I have an ItemsControl that is databound to a ObservableCollection. I have this method in the code behind which adds a new model to the list. I would then like to scroll the new item (at the bottom of the list) into view.
I think the size of the ItemsControl is not yet updated when I am querying the size, since the ActualHeight before and after the addition of the model is the same. The effect of this code is to scroll to a point slightly above the new item.
How would I know what the new ActualHeight is going to be?
Here is my code:
ViewModel.CreateNewChapter();
var height = DocumentElements.ActualHeight;
var width = DocumentElements.ActualWidth;
DocumentElements.BringIntoView(new Rect(0, height - 1, width, 1));
I think you need to call BringIntoView on the item container, not the ItemsControl itself :
var container = DocumentElements.ItemContainerGenerator.ContainerFromItem(model) as FrameworkElement;
if (container != null)
container.BringIntoView();
EDIT: actually this doesn't work, because at this point, the item container hasn't been generated yet... You could probably handle the StatusChanged event of the ItemContainerGenerator. I tried the following code :
public static class ItemsControlExtensions
{
public static void BringItemIntoView(this ItemsControl itemsControl, object item)
{
var generator = itemsControl.ItemContainerGenerator;
if (!TryBringContainerIntoView(generator, item))
{
EventHandler handler = null;
handler = (sender, e) =>
{
switch (generator.Status)
{
case GeneratorStatus.ContainersGenerated:
TryBringContainerIntoView(generator, item);
break;
case GeneratorStatus.Error:
generator.StatusChanged -= handler;
break;
case GeneratorStatus.GeneratingContainers:
return;
case GeneratorStatus.NotStarted:
return;
default:
break;
}
};
generator.StatusChanged += handler;
}
}
private static bool TryBringContainerIntoView(ItemContainerGenerator generator, object item)
{
var container = generator.ContainerFromItem(item) as FrameworkElement;
if (container != null)
{
container.BringIntoView();
return true;
}
return false;
}
}
However it doesn't work either... for some reason, ContainerFromItem still returns null after the status changes to ContainersGenerated, and I have no idea why :S
EDIT : OK, I understand now... this was because of the virtualization : the containers are generated only when they need to be displayed, so no containers are generated for hidden items. If you switch virtualization off for the ItemsControl (VirtualizingStackPanel.IsVirtualizing="False"), the solution above works fine.
Related
The following code is supposed to scroll an item into view and set focus to the first child control in the template:
lv.ScrollIntoView(lv.SelectedItem);
var lvi = lv.SelectedListViewItem();
//get the item's template parent
var templateParent = lvi.GetFrameworkElementByName<ContentPresenter>();
if (templateParent != null) <--but it's always null
{
var ctrl = templateParent.FindVisualChildren<FrameworkElement>().First();
ctrl.Focus();
}
The problem is that if the ListViewItem is not visible, then templateParent is null, and this code doesn't work. And of course this code is only useful when the item isn't already visible.
Is there a way to scroll the item into view and then be notified when it has come into view so that the template will be non-null so that the ctrl.Focus() code would execute?
You could handle the RequestBringIntoView event. Please refer to the following sample code.
public MainWindow()
{
InitializeComponent();
lv.ItemsSource = Enumerable.Range(1, 100);
lv.SelectedItem = 90;
lv.ScrollIntoView(lv.SelectedItem);
lv.RequestBringIntoView += Lv_RequestBringIntoView;
}
private void Lv_RequestBringIntoView(object sender, RequestBringIntoViewEventArgs e)
{
var container = lv.ItemContainerGenerator.ContainerFromItem(lv.SelectedItem);
if (container != null)
{
//...
}
}
I am trying to create a WPF custom slider control that acts as a scrollbar for a Listview. I'm doing this by putting the name of the listview in the Tag attribute of my custom slider and then using the slider's OnValueChange event to scroll the listview. This works great, however, when I scroll in the listview with my mousewheel the slider doesn't move. What I need is a way to attach a method to the listview's MouseWheel event when my custom slider initializes. Here is what I've tried:
Custom slider class:
public class LabeledScrollbar : Slider
{
public override void EndInit()
{
var listbox = (ListBox)this.FindName(this.Tag.ToString());
if (listbox != null)
{
listbox.MouseWheel += new MouseWheelEventHandler(this.OnMouseWheel);
}
base.EndInit();
}
protected void OnMouseWheel(object sender, MouseWheelEventArgs e)
{
this.Value += 5;
}
protected override void OnValueChanged(double oldValue, double newValue)
{
var listBox = (ListBox)this.FindName(this.Tag.ToString());
var collection = (CollectionView)CollectionViewSource.GetDefaultView(listBox.ItemsSource);
if (newValue == this.Maximum)
{
if (VisualTreeHelper.GetChildrenCount(listBox) > 0)
{
var chrome = VisualTreeHelper.GetChild(listBox, 0);
var scrollView = (ScrollViewer)VisualTreeHelper.GetChild(chrome, 0);
scrollView.ScrollToTop();
}
}
else
{
var index = (collection.Count - 1) - (int)Math.Floor(newValue);
var selectedItem = collection.GetItemAt(index);
listBox.ScrollIntoView(selectedItem);
}
}
}
XAML:
<ListView x:Name="listViewCategories">
...
</ListView>
<local:LabeledScrollbar x:Name="categoryScrollbar" Orientation="Vertical" TickPlacement="BottomRight" Tag="listViewCategories"></local:LabeledScrollbar>
While it seems like OnMouseWheel should fire when the I scroll in the listview, it's not happening and I haven't been able to find anything else to try. Is there a way to do what I want in WPF? I know I could put a method in the code behind of my view to make the MouseScroll event of the listview move the slider, but I was hoping to encapsulate as much of the logic for the slider in the slider class as possible.
So it seems that the trick was to use PreviewMouseWheel instead of MouseWheel. For future reference here is my current class:
/// <summary>
/// This class creates a custom control that can be used as a scrollbar for a listbox that displays the current
/// group visible in the listbox on a small label next to the slider thumb.
///
/// To use it, set the Tag value to the name of the listbox the scollbar will be controlling.
/// </summary>
public class LabeledScrollbar : Slider
{
//Tracks control initialization to ensure it only gets loaded once
private bool initialized = false;
//The listview this slider will control
private ListView listView;
public LabeledScrollbar(): base()
{
this.Loaded += LabeledScrollbar_Loaded;
}
void LabeledScrollbar_Loaded(object sender, System.Windows.RoutedEventArgs e)
{
//The tag must be set to the name of a listbox
listView = (ListView)this.FindName(this.Tag.ToString());
if (listView != null && !this.initialized)
{
//Make sure that the mouse wheel event in the linked listbox is handled
listView.PreviewMouseWheel += (s, ev) =>
{
if (ev.Delta > 0)
this.Value += 3;
else
this.Value -= 3;
};
//Move scrollbar and list to the top if the collection changes
((INotifyCollectionChanged)listView.Items).CollectionChanged += (s, ev) =>
{
this.Maximum = ((ItemCollection)listView.Items).Count - 1;
this.Value = this.Maximum;
};
//Get the max value of the slider by checking the tag value and looking up the associated listbox
this.Maximum = ((ItemCollection)listView.Items).Count - 1;
this.Value = this.Maximum;
this.initialized = true;
}
}
protected override void OnValueChanged(double oldValue, double newValue)
{
//Refresh the tickbar so that it will render for a new value
InvalidateTickbar();
//Scroll the list box to the correct location
ScrollToIndex(newValue);
}
private void ScrollToIndex(double newValue)
{
if (newValue == this.Maximum)
{
//ScrollIntoView method does not scroll to the top so
//we need to access the scrollview to move the slider to the top
if (VisualTreeHelper.GetChildrenCount(listView) > 0)
{
var chrome = VisualTreeHelper.GetChild(listView, 0);
var scrollView = (ScrollViewer)VisualTreeHelper.GetChild(chrome, 0);
scrollView.ScrollToTop();
}
}
else
{
var collection = (CollectionView)CollectionViewSource.GetDefaultView(listView.ItemsSource);
var index = (collection.Count - 1) - (int)Math.Floor(newValue);
var selectedItem = collection.GetItemAt(index);
listView.ScrollIntoView(selectedItem);
}
}
private void InvalidateTickbar()
{
//update the tickbar for the new position
if (VisualTreeHelper.GetChildrenCount(this) > 0)
{
var firstChild = VisualTreeHelper.GetChild(this, 0);
if (VisualTreeHelper.GetChildrenCount(firstChild) > 0)
{
var secondChild = (CustomTickBar)VisualTreeHelper.GetChild(firstChild, 0);
secondChild.InvalidateVisual();
}
}
}
}
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 have Accordion which is bound to ObservableCollection. I need to apply workaround to make Accordion resize its children to the content (ie if an item has been deleted from the bound collection I need the accordion to shrink, and if added - to expand).
However all the workaround I found use AccordionItem objects. They all have AccordionItem items set in XAML so their accordion.Items are collections of AccordionItem objects.
Although I am binding to myObject they are placed in AccordionItem object in the ItemContainerStyleTemplate. The only thing I need is to access that AccordionItem somehow. If I try something like accordion.Items[0].GetType() it returns myObject.
So the question is - how do I access AccordionItem object from data bound Accordion?
The workaround I wanted to try: (EDIT: It does work as I needed)
public static void UpdateSize(this AccordionItem item)
{
item.Dispatcher.BeginInvoke(
delegate
{
if (!item.IsLocked && item.IsSelected)
{
item.IsSelected = false;
item.InvokeOnLayoutUpdated(delegate { item.IsSelected = true; });
}
});
}
I've had to do similar things to Accordions, and the only way I was able to get down to the AccordionItems was by walking the visual tree.
Here's how I did it: Given these extension methods :
public static IEnumerable<DependencyObject> GetAllChildrenOfType(this DependencyObject depObject, Type t, bool recursive = true)
{
List<DependencyObject> objList = new List<DependencyObject>();
var childrenList = depObject.GetChildren();
foreach (DependencyObject i in childrenList)
{
Type ct = i.GetType();
if (ct == t)
objList.Add(i);
if (recursive)
objList.AddRange(i.GetAllChildrenOfType(t));
}
return objList.ToArray();
}
public static IEnumerable<DependencyObject> GetChildren(this DependencyObject depObject)
{
int count = depObject.GetChildrenCount();
for (int i = 0; i < count; i++)
{
yield return VisualTreeHelper.GetChild(depObject, i);
}
}
Now you can get all the AccordionItems in a given Accordion:
var accordionItemList = myAccordion.GetAllChildrenOfType(typeof(AccordionItem));
foreach (AccordionItem i in accordionItemList)
{...}
This may be a bit more complicated than needed, in my instance I had an accordion within the accordion, which made things difficult in the end.
I have several Silverlight controls on a page and want query all the controls that are of type TextBox and have that working.
Now the Silverlight form I'm working on could have more TextBox controls added. So when I test to see if a TextBox control has a value, I could do:
if (this.TextBox.Control.value.Text() != String.Empty)
{
// do whatever
}
but I'd rather have if flexible that I can use this on ANY Silverlight form regardless of the number of TextBox controls I have.
Any ideas on how I would go about doing that?
I have already faced this issue and notify it here : http://megasnippets.com/en/source-codes/silverlight/Get_all_child_controls_recursively_in_Silverlight
Here you have a generic method to find recursively in the VisualTree all TextBoxes:
IEnumerable<DependencyObject> GetChildrenRecursively(DependencyObject root)
{
List<DependencyObject> children = new List<DependencyObject>();
children.Add(root);
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(root); i++)
children.AddRange(GetChildrenRecursively(VisualTreeHelper.GetChild(root, i)));
return children;
}
Use this method like this to find all TextBoxes:
var textBoxes = GetChildrenRecursively(LayoutRoot).OfType<TextBox>();
It sounds like you need a recursive routine like GetTextBoxes below:
void Page_Loaded(object sender, RoutedEventArgs e)
{
// Instantiate a list of TextBoxes
List<TextBox> textBoxList = new List<TextBox>();
// Call GetTextBoxes function, passing in the root element,
// and the empty list of textboxes (LayoutRoot in this example)
GetTextBoxes(this.LayoutRoot, textBoxList);
// Now textBoxList contains a list of all the text boxes on your page.
// Find all the non empty textboxes, and put them into a list.
var nonEmptyTextBoxList = textBoxList.Where(txt => txt.Text != string.Empty).ToList();
// Do something with each non empty textbox.
nonEmptyTextBoxList.ForEach(txt => Debug.WriteLine(txt.Text));
}
private void GetTextBoxes(UIElement uiElement, List<TextBox> textBoxList)
{
TextBox textBox = uiElement as TextBox;
if (textBox != null)
{
// If the UIElement is a Textbox, add it to the list.
textBoxList.Add(textBox);
}
else
{
Panel panel = uiElement as Panel;
if (panel != null)
{
// If the UIElement is a panel, then loop through it's children
foreach (UIElement child in panel.Children)
{
GetTextBoxes(child, textBoxList);
}
}
}
}
Instantiate an empty list of TextBoxes. Call GetTextBoxes, passing in the root control on your page (in my case, that's this.LayoutRoot), and GetTextBoxes should recursively loop through every UI element that is a descendant of that control, testing to see if it's either a TextBox (add it to the list), or a panel, that might have descendants of it's own to recurse through.
Hope that helps. :)
From your top most panel you can do this (my grid is called ContentGrid)
var textBoxes = this.ContentGrid.Children.OfType<TextBox>();
var nonEmptyTextboxes = textBoxes.Where(t => !String.IsNullOrEmpty(t.Text));
foreach (var textBox in nonEmptyTextboxes)
{
//Do Something
}
However this will only find the textboxes that are immediate children. Some sort of recursion like below would help, but I'm thinking there must be a better way.
private List<TextBox> SearchForTextBoxes(Panel panel)
{
List<TextBox> list = new List<TextBox>();
list.AddRange(panel.Children.OfType<TextBox>()
.Where(t => !String.IsNullOrEmpty(t.Text)));
var panels = panel.Children.OfType<Panel>();
foreach (var childPanel in panels)
{
list.AddRange(SearchForTextBoxes(childPanel));
}
return list;
}
Took Scott's initial idea and expanded it so that it
Uses generics, so it easily copes with multiple control types.
Supports more container types. In my WP7 I needed to support panaorama's, scroll viewers etc... which aren't Panels. So this allows support for them.
Biggest issue is that string comparing, especially on the Panel and derrived items.
Code:
private static void GetControls<T>(UIElement uiElement, List<T> controlList) where T : UIElement
{
var frameworkFullName = uiElement.GetType().FullName;
if (frameworkFullName == typeof(T).FullName)
{
controlList.Add(uiElement as T);
return;
}
if (frameworkFullName == typeof(Panel).FullName ||
frameworkFullName == typeof(Grid).FullName ||
frameworkFullName == typeof(StackPanel).FullName)
{
foreach (var child in (uiElement as Panel).Children)
{
GetControls(child, controlList);
}
return;
}
if (frameworkFullName == typeof(Panorama).FullName)
{
foreach (PanoramaItem child in (uiElement as Panorama).Items)
{
var contentElement = child.Content as FrameworkElement;
if (contentElement != null)
{
GetControls(contentElement, controlList);
}
}
return;
}
if (frameworkFullName == typeof(ScrollViewer).FullName)
{
var contentElement = (uiElement as ScrollViewer).Content as FrameworkElement;
if (contentElement != null)
{
GetControls(contentElement, controlList);
}
return;
}
}
Similar logic to ideas above to also handle controls with a "Content" attribute like TabItems and Scrollviewers where children might be embedded at a lower level. Finds all children:
IEnumerable<DependencyObject> GetControlsRecursive(DependencyObject root)
{
List<DependencyObject> elts = new List<DependencyObject>();
elts.Add(root);
string type = root.GetType().ToString().Replace("System.Windows.Controls.", "");
switch (root.GetType().ToString().Replace("System.Windows.Controls.", ""))
{
case "TabItem":
var TabItem = (TabItem)root;
elts.AddRange(GetControlsRecursive((DependencyObject)TabItem.Content));
break;
case "ScrollViewer":
var Scroll = (ScrollViewer)root;
elts.AddRange(GetControlsRecursive((DependencyObject) Scroll.Content));
break;
default: //controls that have visual children go here
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(root); i++) elts.AddRange(GetControlsRecursive(VisualTreeHelper.GetChild(root, i)));
break;
}
return elts;
}