Keyboard.LostKeyboardFocus Keyboard.LostKeyboardFocus Keyboard.LostKeyboardFocus Attached Event

定義

項目失去鍵盤焦點時發生。Occurs when an element loses keyboard focus.

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

範例

下列範例會建立TextBox,並將附加事件處理常式GotKeyboardFocus事件和LostKeyboardFocus事件。The following example creates a TextBox and attaches event handlers for the GotKeyboardFocus event and the LostKeyboardFocus event. TextBox取得鍵盤焦點,變更背景色彩和文字TextBox已清除。When the TextBox obtains keyboard focus, the background color is changed and the text of the TextBox is cleared. TextBlock失去鍵盤焦點的背景色彩會變更,且會呼叫方法的範例中使用的變數會重設。When the TextBlock loses keyboard focus, the background color is changed and a method is called that resets variables used in the sample.

<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。This is an attached event. WPFWPF 將附加的事件實作為路由事件。implements attached events as routed events. 附加的事件基本上都XAMLXAML參考可以處理不會定義事件的物件的事件的語言概念的WPFWPF展開時也能周遊路由事件。Attached events are fundamentally a XAMLXAML language concept for referencing events that can be handled on objects that do not define that event, which WPFWPF expands upon by also enabling the event to traverse a route. 附加的事件並沒有直接處理語法在程式碼若要附加的程式碼中的路由事件處理常式,您會使用指定的新增 * 處理常式方法。Attached events do not have a direct handling syntax in code; to attach handlers for a routed event in code, you use a designated Add*Handler method. 如需詳細資訊,請參閱 < 附加事件概觀For details, see Attached Events Overview.

鍵盤焦點是指接收鍵盤輸入的物件。Keyboard focus refers to the object that is receiving keyboard input. 具有鍵盤焦點的項目具有IsKeyboardFocused設定為trueThe element with keyboard focus has IsKeyboardFocused set to true. 可以有鍵盤焦點設在整個桌面只能有一個項目。There can be only one element with keyboard focus on the entire desktop. 邏輯焦點是指具有焦點的焦點範圍內的物件。Logical focus refers to the object within a focus scope that has focus. 如需有關焦點、 鍵盤焦點和邏輯焦點的詳細資訊,請參閱輸入概觀焦點概觀For more information on focus, keyboard focus, and logical focus, see Input Overview and Focus Overview.

如果PreviewGotKeyboardFocus事件或PreviewLostKeyboardFocus處理事件、 鍵盤焦點不會變更。If the PreviewGotKeyboardFocus event or the PreviewLostKeyboardFocus event is handled, keyboard focus does not change.

路由事件資訊Routed Event Information

識別項欄位Identifier field LostKeyboardFocusEvent
路由策略Routing strategy 事件反昇Bubbling
Delegate - 委派Delegate KeyboardFocusChangedEventHandler

適用於