两个窗口程序(进程)之间的通信

   两个进程或者说两个窗口程序之间如何交换信息呢？Windows提供了一个消息机制WM_COPYDATA，可以在两个窗口之间交换数据。WM＿COPYDATA消息在两个窗口程序之间传递一个预定义的数据结构COPYDATASTRUCT。
typedef struct tagCOPYDATASTRUCT
{
　　DWORD dwData;
　　DWORD cbData;
　　PVOID lpData;
} COPYDATASTRUCT;
dwData为32位的自定义数据，lpData为指向数据的指针，cbData为lpData指针指向数据内存的大小（字节数）。

　　发送WM_COPYDATA消息只能用SendMessage而不能用PostMessage，原因是WM_COPYDATA发送的数据是以内存映射文件形式发送的，用PostMessage后内存映射文件的句柄会失效了，造成数据丢失。

发送方窗口程序(进程)的代码

class TForm1 : public TForm
{
        __published:    // IDE-managed Components
            TEdit *edt1;
            TButton *btn1;
            void __fastcall btn1Click(TObject *Sender);
       private:            // User declarations
        public:        // User declarations
            __fastcall TForm1(TComponent* Owner);
            char *cpSendStr,cSendStr[512];
            COPYDATASTRUCT pCopyData;
};
//-----------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{
       cpSendStr = cSendStr;
       cpSendStr = "Losng";
}
//---------------------------------------------------------------------------
void __fastcall TForm1::btn1Click(TObject *Sender)
{
         HANDLE fm;
         fm = FindWindow(NULL,"Recemess");
         if (fm != NULL)
             {
                 pCopyData.dwData = 0;
                 if(edt1->Text != "") cpSendStr = edt1->Text.c_str() ;
                 pCopyData.lpData = cpSendStr ;
                 pCopyData.cbData = strlen(cpSendStr);
                 SendMessage(fm,WM_COPYDATA,0,LPARAM)&pCopyData);
             }
         else ShowMessage("没有找到接收窗口！");
}
//-----------------------------------------------------------------------
                        

 

接收窗口程序(进程)代码

class TForm1 : public TForm
{
　　__published:    // IDE-managed Components
        TEdit *edt1;
　　private:          // User declarations
　　public:           // User declarations

       void __fastcall OnWMCopyData(TMessage &Msg);
      BEGIN_MESSAGE_MAP
          VCL_MESSAGE_HANDLER(WM_COPYDATA,TMessage,OnWMCopyData);
      END_MESSAGE_MAP(TForm)
      __fastcall TForm1(TComponent* Owner);

};
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{
   this->Caption = "Recemess";
}
//---------------------------------------------------------------------------
 void __fastcall TForm1::OnWMCopyData(TMessage &Msg)
 {
   char *cpSendStr,cSendStr[512];
   cpSendStr = cSendStr;
   bool flag = false ;
   if ( Msg.Msg == WM_COPYDATA )
     {
        COPYDATASTRUCT* pCopyData = (COPYDATASTRUCT* )Msg.LParam ;
        cpSendStr = (char *)pCopyData->lpData;
        edt1->Text = cpSendStr ;
        flag = true ;
     }
   if (!flag)
     {
        TForm::WndProc(Msg);
     }
 }