There has to be a better way then the following for getting "childItem"
TaskItem task = (sender as Canvas).DataContext as TaskItem;
TaskItem child = Tasks.CreateTask("New task", task);
TreeViewItem item = treeView.ItemContainerGenerator.ContainerFromItem(task) as TreeViewItem;
item.UpdateLayout();
TreeViewItem childItem = null;
foreach (var i in item.GetDescendantContainers())
{
if (i.GetItem() == child)
childItem = i;
}
For some reason item.ItemGenerator.ContainerFromItem(child) does not work (must be due to the item having just been created)
Item container generation is asynchronous, so you cannot assume the container will exist as soon as the item was added. You will need to attach a handler to the ItemContainerGenerator.StatusChanged event so your code will be informed when container generation is complete.
Dr. WPF's blog entry "ItemsControl: 'G' is for Generator" has a good description of the problem and provides an example of using StatusChanged:
private void AddScooby()
{
_scooby = new Character("Scooby Doo");
Characters.Add(_scooby);
CharacterListBox.ItemContainerGenerator.StatusChanged
+= OnStatusChanged;
}
private void OnStatusChanged(object sender, EventArgs e)
{
if (CharacterListBox.ItemContainerGenerator.Status
== GeneratorStatus.ContainersGenerated)
{
CharacterListBox.ItemContainerGenerator.StatusChanged
-= OnStatusChanged;
ListBoxItem lbi = CharacterListBox.ItemContainerGenerator
.ContainerFromItem(_scooby) as ListBoxItem;
if (lbi != null)
{
lbi.IsSelected = true;
}
}
}
Related
I'm starting out in wpf.
I have a TreeView in which each item has a checkbox.
I'm trying to create an animation in which The checkboxes are checked programmatically inside a loop.
After researching the topic for some time, I came up with the following method -
private void Traverse_Click(object sender, RoutedEventArgs e)
{
ItemCollection items = tvMain.Items;
Task.Factory.StartNew( ()=>
Dispatcher.Invoke( (Action)(() =>
{
foreach (TreeViewItem item in items)
{
UIElement elemnt = getCheckbox();
if (elemnt != null)
{
CheckBox chk = (CheckBox)elemnt;
chk.IsChecked = !chk.IsChecked;
tvMain.Items.Refresh();
tvMain.UpdateLayout();
Thread.Sleep(500);
}
}
})));
And yet despite all of my attempts the the tree doesn't update inside the loop, only at the end. so the checkboxes are all checked at once.
How can I make the tree update inside the loop?
Thanks
Replace Thread.Sleep with Task.Delay to "sleep" asynchronously:
private async void Traverse_Click(object sender, RoutedEventArgs e)
{
ItemCollection items = tvMain.Items;
foreach (TreeViewItem item in items)
{
UIElement elemnt = getCheckbox();
if (elemnt != null)
{
CheckBox chk = (CheckBox)elemnt;
chk.IsChecked = !chk.IsChecked;
await Task.Delay(500);
}
}
}
I have Extended the RowDefinition as RowDefinitionExtended and In that, when can i get the LogicalChildren belongs to this RowDefinition. I mean in which override can i get the LogicalChildren?
public class RowDefinitionExtended : RowDefinition
{
protected override void OnInitialized(EventArgs e)
{
base.OnInitialized(e);
Loaded += OnRowDefinitionExtendedLoaded;
}
void OnRowDefinitionExtendedLoaded(object sender, RoutedEventArgs e)
{
var parent = GetUIParentCore() as Grid;
if (parent == null) return;
if (parent.Children.Cast<UIElement>().Where(c => Grid.GetRow(c) == parent.RowDefinitions.IndexOf(this)).All(ctrl => ctrl.Visibility != Visibility.Visible))
Height = new GridLength(0);
}
}
What my requirement is, I need to check all the LogicalChildren to its Visibility and Change its Height accordingly.
How could i do this? Any idea?
Update:
Code has been updated, On Load I could do this and it works fine. But my problem is, am changing the controls visibility after load... So is there any notification while changing the Visibility? am looking a event when the layout updated like..
Any event can i use it for?
You can't do that by means of a derived RowDefinition, but this little helper method should do the job (if your intention was to get all child elements in a certain row of a Grid):
public static IEnumerable<UIElement> ChildrenInRow(Grid grid, int row)
{
return grid.Children.Cast<UIElement>().Where(c => Grid.GetRow(c) == row);
}
You have to subscribe to the IsVisibleChanged handler for each element in the row when the row is loaded.
When the visibility changed, you could do whatever you need
public class RowDefinitionExtended : RowDefinition
{
protected override void OnInitialized(EventArgs e)
{
base.OnInitialized(e);
Loaded += OnRowDefinitionExtendedLoaded;
}
void OnRowDefinitionExtendedLoaded(object sender, RoutedEventArgs e)
{
var parent = GetUIParentCore() as Grid;
if (parent == null) return;
//Subscribe to the IsVisibleChanged handler for each element in the row
var ElementInGridRow = parent.Children.Cast<UIElement>().Where(c => Grid.GetRow(c) == parent.RowDefinitions.IndexOf(this));
foreach (var element in ElementInGridRow)
{
element.IsVisibleChanged+=new DependencyPropertyChangedEventHandler(OnChildrenIsVisibleChanged);
}
}
private void OnChildrenIsVisibleChanged(object sender,DependencyPropertyChangedEventArgs e)
{
UIElement element = sender as UIElement;
//Do stuff...
var parent = GetUIParentCore() as Grid;
if (parent.Children.Cast<UIElement>().Where(c => Grid.GetRow(c) == parent.RowDefinitions.IndexOf(this)).All(ctrl => ctrl.Visibility != Visibility.Visible))
Height = new GridLength(0);
}
}
I have looked here and here and many other places, but I just can't seem to get the ItemContainerGenerator.ContainerFromItem method to work on a WPF TreeView! I have tried to pass in the actual item I want to see, but not getting anywhere with that, I just tried to get the first item in my TreeView. Here's my sample code:
private static bool ExpandAndSelectItem(ItemsControl parentContainer, object itemToSelect)
{
// This doesn't work.
parentContainer.BringIntoView();
// May be virtualized, bring into view and try again.
parentContainer.UpdateLayout();
parentContainer.ApplyTemplate();
TreeViewItem topItem = (TreeViewItem)parentContainer.ItemContainerGenerator.ContainerFromItem(parentContainer.Items[0]);
// Can't find child container unless the parent node is Expanded once
if ((topItem != null) && !topItem.IsExpanded)
{
topItem.IsExpanded = true;
parentContainer.UpdateLayout();
}
}
As you can see, I have tried to call many "updating" methods to try to get the TreeView to be "visible" and "accessible". The Catch-22 seems to be that you can't use ContainerFromItem() unless the first TreeViewItem is expanded, but I can't grab the TreeViewItem to Expand it until ContainerFromItem() works!
Another funny thing that is happening is this: When I open this window (it is a UserControl), ContainerFromItem() returns nulls, but if I close the window and open it back up, ContainerFromItem() starts returning non-nulls. Is there any event I should be looking for or forcing to fire?
Turns out the event I was looking for was "Loaded". I just attached an event handler onto my treeview in the XAML, and called my logic in that event handler.
<TreeView x:Name="MyTreeView"
Margin="0,5,0,5"
HorizontalAlignment="Left"
BorderThickness="0"
FontSize="18"
FontFamily="Segoe WP"
MaxWidth="900"
Focusable="True"
Loaded="MyTreeView_Load">
...
</TreeView>
The event handler:
private void MyTreeView_Load(object sender, RoutedEventArgs e)
{
ShowSelectedThing(MyTreeView, ThingToFind);
}
// Gotta call the TreeView an ItemsControl to cast it between TreeView and TreeViewItem
// as you recurse
private static bool ShowSelectedThing(ItemsControl parentContainer, object ThingToFind)
{
// check current level of tree
foreach (object item in parentContainer.Items)
{
TreeViewItem currentContainer = (TreeViewItem)parentContainer.ItemContainerGenerator.ContainerFromItem(item);
if ((currentContainer != null) && (item == ThingToFind)
{
currentContainer.IsSelected = true;
currentContainer.BringIntoView();
return true;
}
}
// item is not found at current level, check the kids
foreach (object item in parentContainer.Items)
{
TreeViewItem currentContainer = (TreeViewItem)parentContainer.ItemContainerGenerator.ContainerFromItem(item);
if ((currentContainer != null) && (currentContainer.Items.Count > 0))
{
// Have to expand the currentContainer or you can't look at the children
currentContainer.IsExpanded = true;
currentContainer.UpdateLayout();
if (!ShowSelectedThing(currentContainer, ThingToFind))
{
// Haven't found the thing, so collapse it back
currentContainer.IsExpanded = false;
}
else
{
// We found the thing
return true;
}
}
}
// default
return false;
}
Hope this helps someone. Sometimes in the real world, with demanding customers, weird requirements and short deadlines, ya gotta hack!
When the container generator's status is 'NotStarted' or 'ContainersGenerating', you can't find the container.
Use this method to find the container of data item.
private static async Task<TreeViewItem> FindItemContainer(ItemsControl itemsControl, object item)
{
var generator = itemsControl.ItemContainerGenerator;
if (generator.Status != GeneratorStatus.ContainersGenerated)
{
var tcs = new TaskCompletionSource<object>();
EventHandler handler = null;
handler = (s, e) =>
{
if (generator.Status == GeneratorStatus.ContainersGenerated)
{
generator.StatusChanged -= handler;
tcs.SetResult(null);
}
else if (generator.Status == GeneratorStatus.Error)
{
generator.StatusChanged -= handler;
tcs.SetException(new InvalidOperationException());
}
};
generator.StatusChanged += handler;
if (itemsControl is TreeViewItem tvi)
tvi.IsExpanded = true;
itemsControl.UpdateLayout();
await tcs.Task;
}
var container = (TreeViewItem)generator.ContainerFromItem(item);
if(container == null)
{
foreach (var parentItem in itemsControl.Items)
{
var parentContainer = (TreeViewItem)generator.ContainerFromItem(parentItem);
container = await FindItemContainer(parentContainer, item);
if (container != null)
return container;
}
}
return container;
}
private void Lv_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
ListView Lv = (ListView)sender;
Lv.UpdateLayout(); // 1.step
DependencyObject Dep = Lv.ItemContainerGenerator
.ContainerFromItem(Lv.SelectedItem);
((ListViewItem)Dep).Focus(); //2.step
}
I had come across this issue time ago and now again I got stuck with it for quite a while. Any MessageBox launch or an expand or dropdown on your particular control type, any of these do the job and start the ItemContainerGenerator. The .UpdateLayout() however is the right thing to do, before the .Focus(). Should be analogous for a Treeview, or one of its Items.
I currently have a ListBox whose ItemsSource collection is bound to a property on my viewmodel, of type IEnumerable. When that preoprty's reference changes, the ListBox updates as expected, however I have a problem in that if I have a large collection of items and scroll to the bottom of the ListBox, and then change the reference to another collection containing, say, 1 item, the ListBox view is blank and no scrollbar is displayed. I have to then scroll the listbox up with the mouse wheel, until the 1 item comes into view.
So, what I think I'm after, is a way of resetting the scroll position of the ListBox to the top, whenever the ItemsSource property changes, so that something is always displayed no matter how large or small the collection.
I'm unable to reproduce your problem (for me, the ListBox is scrolled to the last item in the new collection when changing ItemsSource). Anyway, to scroll the ListBox to the top every time its ItemsSource changes you can use some code behind. First listen to changes in the ItemsSourceProperty and then scroll the ListBox to the top once its items has been generated
Update
Made an attached behavior that does this instead to avoid code behind. It can be used like this
<ListBox ...
behaviors:ScrollToTopBehavior.ScrollToTop="True"/>
ScrollToTopBehavior
public static class ScrollToTopBehavior
{
public static readonly DependencyProperty ScrollToTopProperty =
DependencyProperty.RegisterAttached
(
"ScrollToTop",
typeof(bool),
typeof(ScrollToTopBehavior),
new UIPropertyMetadata(false, OnScrollToTopPropertyChanged)
);
public static bool GetScrollToTop(DependencyObject obj)
{
return (bool)obj.GetValue(ScrollToTopProperty);
}
public static void SetScrollToTop(DependencyObject obj, bool value)
{
obj.SetValue(ScrollToTopProperty, value);
}
private static void OnScrollToTopPropertyChanged(DependencyObject dpo,
DependencyPropertyChangedEventArgs e)
{
ItemsControl itemsControl = dpo as ItemsControl;
if (itemsControl != null)
{
DependencyPropertyDescriptor dependencyPropertyDescriptor =
DependencyPropertyDescriptor.FromProperty(ItemsControl.ItemsSourceProperty, typeof(ItemsControl));
if (dependencyPropertyDescriptor != null)
{
if ((bool)e.NewValue == true)
{
dependencyPropertyDescriptor.AddValueChanged(itemsControl, ItemsSourceChanged);
}
else
{
dependencyPropertyDescriptor.RemoveValueChanged(itemsControl, ItemsSourceChanged);
}
}
}
}
static void ItemsSourceChanged(object sender, EventArgs e)
{
ItemsControl itemsControl = sender as ItemsControl;
EventHandler eventHandler = null;
eventHandler = new EventHandler(delegate
{
if (itemsControl.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
{
ScrollViewer scrollViewer = GetVisualChild<ScrollViewer>(itemsControl) as ScrollViewer;
scrollViewer.ScrollToTop();
itemsControl.ItemContainerGenerator.StatusChanged -= eventHandler;
}
});
itemsControl.ItemContainerGenerator.StatusChanged += eventHandler;
}
}
And an implementation of GetVisualChild
private 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;
}
Late answer:
A simple solution is to add an event handler for the TargetUpdated event, and set NotifyOnTargetUpdated=True on the ItemsSource binding:
<ListBox x:Name="listBox"
ItemsSource="{Binding MySource, NotifyOnTargetUpdated=True}"
TargetUpdated="ListBox_TargetUpdated"/>
and in the event handler, scroll to the top item:
private void ListBox_TargetUpdated(object sender, DataTransferEventArgs e)
{
if (listBox.Items.Count > 0)
{
listBox.ScrollIntoView(listBox.Items[0]);
}
}
Try this:
if (listBox.Items.Count > 0) {
listBox.ScrollIntoView(listBox.Items[0]);
}
Improved Fredrik Hedblad's answer to work with ObservableCollection:
public static class ItemsControlAttachedProperties
{
#region ScrollToTopOnItemsSourceChange Property
public static readonly DependencyProperty ScrollToTopOnItemsSourceChangeProperty =
DependencyProperty.RegisterAttached(
"ScrollToTopOnItemsSourceChange",
typeof(bool),
typeof(ItemsControlAttachedProperties),
new UIPropertyMetadata(false, OnScrollToTopOnItemsSourceChangePropertyChanged));
public static bool GetScrollToTopOnItemsSourceChange(DependencyObject obj)
{
return (bool) obj.GetValue(ScrollToTopOnItemsSourceChangeProperty);
}
public static void SetScrollToTopOnItemsSourceChange(DependencyObject obj, bool value)
{
obj.SetValue(ScrollToTopOnItemsSourceChangeProperty, value);
}
static void OnScrollToTopOnItemsSourceChangePropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var itemsControl = obj as ItemsControl;
if (itemsControl == null)
{
throw new Exception("ScrollToTopOnItemsSourceChange Property must be attached to an ItemsControl based control.");
}
DependencyPropertyDescriptor descriptor =
DependencyPropertyDescriptor.FromProperty(ItemsControl.ItemsSourceProperty, typeof(ItemsControl));
if (descriptor != null)
{
if ((bool) e.NewValue)
{
descriptor.AddValueChanged(itemsControl, ItemsSourceChanged);
}
else
{
descriptor.RemoveValueChanged(itemsControl, ItemsSourceChanged);
}
}
}
static void ItemsSourceChanged(object sender, EventArgs e)
{
var itemsControl = sender as ItemsControl;
DoScrollToTop(itemsControl);
var collection = itemsControl.ItemsSource as INotifyCollectionChanged;
if (collection != null)
{
collection.CollectionChanged += (o, args) => DoScrollToTop(itemsControl);
}
}
static void DoScrollToTop(ItemsControl itemsControl)
{
EventHandler eventHandler = null;
eventHandler =
delegate
{
if (itemsControl.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
{
var scrollViewer = GetVisualChild<ScrollViewer>(itemsControl);
scrollViewer.ScrollToTop();
itemsControl.ItemContainerGenerator.StatusChanged -= eventHandler;
}
};
itemsControl.ItemContainerGenerator.StatusChanged += eventHandler;
}
static T GetVisualChild<T>(DependencyObject parent) where T : Visual
{
T child = default(T);
int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
for (var i = 0; i < numVisuals; i++)
{
var v = (Visual) VisualTreeHelper.GetChild(parent, i);
child = v as T ?? GetVisualChild<T>(v);
if (child != null)
{
break;
}
}
return child;
}
#endregion
}
When you format the control, you select a range of cells as the selection choices which are then listed in the list box. You also select a cell as the link to the selected choices in which a number will be displayed depending on the position of the selection in the list. 1 for first in the list, 2 for second etc. The code is quite simply:-
Range("A1")Select
Selection = 1
Change ("A1") to the cell you have linked
and change the 1 to the position in the list you want selected.
The cell reference being a link works both ways - if you change your selection, the number in the cell changes and if you change the number in the cell, the highlighted selection changes.
How to raise a event in usercontrol from the another usercontrol. i tried to do with delegates, but it doesnt work. How can i do this. am using C#(WPF)
usercontrol1.cs
public partial class UserControl1 : UserControl
{
delegate void myDelegate();
public UserControl1()
{
InitializeComponent();
}
private void button1_Click(object sender, RoutedEventArgs e)
{
UserControl2 obj = new UserControl2();
myDelegate d = new myDelegate(obj.CallDelegate);
obj.CallDelegate();
}
}
Usercontrol2.cs
public partial class UserControl2 : UserControl
{
public UserControl2()
{
InitializeComponent();
}
public void CallDelegate()
{
this.Width = 50;
this.Height = 50;
MessageBox.Show("Method called ");
}
}
when i use delegate i can go get the messagebox from the method, but the control doesnt resize. do i want to render it again ?? i have tried to assign explicitly, but doesnt work
In general, only the event owner can raise an event. There are exceptions to this (such as with Button.PerformClick in Windows Forms, but they have to be specifically provided by the class in question.
It's possible that WPF routed events may give an alternative here, but you haven't been clear about what kind of events you're talking about. An example of what you're trying to do would be helpful.
that's because in your code you raise an event on a new UserControl2. for your specific example the code of the UserControl1.button1_Click event should be like this:
private void button1_Click(object sender, RoutedEventArgs e)
{
if (this.Parent != null && this.Parent is StackPanel)
{
StackPanel parentControl = this.Parent as StackPanel;
foreach (UIElement child in parentControl.Children)
{
if (child is UserControl2)
((UserControl2)child).CallDelegate();
}
}
}
EDIT:
kay so it seems you want to get all the usercontrol2 within the window1 to be resized. then what you need is to make a recursive function to get the topmost parent, e.g (modded from hardcodet.net/2008/02/find-wpf-parent)
DependencyObject GetHighestParent(DependencyObject child)
{
ContentElement contentElement = child as ContentElement;
if (contentElement != null)
{
DependencyObject parent = ContentOperations.GetParent(contentElement);
if (parent != null) return parent;
FrameworkContentElement fce = contentElement as FrameworkContentElement;
return fce != null ? fce.Parent : null;
}
FrameworkElement frameworkElement = child as FrameworkElement;
if (frameworkElement != null)
{
DependencyObject parent = frameworkElement.Parent;
if (parent != null)
{
return GetHighestParent(parent);
}
else
{
return child;
}
}
DependencyObject visualParent = VisualTreeHelper.GetParent(child);
if (visualParent != null)
return GetHighestParent(visualParent);
else
return child;
}
then you might want to create a method to walkdown all the children like this:
void CallDelegateInAllControl2(DependencyObject parent)
{
int childCount = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < childCount; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(parent, i);
if (child is UserControl2)
{
((UserControl2)child).CallDelegate();
}
else
{
CallDelegateInAllControl2(child);
}
}
}
and then you call it within button1_click event
private void button1_Click(object sender, RoutedEventArgs e)
{
DependencyObject parent = GetHighestParent(this);
if(parent!=null)
CallDelegateInAllControl2(parent);
}
note: a walk to get parent and child might be tricky and risky i think and i believe it's a long process so you might just want to re-layout your window1 so it has a StackPanel/Grid with a usercontrol1 element and all usercontrol2 elements within it so you can use the first code i post.