Question

Listening for the F12 key

Asked by: AWestEng

Hi guys!

How do I listen for the F12 key even when my application is not in foucs?

just using the
   protected override void OnKeyUp(KeyEventArgs e)
        {
        }

only works when the application is in focus.

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Asked On
2009-10-28 at 01:26:14ID24850042
Tags

VS 2008

,

C# .Net 3.5

Topic

C# Programming Language

Participating Experts
2
Points
500
Comments
7

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Answers

 

by: DarrenDPosted on 2009-10-28 at 02:58:13ID: 25681352

Hi,

If you don't capture the F12 key in your application how will the F12 key know what to do when it is pressed?

You will have to have another application that knows when it is pressed. So you will have to have an application that handles the windows F12 and then does something with it such as activate your application

Here is a link to some Win32 functions
http://www.functionx.com/win32/Lesson05.htm

Hope this helps,

Darren

 

by: DarrenDPosted on 2009-10-28 at 03:25:12ID: 25681532

 

by: AWestEngPosted on 2009-10-28 at 03:28:12ID: 25681547

hmm, don't know if I explained it correct

when registering hotkeys they become global using this native method

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool RegisterHotKey(IntPtr hWnd, int id, int fsModifiers, int vk);

and this method to catch it


protected override void WndProc(ref System.Windows.Forms.Message m)
{
    switch (m.Msg)
    {  
        case 0x312:
               HotkeyPressed((int)m.WParam);
               break;
      }
      base.WndProc(ref m);
}

so even if the application isn't in focus it will catch it, what I like to know is, how do that without using a combination of keys like Ctrl + F12, is that possible?

 

 

by: AWestEngPosted on 2009-10-28 at 03:30:20ID: 25681569

I will check the url's

 

by: DarrenDPosted on 2009-10-28 at 03:39:36ID: 25681635

Hi,

Yep, I found the RegisterHotKey in one of the articles posted above. I was just going on what you had in the original post which was only capturing the event in the application.

I'm not sure how to check without using a combination of keys like Ctrl + F12

I'll see if I can find anything else...

Let me know if you solve it...

Darren


 

by: Idle_MindPosted on 2009-10-28 at 07:50:10ID: 25683860

You need to pass in the flags for the "fsModifiers" parameter (third one) when you register the hotkey:

    [System.Flags()]
     public enum KeyModifiers
    {
      None = 0,
      Alt = 1,    
      Control = 2,    
      Shift = 4,    
      Windows = 8
    }

 

by: Idle_MindPosted on 2009-10-28 at 07:51:13ID: 25683875

*Be aware that if another application has already registered your desired key combo then your request will be denied by the OS.

If you want to guarantee that you can respond to a given key combo then use a low level keyboard hook.

20120131-EE-VQP-002

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