Entry

Delphi: Component: Dynamic: Create: How to dynamically create an event, once component is created?

Sep 12th, 2003 09:40
Knud van Eeden,

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--- Knud van Eeden --- 11 September 2003 - 10:19 am ------------------

Delphi: Component: Dynamic: Create: How to dynamically create an 
event, once component is created?

Steps: Overview:

 1. -Create that component e.g. dynamically
     or otherwise

 2. -Add your event code in the 'implementation' section
     in the source code

     Put there your source code which
     you want to have triggered by the event
     (e.g. the OnClick event, when clicking on the created button)

 3. -You might have to add a dummy parameter like
     ( Sender: TObject ) to your event source code (because
     this is by default expected for this component in Delphi),
     otherwise it might not work

 4. -Then inform about this event, by
     assigning your event code with e.g. the OnClick method
     for that created component

---

Steps: Worked out:

 1. -Create that component e.g. dynamically
     or otherwise

http://www.faqts.com/knowledge_base/view.phtml/aid/24287/fid/175

 2. -Add your event code in the 'implementation' section
     in the source code

     Put there your source code which
     you want to have triggered by the event
     (e.g. the OnClick event, when clicking on the created button)

...

implementation

procedure TForm1.SomeButtonEventCreatedDynamicallyByMe( Sender: 
TObject );
begin
 // do something
 ShowMessage( 'Hello World' );
end;

...

 3. -You might have to add a dummy parameter like
     ( Sender: TObject ) to your event source code (because
     this is by default expected for this component in Delphi),
     otherwise it might not work

 4. -Then inform about this event, by
     assigning your event code with e.g. the OnClick method
     for that created component

Btn.OnClick := SomeButtonEventCreatedDynamicallyByMe;

---

 5. That will create alltogether the following program:

--- cut here ---------------------------------------------------------

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, 
Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Label1: TLabel;
    procedure Label1Click(Sender: TObject);
    procedure SomeButtonEventCreatedDynamicallyByMe( Sender: TObject );
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.SomeButtonEventCreatedDynamicallyByMe( Sender: 
TObject );
begin
  // do something
 ShowMessage( 'Hello World' );
end;

procedure TForm1.Label1Click(Sender: TObject);
var Btn : TButton;
begin
 Btn := TButton.Create(Self);
 Btn.Parent := Self;
 Btn.OnClick := SomeButtonEventCreatedDynamicallyByMe;
end;

end.

--- cut here ---------------------------------------------------------

 6. When you run this program, then 

1. It will show the label

2. After clicking on the label, that will show the button.

3. If you then click on that button it will show you a message
    box with 'Hello World':

       +-------------------+      +-------------+
       |                   |      |             |
       +-------------------+      |             |
                                  | Hello World |
                                  |             |
       +-------------------+      +-------------+
       | Label1            |
       +-------------------+

---

[Internet: see also: http://www.google.com,
search for 'How to dynamically create an event in Delphi':
http://community.borland.com/article/0,1410,16467,00.html]

http://www.faqts.com/knowledge_base/view.phtml/aid/24327/fid/175

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