Dynamically generated Forms?
lazarus / 9-Editor

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forlornity · 2008-01-20 16:41

Hey there, my first post on these forums, I was wondering if any of
you could point me in the direction of how on Earth I can add
buttons/edit boxes etc to forms on the fly.

The reason is that I need to take some information from a MySQL
database and make a list of all the information obtained with buttons
to do things such as delete etc.

Thanks in advance, Forlornity

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gerardus · 2008-01-20 17:24

As easy as:

Code: [Select]
var
  aBtn:TButton;
begin
  aBtn := TButton.Create(aForm); // By passing the form as a Owner
parameter you can forget about freeing it later. Pass Nil if you want
to take care of it.
  aBtn.Top := 100;
  aBtn.Left := 100;
  abtn.Caption := 'Hello';
  aBtn.Parent := aForm; // Important, otherwisr the button won't show
up.
end;

Regards,

Gerard.

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forlornity · 2008-01-20 20:15

Quote from: "gerardus"As easy as:

Code: [Select]
var
  aBtn:TButton;
begin
  aBtn := TButton.Create(aForm); // By passing the form as a Owner
parameter you can forget about freeing it later. Pass Nil if you want
to take care of it.
  aBtn.Top := 100;
  aBtn.Left := 100;
  abtn.Caption := 'Hello';
  aBtn.Parent := aForm; // Important, otherwisr the button won't show
up.
end;

Regards,

Gerard.

Thanks very much, I'm pretty new to Delphi and Lazarus, mostly
experienced with PHP, Actionscript and C but none of these to any
great degree.

Check my next post; I have more questions.

Thanks, Forlornity

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forlornity · 2008-01-21 11:48

Hey again, I was just wondering how I then delete the buttons (etc)
later on, am I missing something glaringly obvious or is it more
difficult than I'd think?

again, thanks in advance, Forlornity

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theo · 2008-01-21 13:01

There are several way to do this. You could hold a TList or
TComponentList (unit contnrs) of all the controls you've inserted or
give each control a unique name ( like abtn.Name:='btn_1'; ) and use
FindComponent:

Code: [Select]procedure TForm1.Button2Click(Sender: TObject);
var Comp:TComponent;
begin
  Comp:=FindComponent('btn_1');
  if (Comp<>nil) and (Comp is TControl) then
  begin
    RemoveControl(TControl(Comp));
    Comp.free;
  end;
end;

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forlornity · 2008-01-21 14:03

Thanks, it was the RemoveControl procedure I needed as I was already
storing them as part of an array from which I can find them, also, I
let the form handle freeing them, are there any caveats in doing this?

Also, is there any way (other than looping through them) of getting
rid of all of the buttons when the form they are on is closed so that
they don't re-appear when I show it again?

thanks again, Forlornity

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gerardus · 2008-01-22 21:53

Quote from: "forlornity"I let the form handle freeing them, are there
any caveats in doing this?


None.

Quote from: "forlornity"
Also, is there any way (other than looping through them) of getting
rid of all of the buttons when the form they are on is closed so that
they don't re-appear when I show it again?


I think looping is the only way (Either having them in an array or
looping TForm.Components[]).

Gerard.

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duncanparsons · 2008-01-24 09:38

Note for speed and efficiency, when iterating the list do something
like:
Code: [Select]
i:=ControlCount-1;
while i>=0 do
  begin
    if controls[i]=<my method of identification> then
      begin
        RemoveControl(controls[i]);
      end;
    dec(i);
  end;


Starting from the end of the list and working backwards ensures that
you don't move memory around that you don't need to.



DSP

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forlornity · 2008-01-24 11:20

Thanks for the help guys, I've got all of this working now thanks to
you

Now I'm having problems with MySQL though, I'll make a new thread.

- Forlornity