接受sendmessage(application.handle..)的消息？

unit   Unit1; 

interface 

uses 
    Windows,   Messages,   SysUtils,   Variants,   Classes,   Graphics,   Controls,   Forms, 
    Dialogs,   StdCtrls,   sockets; 
const 
  wm_mymessage   =   wm_user   +   1; 
type 
    TForm1   =   class(TForm) 
        btn1:   TButton; 
        procedure   FormShow(Sender: TObject);
        procedure   btn1Click(Sender:   TObject); 
    private 
        {   Private   declarations   } 
    public 
        {   Public   declarations   } 
        procedure   mymessage(var   Msg:   TMsg;   var   Handled:   Boolean); 
    end; 

var 
    Form1:   TForm1; 

implementation 

{$R   *.dfm} 

procedure   TForm1.FormShow(Sender: TObject); 
begin 
    application.onmessage   :=   mymessage; 
end; 

procedure   TForm1.mymessage(var   Msg:   TMsg;   var   Handled:   Boolean); 
begin 
    if   msg.message   =   wm_mymessage   then   
        showmessage( 'ok '); 
end; 

procedure   TForm1.btn1Click(Sender:   TObject); 
begin 
//     sendmessage(handle,   wm_mymessage,0,   0); 
  //  sendmessage(application.handle,   wm_mymessage,0,   0);   // 
    postmessage(application.handle,   wm_mymessage,0,   0);   // 

end;