WPF 鍵盤導航附加屬性解決TreeView的Tab導航焦點問題

TreeView是預設對上下左右響應，或者是Ctrl+Tab。

如果單獨用tab則是不起作用的。

如果使用一般treeview可以利用以下方式來讓tab進行導航。

設定Treeview和TreeviewItem的KeyboardNavigation

treeview

<Setter Property="KeyboardNavigation.TabNavigation" Value="Local"/>      

treeviewitem

<Setter Property="KeyboardNavigation.TabNavigation" Value="Local"       />      

其次是對treeviewitem模闆内部的border設定Focusable

<Border x:Name="Bd" Focusable="True"  BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.Column="1" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
                                

      <ContentPresenter x:Name="PART_Header" ContentSource="Header" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>

 </Border>      

如果還是進不去TreeViewItem的内部，還可以使用一下附加屬性

public static readonly DependencyProperty TabProperty = DependencyProperty.RegisterAttached("Tab", typeof(bool), typeof(TabTest), new PropertyMetadata(new PropertyChangedCallback(OnValueChanged)));
        public static bool GetTab(DependencyObject d) => (bool)d.GetValue(TabProperty);
        public static void SetTab(DependencyObject d, bool value) => d.SetValue(TabProperty, value);

        private static void OnValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if (d != null && ((bool)e.NewValue))
            {
                (d as UIElement).Focusable = true;
                (d as UIElement).PreviewKeyDown += TabTest_PreviewKeyDown; 
            }
        }

        private static void TabTest_PreviewKeyDown(object sender, KeyEventArgs e)
                   {
            var Element = Keyboard.FocusedElement as UIElement;
            if (e.Key == Key.Tab)
            {
                e.Handled = true;
                 
                if (!Element.MoveFocus(new TraversalRequest(FocusNavigationDirection.Down)))
                {
                    Element.MoveFocus(new TraversalRequest(FocusNavigationDirection.Next));
                }
              

            }
        }      

在TreeViewItem的内部使用即可

<ItemsPresenter x:Name="ItemsHost"  local:TabTest.Tab="True"    Grid.ColumnSpan="2" Grid.Column="1" Grid.Row="1"  />      

簡單版本

<Style TargetType="TreeView">
            <Setter Property="KeyboardNavigation.TabNavigation" Value="Local"/>
        </Style>
        <Style TargetType="TreeViewItem">
            <Setter Property="KeyboardNavigation.TabNavigation" Value="Local"/>
        </Style>