隐藏空上下文菜单

Question

我在wp7中有一个上下文菜单

<toolkit:ContextMenuService.ContextMenu>
    <toolkit:ContextMenu x:Name="onHoldContextMenu">
        <toolkit:MenuItem Header="Delete" Tag="{Binding}" Click="DeleteVisitorNote_Click" Visibility="{Binding DeleteContextVisibility, Converter={StaticResource BooleanToVisibilityConverter}}"/>
        <toolkit:MenuItem Header="View" Tag="{Binding}" Visibility="{Binding ViewContextVisibility, Converter={StaticResource BooleanToVisibilityConverter}}" Click="ViewVisitorContact_Click"/>
    </toolkit:ContextMenu>
</toolkit:ContextMenuService.ContextMenu>

我正在改变视图模型中两个项目的可见性,它工作正常.我的问题是,当我将两个项目的可见性设置为false时,当我打开上下文菜单时,我有一个空的白线,我不知道如何隐藏...我试过:

<toolkit:ContextMenuService.ContextMenu>
    <toolkit:ContextMenu x:Name="onHoldContextMenu"  Visibility="{Binding ContextVisibility, Converter={StaticResource BooleanToVisibilityConverter}}">
        <toolkit:MenuItem Header="Delete" Tag="{Binding}" Click="DeleteVisitorNote_Click" Visibility="{Binding DeleteContextVisibility, Converter={StaticResource BooleanToVisibilityConverter}}"/>
        <toolkit:MenuItem Header="View" Tag="{Binding}" Visibility="{Binding ViewContextVisibility, Converter={StaticResource BooleanToVisibilityConverter}}" Click="ViewVisitorContact_Click"/>
    </toolkit:ContextMenu>
</toolkit:ContextMenuService.ContextMenu>

但在这种情况下,我得到一个nullrefference异常...

如何在空白时隐藏上下文菜单？

Answer 1

我在另一个论坛上找到了这个解决方案.

        <ListBox.ItemTemplate> 
                <DataTemplate> 
                    <Grid Hold="Grid_Hold"> 
                        <toolkit:ContextMenuService.ContextMenu> 
                            ... context menu items ... 
                        </toolkit:ContextMenuService.ContextMenu> 

                        ... listbox item contents ... 

                    </Grid> 
                </DataTemplate> 
            </ListBox.ItemTemplate> 

    private void Grid_Hold(object sender, System.Windows.Input.GestureEventArgs e) 
    { 
        ItemViewModel listitem = (sender as FrameworkElement).DataContext as ItemViewModel; 
        e.Handled = listitem.DisableContextMenu(); 
    } 

设置e.Handled = true会阻止ContextMenu接收Hold事件.在视图模型中,您将实现一些返回是否显示的属性或方法ContextMenu.