WPF - Animate ListBox.ScrollViewer.HorizontalOffset? - wpf

I have a collection of Visuals in a ListBox. I need to find the XPosition of an element inside it and then animate the HorizontalOffset of the ListBox's ScrollViewer. Essentially I want to created an animated ScrollIntoView method.
This gives me a couple of problems. Firstly, how can I get a reference to the ListBoxs scrollviewer? Secondly, how can i get the relative XPosition or HozintalOfffset of an arbitrary element in the ListBox?
I'm not reponding to any input on the ListBox itself so I can't use Mouse related properties.

I don't think you will be able to use a WPF storyboard for the animation because storyboards animate WPF dependency properties. You will need to call ScrollViewer.ScrollToHorizontalOffset(double) to scroll.
You could try creating a custom dependency property that calls SetHorizontalOffset in the OnDependencyPropertyChanged() function. Then you could animate this property.
public static readonly DependencyProperty ScrollOffsetProperty =
DependencyProperty.Register("ScrollOffset", typeof(double), typeof(YOUR_TYPE),
new FrameworkPropertyMetadata(0.0, new PropertyChangedCallback(OnScrollOffsetChanged)));
public double ScrollOffset
{
get { return (double)GetValue(ScrollOffsetProperty); }
set { SetValue(ScrollOffsetProperty, value); }
}
private static void OnScrollOffsetChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
{
YOUR_TYPE myObj = obj as YOUR_TYPE;
if (myObj != null)
myObj.SCROLL_VIEWER.ScrollToHorizontalOffset(myObj.ScrollOffset);
}
To get the scroll viewer you can use the VisualTreeHelper to search the visual children of the ListBox. Save a reference to the ScrollViewer because you will need it later. Try this:
public static childItem FindVisualChild<childItem>(DependencyObject obj)
where childItem : DependencyObject
{
// Iterate through all immediate children
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
{
DependencyObject child = VisualTreeHelper.GetChild(obj, i);
if (child != null && child is childItem)
return (childItem)child;
else
{
childItem childOfChild = FindVisualChild<childItem>(child);
if (childOfChild != null)
return childOfChild;
}
}
return null;
}
This function returns the first visual child of the parameter type. Call FindVisualChild<ScrollViewer>(ListBox) to get the ScrollViewer.
Finally, try using UIElement.TranslatePoint(Point, UIElement) to get the X position of the item. Call this function on the item, pass in 0,0 for the point, and pass in the ScrollViewer.
Hope this helps.

I'm not sure if my method is good practice but for the limited time I had it seemed to work okay. Instead of using a story board I just used a DispatcherTimer instead.
ScrollLeftButtonCommand = new DelegateCommand(
o =>
{
var scrollViewer = (ScrollViewer)o;
scrollTimer = new DispatcherTimer();
scrollTimer.Start();
scrollTimer.Interval = TimeSpan.FromMilliseconds(30);
scrollTimer.Tick += (s, e) =>
{
scrollViewer.ScrollToHorizontalOffset(scrollViewer.HorizontalOffset - 50);
if (scrollViewer.HorizontalOffset <= 0)
{
scrollTimer.Stop();
}
};
});
Make sure it's a DispatchTimer so the thread is able to take control of the UI element
Also remember to bind to your object in your view!
<Button CommandParameter="{Binding ElementName=MyScrollViewer }"
Command="{Binding ScrollLeftButtonCommand }"/>

Related

How to scroll to the next logical page in a ListBox with physical scrolling

I do have a listbox which must have CanContentScroll==false because i need to be able to scroll it smoothly. This enables physical scrolling.
I also want to scroll the listbox by page, but if i call the PageDown method on the listbox internal ScrollViewer the first row gets cutted because the listbox height is not a multiple of the row height.
I want the first row to be always completely visible, like when using logical scrolling.
Can someone give me a hint on how to do that?
You'll get the same effect for a non virtualizing ItemsControl (ScrollViewer.CanContentScroll="False") as for a virtualizing one if you scroll down and then select the upper visible container with the mouse. This can also be done in code.
When CanContentScroll is set to false, virtualizing is turned off so all containers will be generated at all times. To get the top visible container we can iterate the containers from the top until we reach the VerticalOffset of the ScrollViewer. Once we got it we can simply call BringIntoView on it and it will align nicely at the top just like it would if virtualization was being used.
Example
<ListBox ItemsSource="{Binding MyCollection}"
ScrollViewer.CanContentScroll="False"
ScrollViewer.ScrollChanged="listBox_ScrollChanged" >
Call BringIntoView on the top visible container in the event handler
private void listBox_ScrollChanged(object sender, ScrollChangedEventArgs e)
{
ItemsControl itemsControl = sender as ItemsControl;
ScrollViewer scrollViewer = e.OriginalSource as ScrollViewer;
FrameworkElement lastElement = null;
foreach (object obj in itemsControl.Items)
{
FrameworkElement element = itemsControl.ItemContainerGenerator.ContainerFromItem(obj) as FrameworkElement;
double offset = element.TransformToAncestor(scrollViewer).Transform(new Point(0, 0)).Y + scrollViewer.VerticalOffset;
if (offset > e.VerticalOffset)
{
if (lastElement != null)
lastElement.BringIntoView();
break;
}
lastElement = element;
}
}
To only achieve this effect when you want to call PageDown, in a Button click for example, you can create an extension method for ListBox called LogicalPageDown.
listBox.LogicalPageDown();
ListBoxExtensions
public static class ListBoxExtensions
{
public static void LogicalPageDown(this ListBox listBox)
{
ScrollViewer scrollViewer = VisualTreeHelpers.GetVisualChild<ScrollViewer>(listBox);
ScrollChangedEventHandler scrollChangedHandler = null;
scrollChangedHandler = (object sender2, ScrollChangedEventArgs e2) =>
{
scrollViewer.ScrollChanged -= scrollChangedHandler;
FrameworkElement lastElement = null;
foreach (object obj in listBox.Items)
{
FrameworkElement element = listBox.ItemContainerGenerator.ContainerFromItem(obj) as FrameworkElement;
double offset = element.TransformToAncestor(scrollViewer).Transform(new Point(0, 0)).Y + scrollViewer.VerticalOffset;
if (offset > scrollViewer.VerticalOffset)
{
if (lastElement != null)
lastElement.BringIntoView();
break;
}
lastElement = element;
}
};
scrollViewer.ScrollChanged += scrollChangedHandler;
scrollViewer.PageDown();
}
}
I noticed in your question that you already got the ScrollViewer but I'm adding an implementation to GetVisualChild if anyone else comes across this question
public static T GetVisualChild<T>(DependencyObject parent) where T : Visual
{
T child = default(T);
int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < numVisuals; i++)
{
Visual v = (Visual)VisualTreeHelper.GetChild(parent, i);
child = v as T;
if (child == null)
{
child = GetVisualChild<T>(v);
}
if (child != null)
{
break;
}
}
return child;
}
If you scroll the top item of the "new page" into view, would that achieve what you're looking for?
See ScrollIntoView.

Get the ComboBox that a ComboBoxItem resides in

I need to find the ComboBox that a ComboBoxItem resides in.
In codebehind I catch an event when a ComboBoxItem is clicked, but I don't know which one of several ComboBoxes that the specific ComboBoxItem belongs to. How do I find the ComboBox?
Normally you can use LogicalTreeHelper.GetParent() and traverse up the logical tree from the ComboBoxItem to find the ComboBox. But this only works if the ComboBoxItems are added to the ComboBox manually, not when the items are applied to the ComboBox with databinding. When using databinding, the ComboBoxItems do not have the ComboBox as a logical parent (I don't understand why).
Any ideas?
More info:
Below is some code reconstructing my problem (not my actual code). If I would change from databinding the ComboBoxItems to setting them manually (in the XAML), the variable "comboBox" would be set to the correct ComboBox. Now comboBox is only null.
XAML:
<ComboBox Name="MyComboBox" ItemsSource="{Binding Path=ComboBoxItems, Mode=OneTime}" />
CodeBehind:
public MainWindow()
{
InitializeComponent();
MyComboBox.DataContext = this;
this.PreviewMouseDown += MainWindow_MouseDown;
}
public BindingList<string> ComboBoxItems
{
get
{
BindingList<string> items = new BindingList<string>();
items.Add("Item E");
items.Add("Item F");
items.Add("Item G");
items.Add("Item H");
return items;
}
}
private void MainWindow_MouseDown(object sender, MouseButtonEventArgs e)
{
DependencyObject clickedObject = e.OriginalSource as DependencyObject;
ComboBoxItem comboBoxItem = FindVisualParent<ComboBoxItem>(clickedObject);
if (comboBoxItem != null)
{
ComboBox comboBox = FindLogicalParent<ComboBox>(comboBoxItem);
}
}
//Tries to find visual parent of the specified type.
private static T FindVisualParent<T>(DependencyObject childElement) where T : DependencyObject
{
DependencyObject parent = VisualTreeHelper.GetParent(childElement);
T parentAsT = parent as T;
if (parent == null)
{
return null;
}
else if (parentAsT != null)
{
return parentAsT;
}
return FindVisualParent<T>(parent);
}
//Tries to find logical parent of the specified type.
private static T FindLogicalParent<T>(DependencyObject childElement) where T : DependencyObject
{
DependencyObject parent = LogicalTreeHelper.GetParent(childElement);
T parentAsT = parent as T;
if (parent == null)
{
return null;
}
else if(parentAsT != null)
{
return parentAsT;
}
return FindLogicalParent<T>(parent);
}
This is probably what you are looking for:
var comboBox = ItemsControl.ItemsControlFromItemContainer(comboBoxItem) as ComboBox;
I love how descriptive that method-name is.
On a side-note, there are some other useful methods which can be found in the property ItemsControl.ItemContainerGenerator which let you get the container associated with the templated data and vice versa.
On another side-note, you usually should not be using any of them and instead use data-binding actually.

What is the proper way to handle multiple datagrids in a tab control so that cells leave edit mode when the tabs are changed?

In wpf I setup a tab control that binds to a collection of objects each object has a data template with a data grid presenting the data. If I select a particular cell and put it into edit mode, leaving the grid by going to another tab this will cause the exception below to be thrown on returning the datagrid:
'DeferRefresh' is not allowed during an AddNew or EditItem transaction.
It appears that the cell never left edit mode. Is there an easy way to take the cell out of edit mode, or is something else going on here?
Update: It looks like if I do not bind the tab control to the data source, but instead explicitly define each tab and then bind each item in the data source to a content control this problem goes away. This is not really a great solution, so I would still like to know how to bind the collection directly to the tab control.
Update: So what I have actually done for my own solution is to use a ListView and a content control in place of a tab control. I use a style to make the list view look tab like. The view model exposes a set of child view models and allows the user to select one via the list view. The content control then presents the selected view model and each view model has an associated data template which contains the data grid. With this setup switching between view models while in edit mode on the grid will properly end edit mode and save the data.
Here is the xaml for setting this up:
<ListView ItemTemplate="{StaticResource MakeItemsLookLikeTabs}"
ItemsSource="{Binding ViewModels}"
SelectedItem="{Binding Selected}"
Style="{StaticResource MakeItLookLikeATabControl}"/>
<ContentControl Content="{Binding Selected}">
I'll accept Phil's answer as that should work also, but for me the solution above seems like it will be more portable between projects.
I implemented a behavior for the DataGrid based on code I found in this thread.
Usage:<DataGrid local:DataGridCommitEditBehavior.CommitOnLostFocus="True" />
Code:
using System.Collections.Generic;
using System.Reflection;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Input;
using System.Windows.Media;
/// <summary>
/// Provides an ugly hack to prevent a bug in the data grid.
/// https://connect.microsoft.com/VisualStudio/feedback/details/532494/wpf-datagrid-and-tabcontrol-deferrefresh-exception
/// </summary>
public class DataGridCommitEditBehavior
{
public static readonly DependencyProperty CommitOnLostFocusProperty =
DependencyProperty.RegisterAttached(
"CommitOnLostFocus",
typeof(bool),
typeof(DataGridCommitEditBehavior),
new UIPropertyMetadata(false, OnCommitOnLostFocusChanged));
/// <summary>
/// A hack to find the data grid in the event handler of the tab control.
/// </summary>
private static readonly Dictionary<TabPanel, DataGrid> ControlMap = new Dictionary<TabPanel, DataGrid>();
public static bool GetCommitOnLostFocus(DataGrid datagrid)
{
return (bool)datagrid.GetValue(CommitOnLostFocusProperty);
}
public static void SetCommitOnLostFocus(DataGrid datagrid, bool value)
{
datagrid.SetValue(CommitOnLostFocusProperty, value);
}
private static void CommitEdit(DataGrid dataGrid)
{
dataGrid.CommitEdit(DataGridEditingUnit.Cell, true);
dataGrid.CommitEdit(DataGridEditingUnit.Row, true);
}
private static DataGrid GetParentDatagrid(UIElement element)
{
UIElement childElement; // element from which to start the tree navigation, looking for a Datagrid parent
if (element is ComboBoxItem)
{
// Since ComboBoxItem.Parent is null, we must pass through ItemsPresenter in order to get the parent ComboBox
var parentItemsPresenter = VisualTreeFinder.FindParentControl<ItemsPresenter>(element as ComboBoxItem);
var combobox = parentItemsPresenter.TemplatedParent as ComboBox;
childElement = combobox;
}
else
{
childElement = element;
}
var parentDatagrid = VisualTreeFinder.FindParentControl<DataGrid>(childElement);
return parentDatagrid;
}
private static TabPanel GetTabPanel(TabControl tabControl)
{
return
(TabPanel)
tabControl.GetType().InvokeMember(
"ItemsHost",
BindingFlags.NonPublic | BindingFlags.GetProperty | BindingFlags.Instance,
null,
tabControl,
null);
}
private static void OnCommitOnLostFocusChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs e)
{
var dataGrid = depObj as DataGrid;
if (dataGrid == null)
{
return;
}
if (e.NewValue is bool == false)
{
return;
}
var parentTabControl = VisualTreeFinder.FindParentControl<TabControl>(dataGrid);
var tabPanel = GetTabPanel(parentTabControl);
if (tabPanel != null)
{
ControlMap[tabPanel] = dataGrid;
}
if ((bool)e.NewValue)
{
// Attach event handlers
if (parentTabControl != null)
{
tabPanel.PreviewMouseLeftButtonDown += OnParentTabControlPreviewMouseLeftButtonDown;
}
dataGrid.LostKeyboardFocus += OnDataGridLostFocus;
dataGrid.DataContextChanged += OnDataGridDataContextChanged;
dataGrid.IsVisibleChanged += OnDataGridIsVisibleChanged;
}
else
{
// Detach event handlers
if (parentTabControl != null)
{
tabPanel.PreviewMouseLeftButtonDown -= OnParentTabControlPreviewMouseLeftButtonDown;
}
dataGrid.LostKeyboardFocus -= OnDataGridLostFocus;
dataGrid.DataContextChanged -= OnDataGridDataContextChanged;
dataGrid.IsVisibleChanged -= OnDataGridIsVisibleChanged;
}
}
private static void OnDataGridDataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
{
var dataGrid = (DataGrid)sender;
CommitEdit(dataGrid);
}
private static void OnDataGridIsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
{
var senderDatagrid = (DataGrid)sender;
if ((bool)e.NewValue == false)
{
CommitEdit(senderDatagrid);
}
}
private static void OnDataGridLostFocus(object sender, KeyboardFocusChangedEventArgs e)
{
var dataGrid = (DataGrid)sender;
var focusedElement = Keyboard.FocusedElement as UIElement;
if (focusedElement == null)
{
return;
}
var focusedDatagrid = GetParentDatagrid(focusedElement);
// Let's see if the new focused element is inside a datagrid
if (focusedDatagrid == dataGrid)
{
// If the new focused element is inside the same datagrid, then we don't need to do anything;
// this happens, for instance, when we enter in edit-mode: the DataGrid element loses keyboard-focus,
// which passes to the selected DataGridCell child
return;
}
CommitEdit(dataGrid);
}
private static void OnParentTabControlPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
var dataGrid = ControlMap[(TabPanel)sender];
CommitEdit(dataGrid);
}
}
public static class VisualTreeFinder
{
/// <summary>
/// Find a specific parent object type in the visual tree
/// </summary>
public static T FindParentControl<T>(DependencyObject outerDepObj) where T : DependencyObject
{
var dObj = VisualTreeHelper.GetParent(outerDepObj);
if (dObj == null)
{
return null;
}
if (dObj is T)
{
return dObj as T;
}
while ((dObj = VisualTreeHelper.GetParent(dObj)) != null)
{
if (dObj is T)
{
return dObj as T;
}
}
return null;
}
}
I have managed to work around this issue by detecting when the user clicks on a TabItem and then committing edits on visible DataGrid in the TabControl. I'm assuming the user will expect their changes to still be there when they click back.
Code snippet:
// PreviewMouseDown event handler on the TabControl
private void TabControl_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
if (IsUnderTabHeader(e.OriginalSource as DependencyObject))
CommitTables(yourTabControl);
}
private bool IsUnderTabHeader(DependencyObject control)
{
if (control is TabItem)
return true;
DependencyObject parent = VisualTreeHelper.GetParent(control);
if (parent == null)
return false;
return IsUnderTabHeader(parent);
}
private void CommitTables(DependencyObject control)
{
if (control is DataGrid)
{
DataGrid grid = control as DataGrid;
grid.CommitEdit(DataGridEditingUnit.Row, true);
return;
}
int childrenCount = VisualTreeHelper.GetChildrenCount(control);
for (int childIndex = 0; childIndex < childrenCount; childIndex++)
CommitTables(VisualTreeHelper.GetChild(control, childIndex));
}
This is in the code behind.
This bug is solved in the .NET Framework 4.5. You can download it at this link.
What I think you should do is pretty close to what #myermian said.
There is an event called CellEditEnding end this event would allow you to intercept and make the decision to drop the unwanted row.
private void dataGrid1_CellEditEnding(object sender, DataGridCellEditEndingEventArgs e)
{
DataGrid grid = (DataGrid)sender;
TextBox cell = (TextBox)e.EditingElement;
if(String.IsNullOrEmpty(cell.Text) && e.EditAction == DataGridEditAction.Commit)
{
grid.CancelEdit(DataGridEditingUnit.Row);
e.Cancel = true;
}
}

Allowing item selection indicator in ListBox to overlay all items in Silverlight

I have a ListBox that uses a WrapPanel for its ItemsPanel, a custom ItemTemplate, and a custom ItemContainerStyle. The ItemContainerStyle's template contains a selection box that shows up when an item is selected. The graphics designer would like this selection box to overlap sibling items in the ListBox like it's an overlay.
The first thing I tried was setting the Canvas.ZIndex property of the ItemContainer in the Selected state. That did not seem to have an effect. Then I read that list items might be wrapped inside of a ContentPresenter, so I created an attached property that changes the ZIndex of an item's parent, but then I found out Silverlight storyboards don't let you animate custom attached properties.
Does anyone know of a technique we can use to achieve the effect we desire?
I found a solution. Basically, I created an attached property that sets up an event handler on any Selector (including ListBox) for when its selection changes. When it changes, the code iterates through all of the item containers, adjusting the Canvas.ZIndex based on whether the container represents the selected item:
public static readonly DependencyProperty SetZIndexOnSelectionProperty = DependencyProperty.RegisterAttached(
"SetZIndexOnSelection", typeof(bool), typeof(FrameworkUtils),
new PropertyMetadata(zIndexSettingChanged));
public static bool GetSetZIndexOnSelection(DependencyObject obj)
{
return (bool)obj.GetValue(SetZIndexOnSelectionProperty);
}
public static void SetSetZIndexOnSelection(
DependencyObject obj, bool value)
{
obj.SetValue(SetZIndexOnSelectionProperty, value);
}
private static void zIndexSettingChanged(
DependencyObject obj, DependencyPropertyChangedEventArgs args)
{
if (obj is Selector)
{
var selector = obj as Selector;
selector.SelectionChanged += (s, e) =>
{
if (selector.SelectedItem != null)
{
foreach (var pair in selector.GetItemsAndContainers())
{
pair.Value.SetValue(
Canvas.ZIndexProperty,
(pair.Key == selector.SelectedItem) ? 1 : 0);
}
}
};
}
}

How to deselect all selected items in a WPF treeview when clicking on some empty area?

I've got a rather funny problem with WPF. I have a tree-view, and selecting items works fine so far. The problem is, I want to unselect the currently selected item when the user clicks inside the blank area of the treeview. By default, the treeview keeps the current item selected, and I have added a context-menu option to deselect it, which is rather hardcore:
// Note: This is done recursivly from the start, so it
// works for child items as well
treeView.ItemContainerGenerator.ContainerFromItem(treeView.SelectedItem) as TreeViewItem).IsSelected = false;
Moreover, this is counter-intuitive, as it requires the user to right-click first, and second, after deselecting it with this way, the user cannot select it any more by clicking on the item. How is this supposed to work?
Edit: Some more information: I've added a handler to the TreeView to handle mouse click events, but the sender is always a TreeView instance, even if I click directly on a TreeViewItem. If I add a handler to my TreeView.ItemTemplate instead (i.e. the first child in the template), I never get events when I click on the empty area (which is rather logical). The code looks like this:
private void MyTreeView_MouseUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
if ((sender as TreeViewItem) == null)
{
// Always triggered
System.Diagnostics.Trace.Write("Empty area clicked");
}
}
And the XAML for this is:
<TreeView x:Name="MyTreeView" Margin="3" MouseUp="MyTreeView_MouseUp">
I found this to work much better for me. I check the originalsource which for me if it comes form a treeviewitem will be an image or a textblock. I also use a view object with a HierarchicalDataTemplate and the BasicTreeViewBase is the base class for all of my different objects. Here is the code.
private void TemplateTreeView_MouseDown(object sender, MouseButtonEventArgs e)
{
if (e.ChangedButton == MouseButton.Right && !(e.OriginalSource is Image) && !(e.OriginalSource is TextBlock))
{
BasicTreeViewBase item = TemplateTreeView.SelectedItem as BasicTreeViewBase;
if (item != null)
{
TemplateTreeView.Focus();
item.IsSelected = false;
}
}
}
The un-selectable problem can be solved with a call to Focus on the TreeView after setting TreeViewItem.IsSelected.
There can be two more problem :
The treeview is binded so the SelectedItem is an item of the binded collection.
There is many levels so ItemContainerGenerator do not contain deepest level objects
for all this reason i use this function, but the selection must not fire any events.
private void UnselectTreeViewItem(TreeView pTreeView)
{
if(pTreeView.SelectedItem == null)
return;
if(pTreeView.SelectedItem is TreeViewItem)
{
(pTreeView.SelectedItem as TreeViewItem).IsSelected = false;
}
else
{
TreeViewItem item = pTreeView.ItemContainerGenerator.ContainerFromIndex(0) as TreeViewItem;
if (item != null)
{
item.IsSelected = true;
item.IsSelected = false;
}
}
}
I implemented a general selection control once, and required this behaviour.
This is how my method looked (adapted for treeview):
protected override void OnMouseUp(MouseButtonEventArgs e)
{
base.OnMouseUp(e);
DependencyObject dpSource = e.OriginalSource as DependencyObject;
if (dpSource.FindVisualAncestor(o => typeof(TreeViewItem).IsAssignableFrom(o.GetType())) == null)
UnselectAll();
}
Basically, walk up the tree from the source. If a TreeViewItem was not found, than the user clicked empty space.
Use the extension class below
public static class TreeViewExtensions
{
public static TreeViewItem ContainerFromItem(this TreeView treeView, object item)
{
TreeViewItem containerThatMightContainItem = (TreeViewItem)treeView.ItemContainerGenerator.ContainerFromItem(item);
if (containerThatMightContainItem != null)
return containerThatMightContainItem;
else
return ContainerFromItem(treeView.ItemContainerGenerator, treeView.Items, item);
}
private static TreeViewItem ContainerFromItem(ItemContainerGenerator parentItemContainerGenerator, ItemCollection itemCollection, object item)
{
foreach (object curChildItem in itemCollection)
{
TreeViewItem parentContainer = (TreeViewItem)parentItemContainerGenerator.ContainerFromItem(curChildItem);
TreeViewItem containerThatMightContainItem = (TreeViewItem)parentContainer.ItemContainerGenerator.ContainerFromItem(item);
if (containerThatMightContainItem != null)
return containerThatMightContainItem;
TreeViewItem recursionResult = ContainerFromItem(parentContainer.ItemContainerGenerator, parentContainer.Items, item);
if (recursionResult != null)
return recursionResult;
}
return null;
}
}
Then in MouseDown event of treeview use the extension method as below:
private void trview_MouseDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
if ((sender as TreeViewItem) == null)
{
if (this.trview.ContainerFromItem(trview.SelectedItem) != null)
{
this.trview.ContainerFromItem(trview.SelectedItem).IsSelected = false;
}
}
this.trview.Focus();
}
Hope it works for you. I have it working in this way...
I was running into this situation myself with a custom Tree List View implementation after looking for a long time I finally found a solution that worked for me.
The full explanation can be found at http://social.msdn.microsoft.com/Forums/vstudio/en-US/36aca7f7-0b47-488b-8e16-840b86addfa3/getting-treeviewitem-for-the-selected-item-in-a-treeview
The basic idea is you capture the TreeViewItem.Selected event and save the source of the event into the Tag attribute on your TreeView. Then when you need to clear it, you can access the Tag attribute on your control and set the IsSelected value to False. This works for me with 2 levels of nested children. Hopefully it will work for you.
For persistence sake:
TreeView declaration
<TreeView Name="myTreeView" TreeViewItem.Selected="OnItemSelected"
ItemsSource="{Binding Source={StaticResource myHierarchicalData}}"/>
Event Handler
private void OnItemSelected(object sender, RoutedEventArgs e)
{
myTreeView.Tag = e.OriginalSource;
}
Clear selection logic
if (myTreeView.SelectedItem != null)
{
TreeViewItem selectedTVI = myTreeView.Tag as TreeViewItem;
// add your code here mine was selectedTVI.IsSelected = false;
}
This will deselect the currently selected TreeViewItem if none were clicked:
private void MyTreeView_PreviewMouseDown(object sender, MouseButtonEventArgs e) {
if ((sender as TreeViewItem) == null) {
TreeViewItem item = MyTreeView.SelectedItem as TreeViewItem;
if(item != null){
item.IsSelected = false;
}
}
}
Hope this is what you were looking for!
MVVM: Call this method in the eventhandler righ/left mouse click:
private void SetTreeViewSelection(object sender, MouseButtonEventArgs mouseButtonEventArgs)
{
var treeView = (TreeView)sender;
if (treeView.SelectedItem == null)
{
return;
}
IInputElement dropNode = treeView.InputHitTest(mouseButtonEventArgs.GetPosition(treeView));
if (dropNode is ScrollViewer)
{
var myBindableObject = (MyBindableObject)treeView.SelectedItem;
myBindableObject.IsSelected = false;
}
}
For a C# treeview you use treeview.SelectedNode = null; I'm not sure if this works for WPF.

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