WPF TreeView在ControlTemplate中 - 处理项目扩展

Question

我正在创建一个自定义控件，在控制模板中，我中有一个TreeView类。

<Style TargetType="{x:Type local:MyControl}">

<Setter Property="Template">

    <Setter.Value>

        <ControlTemplate TargetType="{x:Type local:MyControl}">

            <Border>

                <TreeView ItemsSource="{Binding TreeDataItems, RelativeSource={RelativeSource TemplatedParent}}">

                    <i:Interaction.Triggers>
                        <i:EventTrigger EventName="TreeViewItem.Expanded">
                            <i:InvokeCommandAction Command="{Binding TreeItemExpandedCommand, RelativeSource={RelativeSource TemplatedParent}}"
                                                CommandParameter="{Binding}">

                            </i:InvokeCommandAction>
                        </i:EventTrigger>
                    </i:Interaction.Triggers>

                </TreeView>
            </Border>

        </ControlTemplate>

    </Setter.Value>

</Setter>

在自定义控件的代码文件中，我有此命令：

private ICommand _TreeItemExpandedCommand;

public icommand treeTempandedCommand { 得到 { if（_treeItemExpandedCommand == null） _treeItemExpandEdCommand = new RelayCommand（p =＆gt; treeItemExpandExeceCected（p））; 返回_treeItemExpandedCommand; } }

私有void treeTemExpandEdexecected（对象args） { }

我还尝试了

<TreeView TreeViewItem.Expanded="TreeViewItem_Expanded">
...

＆lt;/treeview/＆gt;

但是都没有被解雇。

如何在自定义控件的代码文件中处理TreeView的扩展事件？

谢谢

Answer 1

我不是Pro WPF程序员，但我设法找出解决方案的问题。代码的问题在于，该事件并不完全属于TreeView本身，而是其中的元素（项目属性）。

因此，这种工作无法做到：

...
<i:EventTrigger EventName="TreeViewItem.Expanded">
...

另一方面，这将有效：

...
<i:EventTrigger EventName="SelectedItemChanged">
...

因为此事件基本上属于Treeview

，所以您需要做的是订阅TreeView中所有TreeViewItems的扩展事件。您可以从后面的代码中执行此操作。

这是我的做法：

public class MyCustomControl : Control
{
    public TreeView MyTreeView { get; set; }

    public static readonly DependencyProperty TreeViewItemListProperty = DependencyProperty.Register("TreeViewItemList", 
                                                                                              typeof(List<StorageItem>), 
                                                                                              typeof(MyCustomControl), 
                                                                                              new UIPropertyMetadata(null));

    public List<StorageItem> TreeViewItemList
    {
        get { return (List<StorageItem>)GetValue(TreeViewItemListProperty); }
        set { SetValue(TreeViewItemListProperty, value);}
    }

    public static readonly RoutedEvent MyEventRoutedEvent = EventManager.RegisterRoutedEvent("MyEvent", 
                                                                                              RoutingStrategy.Bubble, 
                                                                                              typeof(EventHandler<RoutedEventArgs>), 
                                                                                              typeof(MyCustomControl));
    public event RoutedEventHandler MyEvent
    {
        add { this.AddHandler(MyEventRoutedEvent, value); }
        remove { this.RemoveHandler(MyEventRoutedEvent, value); }
    }


    public override void OnApplyTemplate()
    {
        MyTreeView = Template.FindName("MyTreeView", this) as TreeView;
        MyTreeView.Items.CurrentChanged += Items_CurrentChanged;
        base.OnApplyTemplate();
    }

    private void Items_CurrentChanged(object sender, EventArgs e)
    {
        SubscribeAllTreeViewItems(MyTreeView);
    }

    private void SubscribeAllTreeViewItems(ItemsControl treeViewItem)
    {
        foreach (object item in treeViewItem.Items)
        {
            TreeViewItem treeItem = treeViewItem.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;
            if (treeItem != null)
            {
                SubscribeAllTreeViewItems(treeItem);
                treeItem.Expanded += TreeViewItem_Expanded;
            }
        }
    }

    private void TreeViewItem_Expanded(object sender, RoutedEventArgs e)
    {
        RoutedEventArgs args = new RoutedEventArgs(MyEventRoutedEvent, this);
        this.RaiseEvent(args);
    }

    static MyCustomControl()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(MyCustomControl), new FrameworkPropertyMetadata(typeof(MyCustomControl)));
    }
}

首先，我们需要获取树景的控制并在事件中订阅项目：

    public override void OnApplyTemplate()
    {
        MyTreeView = Template.FindName("MyTreeView", this) as TreeView;
        MyTreeView.Items.CurrentChanged += Items_CurrentChanged;
        base.OnApplyTemplate();
    }

然后，如果要发射此事，我们知道我们的TreeView中有项目，因此我们可以循环浏览其元素并订阅为了扩展活动：

private void Items_CurrentChanged(object sender, EventArgs e)
    {
        SubscribeAllTreeViewItems(MyTreeView);
    }

    private void SubscribeAllTreeViewItems(ItemsControl treeViewItem)
    {
        foreach (object item in treeViewItem.Items)
        {
            TreeViewItem treeItem = treeViewItem.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;
            if (treeItem != null)
            {
                SubscribeAllTreeViewItems(treeItem);
                treeItem.Expanded += TreeViewItem_Expanded;
            }
        }
    }

之后，我们很高兴！我还添加了代码，以便能够从自定义控件外部订阅此事件：

    public static readonly RoutedEvent MyEventRoutedEvent = EventManager.RegisterRoutedEvent("MyEvent", 
                                                                                              RoutingStrategy.Bubble, 
                                                                                              typeof(EventHandler<RoutedEventArgs>), 
                                                                                              typeof(MyCustomControl));
    public event RoutedEventHandler MyEvent
    {
        add { this.AddHandler(MyEventRoutedEvent, value); }
        remove { this.RemoveHandler(MyEventRoutedEvent, value); }
    }
    ....
    ....
    private void TreeViewItem_Expanded(object sender, RoutedEventArgs e)
    {
        RoutedEventArgs args = new RoutedEventArgs(MyEventRoutedEvent, this);
        this.RaiseEvent(args);
    }

因此，这样，您可以从外部订阅它：

  <local:MyCustomControl TreeViewItemList="{Binding Path=Items}"
                         MyEvent="MyCustomControl_MyEvent"/>

最后，这是.xaml

<Style TargetType="{x:Type local:MyCustomControl}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type local:MyCustomControl}">
                <TreeView ItemsSource="{TemplateBinding TreeViewItemList}"
                              x:Name="MyTreeView">
                    <TreeView.Resources>
                        <!--Here we specify how to display a FolderItem-->
                        <HierarchicalDataTemplate DataType="{x:Type localviewmodels:FolderItem}"
                                                  ItemsSource="{Binding Path=Items}">
                            <TextBlock Text="{Binding Path=Name}"
                                       Margin="0 0 35 0"/>
                        </HierarchicalDataTemplate>

                        <!--Here we specify how to display a FileItem-->
                        <DataTemplate DataType="{x:Type localviewmodels:FileItem}">

                            <TextBlock Text="{Binding Path=Name}"
                                           Margin="0 0 35 0"/>
                        </DataTemplate>
                    </TreeView.Resources>
                </TreeView>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

Update

如果您想要在自定义控件中设置树视图项目，您应该
订阅MyTreeView.loaded事件，以捕获其获得值时的第一次。

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