I use VS2010, C# to develop Silverlight 4 app, I use following code in my XAML file:
<Canvas x:Name="Scene" FlowDirection="LeftToRight" Background="White" KeyDown="Scene_KeyDown" MouseMove="Scene_MouseMove">
and this is my XAML.cs file, I want to display a message box if any key is pressed (it is for test only):
private void Scene_KeyDown(object sender, KeyEventArgs e)
{
MessageBox.Show("1");
}
but nothing is displayed after keys are pressed! what is going wrong? should I set any property? command? tabstop? keypreview?
please help me
Looks like this answer will solve your problem:
You need to have at least something inside the Canvas that can receive
focus, and you will find that the event will bubble up.
I have seen a few posts addressing how to remove an UserControl that has been added during runtime, but my problem is a little different. I have a UserControl that consists of an image with a small "x" button on the top right corner that is used to remove itself (the UserControl) from its parent canvas. Also to note is that the UserControl is added during runtime when the user doubleclicks on a ListboxItem. I have a Click event handler for the top right corner button but this code is not running at all. I know this because I have a breakpoint in this code which is not reached when I click the button.
So,
Why isn't the click event of the remove button being handled?
Maybe there is a better way to implement this. Please advise.
Here's the code used for adding it:
private void MyListBox_MouseDoubleClick(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
if (e.OriginalSource.ToString() == "System.Windows.Controls.Border" || e.OriginalSource.ToString() == "System.Windows.Controls.Image" || e.OriginalSource.ToString() == "System.Windows.Controls.TextBlock")
{
Expression.Blend.SampleData.MyCollection.Dataset lbi = ((sender as ListBox).SelectedItem as Expression.Blend.SampleData.MyCollection.Dataset);
var new_usercontrol = new MyUserControl();
new_usercontrol.MyImageSourceProperty = lbi.Image;
MyCanvas.Children.Add(new_usercontrol);
Canvas.SetLeft(new_usercontrol, 100);
Canvas.SetTop(new_usercontrol, 100);
Canvas.SetZIndex(new_usercontrol, 100);
}
}
The following is the cs code for the UserControl:
public partial class ModuleElement : UserControl
{
public ImageSource MyProperty
{
get { return (ImageSource)this.image.Source; }
set { this.image.Source = value; }
}
public ModuleElement()
{
this.InitializeComponent();
}
private void RemoveButton_Click(object sender, RoutedEventArgs e)
{
((Canvas)this.Parent).Children.Remove(this);
}
}
The XAML:
<Grid x:Name="LayoutRoot">
<Image x:Name="image" />
<Button x:Name="RemoveButton" Content="X" HorizontalAlignment="Right" Height="17.834" Margin="0" VerticalAlignment="Top" VerticalContentAlignment="Center" HorizontalContentAlignment="Center" Click="RemoveButton_Click">
</Button>
</Grid>
Thanks in advance,
Bryan
So I tried your code here exactly except for some name changes and could not reproduce your issue. In my personal experience your issue here has to be that for some reason the event for the click isn't subscribed to properly. For this I would go into designer for the user control, wipe out the current event for the button and double click in the designer event textbox such that VS or Blend generates all the code necessary for a proper subscription.
I have created a sample based on your code here. Feel free to pull it down and take a look to see if you can find any inconsistencies.
As far as a better way to implement this, check out the good old MVVM pattern and the MVVM Light Toolkit. With this you can have a central ViewModel class that will handle all of your button commands and binding without code behind.
I am trying to bubble an event from a child usercontrol to its parent.
The child usercontrol is a button inside a grid:
<UserControl>
<Grid>
<Button Click="Button_Click" />
</Grid>
</UserControl>
The parent usercontrol is composed by many instances of the child control:
<UserControl>
<StackPanel>
<customs:myButton CustomClick="something" />
<customs:myButton CustomClick="something" />
<customs:myButton CustomClick="something" />
etc.
</StackPanel>
</UserControl>
In the child usercontrol I have defined:
public delegate void CustomClickHandler(object sender, EventArgs e);
public event CustomClickHandler CustomClick;
and the "inner" button handles the click event in this way:
private void Button_Click(object sender, EventArgs e)
{
if (CustomClick != null)
CustomClick (sender, e);
}
I've tried to check what it is going on, and I can see the Button_Click is invoked, CustomClick is not null and it gets executed. However nothing seems to happen, the code attached to that even in the parent usercontrol is not called.
Any suggestion?
Thanks in advance,
Cheers,
Gianluca.
What you are seeking is called routed events. You can write your own custom ones or take a look at this library.
Ok, I have sorted this out, there were few problems though.
The first issue was caused by IsHitTestVisible. In some online articles it was said to set that property to false, in order to resolve some mouse-event related issues. I did so, but that was wrong because the element with that property set to false was "catching" the mouse events, and they were not arriving anymore to the inner usercontrols.
Secondly, in the most internal button (see my post above to understand the scenario), in order to get this to work, I've had to set the ClickMode="Hover" and to handle the MouseLeftButtonUp event. I'll try to use the standard click but I read somewhere that only certain event bubble up...
e.Handled did not need any change: I've checked and it was already false.
Neither I had to use any RoutedEvent library...
I cannot think of anything else I did to resolve the issue.
I guess this is all.
As always, if you have any suggestion, please feel free to add them here.
Cheers,
Gianluca.
When trying to use a Slider control I'd like to listen to the MouseLeftButtonDown and MouseLeftButtonUp. I have handlers set up for both events. The MouseLeftButtonUp works as expected. MouseLeftButtonDown is not raised at all.
Any ideas why?
I've done a bit of googling and it seems that the WPF doesn't fire either. One of the solutions (in this post) was to use the Preview version of the events which is something silverlight doesn't support.
Is there any simple solution to this that I'm not seeing?
Thanks
J
It happens because Slider handles mouse down/up events. Internally its implemented as two RepeatButtons and a thumb in the middle. When you click on left or right side of the slider your mouse events are handled by RepeatButtons, and you don't get them.
If you still want to handle handled event you can use AddHandler() method. Here is Silverlight example:
XAML
<Slider Width="100"
VerticalAlignment="Top"
Minimum="0"
Maximum="100"
Name="sl" />
C#
public partial class MainPage : UserControl
{
public MainPage()
{
InitializeComponent();
sl.AddHandler(MouseLeftButtonDownEvent, new MouseButtonEventHandler(Slider_MouseLeftButtonDown), true);
sl.AddHandler(MouseLeftButtonUpEvent, new MouseButtonEventHandler(Slider_MouseLeftButtonUp), true);
}
private void Slider_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
}
private void Slider_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
}
}
In WPF situation is almost same (small differences in names).
I have a UserControl which contains a TextBox. When my main window loads I want to set the focus to this textbox so I added Focusable="True" GotFocus="UC_GotFocus" to the UserControls definition and FocusManager.FocusedElement="{Binding ElementName=login}" to my main windows definition. In the UC_GotFocus method i simply call .Focus() on the control i want to focus on but this doesn't work.
All i need to do is have a TextBox in a UserControl receive focus when the application starts.
Any help would be appreciated, thanks.
I recently fixed this problem for a login splash screen that is being displayed via a storyboard when the main window is first loaded.
I believe there were two keys to the fix. One was to make the containing element a focus scope. The other was to handle the Storyboard Completed event for the storyboard that was triggered by the window being loaded.
This storyboard makes the username and password canvas visible and then fades into being 100% opaque. The key is that the username control was not visible until the storyboard ran and therefore that control could not get keyboard focus until it was visible. What threw me off for awhile was that it had "focus" (i.e. focus was true, but as it turns out this was only logical focus) and I did not know that WPF had the concept of both logical and keyboard focus until reading Kent Boogaart's answer and looking at Microsoft's WPF link text
Once I did that the solution for my particular problem was straightforward:
1) Make the containing element a focus scope
<Canvas FocusManager.IsFocusScope="True" Visibility="Collapsed">
<TextBox x:Name="m_uxUsername" AcceptsTab="False" AcceptsReturn="False">
</TextBox>
</Canvas>
2) Attach a Completed Event Handler to the Storyboard
<Storyboard x:Key="Splash Screen" Completed="UserNamePassword_Storyboard_Completed">
...
</Storyboard>
and
3) Set my username TextBox to have the keyboard focus in the storyboard completed event handler.
void UserNamePassword_Storyboard_Completed(object sender, EventArgs e)
{
m_uxUsername.Focus();
}
Note that calling item.Focus() results in the call Keyboard.Focus(this), so you don't need to call this explicitly. See this question about the difference between Keyboard.Focus(item) and item.Focus.
Its stupid but it works:
Pop a thread that waits a while then comes back and sets the focus you want. It even works within the context of an element host.
private void ListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
System.Threading.ThreadPool.QueueUserWorkItem(
(a) =>
{
System.Threading.Thread.Sleep(100);
someUiElementThatWantsFocus.Dispatcher.Invoke(
new Action(() =>
{
someUiElementThatWantsFocus.Focus();
}));
}
);
}
Just recently I had a list-box that housed some TextBlocks. I wanted to be able to double click on the text block and have it turn into a TextBox, then focus on it and select all the text so the user could just start typing the new name (Akin to Adobe Layers)
Anyway, I was doing this with an event and it just wasn't working. The magic bullet for me here was making sure that I set the event to handled. I figure it was setting focus, but as soon as the event went down the path it was switching the logical focus.
The moral of the story is, make sure you're marking the event as handled, that might be your issue.
“When setting initial focus at application startup, the element to
receive focus must be connected to a PresentationSource and the
element must have Focusable and IsVisible set to true. The recommended
place to set initial focus is in the Loaded event handler"
(MSDN)
Simply add a "Loaded" event handler in the constructor of your Window (or Control), and in that event handler call the Focus() method on the target control.
public MyWindow() {
InitializeComponent();
this.Loaded += new RoutedEventHandler(MyWindow_Loaded);
}
void MyWindow_Loaded(object sender, RoutedEventArgs e) {
textBox.Focus();
}
since i tried a fuzquat's solution and found it the most generic one, i thought i'd share a different version, since some complained about it looking messy. so here it is:
casted.Dispatcher.BeginInvoke(new Action<UIElement>(x =>
{
x.Focus();
}), DispatcherPriority.ApplicationIdle, casted);
no Thread.Sleep, no ThreadPool. Clean enough i hope.
UPDATE:
Since people seem to like pretty code:
public static class WpfExtensions
{
public static void BeginInvoke<T>(this T element, Action<T> action, DispatcherPriority priority = DispatcherPriority.ApplicationIdle) where T : UIElement
{
element.Dispatcher.BeginInvoke(priority, action);
}
}
now you can call it like this:
child.BeginInvoke(d => d.Focus());
WPF supports two different flavors of focus:
Keyboard focus
Logical focus
The FocusedElement property gets or sets logical focus within a focus scope. I suspect your TextBox does have logical focus, but its containing focus scope is not the active focus scope. Ergo, it does not have keyboard focus.
So the question is, do you have multiple focus scopes in your visual tree?
I found a good series of blog posts on WPF focus.
Part 1: It’s Basically Focus
Part 2: Changing WPF focus in code
Part 3: Shifting focus to the first available element in WPF
They are all good to read, but the 3rd part specifically deals with setting focus to a UI element in a UserControl.
Set your user control to Focusable="True" (XAML)
Handle the GotFocus event on your control and call yourTextBox.Focus()
Handle the Loaded event on your window and call yourControl.Focus()
I have a sample app running with this solution as I type. If this does not work for you, there must be something specific to your app or environment that causes the problem. In your original question, I think the binding is causing the problem.
I hope this helps.
After having a 'WPF Initial Focus Nightmare' and based on some answers on stack, the following proved for me to be the best solution.
First, add your App.xaml OnStartup() the followings:
EventManager.RegisterClassHandler(typeof(Window), Window.LoadedEvent,
new RoutedEventHandler(WindowLoaded));
Then add the 'WindowLoaded' event also in App.xaml :
void WindowLoaded(object sender, RoutedEventArgs e)
{
var window = e.Source as Window;
System.Threading.Thread.Sleep(100);
window.Dispatcher.Invoke(
new Action(() =>
{
window.MoveFocus(new TraversalRequest(FocusNavigationDirection.First));
}));
}
The threading issue must be use as WPF initial focus mostly fails due to some framework race conditions.
I found the following solution best as it is used globally for the whole app.
Hope it helps...
Oran
I converted fuzquat's answer to an extension method. I'm using this instead of Focus() where Focus() did not work.
using System;
using System.Threading;
using System.Windows;
namespace YourProject.Extensions
{
public static class UIElementExtension
{
public static void WaitAndFocus(this UIElement element, int ms = 100)
{
ThreadPool.QueueUserWorkItem(f =>
{
Thread.Sleep(ms);
element.Dispatcher.Invoke(new Action(() =>
{
element.Focus();
}));
});
}
}
}
I've noticed a focus issue specifically related to hosting WPF UserControls within ElementHosts which are contained within a Form that is set as an MDI child via the MdiParent property.
I'm not sure if this is the same issue others are experiencing but you dig into the details by following the link below.
Issue with setting focus within a WPF UserControl hosted within an ElementHost in a WindowsForms child MDI form
I don't like solutions with setting another tab scope for UserControl. In that case, you will have two different carets when navigating by keyboard: on the window and the another - inside user control. My solution is simply to redirect focus from user control to inner child control. Set user control focusable (because by default its false):
<UserControl ..... Focusable="True">
and override focus events handlers in code-behind:
protected override void OnGotFocus(RoutedEventArgs e)
{
base.OnGotFocus(e);
MyTextBox.Focus();
}
protected override void OnGotKeyboardFocus(KeyboardFocusChangedEventArgs e)
{
base.OnGotKeyboardFocus(e);
Keyboard.Focus(MyTextBox);
}
What did the trick for me was the FocusManager.FocusedElement attribute. I first tried to set it on the UserControl, but it didn't work.
So I tried putting it on the UserControl's first child instead:
<UserControl x:Class="WpfApplication3.UserControl1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Grid FocusManager.FocusedElement="{Binding ElementName=MyTextBox, Mode=OneWay}">
<TextBox x:Name="MyTextBox"/>
</Grid>
... and it worked! :)
I have user control - stack panel with two text boxes.The text boxes were added in contructor, not in the xaml. When i try to focus first text box, nothing happend.
The siggestion with Loaded event fix my problem. Just called control.Focus() in Loaded event and everthing.
Assuming you want to set focus for Username textbox, thus user can type in directly every time it shows up.
In Constructor of your control:
this.Loaded += (sender, e) => Keyboard.Focus(txtUsername);
After trying combinations of the suggestions above, I was able to reliably assign focus to a desired text box on a child UserControl with the following. Basically, give focus to the child control and have the child UserControl give focus to its TextBox. The TextBox's focus statement returned true by itself, however did not yield the desired result until the UserControl was given focus as well. I should also note that the UserControl was unable to request focus for itself and had to be given by the Window.
For brevity I left out registering the Loaded events on the Window and UserControl.
Window
private void OnWindowLoaded(object sender, RoutedEventArgs e)
{
ControlXYZ.Focus();
}
UserControl
private void OnControlLoaded(object sender, RoutedEventArgs e)
{
TextBoxXYZ.Focus();
}
I set it in the PageLoaded() or control loaded, but then I'm calling WCF async service and doing stuff that seems to lose the focus. I have to to set it at the end of all the stuff I do. That's fine and all, but sometimes I make changes to the code and then I forget that I'm also setting the cursor.
I had same problem with setting keyboard focus to canvas in WPF user control.
My solution
In XAML set element to Focusable="True"
In element_mousemove event create simple check:
if(!element.IsKeyBoardFocused)
element.Focus();
In my case it works fine.