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Create Event Handler for TreeViewItem in WPF

开发者 https://www.devze.com 2022-12-26 23:20 出处:网络
Im adding items to TreeView control via ItemsSource property and ItemTemplate property to set the template for TreeViewItem. How can i add an event handler to handle selection change event on TreeView

Im adding items to TreeView control via ItemsSource property and ItemTemplate property to set the template for TreeViewItem. How can i add an event handler to handle selection change event on TreeViewItems?

For now my ItemTemplate looks like this:

<Window.Resources><DataTemplate x:Key="PeerDetailTemplate">
        <TextBlock Text="{Binding DESCRIPTION}" Tag="{Binding ID}" GotFocus="GetModules"/>
</DataTemplate></Window.Resources>

But it doesnt work (GetModules is not开发者_StackOverflow中文版 called). Im new to WPF, so show me the right direction to do such things, please.


If you want to capture the SelectedItemChanged event in a TreeView, then you need to set the event handler on the parent node, i.e.,

XAML

<StackPanel>
    <TreeView SelectedItemChanged="OnTreeViewSelectedItemChanged">          
        <TreeViewItem Header="Desktop">
            <TreeViewItem Header="Computer" />
            <TreeViewItem Header="My Documents" />
            <TreeViewItem Header="c:\" />
        </TreeViewItem>
        <TreeViewItem Header="Recyle Bin" >
            <TreeViewItem Header="foo.txt" />
            <TreeViewItem Header="bar.txt" />
            <TreeViewItem Header="fizz.buzz" />
        </TreeViewItem>
        <TreeViewItem Header="Control Panel" >
            <TreeViewItem Header="Programs" />
            <TreeViewItem Header="Security" />
            <TreeViewItem Header="User Accounts" />
        </TreeViewItem>
    </TreeView>

    <TextBlock Margin="20" x:Name="MyTextBlock" />
</StackPanel>

Code Behind:

private void OnTreeViewSelectedItemChanged( object sender, RoutedPropertyChangedEventArgs<object> e )
{
    MyTextBlock.Text = ( (TreeViewItem) ( (TreeView) sender ).SelectedItem ).Header.ToString();
}


You'll need to add an event handler to the TreeView's SelectedItemChanged event.

<TreeView x:Name="myTreeView"
          SelectedItemChanged="myTreeView_SelectedItemChanged"
          ItemTemplate="{StaticResource PeerDetailTemplate} />

Since this is fired after the selection is changed, you can use the TreeView's selected item property to access the tree view item:

private void myTreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
    {
        TreeViewItem selectedItem = (TreeViewItem)myTreeView.SelectedItem;
        // do stuff
    }


Selection and Selection and focus are two different concepts. It sounds like you're interested in selection, which in this case is a property of the TreeView. Event TreeView.SelectedItemChanged will notify you of selection changes and property TreeView.SelectedItem will tell you what is selected.


There are different ways to Bind of the SelectedItemChanged event of TreeviewItem:

Method 1: Direct Attaching Event

The attachment of the event can be done in Xaml

<TreeView x:Name="treeview1" HorizontalAlignment="Left" Height="243" Margin="30,211,0,0" VerticalAlignment="Top" Width="667" SelectedItemChanged="TreeView_SelectedItemChanged">
        <TreeViewItem Header="TreeViewItem"/>
</TreeView>
Private void TreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{

}

Or on code Behind

myTreeview.SelectedItemChanged += new RoutedPropertyChangedEventHandler<object>(TreeView_SelectedItemChanged);

private void TreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{

}

Method 2 Usage of Extended Class

public class ExtendedTreeView : TreeView
{
    public ExtendedTreeView()
        : base()
    {
        this.SelectedItemChanged += new RoutedPropertyChangedEventHandler<object>(TreeView_SelectedItemChanged);
    }

    void TreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
    {
        if (SelectedItem != null)
        {
            SetValue(SelectedItem_Property, SelectedItem);
        }
    }

    public object SelectedItem_
    {
        get { return (object)GetValue(SelectedItem_Property); }
        set { SetValue(SelectedItem_Property, value); }
    }
    public static readonly DependencyProperty SelectedItem_Property = DependencyProperty.Register("SelectedItem_", typeof(object), typeof(ExtendedTreeView), new UIPropertyMetadata(null));
}

Next just create the Treeview with the new custom class object.

ExtendedTreeView  myTreeview = new ExtendedTreeView();

Method 3 Usage of Behavior

public class BindableSelectedItemBehavior : Behavior<TreeView>
{
    #region SelectedItem Property

    public object SelectedItem
    {
        get { return (object)GetValue(SelectedItemProperty); }
        set { SetValue(SelectedItemProperty, value); }
    }

    public static readonly DependencyProperty SelectedItemProperty =
        DependencyProperty.Register("SelectedItem", typeof(object), typeof(BindableSelectedItemBehavior), new UIPropertyMetadata(null, OnSelectedItemChanged));

    private static void OnSelectedItemChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    {
        var item = e.NewValue as TreeViewItem;
        if (item != null)
        {
            item.SetValue(TreeViewItem.IsSelectedProperty, true);
        }
    }

    #endregion

    protected override void OnAttached()
    {
        base.OnAttached();

        this.AssociatedObject.SelectedItemChanged += OnTreeViewSelectedItemChanged;
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();

        if (this.AssociatedObject != null)
        {
            this.AssociatedObject.SelectedItemChanged -= OnTreeViewSelectedItemChanged;
        }
    }

Next just attach the Treeview to the Behavior On Xaml file

<TreeView>
    <e:Interaction.Behaviors>
        <behaviours:BindableSelectedItemBehavior SelectedItem="{Binding SelectedItem, Mode=TwoWay}" />
    </e:Interaction.Behaviors>
</TreeView>

Or on Code Behind

BindableSelectedItemBehavior selectedItemBehavior = new BindableSelectedItemBehavior();
System.Windows.Interactivity.Interaction.GetBehaviors(treeview1).Add(selectedItemBehavior);

Cordially

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