Question

我有一个TabControl，其中许多TabItems绑定到ViewModel，该ViewModel具有每个TabItem可见性的属性。

<sdk:TabControl>
    <sdk:TabItem Name="Inventory" Header="Inventory" 
        Style="{StaticResource TabItemStyle}"
        Visibility="{Binding Permissions.Inventory,
        Converter={StaticResource PermissiveVisibilityConverter}, 
            ConverterParameter='Viewer'}"
        DataContext="{Binding VM}" />

</sdk:TabControl>

所有TabItem都默认为折叠的可见性。但是当VM将TabItem更改为Visible时，只有将鼠标移到控件上才会生效...

即使我使用按钮以编程方式设置可见性，它的行为也一样！

我已经检查过虚拟机的属性是否通知用户界面，而且他们使用的是NotifyOnPropertyChanged。如果我将数据绑定到按钮的可见性，它就可以正常工作......只是TabItems似乎有一个bug。

有没有办法让TabItem UI刷新？或者为此解决这个问题？

谢谢！

Answer 1

我遇到了同样的问题，我能够使用附加的＆＃34; Visibility＆＃34;来克服它。财产而不是原来的财产。在这个新属性中，我可以将值传递给原始的＆＃34; Visibility＆＃34;属性和，如果父标签控件＆＃34; SelectedItem＆＃34;正在折叠选择下一个可见的tabItem。

但是，正如所提到的here，只有当TabControl加载时第一个项目被折叠时，这可能还不够。这个案例必须在TabControl本身修复，因为测试显示假的＆＃34; Visility＆＃34; TabItem第一次无法访问它的TabControl。因此我还使用了TabControl的附加属性来纠正这个问题。

完整的解决方案：

public static class TabControlExtensions
{
    /// <summary>
    /// Use this property on a TabControl to correct the behavior
    /// of selecting Collapsed TabItems.
    /// </summary>
    /// <param name="obj"></param>
    /// <returns></returns>
    public static bool GetSelectOnlyVisibleTabs(DependencyObject obj)
    {
        return (bool)obj.GetValue(SelectOnlyVisibleTabsProperty);
    }
    public static void SetSelectOnlyVisibleTabs(DependencyObject obj, bool value)
    {
        obj.SetValue(SelectOnlyVisibleTabsProperty, value);
    }
    public static readonly DependencyProperty SelectOnlyVisibleTabsProperty =
        DependencyProperty.RegisterAttached("SelectOnlyVisibleTabs", typeof(bool), typeof(TabControlExtensions), new PropertyMetadata(false, SelectOnlyVisibleTabsChanged));
    public static void SelectOnlyVisibleTabsChanged(object sender, DependencyPropertyChangedEventArgs args)
    {
        var tabControl = sender as TabControl;
        if (tabControl == null) return;

        if ((bool)args.NewValue)
        {
            tabControl.SelectionChanged += TabControl_SelectionChanged;
            CorrectSelection(tabControl);
        }
        else
        {
            tabControl.SelectionChanged -= TabControl_SelectionChanged;
        }
    }

    private static void TabControl_SelectionChanged(object sender, SelectionChangedEventArgs args)
    {
        var tabControl = sender as TabControl;
        if (tabControl == null) return;

        CorrectSelection(tabControl);
    }

    public static void CorrectSelection(TabControl tabControl)
    {
        var selected = tabControl.SelectedItem as UIElement;
        if (selected == null) return;

        // If the selected element is not suposed to be visible,
        // selects the next visible element
        if (selected.Visibility == System.Windows.Visibility.Collapsed)
            tabControl.SelectedItem = tabControl.Items.OfType<UIElement>()
                .Where(e => e.Visibility == System.Windows.Visibility.Visible)
                .FirstOrDefault();
    }
}

public static class TabItemExtensions
{
    /// <summary>
    /// Use this property in a TabItem instead of the original "Visibility" to 
    /// correct the behavior of a TabControl when a TabItem's Visibility changes.
    /// </summary>
    /// <param name="obj"></param>
    /// <returns></returns>
    public static Visibility GetVisibility(DependencyObject obj)
    {
        return (Visibility)obj.GetValue(VisibilityProperty);
    }
    public static void SetVisibility(DependencyObject obj, Visibility value)
    {
        obj.SetValue(VisibilityProperty, value);
    }
    public static readonly DependencyProperty VisibilityProperty =
        DependencyProperty.RegisterAttached("Visibility", typeof(Visibility), typeof(TabItemExtensions), new PropertyMetadata(Visibility.Visible, VisibilityChanged));

    public static void VisibilityChanged(object sender, DependencyPropertyChangedEventArgs args)
    {
        var tabItem = sender as TabItem;
        if (tabItem == null) return;

        var visibility = (Visibility)args.NewValue;
        if (tabItem.Visibility == visibility) return;

        tabItem.Visibility = visibility;
        if (visibility == Visibility.Visible) return;

        // Finds the tab's parent tabcontrol and corrects the selected item, 
        // if necessary.
        var tabControl = tabItem.Ancestors().OfType<TabControl>().FirstOrDefault();
        if (tabControl == null) return;

        TabControlExtensions.CorrectSelection(tabControl);
    }
}

用法：

<sdk:TabControl local:TabControlExtensions.SelectOnlyVisibleTabs="True">
        <sdk:TabItem Header="tabItem1" Visibility="Collapsed">
            <TextBlock HorizontalAlignment="Center"
                       VerticalAlignment="Center"
                       Text="TabItem1 which should not be visible (1)" />
        </sdk:TabItem>
        <sdk:TabItem Header="tabItem2">
            <TextBlock HorizontalAlignment="Center"
                       VerticalAlignment="Center"
                       Text="TabItem2 which should be visible (2)" />
        </sdk:TabItem>
        <sdk:TabItem DataContext="{Binding ViewModel}"
                     Header="tabItem3"
                     local:TabItemExtensions.Visibility="{Binding MyProperty,
                                                                 Converter={StaticResource BoolToVisibilityConverter}}">
            <TextBlock HorizontalAlignment="Center"
                       VerticalAlignment="Center"
                       Text="TabItem with binded Visibility (3)" />
        </sdk:TabItem>
    </sdk:TabControl>

Answer 2

如果您更改xaml以便首先设置DataContext，那该怎么办：

 <sdk:TabItem Name="Inventory" Header="Inventory" 
    Style="{StaticResource TabItemStyle}"
    DataContext="{Binding VM}"
    Visibility="{Binding Permissions.Inventory,
    Converter={StaticResource PermissiveVisibilityConverter}, 
        ConverterParameter='Viewer'}" />

我假设Permissions.Inventory是您的视图模型上的属性，但由于您尚未在此处设置上下文，因此绑定似乎不起作用。

另外，如果你设置一个断点并且是否调用了Permissions.Inventory上的getter，你的转换器是否被命中？

Silverlight TabItem可见性不变

2 个答案: