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Keyboard.LostKeyboardFocus 附加事件

  • 參考

定義

命名空間:
System.Windows.Input
組件:
PresentationCore.dll

項目失去鍵盤焦點時發生。

see AddLostKeyboardFocusHandler, and RemoveLostKeyboardFocusHandler
see AddLostKeyboardFocusHandler, and RemoveLostKeyboardFocusHandler
see AddLostKeyboardFocusHandler, and RemoveLostKeyboardFocusHandler

範例

下列範例會TextBox建立 並附加 事件和 LostKeyboardFocus 事件的事件處理程式GotKeyboardFocus。 TextBox取得鍵盤焦點時，背景色彩會變更，並清除的TextBox文字。 TextBlock當 失去鍵盤焦點時，背景色彩會變更，而且會呼叫方法來重設範例中使用的變數。

<Border BorderBrush="Black" BorderThickness="1"
        Width="200" Height="100" Margin="5">
  <StackPanel>
    <Label HorizontalAlignment="Center" Content="Type Text In This TextBox" />
    <TextBox Width="175"
             Height="50" 
             Margin="5"
             TextWrapping="Wrap"
             HorizontalAlignment="Center"
             VerticalScrollBarVisibility="Auto"
             GotKeyboardFocus="TextBoxGotKeyboardFocus"
             LostKeyboardFocus="TextBoxLostKeyboardFocus"
             KeyDown="SourceTextKeyDown"/>
  </StackPanel>
</Border>

private void TextBoxGotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
    TextBox source = e.Source as TextBox;

    if (source != null)
    {
        // Change the TextBox color when it obtains focus.
        source.Background = Brushes.LightBlue;

        // Clear the TextBox.
        source.Clear();
    }
}

Private Sub TextBoxGotKeyboardFocus(ByVal sender As Object, ByVal e As KeyboardFocusChangedEventArgs)
    Dim source As TextBox = TryCast(e.Source, TextBox)

    If source IsNot Nothing Then
        ' Change the TextBox color when it obtains focus.
        source.Background = Brushes.LightBlue

        ' Clear the TextBox.
        source.Clear()
    End If
End Sub

private void TextBoxLostKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
    TextBox source = e.Source as TextBox;

    if (source != null)
    {
        // Change the TextBox color when it loses focus.
        source.Background = Brushes.White;

        // Set the  hit counter back to zero and updates the display.
        this.ResetCounter();
    }
}

Private Sub TextBoxLostKeyboardFocus(ByVal sender As Object, ByVal e As KeyboardFocusChangedEventArgs)
    Dim source As TextBox = TryCast(e.Source, TextBox)

    If source IsNot Nothing Then
        ' Change the TextBox color when it loses focus.
        source.Background = Brushes.White

        ' Set the  hit counter back to zero and updates the display.
        Me.ResetCounter()
    End If
End Sub

備註

這是附加的事件。 WPF 會將附加事件實作為路由事件。 附加事件基本上是一種 XAML 語言概念，可參考未定義該事件的物件上可處理的 XAML 語言概念，WPF 也會藉由讓事件周遊路由來擴充該事件。 附加事件在程式代碼中沒有直接處理語法;若要在程式代碼中附加路由事件的處理程式，您可以使用指定的 Add*Handler 方法。 如需詳細資訊，請參閱 附加事件概觀。

鍵盤焦點是指接收鍵盤輸入的物件。 具有鍵盤焦點的項目已 IsKeyboardFocused 設定為 true。 整個桌面上只能有一個鍵盤焦點的專案。 邏輯焦點是指焦點範圍內具有焦點的物件。 如需焦點、鍵盤焦點和邏輯焦點的詳細資訊，請參閱 輸入 概觀和 焦點概觀。

PreviewGotKeyboardFocus如果已處理事件或PreviewLostKeyboardFocus事件，鍵盤焦點就不會變更。

路由事件資訊
標識元欄位 LostKeyboardFocusEvent
路由策略 鼓 泡
代理人 KeyboardFocusChangedEventHandler

適用於