Solved

onKeypress Event

Posted on 1998-09-28
7
410 Views
Last Modified: 2010-04-06
I would like to have a editbox in which we can only type numbers and the backspace. I think I have to use the onKeypress event and limit the access to ascii codes but the onkeypress event returns a char.  

Thanks
0
Comment
Question by:deha2228
7 Comments
 
LVL 5

Expert Comment

by:JimBob091197
ID: 1340990
What about trapping the WM_CHAR message?

E.g.
In your component's declaration:
procedure WMChar(var Msg: TMessage); message WM_CHAR;

In your code:
procedure TMyEdit.WMChar(var Msg: TMessage);
begin
  // Only allow backspace, ENTER, Escape and 0..9
  if (TWMKey(Msg).CharCode in [8, 13, 27, 48..57]) then
    inherited;
end;

Cheers,
JB
0
 
LVL 2

Accepted Solution

by:
Thaddy earned 100 total points
ID: 1340991
The easy way would be to use a TMaskedEdit. It has all the features you want, Just create an editmask that satisfies your input limitations.
0
 
LVL 10

Expert Comment

by:viktornet
ID: 1340992
Hello all!

I dont like TMaskEdit. It's kinda crappy. I rahter create my own EditBox as deha2228 is going to do. JimBob's solution is prefect for that task and is very easy to implement ;-)

Gotta get back to class ;->

Regards,
Viktor Ivanov
0
Best Practices: Disaster Recovery Testing

Besides backup, any IT division should have a disaster recovery plan. You will find a few tips below relating to the development of such a plan and to what issues one should pay special attention in the course of backup planning.

 
LVL 27

Expert Comment

by:kretzschmar
ID: 1340993
hi deho2228,

help this codesample

procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
const validchars = [#8,'0','1','2','3','4','5','6','7','8','9'];
begin
  if not(key in validchars) then key := #0
end;

meikl
0
 
LVL 10

Expert Comment

by:viktornet
ID: 1340994
Here is an easier way...

procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
begin
  if not key in [#8, #13, #27 '.', '0'..'9'] then key := #0;
end;

Regards,
Viktor Ivanov
0
 
LVL 27

Expert Comment

by:kretzschmar
ID: 1340995
hi viktor,

your comment is just the same, but i ask you for what do you use enter and Escapekey in an editfield?

well my const line could like shown as follows

      const validchars = [#8,'0'..'9'];

and the point if want to use can be added

meikl
0
 
LVL 10

Expert Comment

by:viktornet
ID: 1340996
My point is that you could use the shorter way instead of writing all the chars like so...
const validchars = [#8,'0','1','2','3','4','5','6','7','8','9'];

I added some other characters indeed
0

Featured Post

Master Your Team's Linux and Cloud Stack!

The average business loses $13.5M per year to ineffective training (per 1,000 employees). Keep ahead of the competition and combine in-person quality with online cost and flexibility by training with Linux Academy.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

This article explains how to create forms/units independent of other forms/units object names in a delphi project. Have you ever created a form for user input in a Delphi project and then had the need to have that same form in a other Delphi proj…
Objective: - This article will help user in how to convert their numeric value become words. How to use 1. You can copy this code in your Unit as function 2. than you can perform your function by type this code The Code   (CODE) The Im…
This video shows how to quickly and easily add an email signature for all users on Exchange 2016. The resulting signature is applied on a server level by Exchange Online. The email signature template has been downloaded from: www.mail-signatures…
Established in 1997, Technology Architects has become one of the most reputable technology solutions companies in the country. TA have been providing businesses with cost effective state-of-the-art solutions and unparalleled service that is designed…

803 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question