如何将ApplicationCommands绑定到ViewModel？

Question

我已经使用MVVM-Light成功使用了一些自定义命令,但我希望我的应用程序能够响应标准的ApplicationCommands,而不仅仅是在Window级别,而是在详细的项目级别.

我有一个TreeView我希望能够复制和粘贴节点.每个TreeViewItem都有自己的ViewModel,它们通过HierarchicalDataTemplatesXAML 显示,因为有几种不同的类型.我已经在我的ViewModel类上实现了复制,粘贴以及CanCopy和CanPaste的方法.如果合适的话,我可以很容易地实现指向这些的MVVM-Light RelayCommands,但这似乎不对.

我想使用菜单,Ctrl + C和Ctrl + V或最终的上下文菜单来访问命令.我也不想破坏我的UI中其他元素的复制/粘贴功能,例如TextBoxes.为此目的使用内置的ApplicationCommands似乎是合适的.但是,我只看到在UserControl代码隐藏中处理这些示例.我没有(或需要)UserControl,也不是真正关注MVVM.

有没有办法可以绑定ApplicationCommand.Copy和ApplicationCommand.Paste命令我的ViewModel,即在数据模板中？

Answer 1

我已使用附加到TreeView的行为解决了这个问题.TreeViewItems或模板似乎没有得到路由到它们的命令.幸运的是,TreeView还有一个SelectedItem属性,可用于获取ViewModel!

(行为在概念上与@ Natxo的答案中的链接解决方案类似,但它并不能解决所有问题.)

行为类:

public class TreeViewClipboardBehavior : Behavior<TreeView>
{
    protected override void OnAttached()
    {
        base.OnAttached();

        CommandBinding CopyCommandBinding = new CommandBinding(
            ApplicationCommands.Copy,
            CopyCommandExecuted,
            CopyCommandCanExecute);
        AssociatedObject.CommandBindings.Add(CopyCommandBinding);

        CommandBinding CutCommandBinding = new CommandBinding(
            ApplicationCommands.Cut,
            CutCommandExecuted,
            CutCommandCanExecute);
        AssociatedObject.CommandBindings.Add(CutCommandBinding);

        CommandBinding PasteCommandBinding = new CommandBinding(
            ApplicationCommands.Paste,
            PasteCommandExecuted,
            PasteCommandCanExecute);
        AssociatedObject.CommandBindings.Add(PasteCommandBinding);
    }

    private void CopyCommandExecuted(object target, ExecutedRoutedEventArgs e)
    {
        NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
        if (item != null && item.CanCopyToClipboard)
        {
            item.CopyToClipboard();
            e.Handled = true;
        }
    }

    private void CopyCommandCanExecute(object target, CanExecuteRoutedEventArgs e)
    {
        NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
        if (item != null)
        {
            e.CanExecute = item.CanCopyToClipboard;
            e.Handled = true;
        }
    }

    private void CutCommandExecuted(object target, ExecutedRoutedEventArgs e)
    {
        NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
        if (item != null && item.CanCutToClipboard)
        {
            item.CutToClipboard();
            e.Handled = true;
        }
    }

    private void CutCommandCanExecute(object target, CanExecuteRoutedEventArgs e)
    {
        NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
        if (item != null)
        {
            e.CanExecute = item.CanCutToClipboard;
            e.Handled = true;
        }
    }


    private void PasteCommandExecuted(object target, ExecutedRoutedEventArgs e)
    {
        NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
        if (item != null && item.CanPasteFromClipboard)
        {
            item.PasteFromClipboard();
            e.Handled = true;
        }
    }

    private void PasteCommandCanExecute(object target, CanExecuteRoutedEventArgs e)
    {
        NestingItemTreeViewModelBase item = AssociatedObject.SelectedItem as NestingItemTreeViewModelBase;
        if (item != null)
        {
            e.CanExecute = item.CanPasteFromClipboard;
            e.Handled = true;
        }
    }
}

XAML

<TreeView Grid.Row="2" ItemsSource="{Binding SystemTreeRoot}">
    <i:Interaction.Behaviors>
        <local:TreeViewClipboardBehavior/>
    </i:Interaction.Behaviors>
    <TreeView.Resources>
        <HierarchicalDataTemplate DataType="{x:Type local:MyViewModel}" ItemsSource="{Binding Children}">
            <!-- Template content -->
        </HierarchicalDataTemplate>
</TreeView>