event handling for dynamically generated components

[ladoota]

In my application I need to generate a number of components (of the same kind) on the fly. I ran into difficulties how to handle the events, triggered by them as I have to know where it comes from. Browsing the docs, faq's and forums did not give me an idea, how can I detect which of the components triggered the event?

So for example: I create 2 TButton components on-the-fly (Btn1, Btn2). In both I declare OnClick:=HandleTheclicks;
Now procedure HandleTheClicks(Sender:TObject) works OK, except that I need to find out which button fired the event.

An example or a pointer to an explanation is welcome.

Regards, Vladimir

 

[mikeEd]

TButton(Sender) gives you the button that called the event.
For example;

if TButton(Sender) = Btn1 then //btn1 was pressed
etc

 

[TonHu]

And then there is also the ever usefull Tag property that can bet set to some integer value during creation of the TButtons() and to be checked later... like in:

case TButton(sender).tag of
1 : Close; // Kill app
2 : ProcessSecondButton; // Do something else
...
end;

HTH,
TonHu

 

[GolezTrol]

I would like to say I prefer MikeEd's method, but I don't. This code won't compile since btn1 isn't created at designtime yet.

You also don't have to typecast the component unless you need some specific properties of the component:

procedure HandleMyEvents(Sender: TObject);
begin
if not (Sender is TWinControl) then
Exit;
if TWinControl(Sender).Tag = 1 then
Close; // Tag 1 components kill the app in this exmpl.

if (Sender is TCombobox) then
with TComboBox(Sender) do
if ItemIndex > -1 then // Yay! I selected something.
ShowMessage( 'You selected ' + Items[ItemIndex] + ' from the list.' );
end;

 

[mikeEd]

GolezTrol, that code will compile as long as the variable Btn1 is visible to the HandleTheClicks procedure.

 

[bbegley]

If you name the component on creation, then you can address the button this way:

If (Sender as TWinControl).Name = 'Button1' then