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OnKeyDown event...

Posted on 1998-04-14
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Last Modified: 2012-06-22
Hi

For the OnKeyPress event, the Key can be set to Null, ie #0 to cancel the keypress. For the OnKeyDown event, what value do i set the Key if i want to cancel the keydown?

Cheers
Keith
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Question by:keithcsl
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7 Comments
 
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Author Comment

by:keithcsl
ID: 1361508
Edited text of question
0
 
LVL 1

Author Comment

by:keithcsl
ID: 1361509
Edited text of question
0
 
LVL 1

Expert Comment

by:Edo082297
ID: 1361510
Hi Keithcsl

   You can "cancel" any event by setting the method pointer to nil like this:

procedure TForm1.Button1Click(Sender: TObject);
begin
  Form1.OnMouseDown := nil;
end;

Then later on you can "reactivate" the event:

procedure TForm1.Button2Click(Sender: TObject);
begin
  Form1.OnMouseDown := Form1.FormMouseDown;
end;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
   showmessage ('hello');
end;

Regards,

Edo

P.S. This isn't the greatest programming practice; you should code for whether or not the event's code should be executed; otherwise, you (or the person who has to modify the code) will end up with a hard to trace bug :)


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LVL 1

Author Comment

by:keithcsl
ID: 1361511
Edo

i am sorry but I should have structured my question more clearly. My intention is not to cancel the event, but rather trap the event, cancel the original Key and run my process.  For example in the OnKeyDown event,

  if (Key = 13) then
  begin
    // Set new Key here, maybe Key := 0
    RunProcedure;
  end;

PS: I have found setting Key := 0 does the job, but is it correct to do so??

Keith
0
 

Expert Comment

by:raunol
ID: 1361512
Yes, key:=0 (word) correspond to key:=#0 (char)
also key:=Ord(#0)(word) correspond key:=chr(0);

- Rauno -
0
 
LVL 1

Author Comment

by:keithcsl
ID: 1361513
Rauno

Hmm, why didn't I think of checking it like that? Thanks. Could you post ur comment as an answer?

Keith
0
 

Accepted Solution

by:
raunol earned 80 total points
ID: 1361514
Hi, Keith

>Hmm, why didn't I think of checking it like that?

Sometimes known for me, too ;-)

> Could you post ur comment as an answer?

Well, that wasn't very proper answer for Your
original question. But..
..my expert score is still zerou.. ;-) ;-)
So, if You will, here You are:

Yes, key:=0 (word) correspond to key:=#0 (char)
also key:=Ord(#0)(word) correspond key:=chr(0);

- Rauno -
0

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