MVVM菜单中的绑定头模板
本文关键字:绑定 菜单 MVVM | 更新日期: 2023-09-27 18:00:54
我有一个MVVM风格的菜单,它使用2个视图模型和一个样式:
ViewModel:
public class CommandViewModel : ViewModelBase
{
private bool _isOpen;
private IEnumerable<object> _items;
private UIElement _placementTarget;
/// <summary>
/// the command itself
/// </summary>
public ICommand Command { get; set; }
/// <summary>
/// parameter object for the command
/// </summary>
public Object CommandParameter { get; set; }
/// <summary>
/// header string for the command, e.g. in menus
/// </summary>
public string Header { get; set; }
/// <summary>
/// oprional Tooltip for the command, e.g. on buttons
/// </summary>
public string Tooltip { get; set; }
/// <summary>
/// optional icon for the command, e.g. on buttons or in menus
/// </summary>
public ControlTemplate Icon { get; set; }
/// <summary>
/// optional item list. e.g. submenu entries.
/// For a submenu set the command to null and fill the Items list with CommandViewModels or other ViewModels you have a template for
/// </summary>
public IEnumerable<Object> Items
{
get { return _items; }
set
{
_items = value;
Command = new RelayCommand<UIElement>((param) =>
{
PlacementTarget = param;
IsOpen = true;
});
}
}
public bool IsOpen
{
get
{
return _isOpen;
}
set
{
_isOpen = value;
RaisePropertyChanged(() => IsOpen);
}
}
public virtual bool IsSeparator { get { return false; } }
public UIElement PlacementTarget
{
get { return _placementTarget; }
set
{
_placementTarget = value;
RaisePropertyChanged(() => PlacementTarget);
}
}
}
分离器:
public class SeparatorViewModel : CommandViewModel
{
public override bool IsSeparator
{
get { return true; }
}
}
样式:
<Style TargetType="MenuItem" BasedOn="{StaticResource {x:Type MenuItem}}" x:Key="MvvmMenuItemStyle">
<Setter Property="Header" Value="{Binding Header}"/>
<Setter Property="ItemsSource" Value="{Binding Items}"/>
<Setter Property="Command" Value="{Binding Command}"/>
<Setter Property="CommandParameter" Value="{Binding CommandParameter}"/>
<Setter Property="ToolTip" Value="{Binding Tooltip}"/>
<Style.Triggers>
<DataTrigger Binding="{Binding IsSeparator}" Value="true">
<DataTrigger.Setters>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<Rectangle Height="1" Fill="{StaticResource WindowButtonsBackground}" Margin="3,5"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</DataTrigger.Setters>
</DataTrigger>
</Style.Triggers>
</Style>
用法:
<MenuItem Header="Device" ItemsSource="{Binding DevicesMenu}" Visibility="{Binding IsDevicesMenuVisible, Converter={StaticResource BoolToVisConverter}}">
<MenuItem.Resources>
<Style TargetType="MenuItem" BasedOn="{StaticResource MvvmMenuItemStyle}"/>
</MenuItem.Resources>
</MenuItem>
我将(顶部(菜单项的项绑定到CommandViewModels列表,该列表可以有子项、Header、Command、CommandParameter等。。。当我将IsOpen Prop与ContextMenus一起使用时,它是适用的,但这里的情况并非如此。
到目前为止,这一切都很顺利。
现在我想在每个条目中添加和Icon。我想我可以在我的样式中添加一个HeaderTemplate,它显示图标和Header文本,但它不起作用,什么都不显示。
这是我添加到样式中的HeaderTemplate设置器:
<Setter Property="HeaderTemplate">
<Setter.Value>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<ContentControl Template="{Binding Icon}" Width="26"/>
<TextBlock Text="{Binding Header}" />
</StackPanel>
</DataTemplate>
</Setter.Value>
</Setter>
注意:我的图标是ControlTemlates,它在XAML中包含矢量图形,所以我不能使用MenuItem的"Icon"-属性。一旦我将HeaderTemplate添加到样式中,菜单条目就不会显示文本和图标。我知道应用了HeaderTemplate,因为如果我增加图标ContentControl的宽度(例如从26增加到260(,我的菜单就会变宽。这意味着我在HeaderTemplate中的绑定有问题。
有人看到问题了吗?
图标和标头的绑定不在可视化树中,在可视化树上可以轻松访问数据上下文(所需的通过VM继承数据上下文的绑定(和其他项。绑定将需要是一个相对源路径。
以下是用于访问具有VM:的主数据上下文的路径的近似值
Text="{Binding Header,
RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type Page}}}"/>