WPF TabIndex 无法正常工作

WPF TabIndex doesn't work correctly

我在正确设置 TabIndexes 时遇到问题。我有一个 Usercontrol 和一个 GroupBox.

<GroupBox KeyboardNavigation.TabNavigation="Local" TabIndex="0">
        <Grid KeyboardNavigation.TabNavigation="Continue">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*" />
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="Auto" />
            </Grid.RowDefinitions>
            <StackPanel Orientation="Horizontal" Grid.Row="0" KeyboardNavigation.TabNavigation="Continue">
                <my:uscZeitraum TabIndex="1" />
                <Label />
                <ComboBox TabIndex="2" />
                <Label />
                <ComboBox TabIndex="3" HorizontalAlignment="Right" VerticalAlignment="Top" Width="88" />
                <Label />
                <ComboBox TabIndex="4" HorizontalAlignment="Right" VerticalAlignment="Top" Width="67" />
                <Label />
                <ComboBox TabIndex="5" IsEditable="True" GotFocus="cboVorgang_GotFocus" HorizontalAlignment="Right" VerticalAlignment="Top" Width="93" />
            </StackPanel>
            <StackPanel Orientation="Horizontal" Grid.Row="1" KeyboardNavigation.TabNavigation="Continue">
                <Label />
                <ComboBox TabIndex="6" HorizontalAlignment="Left" Width="192" Height="23" VerticalAlignment="Bottom" />
                <Label />
                <ComboBox TabIndex="7" Height="23" VerticalAlignment="Bottom" HorizontalAlignment="Left" Width="225" />
                <Label />
                <ComboBox IsEditable="True" TabIndex="8" HorizontalAlignment="Right" VerticalAlignment="Bottom" Width="67" />
                <Label />
                <ComboBox IsEditable="True" TabIndex="9" Width="80" />                                 
            </StackPanel>
        </Grid>
    </GroupBox>

第一个 Control 也是一个 UserControl 但这就像我想要的那样。但是,如果我在第一个 StackPanel 中到达第三个 ComboBox,它就会再次从头开始。它不会关注第四个 ComboBox,也不会跳转到第二个 Row/Stackpanel。那会是什么?

cboVorgang_GotFocus 中一定有一些代码正在执行此操作。那里编写的代码会更改 Tab 键顺序。