I am building an application where all the key input must be handled by the windows itself.
I set tabstop to false for each control witch could grab the focus except a panel (but I don't know if it has effect).
I set KeyPreview to true and I am handling the KeyDown event on this form.
My problem is that sometimes the arrow key aren't responsive anymore:
The keydown event is not fired when I pressed only an arrow key.
The keydown event is fired if I press an arrow key with the control modifier.
Have you an idea why my arrow key suddenly stop firing event?
In order to capture keystrokes in a Forms control, you must derive a new class that is based on the class of the control that you want, and you override the ProcessCmdKey().
protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
//handle your keys here
}
Example :
protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
{
//capture up arrow key
if (keyData == Keys.Up )
{
MessageBox.Show("You pressed Up arrow key");
return true;
}
return base.ProcessCmdKey(ref msg, keyData);
}
Full source...Arrow keys in C#
Vayne
protected override bool IsInputKey(Keys keyData)
{
if (((keyData & Keys.Up) == Keys.Up)
|| ((keyData & Keys.Down) == Keys.Down)
|| ((keyData & Keys.Left) == Keys.Left)
|| ((keyData & Keys.Right) == Keys.Right))
return true;
else
return base.IsInputKey(keyData);
}
Unfortunately, it is quite difficult to accomplish this with the arrow keys, due to restrictions in KeyDown events. However, there are a few ways to get around this:
I recommend trying to use that class. It's quite simple to do so:
var left = KeyboardInfo.GetKeyState(Keys.Left);
var right = KeyboardInfo.GetKeyState(Keys.Right);
var up = KeyboardInfo.GetKeyState(Keys.Up);
var down = KeyboardInfo.GetKeyState(Keys.Down);
if (left.IsPressed)
{
//do something...
}
//etc...
If you use this in combination with the KeyDown event, I think you can reliably accomplish your goal.
The best way to do, I think, is to handle it like the MSDN said on http://msdn.microsoft.com/en-us/library/system.windows.forms.control.previewkeydown.aspx
But handle it, how you really need it. My way (in the example below) is to catch every KeyDown ;-)
/// <summary>
/// onPreviewKeyDown
/// </summary>
/// <param name="e"></param>
protected override void OnPreviewKeyDown(PreviewKeyDownEventArgs e)
{
e.IsInputKey = true;
}
/// <summary>
/// onKeyDown
/// </summary>
/// <param name="e"></param>
protected override void OnKeyDown(KeyEventArgs e)
{
Input.SetFlag(e.KeyCode);
e.Handled = true;
}
/// <summary>
/// onKeyUp
/// </summary>
/// <param name="e"></param>
protected override void OnKeyUp(KeyEventArgs e)
{
Input.RemoveFlag(e.KeyCode);
e.Handled = true;
}
See Rodolfo Neuber's reply for the best answer
(My original answer):
Derive from a control class and you can override the ProcessCmdKey method. Microsoft chose to omit these keys from KeyDown events because they affect multiple controls and move the focus, but this makes it very difficult to make an app react to these keys in any other way.
I had a similar issue when calling the WPF window out of WinForms.
var wpfwindow = new ScreenBoardWPF.IzbiraProjekti();
ElementHost.EnableModelessKeyboardInterop(wpfwindow);
wpfwindow.Show();
However, showing window as a dialog, it worked
var wpfwindow = new ScreenBoardWPF.IzbiraProjekti();
ElementHost.EnableModelessKeyboardInterop(wpfwindow);
wpfwindow.ShowDialog();
Hope this helps.
I was having the exact same problem. I considered the answer @Snarfblam provided; however, if you read the documentation on MSDN, the ProcessCMDKey method is meant to override key events for menu items in an application.
I recently stumbled across this article from microsoft, which looks quite promising: http://msdn.microsoft.com/en-us/library/system.windows.forms.control.previewkeydown.aspx. According to microsoft, the best thing to do is set e.IsInputKey=true;
in the PreviewKeyDown
event after detecting the arrow keys. Doing so will fire the KeyDown
event.
This worked quite well for me and was less hack-ish than overriding the ProcessCMDKey.
i had the same problem and was already using the code in the selected answer. this link was the answer for me; maybe for others also.
I'm using PreviewKeyDown
private void _calendar_PreviewKeyDown(object sender, PreviewKeyDownEventArgs e){
switch (e.KeyCode){
case Keys.Down:
case Keys.Right:
//action
break;
case Keys.Up:
case Keys.Left:
//action
break;
}
}
Source: Stackoverflow.com