i have a WPF Application with 50 comboboxes. When i started to write this application a month ago, i forgot to add a KeyUp event to all comboboxes...
Is there a way of adding this event without going to each comboboxes and write xaml code ?
<ComboBox x:Name="Actif_Vent_CB" Grid.Column="1"
SelectionChanged="Actif_Vent_CB_SelectionChanged"
KeyUp="Actif_Vent_CB_KeyUp"/>
private void Actif_Vent_CB_KeyUp(object sender, KeyEventArgs e)
{
switch (e.Key)
{
default:
break;
case Key.Delete:
case Key.Back:
((ComboBox)sender).SelectedIndex = -1;
break;
}
}
With a Dictionary ?? or something else ??
Thank you for your help
You can traverse through the layout one by one and check if the element is ComboBox and assign event listeners to them.
Call the following method in the Loaded event of your window and pass current window as visual.
public void SetEventToComboBox(Visual myVisual)
{
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(myVisual); i++)
{
// Retrieve child visual at specified index value.
Visual childVisual = (Visual)VisualTreeHelper.GetChild(myVisual, i);
// Do processing of the child visual object.
if (childVisual is ComboBox)
{
((ComboBox)childVisual).KeyUp += Actif_Vent_CB_KeyUp;
}
// Enumerate children of the child visual object.
SetEventToComboBox(childVisual);
}
}
Source:
MSDN Documentation
Related
I noticed this problem in a ListBox in my application, and then determined that the example given on MSDN for ListBox.MeasureItem suffers from the same problem.
When you set a ListBox's DrawMode to OwnerDrawVariable in order to handle the MeasureItem event ( say to draw the list items with an increased height ), the control will select the last item if you click on the empty region below the last item.
I would like it to behave the way it does when DrawMode is set to OwnerDrawFixed or Normal, and not change the item selection if the user clicks on the control below the list of items.
I tried to achieve this behavior by handling the MouseDown event and found that the control selects the bottommost item before it fires the MouseDown event.
I wonder if I need to subclass ListBox, or if there is a better way to do this.
In order to see the behavior, the code sample from MSDN suffices:
https://msdn.microsoft.com/en-us/library/system.windows.forms.listbox.measureitem(v=vs.110).aspx
You can do this by inspecting the mouse down message and not letting it process the message if the user isn't clicking on an item:
public class ListBoxEx : ListBox {
private const int WM_LBUTTONDOWN = 0x201;
protected override void WndProc(ref Message m) {
int lParam = m.LParam.ToInt32();
int wParam = m.WParam.ToInt32();
if (m.Msg == WM_LBUTTONDOWN) {
Point clickedPt = new Point();
clickedPt.X = lParam & 0x0000FFFF;
clickedPt.Y = lParam >> 16;
bool lineOK = false;
for (int i = 0; i < Items.Count; i++) {
if (GetItemRectangle(i).Contains(clickedPt)) {
lineOK = true;
}
}
if (!lineOK) {
return;
}
}
base.WndProc(ref m);
}
}
This is built-in behavior down in the Win32 control. Essentially, when you click the ListBox, a method called IndexFromPoint (you can call this yourself via the control instance) is called to determine the index of the selected item.
I tried taking full control over the process, but I couldn't find any evidence that even then you can tell the difference between clicking on an actual item or not when the control is using DrawMode.OwnerDrawVariable.
As such, it is my belief that you cannot control it. But you might dodge it:
private void ListBox1_MouseDown(object sender, MouseEventArgs e)
{
for (Int32 i = 0; i < ListBox1.Items.Count; i++)
{
var rect = ListBox1.GetItemRectangle(i);
if (rect.Contains(e.Location))
return;
}
ListBox1.SelectedIndex = -1;
}
As you noticed, the item will already be selected by the time this event fires. This simply tries to un-select it fast enough to not be noticeable. If the ListBox has a lot of items in it, you might notice it as a flicker.
This is probably the best you could do.
I need to add some decoration to the contents of a WPF TextBox control. That works fine basically, I can get the position of specified character indices and layout my other elements accordingly. But it all breaks when the TextBox is scrolled. My layout positions don't match with the displayed text anymore because it has moved elsewhere.
Now I'm pretty surprised that the TextBox class doesn't provide any information about its scrolling state, nor any events when the scrolling has changed. What can I do now?
I used Snoop to find out whether there is some scrolling sub-element that I could ask, but the ScrollContentPresenter also doesn't have any scrolling information available. I'd really like to put my decoration elements right into the scrolled area so that the scrolling can affect them, too, but there can only be a single content control and that's one of the TextBox internals already.
I'm not sure how to capture an event when the textbox has been scrolled (probably use narohi's answer for that), but there is a simple way to see what the current scroll position is:
// Gets or sets the vertical scroll position.
textBox.VerticalOffset
(From http://msdn.microsoft.com/en-us/library/system.windows.controls.primitives.textboxbase.verticaloffset(v=vs.100).aspx)
I'm using it to see if the textbox is scrolled to the end, like this:
public static bool IsScrolledToEnd(this TextBox textBox)
{
return textBox.VerticalOffset + textBox.ViewportHeight == textBox.ExtentHeight;
}
You can get the ScrollViewer with this method by passing in your textbox as the argument and the type ScrollView. Then you may subscribe to the ScrollChanged event.
public static T FindDescendant<T>(DependencyObject obj) where T : DependencyObject
{
if (obj == null) return default(T);
int numberChildren = VisualTreeHelper.GetChildrenCount(obj);
if (numberChildren == 0) return default(T);
for (int i = 0; i < numberChildren; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(obj, i);
if (child is T)
{
return (T)(object)child;
}
}
for (int i = 0; i < numberChildren; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(obj, i);
var potentialMatch = FindDescendant<T>(child);
if (potentialMatch != default(T))
{
return potentialMatch;
}
}
return default(T);
}
Example:
public MainWindow()
{
InitializeComponent();
Loaded += new RoutedEventHandler(MainWindow_Loaded);
}
void MainWindow_Loaded(object sender, RoutedEventArgs e)
{
ScrollViewer s = FindDescendant<ScrollViewer>(txtYourTextBox);
s.ScrollChanged += new ScrollChangedEventHandler(s_ScrollChanged);
}
void s_ScrollChanged(object sender, ScrollChangedEventArgs e)
{
// check event args for information needed
}
I have UserControl in wpf 4.0 which contains buttons , labels , textboxes etc....
I want to loop those controls and when I get a buuton , I want to take it's name and save it to my list . Basically , all I want to do is to create a Names_list of all my buttons in the UserControl.
I have a method that iterates all the controls and if it finds a button , it saves it's name -
public void EnumVisual(Visual myVisual)
{
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(myVisual); i++)
{
// Retrieve child visual at specified index value.
Visual childVisual = (Visual)VisualTreeHelper.GetChild(myVisual, i);
Button _button = childVisual as Button;
if (_button != null)
{
Class_Button _newButtonClass = new Class_Button();
if (_button.Name != null)
{
_newButtonClass.ButtonName = _button.Name;
}
ButtonsList.Add(_newButtonClass);
}
// Enumerate children of the child visual object.
EnumVisual(childVisual);
}
}
I always get an empty list.
When I enter in to the code by debugging it and I watch the VisualTree of my UserControl , I see all the Panels and GroupBoxes and Grids but I dont see buttons , labels and texboxes although every control has a x:Name and every control is x:FieldModifier="public". This is very odd....And I cant understand the reason for that as well as how to solve this problem...
can anyone tell what I am doing wrong?
thanks
As suggested by #GazTheDestroyer you want to make sure the control template has been applied before trying to use VisualTreeHelper. Try:
public void EnumVisual(Visual myVisual)
{
if(myVisual is FrameworkElement)
((FrameworkElement)myVisual).ApplyTemplate();
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(myVisual); i++)
{
// Retrieve child visual at specified index value.
Visual childVisual = (Visual)VisualTreeHelper.GetChild(myVisual, i);
Button _button = childVisual as Button;
if (_button != null)
{
Class_Button _newButtonClass = new Class_Button();
if (_button.Name != null)
{
_newButtonClass.ButtonName = _button.Name;
}
ButtonsList.Add(_newButtonClass);
}
// Enumerate children of the child visual object.
EnumVisual(childVisual);
}
}
You can use a tool like Snoop
or WPF Inspector
to examine the visual tree of your control.
If these tools are able to do so, the error must be somewhere in your code, right?
One great feature of Microsoft Outlook is its spacebar reading mode (with the reading pane turned on). Say there are 5 messages in your inbox and the first one is displayed. The displayed message does not entirely fit on the screen, so when you press the spacebar, that is like pagedown within the message. You hit spacebar again, and it pages down again. When you've reached the bottom of the page, and you press spacebar again, it goes to the next message.
What is a good way to do this in WPF (where the application is built using the MVVM pattern)? With MVVM, I use a bunch of DataTemplates instead of usercontrols.
Edit: I should mention that I am using a ListBox for the messages and a FlowDocumentScrollViewer for the message body.
Use Expression Blend's KeyTrigger to invoke the Command in your view model
http://msdn.microsoft.com/en-us/library/microsoft.expression.interactivity.input.keytrigger%28v=expression.40%29.aspx
OR
Use CommandReference from MVVM Toolkit How do I associate a keypress with a DelegateCommand in Composite WPF?
For posterity, here's my solution to the scrolling part of the question. This code handles the space first, then, if the scroll bar is already at the bottom, it doesn't handle the KeyDown. #Hasan's recomended commend fires at that point.
internal class FlowDocumentScrollViewer2 : FlowDocumentScrollViewer
{
private static bool PageDown<T>(T listView)
where T : DependencyObject
{
var scrollViewer = GetVisualChild<ScrollViewer>(listView, null);
var scrollBar = GetVisualChild<ScrollBar>(listView,
bar => bar.Orientation == Orientation.Vertical);
var formerOffset = scrollBar.Track.Value;
scrollViewer.PageDown();
scrollBar.Track.UpdateLayout();
return formerOffset < scrollBar.Track.Value;
}
private static T GetVisualChild<T>(DependencyObject parent, Predicate<T> predicate)
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(v, predicate);
}
if (child != null && (predicate == null || predicate(child)))
{
break;
}
}
return child;
}
public FlowDocumentScrollViewer2()
{
PreviewKeyDown += PreviewSpaceDown;
}
private void PreviewSpaceDown(object sender, KeyEventArgs e)
{
if (e.Handled)
return;
if (e.Key == Key.Space)
{
e.Handled = PageDown(this);
}
}
}
I am trying to create a Blend behavior related to ComboBoxes. In order to get the effect I want, the ItemsPanel of the ComboBox has to have a certain element added to it. I don't want to do this in every ComboBox that uses the behavior, so I want the Behavior to be able to inject the ItemsPanelTemplate programmatically. However, I can't seem to find a way to do this. ItemsPanelTemplate does not seem to have a property/method that lets me set the visual tree. WPF ItemsPanelTemplate has the VisualTree but Silverlight does not.
Basically, what is the programmatic equivalent of this XAML?
<ComboBox>
<ComboBox.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel/>
</ItemsPanelTemplate>
</ComboBox.ItemsPanel>
</ComboBox>
Edit:
Okay apparently that is not an easy question, so I started a bounty and I'm going to give some more background in case there is another way to go about this. I want to provide keyboard support for the Silverlight ComoboBox. Out of the box it only supports the up and down arrows but I also want it to work so that when the user hits a letter, the ComboBox jumps to the first item of that letter, similar to how ComboBoxes work in a browser or Windows app.
I found this blog post, which got me half way. Adapting that behavior code, the ComboBox will change selection based on letter input. However, it does not work when the ComboBox is opened. The reason for this, according to this blog post is that when the ComboBox is opened, you are now interacting with its ItemsPanel and not the ComboBox itself. So according to that post I actually need to add a StackPanel to the ItemsPanelTemplate and subscribe to the StackPanel's KeyDown event, in order to take action when the ComboBox is opened.
So that is what prompted my question of how to get a StackPanel into the ItemsPanelTemplate of a ComboBox, from a behavior. If that is not possible, are there alternative ways of getting this to work? Yes, I know I could go to each ComboBox in the application and add a StackPanel and the event. But I want to do this through a behavior so that I don't have to modify every ComboBox in the app, and so I can reuse this logic across applications.
AnthonyWJones' answer below using XamlReader gets me part way, in that I can create the StackPanel and get it into the template. However, I need to be able to get at that SP programmatically in order to subscribe to the event.
This should work. I've shown how you can change the orientation below. You can add additional SetValue calls to modify other properties.
cb.ItemsPanel = new ItemsPanelTemplate();
var stackPanelFactory = new FrameworkElementFactory(typeof (StackPanel));
// Modify it like this:
stackPanelFactory.SetValue(StackPanel.OrientationProperty, Orientation.Horizontal);
// Set the root of the template to the stack panel factory:
cb.ItemsPanel.VisualTree = stackPanelFactory;
You can find more detailed information in this article: http://www.codeproject.com/KB/WPF/codeVsXAML.aspx
What you actually want to build programmatically is this:-
<ItemsPanelTemplate>
<StackPanel />
</ItemsPanelTemplate>
Your behaviour will then assign this to the ItemsPanel property of the ComboBox it is attached to. Currently your behaviour is pure code but there is no way to create the above purely in code.
Since this is such a small piece for of Xaml the easiest approach is to use the XamlReader:-
ItemsPanelTemplate itemsPanelTemplate = XamlReader.Load("<ItemsPanelTemplate><StackPanel /></ItemsPanelTemplate>");
I think, best way for you - extend combobox functionality not via behavior but using inheritance.
So, you can create own control MyComboBox:ComboBox. Create style for it - get default ComboBox Style
here
And write instead (look for ScrollViewer by name):
< ScrollViewer x:Name="ScrollViewer" BorderThickness="0" Padding="1" >
< ItemsPresenter />
< /ScrollViewer >
this
< ScrollViewer x:Name="ScrollViewer" BorderThickness="0" Padding="1" >
< StackPanel x:Name="StackPanel" >
< ItemsPresenter />
< /StackPanel >
< /ScrollViewer >
This StackPanel you can get in code:
public class MyComboBox: ComboBox{
public CM()
{
DefaultStyleKey = typeof (MyComboBox);
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
StackPanel stackPanel = (StackPanel)GetTemplateChild("StackPanel");
stackPanel.KeyUp += (s, e) => { /*do something*/ };
}
}
Inheritance is more powerful. It's allow work with template elements.
If you decided to inject ItemsPanel, you must understand that:
1)it's impossible from code with keeping reference on injected panel.
2)to get reference to injected panel, this panel must registered itself in some storage, e.g.
< ComboBox>
< ComboBox.ItemsPanel>
< ItemsPanelTemplate>
< StackPanel>
< i:Interaction.EventTriggers>
< i:EventTrigger EventName="Loaded">
< RegisterMyInstanceInAccessibleFromCodePlaceAction/>
< /i:EventTrigger>
< /i:Interaction.EventTriggers>
< /StackPanel>
< /ItemsPanelTemplate>
< /ComboBox.ItemsPanel>
< /ComboBox>
Good luck!
I found your post while trying to set the ItemsPanel from code so that I can implement a VirtualizingStackPanel. When there are hundreds of items in my list, performance sucks. Anyway .. here's how I did it.
1) Custom control
2) Custom Behavior
-- you could also just apply this behavior to the normal ComboBox - either at each instance, or through a style.
-- you might also expose the timeout value so that can be overridden in xaml ..
-- also, it seems this doesn't work when the dropdown itself is open. not sure why exactly .. never looked into it
1..
public class KeyPressSelectionComboBox : ComboBox
{
private BindingExpression _bindingExpression;
public KeyPressSelectionComboBox()
: base()
{
Interaction.GetBehaviors(this).Add(new KeyPressSelectionBehavior());
Height = 22;
this.SelectionChanged += new SelectionChangedEventHandler(KeyPressSelectionComboBox_SelectionChanged);
}
void KeyPressSelectionComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (_bindingExpression == null)
{
_bindingExpression = this.GetBindingExpression(ComboBox.SelectedValueProperty);
}
else
{
if (this.GetBindingExpression(ComboBox.SelectedValueProperty) == null)
{
this.SetBinding(ComboBox.SelectedValueProperty, _bindingExpression.ParentBinding);
}
}
}
}
2...
/// <summary>
/// This behavior can be attached to a ListBox or ComboBox to
/// add keyboard selection
/// </summary>
public class KeyPressSelectionBehavior : Behavior<Selector>
{
private string keyDownHistory = string.Empty;
private double _keyDownTimeout = 2500;
private DateTime _lastKeyDownTime;
private DateTime LastKeyDownTime
{
get
{
if (this._lastKeyDownTime == null)
this._lastKeyDownTime = DateTime.Now;
return this._lastKeyDownTime;
}
set { _lastKeyDownTime = value; }
}
/// <summary>
/// Gets or sets the Path used to select the text
/// </summary>
public string SelectionMemberPath { get; set; }
/// <summary>
/// Gets or sets the Timeout (ms) used to reset the KeyDownHistory item search string
/// </summary>
public double KeyDownTimeout
{
get { return _keyDownTimeout; }
set { _keyDownTimeout = value; }
}
public KeyPressSelectionBehavior() { }
/// <summary>
/// Attaches to the specified object: subscribe on KeyDown event
/// </summary>
protected override void OnAttached()
{
base.OnAttached();
this.AssociatedObject.KeyDown += DoKeyDown;
}
void DoKeyDown(object sender, KeyEventArgs e)
{
// Create a list of strings and indexes
int index = 0;
IEnumerable<Item> list = null;
var path = SelectionMemberPath ??
this.AssociatedObject.DisplayMemberPath;
var evaluator = new BindingEvaluator();
if (path != null)
{
list = this.AssociatedObject.Items.OfType<object>()
.Select(item =>
{
// retrieve the value using the supplied Path
var binding = new Binding();
binding.Path = new PropertyPath(path);
binding.Source = item;
BindingOperations.SetBinding(evaluator,
BindingEvaluator.TargetProperty, binding);
var value = evaluator.Target;
return new Item
{
Index = index++,
Text = Convert.ToString(value)
};
});
}
else
{
list = this.AssociatedObject.Items.OfType<ListBoxItem>()
.Select(item => new Item
{
Index = index++,
Text = Convert.ToString(item.Content)
});
}
// Sort the list starting at next selectedIndex to the end and
// then from the beginning
list = list.OrderBy(item => item.Index <=
this.AssociatedObject.SelectedIndex ?
item.Index + this.AssociatedObject.Items.Count : item.Index);
// calculate how long has passed since the user typed a letter
var elapsedTime = DateTime.Now - this.LastKeyDownTime;
if (elapsedTime.TotalMilliseconds <= this.KeyDownTimeout)
{ /* if it's less than the timeout, add to the search string */
this.keyDownHistory += GetKeyValue(e);
}
else
{ /* otherwise replace it */
this.keyDownHistory = GetKeyValue(e);
}
// Find first starting with the search string
var searchText = this.keyDownHistory;
var first = list.FirstOrDefault(item =>
item.Text.StartsWith(searchText, StringComparison.InvariantCultureIgnoreCase));
if (first != null)
{ /* found */
this.AssociatedObject.SelectedIndex = first.Index;
}
else
{ /* not found - so reset the KeyDownHistory */
this.keyDownHistory = string.Empty;
}
// reset the last time a key was pressed
this.LastKeyDownTime = DateTime.Now;
}
/// <summary>
/// Gets the value of the pressed key,
/// specifically converting number keys from their "Dx" value to their expected "x" value
/// </summary>
/// <param name="e"></param>
/// <returns></returns>
private static string GetKeyValue(KeyEventArgs e)
{
string rValue = string.Empty;
switch (e.Key)
{
default:
rValue = e.Key.ToString();
break;
case Key.D0:
case Key.NumPad0:
rValue = (0).ToString();
break;
case Key.D1:
case Key.NumPad1:
rValue = (1).ToString();
break;
case Key.D2:
case Key.NumPad2:
rValue = (2).ToString();
break;
case Key.D3:
case Key.NumPad3:
rValue = (3).ToString();
break;
case Key.D4:
case Key.NumPad4:
rValue = (4).ToString();
break;
case Key.D5:
case Key.NumPad5:
rValue = (5).ToString();
break;
case Key.D6:
case Key.NumPad6:
rValue = (6).ToString();
break;
case Key.D7:
case Key.NumPad7:
rValue = (7).ToString();
break;
case Key.D8:
case Key.NumPad8:
rValue = (8).ToString();
break;
case Key.D9:
case Key.NumPad9:
rValue = (9).ToString();
break;
}
return rValue;
}
/// <summary>
/// Helper class
/// </summary>
private class Item
{
public int Index;
public string Text;
}
/// <summary>
/// Helper class used for property path value retrieval
/// </summary>
private class BindingEvaluator : FrameworkElement
{
public static readonly DependencyProperty TargetProperty =
DependencyProperty.Register(
"Target",
typeof(object),
typeof(BindingEvaluator), null);
public object Target
{
get { return GetValue(TargetProperty); }
set { SetValue(TargetProperty, value); }
}
}
}