BCB中自訂訊息

在C++BUILDER中如何使用自訂訊息和編寫自訂訊息的訊息處理函數
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unit1.h
//---------------------------------------------------------------------------

#ifndef  Unit1H
#define  Unit1H
//---------------------------------------------------------------------------
#include  <Classes.hpp>
#include  <Controls.hpp>
#include  <StdCtrls.hpp>
#include  <Forms.hpp>
#define  WM_MYMESSAGE  WM_APP+1    //自訂訊息ID
//---------------------------------------------------------------------------
class  TForm1  :  public  TForm
{
__published:            //  IDE-managed  Components
       TButton  *Button1;
       TButton  *Button2;
       void  __fastcall  Button1Click(TObject  *Sender);
       void  __fastcall  Button2Click(TObject  *Sender);
private:            //  User  declarations
       void  __fastcall  CMMessage(TMessage  &msg);    //訊息接收處理函數
public:                        //  User  declarations
       __fastcall  TForm1(TComponent*  Owner);
       BEGIN_MESSAGE_MAP
               VCL_MESSAGE_HANDLER(WM_MYMESSAGE,TMessage,CMMessage)
               //決定WM_MYMESSAGE訊息交給CMMessage  函數處理
       END_MESSAGE_MAP(TForm)
};
//---------------------------------------------------------------------------
extern  PACKAGE  TForm1  *Form1;
//---------------------------------------------------------------------------
#endif

unit.cpp

//---------------------------------------------------------------------------

#include  <vcl.h>
#pragma  hdrstop

#include  "Unit1.h"
//---------------------------------------------------------------------------
#pragma  package(smart_init)
#pragma  resource  "*.dfm"
TForm1  *Form1;
//---------------------------------------------------------------------------
__fastcall  TForm1::TForm1(TComponent*  Owner)
       :  TForm(Owner)
{
}
//---------------------------------------------------------------------------
void  __fastcall  TForm1::CMMessage(TMessage  &msg)
{
         if(msg.WParam  ==  0){
               ShowMessage("haha");
         }else
         if(msg.WParam  ==  1){
               ShowMessage("xixi");
         }
}
void  __fastcall  TForm1::Button1Click(TObject  *Sender)
{
             SendMessage(Handle,WM_MYMESSAGE,1,0);  //發送訊息
}
//---------------------------------------------------------------------------

void  __fastcall  TForm1::Button2Click(TObject  *Sender)
{
             SendMessage(Handle,WM_MYMESSAGE,0,0);//發送訊息

}
//---------------------------------------------------------------------------