I want the Escape key to close my WPF window. However if there is a control that can consume that Escape key, I don't want to close the Window. There are multiple solutions on how to close the WPF Window when ESC key is pressed. eg. How does the WPF Button.IsCancel property work?
However this solution closes the Window, without regard to if there is an active control that can consume the Escape key.
For eg. I have a Window with a DataGrid. One of the columns on the dataGrid is a combobox. If I am changing the ComboBox, and hit Escape, then the control should come out of editing of the comboBox (Normal Behavior). And if I now hit Escape again, then the Window should close. I would like a generic solution, instead of writing a lot of custom code.
If you can provide a solution in C# it would be great.
You should just use the KeyDown event instead of the PreviewKeyDown event. If any child of the Window handles the event, it won't be bubbled up to the Window (PreviewKeyDown tunnels from the Window down), and therefore your event handler won't be called.
There may be an easier way, but you could do it with the hash code. Keys.Escape is another option, but sometimes I cannot get that to work for some reason. You didn't specify a language so here is an example in VB.NET:
Private Sub someTextField_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles someTextField.KeyPress
If e.KeyChar.GetHashCode = 1769499 Then ''this number is the hash code for escape on my computer, do not know if it is the same for all computers though.
MsgBox("escape pressed") ''put some logic in here that determines what ever you wanted to know about your "active control"
End If
End Sub
class Commands
{
static Command
{
CloseWindow = NewCommand("Close Window", "CloseWindow", new KeyGesture(Key.Escape));
CloseWindowDefaultBinding = new CommandBinding(CloseWindow,
CloseWindowExecute, CloseWindowCanExecute);
}
public static CommandBinding CloseWindowDefaultBinding { get; private set; }
public static RoutedUICommand CloseWindow { get; private set; }
static void CloseWindowCanExecute(object sender, CanExecuteRoutedEventArgs e)
{
e.CanExecute = sender != null && sender is System.Windows.Window;
e.Handled = true;
}
static void CloseWindowExecute(object sender, ExecutedRoutedEventArgs e)
{
((System.Windows.Window)sender).Close();
}
}
// In your window class's constructor. This could also be done
// as a static resource in the window's XAML resources.
CommandBindings.Add(Commands.CloseWindowDefaultBinding);
Related
I'm creating a new window in On_Click method. First I tried this;
public partial class MainWindow : Window
{
CustomerOperations customerOperationsWindow;
public MainWindow()
{
customerOperationsWindow = new CustomerOperations();
InitializeComponent();
}
private void btnCustomer_Click(object sender, RoutedEventArgs e)
{
customerOperationsWindow.Owner = this;
customerOperationsWindow.Show();
}
}
It's not working so I started creating the window instance every time the user clicks on the Customers button. And I used the following codes.
private void btnCustomer_Click(object sender, RoutedEventArgs e)
{
CustomerOperations customerOperationsWindow = new CustomerOperations();
customerOperationsWindow.Owner = this;
customerOperationsWindow.Show();
}
In the new window, If user clicks to Main button, I want to navigate to main window.
private void btnMain_Click(object sender, RoutedEventArgs e)
{
this.Close();
this.Owner.Show();
}
First question: Does this.Close() releases the window instance?
Second question: Is this usage correct?
What do you think is the best practice?
Thank you all.
Window.Close() will dispose all resources allocated by the instance. That's why you cannot show it again once it was closed.
If you want to reuse the same Window instance, you should cancel the closing procedure to prevent disposal of internal resources and collapse the Window instead (by setting Window.Visibility to Visibility.Collapsed - Visibility.Collapsed is also the default value of an instantiated Window before Window.Show() is called).
Alternatively hide the Window by calling Window.Hide() (which will set the Visibility to Visibility.Hidden) instead of Window.Close().
Calling Window.Show will also set the window's visibility to Visibility.Visible.
As a matter of fact, showing a Window by setting Window.Visibility is the asynchronous version of Window.Show().
Generally, you switch between Window instances by using the Window.Activate method. Calling Window.Show on a Window that is currently showing/visible, does nothing.
public partial class MainWindow : Window
{
CustomerOperations CustomerOperationsWindow { get; }
public MainWindow()
{
InitializeComponent();
this.CustomerOperationsWindow = new CustomerOperations();
// Consider to move this logic to CustomerOperations class,
// where you can override the OnClosing method instead of subscribing to the event
this.CustomerOperationsWindow.Closing += CollapseWindow_OnClosing;
}
// Cancel close to prevent disposal and collapse Window instead
private void CollapseWindow_OnClosing(object sender, CancelEventArgs e)
{
e.Cancel = true;
this.CustomerOperationsWindow.Visibility = Visibility.Collapsed;
this.CustomerOperationsWindow.Owner.Activate();
}
private void btnCustomer_Click(object sender, RoutedEventArgs e)
{
this.CustomerOperationsWindow.Owner = this;
// Calling Show will set the Visibility to Visibility.Visible
this.CustomerOperationsWindow.Show();
}
}
Creating a Window instance allocates unmanaged resources. If this happens very frequently, you will keep the garbage collector busy. From a performance point of view you may want to avoid it and prefer to reuse the same instance.
In a common scenario this is not necessary. But since Window exposes a Hide() method, you may consider to use it instead of Close().
If you want to switch to the parent window, you can use the code this.Owner.Activate(); and if you want to close the current window, first this.Owner.Activate(); and then this.Close();.
When you enter this.Close(), the compiler does not execute the following lines after reaching it. And when a sample window still exists there is no need to recreate it
private void btnMain_Click(object sender, RoutedEventArgs e)
{
this.Owner.Activate();
this.Close();
}
I have multiple children of the same WinForms form, each with its own handler for a keyboard event. For a minimal example (C#):
public Form1() {
InitializeComponent();
c1 = new Control();
c2 = new Control();
c1.KeyPress += c1_KeyPress;
c2.KeyPress += c2_KeyPress;
Controls.Add(c1);
Controls.Add(c2);
}
void c1_KeyPress(object sender, KeyPressEventArgs e) {
Text += " c1";
e.Handled = true;
}
void c2_KeyPress(object sender, KeyPressEventArgs e) {
Text += " c2";
e.Handled = true;
}
When the event fires, it always gets handled by whichever child was originally added to the form first. Reordering the children with c2.BringToFront() or Controls.SetChildIndex(c2, 0) doesn't change the priority. Reordering the constructions or the delegate assignments doesn't change anything either. Calling c2.Focus() doesn't either. Changing the order of the Add calls is the only thing that seems to affect it.
(By contrast, for mouse events the priority gets resolved in an expected way: the topmost control under the pointer hotspot gets dibs on the event, and "topmost" is a clear concept I can control using BringToFront and friends.)
In my real case, c1 is a simple custom control derived from WinForms.UserControl, and c2 is a CefSharp.WinForms.ChromiumWebBrowser. There the keyboard events are caught by c2 no matter what I do.
What decides this priority of handlers? How can I change it?
There is no "priority", keyboard events are raised on the control that has the focus. Intuitively simple to understand, entering text in a TextBox requires selecting it first. A very significant flaw in the posted snippet is that you cannot tell which one has the focus. Although the Control class is usable as-is, in practice you almost always need to derive your own class from it to give it desirable behavior.
Add a new class to your project and paste the code shown below. Replace new Control() with new MyControl(). Now you can tell.
using System;
using System.Windows.Forms;
class MyControl : Control {
protected override void OnEnter(EventArgs e) {
this.Invalidate();
base.OnEnter(e);
}
protected override void OnLeave(EventArgs e) {
this.Invalidate();
base.OnLeave(e);
}
protected override void OnPaint(PaintEventArgs e) {
if (this.Focused) {
ControlPaint.DrawFocusRectangle(e.Graphics, this.DisplayRectangle);
}
base.OnPaint(e);
}
}
I have am making a map editor for a game which has a user control that has an image. Inside that control I attached the MouseWheel event to it, but I've noticed two issues that I hope to have a better understanding of why it behaves the way it does and how to properly implement it.
For one the event only seems to fire when the mouse is hovering over it instead of when the control is in focus. If possible I would like to switch that and be able to fire the event no matter where the mouse is as long as that control is in focus and the second issue is that checking the delta when the number is positive works fine, but when I get a number back when it's negative I get a value of 0xfffffffd or something in that range. How would I go about differentiating the difference between a positive balue and a negative value if I always get something positive?
Thanks in advance for the help.
If you want to fire MouseWheel event for focused element try:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
this.MouseWheel += OnMouseWheel;
}
IInputElement focusedElement;
private void OnMouseWheel(object sender, MouseWheelEventArgs e)
{
if (focusedElement is TextBox)
{
var tbx = focusedElement as TextBox;
//do something
}
}
protected override void OnPreviewLostKeyboardFocus(KeyboardFocusChangedEventArgs e)
{
focusedElement = e.NewFocus;
}
}
In order to take advantage of the spell checking ability of WPF textboxes, I have added one to a user control (with the use of elementhost). This user control is used in various window forms. My current problem is trying to handle keyup events from this textbox but the windows form is unable to "get" any event from the control. I can access the properties of the textbox just fine (i.e. text, length, etc.) but keyboard events don't seem to work.
I have found, however, that the following will bring back events from the WPF textbox:
Public Class MyUserControl
Private _elementHost As New ElementHost
Private _wpfTextbox As New System.Windows.Controls.Textbox
Private Sub MyUserControl_Load(...) Handles Me.Load
Me.Controls.Add(_elementHost)
_elementHost.Dock = DockStyle.Fill
_elementHost.Child = _wpfTextbox
Dim MyEventInfo As EventInfo
Dim MyMethodInfo As MethodInfo
MyMethodInfo = Me.GetType().GetMethod("WPFTextbox_KeyUp")
MyEventInfo = _wpfTextBox.GetType().GetEvent("PreviewKeyUp")
Dim dlg As [Delegate] = [Delegate].CreateDelegate(MyEventInfo.EventHandlerType, Me, MyMethodInfo)
MyEventInfo.AddEventHandler(_wpfTextBox, dlg)
End Sub
Public Sub WPFTextbox_KeyUp(ByVal sender As Object, ByVal e As RoutedEventArgs)
' something goes here
End Sub
End Class
The user control is now able to do something after the PreviewKeyUp event is fired in the WPF textbox. Now, I'm not completely sure how to have the window form containing this user control to work with this.
Im a C# person not VB so please bear with me.. Basically you could assign the event from your Window rather than within your UserControl.. So in the constructor of your Window assign the PreviewKeyUp:
this.myUserContorl.PreviewKeyUp += new System.Windows.Input.KeyEventHandler(WPFTextbox_KeyUp);
then place the event handler in your Window:
private void WPFTextbox_KeyUp(object sender, System.Windows.Input.KeyEventArgs e)
{
}
Incidentally you needn't go through the hassle of capturing the event in your UserControl as you can still access your TextBox within you UserControl directly from your Window (if you make it public), again from your constructor in your Window:
this.myUserContorl.wpfTextbox.PreviewKeyUp += new System.Windows.Input.KeyEventHandler(WPFTextbox_KeyUp);
I imagine it would look like this in VB (at a guess):
AddHandler myUserContorl.wpfTextbox.PreviewKeyUp, AddressOf WPFTextbox_KeyUp
ElementHost has a static method called EnableModelessKeyboardInterop(). Try calling it?
ElementHost.EnableModelessKeyboardInterop();
Read more here
Seems basic, but did you set the KeyPreview to TRUE on your form?
I'd like the main menu in my WPF app to behave like the main menu in IE8:
it's not visible when the app starts
pressing and releasing Alt makes it visible
pressing and releasing Alt again makes it invisible again
repeat until bored
How can I do this? Does it have to be code?
Added in response to answers submitted, because I'm still having trouble:
My Shell code-behind now looks like this:
public partial class Shell : Window
{
public static readonly DependencyProperty IsMainMenuVisibleProperty;
static Shell()
{
FrameworkPropertyMetadata metadata = new FrameworkPropertyMetadata();
metadata.DefaultValue = false;
IsMainMenuVisibleProperty = DependencyProperty.Register(
"IsMainMenuVisible", typeof(bool), typeof(Shell), metadata);
}
public Shell()
{
InitializeComponent();
this.PreviewKeyUp += new KeyEventHandler(Shell_PreviewKeyUp);
}
void Shell_PreviewKeyUp(object sender, KeyEventArgs e)
{
if (e.SystemKey == Key.LeftAlt || e.SystemKey == Key.RightAlt)
{
if (IsMainMenuVisible == true)
IsMainMenuVisible = false;
else
IsMainMenuVisible = true;
}
}
public bool IsMainMenuVisible
{
get { return (bool)GetValue(IsMainMenuVisibleProperty); }
set { SetValue(IsMainMenuVisibleProperty, value); }
}
}
You can use the PreviewKeyDown event on the window. To detect the Alt key you will need to check the SystemKey property of the KeyEventArgs, as opposed to the Key property which you normally use for most other keys.
You can use this event to set a bool value which has been declared as a DependencyProperty in the windows code behind.
The menu's Visibility property can then be bound to this property using the BooleanToVisibilityConverter.
<Menu
Visibility={Binding Path=IsMenuVisibile,
RelativeSource={RelativeSource AncestorType=Window},
Converter={StaticResource BooleanToVisibilityConverter}}
/>
I just came across this problem myself. I tried hooking into the PreviewKeyDown event, but found it to be unreliable. Instead I found the InputManager class where you can hook into the EnterMenuMode from managed code. The manager exposes two events, for enter and exit. The trick is to not collapse the menu, but set it's container height to zero when it is to be hidden. To show it, simply clear the local value and it will take its previous height.
From my TopMenu user control:
public TopMenu()
{
InitializeComponent();
InputManager.Current.EnterMenuMode += OnEnterMenuMode;
InputManager.Current.LeaveMenuMode += OnLeaveMenuMode;
Height = 0;
}
private void OnLeaveMenuMode(object sender, System.EventArgs e)
{
Height = 0;
}
private void OnEnterMenuMode(object sender, System.EventArgs e)
{
ClearValue(HeightProperty);
}
I'd try looking into handling the PreviewKeyDown event on your window. I'm not sure if pressing Alt triggers this event or not, but if it does, then I'd toggle a bool which is bound to the visibility of the main menu of the window.
If PreviewKeyDown doesn't work, I'm not sure what else to try. You could look into getting at the actual Windows messages sent to your window, but that could get messy very quickly.
It would be better to use GetKeyboardState with VK_MENU to handle both left and right Alt, to mimic the behavior of IE / Windows Explorer (Vista+) you'll need to track the previously focused element to store focus, on a VK_MENU press whilst the focused element is within your main menu. You also want to be doing this work on PreviewKeyUp (not down).
See my answer to the following thread:
How to make WPF MenuBar visibile when ALT-key is pressed?
There I describe how to solve your problem with the class InputManager (from namespace System.Windows.Input).
You can register the classes events EnterMenuMode and LeaveMenuMode.