WPF學習日誌 ~ 事件傳遞 ~

這篇簡單的說明一下在WPF中事件傳遞的部分，下面是測試的程式碼

Class Window1
    Dim sp As StackPanel

    Private Sub Window1_Loaded(ByVal sender As Object, ByVal e As System.Windows.RoutedEventArgs) Handles Me.Loaded
        sp = New StackPanel
        Me.Content = sp
        Dim tb As New TextBlock
        tb.Text = "I am a TextBlock"
        sp.Children.Add(tb)
        Dim btn As New Button
        btn.Content = "Button"
        sp.Children.Add(btn)
        Dim txt As New TextBox
        txt.Text = "Test words"
        sp.Children.Add(txt)
        AddHandler Me.MouseDown, AddressOf El_OnMouseDown
    End Sub

    Protected Sub El_OnMouseDown(ByVal sender As Object, ByVal e As MouseButtonEventArgs)
        If e.ChangedButton = MouseButton.Right Then
            Me.Title = "Source:" & e.Source.ToString & " OriginalSource:" & e.OriginalSource.ToString
            If CType(e.Source, FrameworkElement).Margin = New Thickness(5) Then
                CType(e.Source, FrameworkElement).Margin = New Thickness(1)
            Else
                CType(e.Source, FrameworkElement).Margin = New Thickness(5)
            End If
        End If
    End Sub
End Class

執行程式碼之後，在Button或是TextBlock的上面按下滑鼠右鍵，你會發現該元素的邊界變大了，要留意的是，我們只有在"Me"(Window)的MouseDown掛載事件喔，以往如果是Windows Form，點在Button上面，那麼Form就收不到事件了。
事件傳遞會牽涉到"邏輯樹"以及"視覺樹"，這部分等之後有機會我們再來說明，有興趣的可以先到書店翻翻書