Problem with caption a text(Label) or edit a text(Editbox) in Loop
statement
lazarus / 12-Debugger

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nocuttree · 2014-09-05 16:12

I am a new member so I sorry all member!
I have a button1, label1, edir1
my code:
Quoteprocedure TForm1.Button1Click(Sender: TObject);
var a: integer;
begin
  for a:=1 to 10000 do
  begin
  Label1.caption:=inttostr(a);
  Edit1.text:=inttostr(a);
  delay(1000);
  end;
end;
I want to after a second it caption a but it finish loop statement it
caption 10000.
Sorry my English, thanks all!

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Mike.Cornflake · 2014-09-05 16:22

You're not giving the OS any chance to Paint the updates...

You've got a couple of choices.  Call Application.ProcessMessages once
per loop (allow all pending Paint messages to be performed
automatically), or manually force the Label and Edit to repaint
themselves.  See below for both options...

Code: [Select]procedure TForm1.Button1Click(Sender: TObject);
var a: integer;
begin
  for a:=1 to 10000 do
  begin
  Label1.caption:=inttostr(a);
  Edit1.text:=inttostr(a);
  Application.ProcessMessages;  //  <---  This will allow all pending
paint operations to complete
  //Label1.Invalidate;          //  <--- If you don't want to allow
pending messages to be processed, then this approach may force the
label to repaint
  //Edit1.Invalidate;           //  <---  I'm less certain if this
approach will work on a TEdit, you may need to use ProcessMessages
  delay(1000);
  end;
end;

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nocuttree · 2014-09-05 16:59

Quote from: Mike.Cornflake on September 05, 2014, 06:22:51 pmYou're
not giving the OS any chance to Paint the updates...

You've got a couple of choices.  Call Application.ProcessMessages once
per loop (allow all pending Paint messages to be performed
automatically), or manually force the Label and Edit to repaint
themselves.  See below for both options...

Code: [Select]procedure TForm1.Button1Click(Sender: TObject);
var a: integer;
begin
  for a:=1 to 10000 do
  begin
  Label1.caption:=inttostr(a);
  Edit1.text:=inttostr(a);
  Application.ProcessMessages;  //  <---  This will allow all pending
paint operations to complete
  //Label1.Invalidate;          //  <--- If you don't want to allow
pending messages to be processed, then this approach may force the
label to repaint
  //Edit1.Invalidate;           //  <---  I'm less certain if this
approach will work on a TEdit, you may need to use ProcessMessages
  delay(1000);
  end;
end;Thasks you very much!

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nocuttree · 2014-09-05 18:24

It works with "for... to....do" but "while......... do.........."?
Thanks you!

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Mike.Cornflake · 2014-09-05 18:27

Quote from: nocuttree on September 05, 2014, 08:24:49 pmIt works with
"for... to....do" but "while......... do.........."?
Doesn't matter which loop method you use.  After you've finished
setting all your properties (.text, .caption etc), call
Application.ProcessMessages :-)

Something to be wary of (which is why you may want to investigate the
.invalidate option instead) is that Application.ProcessMessages will
process ALL pending messages, include any button presses the user may
do.  So, if you run your loop in one button press, then call
Application.ProcessMessages, the user will have an opportunity to
continue interacting with your form while your first loop is
cycling...

If .Invalidate doesn't work, then try .Repaint or .Update instead.  I
must admit, I'm pretty terrible when it comes to working out which one
to use, I just keep trying one then the other until I find something
which works :-)

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nocuttree · 2014-09-06 02:39

Thanks you! I am sorry, error come from another place.

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BigChimp · 2014-09-06 14:10

Could you please start a new thread when you have a new problem? That
will hopefully attract more people, make it easier for other people
having the same problem to search the forum, and avoid confusion when
responding to your questions...

PS: Looking at the code it should work as long as you click button1
first... I may be missing something obvious here (haven't compiled the
code either)

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nocuttree · 2014-09-06 14:47

Quote from: BigChimp on September 06, 2014, 04:10:26 pmCould you
please start a new thread when you have a new problem? That will
hopefully attract more people, make it easier for other people having
the same problem to search the forum, and avoid confusion when
responding to your questions...

PS: Looking at the code it should work as long as you click button1
first... I may be missing something obvious here (haven't compiled the
code either)
Thanks you! I will start a new thread in next post! Sorry all!