3

我在 wpf 树视图上使用上下文菜单,我几乎在那里我想要什么。在解释问题之前,让我解释一下上下文菜单的 XAML 定义在做什么。

对于上下文菜单中的每个菜单项,我们都有一个基于命令 CanExecute 方法禁用或启用菜单项的命令。每个命令都会根据 CanExecute 的结果设置相应菜单项的 IsEnabled 属性。

每个菜单项的 IsEnabled 都绑定到 BooleanToVisibilityConverter,它将 IsEnabled 布尔值转换为 Collapse 或 Visible 值以绑定菜单项的 Visibility 属性。这再次正常工作,我的菜单项显示和隐藏都很好。

现在解决问题。在下面的 XAML 中,我们在分隔符上方有两个菜单项(addCategoryMenuItem 和 removeCategoryMenuItem)。我正在尝试通过 IMultiValueConverter (MultiBooleanToVisibilityConverter) 的自定义实现对这两个菜单项的 IsEnabled 属性进行 MultiBinding,以便当禁用这两个菜单项时,我可以将 Separator 的 Visibility 属性设置为折叠,从而在菜单项被禁用。

对于我的 Converter(MultiBooleanToVisibilityConverter) 中的 Convert 方法,参数值(对象 [] 值)我在数组中获得了两个包含值“{DependencyProperty.UnsetValue}”的项目。这些不能转换为布尔值,因此无法计算出我的 Visibility 值。

可能与 MultiBinding 中使用的 ElementName 有关。它找不到元素吗?我曾尝试使用RelativeSource,即查找祖先等。但我只是感到困惑。我已经花了几个小时在这上面,所以现在我把它留给了社区。

亲切的问候

穆罕默德

<ContextMenu x:Key="CategoryMenu">
    <ContextMenu.ItemContainerStyle>
        <Style TargetType="{x:Type Control}">
            <Setter Property="Visibility" Value="{Binding Path=IsEnabled, RelativeSource={RelativeSource Self}, Mode=OneWay, Converter={StaticResource booleanToVisibilityConverter}}" />
        </Style>
    </ContextMenu.ItemContainerStyle>
    <ContextMenu.Items>
        <MenuItem x:Name="addCategoryMenuItem" Header="add category" Command="{Binding AddCategory}">
            <MenuItem.Icon>
                <Image Source="/Images/add.png" Width="16" Height="16" />
            </MenuItem.Icon>
        </MenuItem>
        <MenuItem x:Name="removeCategoryMenuItem" Header="remove category" Command="{Binding RemoveCategory}">
            <MenuItem.Icon>
                <Image Source="/Images/remove.png" Width="16" Height="16" />
            </MenuItem.Icon>
        </MenuItem>
        <Separator>
            <Separator.Visibility>
                <MultiBinding Converter="{StaticResource multiBooleanToVisibilityConverter}">
                    <Binding Mode="OneWay" ElementName="addCategoryMenuItem" Path="IsEnabled" />
                    <Binding Mode="OneWay" ElementName="removeCategoryMenuItem" Path="IsEnabled" />
                </MultiBinding>
            </Separator.Visibility>
        </Separator>
        <MenuItem x:Name="refreshCategoryMenuItem" Header="refresh" Command="{Binding RefreshCategory}">
            <MenuItem.Icon>
                <Image Source="/Images/refresh.png" Width="16" Height="16" />
            </MenuItem.Icon>
        </MenuItem>
    </ContextMenu.Items>
</ContextMenu>
4

2 回答 2

2

好的,经过一段时间的休息,我已经设法解决了。我必须使用 RelativeSource 和 FindAncestor 来获取上下文菜单对象,然后访问项目集合,然后使用索引器值来获取菜单项。我认为如果我可以使用菜单项名称会更好,因为我不喜欢我的代码或 xaml 中的幻数。

<Separator>
    <Separator.Visibility>
        <MultiBinding Converter="{StaticResource multiBooleanToVisibilityConverter}">
            <Binding Mode="OneWay" RelativeSource="{RelativeSource FindAncestor, AncestorType={x:Type ContextMenu}}" Path="Items[0].IsEnabled" />
            <Binding Mode="OneWay" RelativeSource="{RelativeSource FindAncestor, AncestorType={x:Type ContextMenu}}" Path="Items[1].IsEnabled" />
        </MultiBinding>
    </Separator.Visibility>
</Separator>
于 2011-02-19T09:22:40.430 回答
2

我扩展了普通分隔符以创建一个自动确定它是否应该根据父 ItemsControl 中的其他项目显示的分隔符。

public class AutoVisibilitySeparator : Separator
{
    public AutoVisibilitySeparator()
    {
        if (DesignerProperties.GetIsInDesignMode(this))
            return;

        Visibility = Visibility.Collapsed; // Starting collapsed so we don't see them disappearing

        Loaded += OnLoaded;
    }

    private void OnLoaded(object sender, RoutedEventArgs e)
    {
        // We have to wait for all siblings to update their visibility before we update ours.
        // This is the best way I've found yet. I tried waiting for the context menu opening or visibility changed, on render and lots of other events
        Dispatcher.BeginInvoke(new Action(UpdateVisibility), DispatcherPriority.Render);
    }

    private void UpdateVisibility()
    {
        var showSeparator = false;

        // Go through each sibling of the parent context menu looking for a visible item before and after this separator
        var foundThis = false;
        var foundItemBeforeThis = false;
        foreach (var visibleItem in ((ItemsControl)Parent).Items.OfType<UIElement>().Where(i => i.Visibility == Visibility.Visible || i == this))
        {
            if (visibleItem == this)
            {
                // If there were no visible items prior to this separator then we hide it
                if (!foundItemBeforeThis)
                    break;

                foundThis = true;
            }
            else if (visibleItem is AutoVisibilitySeparator || visibleItem is Separator)
            {
                // If we already found this separator and this next item is not a visible item we hide this separator
                if (foundThis)
                    break;

                foundItemBeforeThis = false; // The current item is a separator so we reset the search for an item
            }
            else
            {
                if (foundThis)
                {
                    // We found a visible item after finding this separator so we're done and should show this
                    showSeparator = true;
                    break;
                }

                foundItemBeforeThis = true;
            }
        }

        Visibility = showSeparator ? Visibility.Visible : Visibility.Collapsed;
    }
}
于 2016-12-15T18:18:13.050 回答