一、TApplication的OnMessage事件
OnMessage事件只处理消息队列中的消息，SendMessage()发送的消息不会被截获。
任何窗体接收到一个windows消息，都会触发一次此事件
函数原型：
typedef void __fastcall (__closure *TMessageEvent) (tagMSG &Msg,bool &Handled);
Msg表示被截获的消息，Handled表示是否处理完成，为TRUE则防止被再次处理，设为FALSE则可以继续处理。
代码
//计算程序响应的消息数
//---------------------------------------------------------------------------
#ifndef Msg_testH
#define Msg_testH
//---------------------------------------------------------------------------
#include
#include
#include
#include
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published: // IDE-managed Components
TLabel *Label1;
void __fastcall FormCreate(TObject *Sender);
private: // User declarations
//自定义消息响应函数
void __fastcall AppMessage(tagMSG &MSG,bool &Handled);
public: // User declarations
__fastcall TForm1(TComponent* Owner);
int Num;
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif
//---------------------------------------------------------------------------
#include
#pragma hdrstop
#include "Msg_test.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
: TForm(Owner)
{
Num = 0;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormCreate(TObject *Sender)
{
//将自定义函数与OnMessage事件联系起来
Application->OnMessage = AppMessage;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::AppMessage(tagMSG &MSG,bool &Handled)
{
Num++;
Label1->Caption = AnsiString(Num);
Handled = false;
}