Question

Remove alert beep in treeview on KeyDown

Asked by: devilduck

I have a form with just a treeview on it.  I am trying to add ctrl+a to select all nodes.  Each time I press ctrl+a, I get an alert beep.

I have looked through EE and found multiple references to setting Key := Ord(#0); but that doesn't help.

Below is the KeyDown code that I am using.

Thanks,

DD

procedure TForm1.TreeView1KeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
  if (ssCTRL IN SHIFT) and ((Key = Ord('a')) or (Key = Ord('A')))then
  begin
    //  Do my selection stuff here.
    Key := Ord(#0);   //  EE line to remove beep - doesn't work
    Shift := Shift - [ssCTRL];   //  I tried this to see if it would work too.  Nope.
  end;
end;

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Asked On
2004-04-19 at 14:39:45ID20959662
Tags

beep

,

keydown

Topic

Delphi Programming

Participating Experts
3
Points
250
Comments
6

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Answers

 

by: rllibbyPosted on 2004-04-19 at 14:50:30ID: 10863970

Its actually the KeyPress event that is causing the beep, so all you need to do is zero the (#0) char value for key in that event. You can also check for the control state, and conditionally clear it if you wanted to as well (code below)

Regards,
Russell



procedure TForm1.TreeView1KeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
begin

  if (ssCtrl in Shift) and (Key in [65, 97]) then
     ShowMessage('Control+A');

end;

procedure TForm1.TreeView1KeyPress(Sender: TObject; var Key: Char);
var  intKey:        SHORT;
begin

  if (HiByte(GetAsyncKeyState(VK_CONTROL)) <> 0) then Key:=#0;

end;

 

by: DaFoxPosted on 2004-04-19 at 15:02:06ID: 10864061

Hi devilduck,

try

var
  Mgs: TMsg;
begin
  {...}
  PeekMessage(Mgs, 0, WM_KEYFIRST, WM_KEYLAST, PM_REMOVE);
  {...}
end;

instead "Key := 0;"

Regards,
Markus

 

by: devilduckPosted on 2004-04-19 at 16:41:04ID: 10864596

Wow, Russell you are fast.  I am doing all of my keydown checks in the treeview keydown event.  I just created a keypress event and added Key:=#0;

procedure TmainForm.TreeView1KeyPress(Sender: TObject; var Key: Char);
begin
  Key:=#0;
end;

1. Will this cause me interaction problems with keydown?
2. Is the call to GetAsyncKeyState necessary considering I am doing everything on keydown?
3. I didn't have a keypress event defined for my treeview (or anywhere else) I am going to assume that it is a windows event that occurs whether I define it in delphi or not.

Thanks,

DD

 

by: rllibbyPosted on 2004-04-19 at 16:55:39ID: 10864656

DD,

1.) No. It won't cause problems, as the keydown happens before the WM_CHAR (KeyPress event)
2.) GetAsyncKeyState was just to show you how to get the control state in the KeyPress (vs KeyDown/KeyUp). If your not doing anything with keypress in the tree, then "Key:=#0" is fine 'as is'.

Russell

 

by: devilduckPosted on 2004-04-20 at 07:41:40ID: 10869326

Cool.  Thanks again.

devilduck

 

by: BSCPaulPosted on 2010-12-07 at 13:17:43ID: 34295785

Another option is to check for the key in the FormKeyPress evert and then clear it (KeyPreview must be true):

procedure Tfrorm.FormKeyPress(Sender: TObject; var Key: Char);
begin
  if key=#27
  then begin
    key:=#0;
    close;
  end;
end;

20120131-EE-VQP-002

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