Say for example you have a stackpanel that you would like to programmatically add buttons to.
The code behind for the button generation and addition to the stackpanel is:
Button button = new Button();
button.Content = "Button";
button.HorizontalAlignment = HorizontalAlignment.Left;
button.Name = "Button" + i
stackPanel1.Children.Add(button);
My question is - Is it possible to generate the button once and have it as some kind of template that can be added to the stackpanel whenever it is needed without going through the generation code again?
In WPF each UIElement can only be the logical child of one control at any given time, see WPF Error: Specified element is already the logical child of another element. Disconnect it first, so no you can't use the same button and add it to another control later on, unless you're sure you've gotten rid of that stackpanel
But, you can do recycling. See Optimizing Performance: Controls. especially if you are willing to override MeasureOverride and ArrangeOverride of you stackpanel
I've actually written such a recycler because I had grids with many controls, and I wanted to implement some kind of virtualizing grid. These are the main methods of my class:
internal class Recycler
{
private UIElementCollection _children;
public Recycler(UIElementCollection children)
{
_children = children;
//You need this because you're not going to remove any
//UIElement from your control without calling this class
}
public void Recycle(UIElement uie)
{
//Keep this element for recycling, remove it from Children
}
public UIElement GiveMeAnElement(Type type)
{
//Return one of the elements you kept of this type, or
//if none remain create one using the default constructor
}
}
I have an MVVM setup with a mainwindow that contains a ContentControl.
I set this to a particular viewmodel which then maps to a view.
A view is a usercontrol.
I want to be able to set the default keyboard focus to a default element in the usercontrol(View) when it loads so the application can eventually be driven just by using up, down, left, right and enter.
Some of my failed attempts are setting
FocusManager.FocusedElement="{Binding ElementName=DefaultElement}"
in my content control tag. This sets the logical focus but not the keyboard focus
I'd rather keep the solution in xaml if possable but have tried placing the following in code behind.
Keyboard.Focus(DefaultElement);
This does not work but if I popup a message box first it does. I'm a little confused as to why.
MessageBox.Show(Keyboard.FocusedElement.ToString());
Keyboard.Focus(DefaultElement);
EDIT::::
I just placed this in my onloaded event of my user control. It seems to work but can anyone see any issues that might arrise at this priority level. I.E a circumstance when the action will never run?
Dispatcher.BeginInvoke(
DispatcherPriority.ContextIdle,
new Action(delegate()
{
Keyboard.Focus(DefaultElement);
}));
It seems that this wpf the you have to implement a workaround on a case by case basis. The solution that seemed to work best, most of the time for me was to insert the focus code inside the dispatcher when OnVisible was changed. This sets the focus not only when the View/Usercontrol loads but also if you a changing Views by way of Visibility. If you Hide and then Show a ContentControl that is mapped to your ViewModels then the Loaded event won't fire and you'll be forced to Mouse input, or tabbing (Not so good if you want to navigate your app with a remote control).
VisibilityChanged will always fire however. This is what I ended up with for my listbox.
private void ItemsFlowListBox_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
{
if ((bool)e.NewValue == true)
{
Dispatcher.BeginInvoke(
DispatcherPriority.ContextIdle,
new Action(delegate()
{
ItemsFlowListBox.Focus();
ItemsFlowListBox.ScrollIntoView(ItemsFlowListBox.SelectedItem);
}));
}
}
I had the same symptom for a WPF UserControl hosted in a Winforms application. Just wanted to note I was about to try this solution when I found a normal TabIndex in the Winforms app fixed it
Per How to set which control gets the focus on application start
"The one with the minimum tab index automatically gets the focus
(assuming the TabStop property is set to true). Just set the tab
indices appropriately."
It's a tricky one with no easy answer. I'm currently doing this, although I'm not sure I like it:
public MyView()
{
InitializeComponent();
// When DataContext changes hook the txtName.TextChanged event so we can give it initial focus
DataContextChanged +=
(sender, args) =>
{
txtName.TextChanged += OnTxtNameOnTextChanged;
};
}
private void OnTxtNameOnTextChanged(object o, TextChangedEventArgs eventArgs)
{
// Setting focus will select all text in the TextBox due to the global class handler on TextBox
txtName.Focus();
// Now unhook the event handler, since it's no longer required
txtName.TextChanged -= OnTxtNameOnTextChanged;
}
And in case you're wondering what the global class handler does, it's this:
protected override void OnStartup(StartupEventArgs e)
{
...
// Register a global handler for this app-domain to select all text in a textBox when
// the textBox receives keyboard focus.
EventManager.RegisterClassHandler(
typeof (TextBox), UIElement.GotKeyboardFocusEvent,
new RoutedEventHandler((sender, args) => ((TextBox) sender).SelectAll()));
which auto selects TextBox text when receiving keyboard focus.
I have a WPF UserControl that contains a button. I also have a WPF Window that contains a button.
In both the UserControl and the Window I place the following line in XAML:
UIElement.PreviewMouseLeftButtonDown="OnPreviewMouseLeftButtonDown"
and in 'OnPreviewMouseLeftButtonDown' I've place a debug print that displays args.Source.
When I click on the button that is inside the window, I get the button as the EventArgs source. However, when I click the button that inside the UserControl (which is also inside a window, so I could test it, but not the same window) I get the UserControl as the EventArgs source.
I tired to see if there is some decorator around the UserControl (using snoop) but it seems straight forward.
I can't understand what is so special about UserControl in WPF that I don't get the right sender. Can someone please explain to me what am I missing?
While the question is old, I recently ran into a similar problem myself, involving the ContextMenuOpening event. Some amount of searching yielded the source code to UserControl here, which contains the following section:
// Set the EventArgs' source to be this UserControl
internal override void AdjustBranchSource(RoutedEventArgs e)
{
e.Source=this;
}
So, apparently UserControl sets the Source of ANY routed event to itself. I have no idea why it does this, though...
Use e.OriginalSource as mentioned above. If you need to find the button, then you can use VisualTreeHelper.GetParent to find the actual Button control.
within my current project file I have a user control that has a storyboard animation applied to the control. When a button is clicked in the page the storyboard starts and basically visually presents the control to the user. The storyboard resides in the current page as a resource
<navigation:Page.Resources>
<Storyboard x:Name="PreferncesOpen">....</Storyboard x:Name="PreferncesOpen">
</navigation:Page.Resources>
Within the page I have button that I have a click event on that starts the storyboard
private void btnOpenPreferences_Click(object sender, RoutedEventArgs e)
{
preferencesPanel.Visibility = System.Windows.Visibility.Visible;
PreferncesOpen.Begin();
}
Within the userControl (preferencesPanel) I have a button that when clicked needs to close/collapse the user control. I plan to do this using Visibility.collapsed. I assume that I need to use routed commands since the button is within the user control but the actions need to be called within the page that contains the control? I'm still new to routed commands and I assume this is the correct approach. I'm just unsure how to click on a button within the user control and have it modify or execute commands that would impact how the page (in which this control resides) may change or for that part affect other elements within the page? For example when the button is clicked within the user control I would like the visibility of the user control to be set to collapsed. I also would like to have the width of one of the grid columns within the main page re-size. I have done this in the past using the code behind for the page but I am trying to separate some of this and I thought routed commands would be the way to go?
I'd greatly appreciate any tips.
Thank you in advance
The title is a bit misleading, you're asking about commands rather then routed events if I understand you correctly.
Here's an example of using a DelegateCommand<T> from the Prism library; It happens to be my personal preference.
Markup :
<Button x:Name="MyButton" Content="Btn" Command="{Binding DoSomethingCommand}"/>
Code-behind* or ViewModel :
(* if you're not using MVVM make sure to add MyButton.DataContext = this; so you're sure that the button can databind to your code behind effectively)
public DelegateCommand<object> DoSomethingCommand
{
get
{
if(mDoSomethingCommand == null)
mDoSomethingCommand = new DelegateCommand(DoSomething, canDoSomething);
return mDoSomethingCommand;
}
private DelegateCommand<object> mDoSomethingCommand;
// here's where the command is actually executed
void DoSomething(object o)
{}
// here's where the check is made whether the command can actually be executed
// insert your own condition here
bool canDoSomething(object o)
{ return true; }
// here's how you can force the command to check whether it can be executed
// typically a reaction for a PropertyChanged event or whatever you like
DoSomethingCommand.RaiseCanExecuteChanged();
The argument that's passed to the above function is the CommandParameter dependency property (in Prism it's an attached property as well as the Command property if memory serves me right).
When it's set, you can pass a value of your choosing to the command that you wish to execute.
Hope that helps.
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.