Tuesday, March 1, 2011

How to add components to forms at run time

It's easy and fun to create setup components at design time, but if you must, it's not difficult to create them at run time as well.

For example, let's say you want to create a "TLabel" object called "Label1" with the caption "hello, world!" at run time and place it on your form at (50, 60) x and y coordinates:
//
// assuming: your form is called "Form1"
//
with TLabel.Create( Form1 ) do
begin
  Parent  := Form1;  // this is important
  Left    := 50;     // X coordinate
  Top     := 60;     // Y coordinate
  Caption := 'hello, world';

  //
  // set your other parameters here...
  //

  //
  // you don't have to set the Name
  // parameter, but...
  //
  Name    := 'Label1';

  //
  // finally make it visible
  //
  Visible := True;
end;
Listing #1 : Delphi code. Download runtime (0.39 KB).
The same example, this time using a variable to keep track of the "TLabel" component:
var
  l : TLabel;

begin
  //
  // assuming: your form is called "Form1"
  //
  l := TLabel.Create( Form1 );

  l.Parent  := Form1;  // this is important
  l.Left    := 50;     // X coordinate
  l.Top     := 60;     // Y coordinate
  l.Caption := 'hello, world';

  //
  // set your other parameters here...
  //

  //
  // you don't have to set the Name
  // parameter, but...
  //
  l.Name    := 'Label1';

  //
  // finally make it visible
  //
  l.Visible := True;
end;
Listing #2 : Delphi code. Download runtime2 (0.4 KB).

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