Question

这似乎是一种非常常见的情况，但是当剪贴板中没有任何内容时，我无法弄清楚如何将菜单项绑定到禁用状态。

我决定不使用Windows剪贴板，而是将实际对象存储在名为NodeClipboard的UserControl上的引用变量中。由于它是强类型的并且实现了INotifyProperty，因此它对我来说比Windows剪贴板更有用。

绑定到单个项目可以正常工作，但它非常冗长，因为您无法在不使用样式事件设置器的情况下在资源中设置EventHandlers。

看起来像这样...

<UserControl x:Name="PART_Root">
    <TreeView x:Name="PART_Tree" ItemsSource="{Binding ElementName=PART_Root, Path=RootItemContainer}">
        <TreeView.Resources>
            <ContextMenu x:Key="ContextMenu">
                <ContextMenu.Style>
                    <Style TargetType="ContextMenu">
                        <!-- I use this event to select the tree view item otherwise it is actually pretty difficult to know what item you right clicked on -->
                        <EventSetter Event="Opened" Handler="ContextMenu_Opened"/>
                    </Style>
                </ContextMenu.Style>
                <MenuItem Header="Cut">
                    <MenuItem.Style>
                        <Style TargetType="MenuItem">
                            <EventSetter Event="Click" Handler="CutNode_Click"/>
                            <Style.Triggers>
                                <!-- This binding is fine because it binds to the item that was right clicked on -->
                                <DataTrigger Binding="{Binding Path=IsRoot}" Value="True">
                                    <Setter Property="IsEnabled" Value="False"/>
                                </DataTrigger>
                            </Style.Triggers>
                        </Style>
                    </MenuItem.Style>
                </MenuItem>
                <MenuItem Header="Paste">
                    <MenuItem.Style>
                        <Style TargetType="MenuItem">
                            <EventSetter Event="Click" Handler="PasteNode_Click"/>
                            <!-- This binding always fails because ContextMenu lives outside of the logical tree -->
                            <Style.Triggers>
                                <DataTrigger Binding="{Binding ElementName=PART_Root, Path=NodeClipboard" Value="{x:Null}">
                                    <Setter Property="IsEnabled" Value="False"/>
                                </DataTrigger>
                            </Style.Triggers>
                    </Style>
                    </MenuItem.Style>
                </MenuItem>
            </ContextMenu>
            <Style TargetType="TreeViewItem">
                <Setter Property="ContextMenu" Value="{StaticResource ContextMenu}"/>
            </Style>
            <HierarchicalDataTemplate DataType="{x:Type local:Node}" ItemsSource="{Binding Path=Children}">
                <TextBlock Text="{Binding Path=Id}"/>
            </HierarchicalDataTemplate>
        </TreeView.Resources>
    </TreeView>
</UserControl>

这里不起作用的关键部分是：

                        <!-- This binding always fails because ContextMenu lives outside of the logical tree -->
                        <Style.Triggers>
                            <DataTrigger Binding="{Binding ElementName=PART_Root, Path=NodeClipboard" Value="{x:Null}">
                                <Setter Property="IsEnabled" Value="False"/>
                            </DataTrigger>
                        </Style.Triggers>

我尝试使用相对来源导致同样的问题。到目前为止我唯一想到的解决方案是制作两个上下文菜单，一个启用了粘贴，一个没有，并在TreeViewItem样式的ContextMenu设置器上切换样式的上下文菜单，如此......

<TreeView.Resources>
    <Style TargetType="TreeViewItem">
        <Setter Property="ContextMenu" Value="{StaticResource ContextMenu_PasteEnabled}"/>
        <Style.Triggers>
            <DataTrigger Binding="{Binding ElementName=PART_Root, Path=NodeClipboard" Value="{x:Null}">
                <Setter Property="ContextMenu" Value="{StaticResource ContextMenu_PasteDisabled}"/>
            </DataTrigger>
        </Style.Triggers>
    </Style>
</TreeView.Resources>

Answer 1

使用Clipboard类。然后，您可以使用ContainsText方法来确定剪贴板上是否有任何数据。

http://msdn.microsoft.com/en-us/library/system.windows.forms.clipboard.aspx

Treeview ContextMenu绑定剪切和粘贴到逻辑树

1 个答案: