Wpf 如何设置以TreeView样式定义的ContextMenu的DataContext
我有一个树状视图,它在一个样式中定义了它的上下文菜单。菜单项有绑定到它们的命令,但绑定这些命令时遇到问题。我意识到这是因为可视化树中不存在ContextMenu,所以我尝试使用了PlacementTarget对象和标记属性,我在其他示例中看到了该属性,但它仍然不起作用。知道我做错了什么吗Wpf 如何设置以TreeView样式定义的ContextMenu的DataContext,wpf,mvvm,treeview,contextmenu,menuitem,Wpf,Mvvm,Treeview,Contextmenu,Menuitem,我有一个树状视图,它在一个样式中定义了它的上下文菜单。菜单项有绑定到它们的命令,但绑定这些命令时遇到问题。我意识到这是因为可视化树中不存在ContextMenu,所以我尝试使用了PlacementTarget对象和标记属性,我在其他示例中看到了该属性,但它仍然不起作用。知道我做错了什么吗 <Grid Name="MyGrid" DataContext="{Binding}"> <TreeView Name="TreeView" ItemsSource="
<Grid Name="MyGrid" DataContext="{Binding}">
<TreeView Name="TreeView"
ItemsSource="{Binding TreeViewElements}"
Tag="{Binding DataContext, ElementName=MyGrid}">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="ContextMenu">
<Setter.Value>
<ContextMenu DataContext="{Binding PlacementTarget.Tag, RelativeSource={x:Static RelativeSource.Self}}">
<MenuItem Header="Do Something"
Command="{Binding DoSomethingCommand}"/>
</ContextMenu>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding SubElements}">
<StackPanel Orientation="Horizontal">
<TextBlock Margin="2" Text="{Binding HeaderText}" ></TextBlock>
</StackPanel>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
</Grid>
更新
下面的答案是完全正确的,但经过思考后,我意识到我对这个问题的看法是错误的。我看了一眼,他解释说,使用ViewModel模式意味着使用TreeView来显示数据,而不是放置数据。因此,我能够将树状视图中的每个项目作为自己的视图模型来处理。这意味着我可以对特定的ViewModel执行上下文菜单中的任何命令(如果需要,可以在新ViewModel上使用父属性导航到父视图模型)。上下文菜单确实具有DataContext。您不需要显式设置它 在您的情况下,ContextMenu中的DataContext与TreeView中的DataContext相同。这意味着它不是ViewModel,而是项本身 假设您有一个Person类型的对象列表。然后命令应该放在人的内部
public class Person : INotifyPropertyChanged
{
private string name;
public string Name
{
get { return name; }
set { name = value; this.OnPropertyChanged("Name"); }
}
public ICommand DoSomethingCommand
{
get
{
return new RelayCommand(x => MessageBox.Show("Works!"));
}
}
...
然后XAML应该是这样的:
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="ContextMenu">
<Setter.Value>
<ContextMenu>
<MenuItem Header="Do Something"
Command="{Binding DoSomethingCommand}"/>
</ContextMenu>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
<TreeView x:Name="treeView" ItemsSource="{Binding Employee}">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="Tag" Value="{Binding RelativeSource={RelativeSource AncestorType=TreeView}, Path=DataContext}"></Setter>
<Setter Property="ContextMenu">
<Setter.Value>
<ContextMenu DataContext="{Binding Path=PlacementTarget.Tag, RelativeSource={RelativeSource Self}}">
<MenuItem Header="Do Something"
Command="{Binding DoSomethingCommand}"/>
</ContextMenu>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
<TreeView x:Name="treeView" ItemsSource="{Binding Employee}">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="ContextMenu">
<Setter.Value>
<ContextMenu DataContext="{x:Reference treeView}">
<MenuItem Header="Do Something"
Command="{Binding DataContext.DoSomethingCommand}"/>
</ContextMenu>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
但是,如果在ViewModel中有该命令,则需要将ViewModel实例提供给ContextMenu的DataContext
以下是一个例子:
class MainWindowViewModel : INotifyPropertyChanged
{
private ObservableCollection<Person> employee;
public MainWindowViewModel()
{
this.Employee = new ObservableCollection<Person>();
this.Employee.Add(new Person { Name = "Test" });
}
public ObservableCollection<Person> Employee
{
get { return this.employee; }
set { this.employee = value; this.OnPropertyChanged("Employee"); }
}
public ICommand DoSomethingCommand
{
get
{
return new RelayCommand(x => MessageBox.Show("Works!"));
}
}
...
class MainWindowViewModel:INotifyPropertyChanged
{
私人可观察收集员工;
公共主窗口视图模型()
{
this.Employee=新的ObservableCollection();
this.Employee.Add(newperson{Name=“Test”});
}
公开收集雇员
{
获取{返回this.employee;}
设置{this.employee=value;this.OnPropertyChanged(“employee”);}
}
公共ICommand dosomething命令
{
得到
{
返回新的RelayCommand(x=>MessageBox.Show(“Works!”);
}
}
...
那么XAML将如下所示:
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="ContextMenu">
<Setter.Value>
<ContextMenu>
<MenuItem Header="Do Something"
Command="{Binding DoSomethingCommand}"/>
</ContextMenu>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
<TreeView x:Name="treeView" ItemsSource="{Binding Employee}">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="Tag" Value="{Binding RelativeSource={RelativeSource AncestorType=TreeView}, Path=DataContext}"></Setter>
<Setter Property="ContextMenu">
<Setter.Value>
<ContextMenu DataContext="{Binding Path=PlacementTarget.Tag, RelativeSource={RelativeSource Self}}">
<MenuItem Header="Do Something"
Command="{Binding DoSomethingCommand}"/>
</ContextMenu>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
<TreeView x:Name="treeView" ItemsSource="{Binding Employee}">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="ContextMenu">
<Setter.Value>
<ContextMenu DataContext="{x:Reference treeView}">
<MenuItem Header="Do Something"
Command="{Binding DataContext.DoSomethingCommand}"/>
</ContextMenu>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
或者XAML可以如下所示:
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="ContextMenu">
<Setter.Value>
<ContextMenu>
<MenuItem Header="Do Something"
Command="{Binding DoSomethingCommand}"/>
</ContextMenu>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
<TreeView x:Name="treeView" ItemsSource="{Binding Employee}">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="Tag" Value="{Binding RelativeSource={RelativeSource AncestorType=TreeView}, Path=DataContext}"></Setter>
<Setter Property="ContextMenu">
<Setter.Value>
<ContextMenu DataContext="{Binding Path=PlacementTarget.Tag, RelativeSource={RelativeSource Self}}">
<MenuItem Header="Do Something"
Command="{Binding DoSomethingCommand}"/>
</ContextMenu>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
<TreeView x:Name="treeView" ItemsSource="{Binding Employee}">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="ContextMenu">
<Setter.Value>
<ContextMenu DataContext="{x:Reference treeView}">
<MenuItem Header="Do Something"
Command="{Binding DataContext.DoSomethingCommand}"/>
</ContextMenu>
</Setter.Value>
</Setter>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
ItemContainerStyle应用于包装每个项目的ContentPresenter
,我不相信Tag
属性是由ContentPresenter
设置的。请尝试使用ItemContainerStyle
中的另一个Style
setter绑定Tag
属性根据下面的#dev hedgehog的代码。在我的后续评论中,你知道我如何仍然可以访问我右键单击的菜单项的datacontext,因为我需要它来查看菜单项吗?我不确定我是否理解这个问题。假设你已经将标记
属性绑定到当前的树项
数据上下文,你知道吗您应该可以访问DoSomethingCommand
和属性来确定可见性。抱歉,我想我没有解释清楚。该命令绑定到基础viewModel(而不是treeView)根据#devhedgehog提供的第一个XML示例。这意味着我丢失了刚才右键单击的TreeViewItem的datacontext。我需要它,以便可以在MenuItem上设置可见性。我现在明白了。您应该能够进行两个单独的绑定。也许可以将ContextMenu.datacontext
绑定到PlacementTarget.DataC将命令绑定到PlacementTarget.Tag.DoSomethingCommand
。您可能需要一个相对资源
与第二个绑定到targetContextMenu.PlacementTarget.Tag
很好,我只需将标记从移动到Setter属性中-谢谢。好的,现在我意识到了无法绑定MeNuItitem的可视性,因为我已经更改了DATACONTRONT。在这种情况下,如何获取MeNuItIt的DATACONTRONT?您必须考虑绑定中的源更改为VIEW模型或项目本身。