurrencyGotFocus(sender, e);
}
private void TextBoxCurrencyLostFocus(object sender, RoutedEventArgs e)
{
    ExpandedTextBoxEvents.TextBoxCurrencyLostFocus(sender, e);
}

但这并不那么优雅。

另一个类中的 WPF 事件处理程序

附加属性是实现所需内容的一种方法。我经常使用它们。

附加物业代码：

Public Class TextBoxFormatter
    ' ------------------------------------------------------
    ' Define the FormatType attached property
    Public Shared ReadOnly FormatTypeProperty As DependencyProperty = _
        DependencyProperty.RegisterAttached( _
            name:="FormatType", _
            propertyType:=GetType(TextBoxFormatterType), _
            ownerType:=GetType(TextBoxFormatter), _
            defaultMetadata:=New FrameworkPropertyMetadata( _
                defaultValue:=TextBoxFormatterType.None, _
                PropertyChangedCallback:=New PropertyChangedCallback(AddressOf FormatTypePropertyChanged) _
            ) _
        )
    ' ------------------------------------------------------
    ' Define the "getter" and "setter" for FormatType
    Public Shared Function GetFormatType(ByVal target As DependencyObject) As TextBoxFormatterType
        target.GetValue(FormatTypeProperty)
    End Function
    Public Shared Sub SetFormatType(ByVal target As DependencyObject, ByVal value As TextBoxFormatterType)
        target.SetValue(FormatTypeProperty, value)
    End Sub
    ' ------------------------------------------------------
    ' Define the FormatType "PropertyChanged" event handler
    Private Shared Sub FormatTypePropertyChanged(ByVal target As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs)
        If CType(e.NewValue, TextBoxFormatterType) = TextBoxFormatterType.None Then
            UnregisterFormatTypeControl(target)
        Else
            RegisterFormatTypeControl(target)
        End If
    End Sub
    ' ------------------------------------------------------
    ' Define the a collection of event listerns for the
    ' FormatType "PropertyChanged" event
    Private Shared _registeredFormatTypeControlDelegates As New Dictionary(Of TextBox, RoutedEventHandler)
    ' ------------------------------------------------------
    ' Register a control as an event listener
    ' (also, attach to the control's LostFocus event)
    Private Shared Sub RegisterFormatTypeControl(ByVal candidate As DependencyObject)
        Dim l_control = TryCast(candidate, TextBox)
        If l_control IsNot Nothing Then
            Dim l_handler = New RoutedEventHandler(AddressOf FormatTypeControl_LostFocus)
            _registeredFormatTypeControlDelegates.Add(l_control, l_handler)
            l_control.AddHandler(TextBox.LostFocusEvent, l_handler)
        End If
    End Sub
    ' ------------------------------------------------------
    ' Unregister a control as an event listener
    ' (also, unattach from the control's LostFocus event)
    Private Shared Sub UnregisterFormatTypeControl(ByVal candidate As DependencyObject)
        Dim l_control = TryCast(candidate, TextBox)
        If l_control IsNot Nothing AndAlso _registeredFormatTypeControlDelegates.ContainsKey(l_control) Then
            Dim l_handler = _registeredFormatTypeControlDelegates(l_control)
            l_control.RemoveHandler(TextBox.LostFocusEvent, l_handler)
            _registeredFormatTypeControlDelegates.Remove(l_control)
        End If
    End Sub
    ' ------------------------------------------------------
    ' On the control's LostFocus event, apply the format
    ' (You could apply the format based on another event,
    ' just be careful if using the TextChanged event - it
    ' will fire whether the user has changed the text or
    ' your code has changed the text - could introduce an
    ' infinite loop)
    Private Shared Sub FormatTypeControl_LostFocus(ByVal sender As Object, ByVal e As RoutedEventArgs)
        Dim l_textBox = TryCast(e.Source, TextBox)
        If l_textBox IsNot Nothing Then
            Dim l_formatType = CType(l_textBox.GetValue(FormatTypeProperty), TextBoxFormatterType)
            Select Case l_formatType
                Case TextBoxFormatterType.SocialSecurityNumber
                    ' Apply the format to the l_textBox
                    ' (What do you want a social security number to look like?)
                Case TextBoxFormatterType.ZipCode
                    ' Apply the format to the l_textBox
                    ' (What do you want a zip code to look like?)
                Case TextBoxFormatterType.Etc
                    ' Apply the format to the l_textBox
            End Select
        End If
    End Sub
End Class
Public Enum TextBoxFormatterType
    None
    ZipCode
    SocialSecurityNumber
    Etc
End Enum

上面看起来有点混乱，但是一旦编写了代码（一次），您就可以在UI中一遍又一遍地使用它：

<Window x:Class="Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:this="clr-namespace:WpfApplication1"
        Title="Window1">
  <Grid>
    <StackPanel>
      <TextBox this:TextBoxFormatter.FormatType="SocialSecurityNumber" />
      <TextBox this:TextBoxFormatter.FormatType="ZipCode" />
      <TextBox this:TextBoxFormatter.FormatType="None" />
    </StackPanel>
  </Grid>
</Window>

这种方法的一个优点是"FormatType"成为依赖属性，这意味着您可以在运行时将值绑定到它（而不仅仅是harcoding，如上例所示）。例如：

<TextBox this:TextBoxFormatter.FormatType="{Binding ViewModel.DesiredFormat}" />

可以创建一个依赖项属性并在 XAML 中使用它，如下所示： 

ExpandedTextBoxEvents.Subscribe="True"

依赖项属性将存在于 ExpandedTextBoxEvents 类中，并且 Subscribe 属性可以在设置为 True 时建立所有必要的事件订阅。

这将给你留下一个单独的类，由 XAML（或 C#，如果你愿意）在一个简单的语句中拉入。

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