Delphi通过SendMessage函数发消息和传值实例

unit Unit1;

interface

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

type
   TForm1 = class(TForm)
      btn1: TButton;
      procedure btn1Click(Sender: TObject);
   private
      { Private declarations }

      procedure MyMessage(var message: TMessage); message wm_user + 999;
   public
      { Public declarations }
   end;

var
   Form1: TForm1;

implementation

{$R *.dfm}

{ TForm1 }

procedure TForm1.MyMessage(var message: TMessage);
begin
   case message.LParam of
      1: PString(message.WParam)^ := '消息方式改变值';
      2: PBoolean(message.WParam)^ := True;
      3: PInteger(message.WParam)^ := 456;
      4: PDateTime(message.WParam)^ := Now;
   end;
end;

procedure TForm1.btn1Click(Sender: TObject);
var
   s : string;
   b : Boolean;
   i : Integer;
   d : TDateTime;
begin
   s := '000'; {s=000}
   PString(Integer(@s))^ := '123'; {s=123}
   b := False; {b=False}
   i := 123; {i=123}
   d := 0; {d=0}

   SendMessage(Handle, wm_user + 999, Integer(@s), 1);
   SendMessage(Handle, wm_user + 999, Integer(@b), 2);
   SendMessage(Handle, wm_user + 999, Integer(@i), 3);
   SendMessage(Handle, wm_user + 999, Integer(@d), 4);

   ShowMessage(
      's=' + s + #13#10 + {s=消息方式改变值}
      'b=' + BoolToStr(b) + #13#10 + {b=True}
      'i=' + IntToStr(i) + #13#10 + {i=456}
      'd=' + DateTimeToStr(d) {d=2014-10-23 14:04:04}
      );
end;

end.