对MFC创建COM组件和实现COM连接点的小结

1．如果要在普通工程中使用COM组件，包含以下ATL头文件：

#include <afxdisp.h>

#include <atlbase.h>

//You may derive a class from CComModule and use it if you want to override

//something, but do not change the name of _Module

extern CComModule _Module;

#include <atlcom.h>

注意：头文件顺序不能改变。（不太清楚原因，但是只要头文件顺序改变，complile错误。）

 

 

2．从一个连接点机制的实例看开来：

（1）按照COM规范来写自定义组件：

一个在client端实现的普通双接口的组件，继承服务器端定义的事件接口如下：

 

 

class CMyEvent :

       public IDispatchImpl<_IConnectionObjEvents, &DIID__IConnectionObjEvents, &LIBID_COM_CPLib>,

       public CComObjectRoot

{

public:

       CMyEvent()

       {

       }

BEGIN_COM_MAP(CMyEvent)

       COM_INTERFACE_ENTRY(IDispatch)

       COM_INTERFACE_ENTRY(_IConnectionObjEvents)

END_COM_MAP()

 

 

   // IMyEvent methods

       STDMETHODIMP CMyEvent::Click()

       {

              AfxMessageBox("Get message from IConnetionObj");

              return S_OK;

       }

};

其中Click（）是自定义事件。

（2）客户端工程中按步骤和COM组件建立连接。(思路如此，但我在调试时会弹出调对话框，跟踪发现连接已建立...暂时没有找到原因，如果哪位知道原因请告诉我。)

              HRESULT hr = CoInitialize(NULL);

              if(FAILED(hr))

              {

                     AfxMessageBox("Coinitialize（） failed!");

                     return 0 ;

              }

              IUnknown *pIUnknown = NULL;

              hr = CoCreateInstance( CLSID_ConnectionObj , NULL ,

                     CLSCTX_INPROC_SERVER, IID_IUnknown, (void **)&pIUnknown) ;

              if( FAILED(hr) )

              {

                     AfxMessageBox("Con't get IUnknown interface!");

                     return 0 ;

              }    

              IConnectionObj *pIConnectionObj = NULL; 

              if( pIUnknown!= NULL)

              {

                     hr = pIUnknown->QueryInterface(IID_IConnectionObj, (void **)&pIConnectionObj);

                     if(FAILED(hr))

                     {

                            AfxMessageBox("Can't get IConnectionObj interface!") ;

                            return 0 ;

                     }

              }

              IConnectionPointContainer *pIConnPtCont = NULL;

              if(pIConnectionObj!=NULL)

              {

hr=pIConnectionObj->QueryInterface(IID_IConnectionPointContainer,(LPVOID*)&pIConnPtCont) ;

                     if(FAILED(hr))

                     {

                            AfxMessageBox("Can't get IConnectionPointContainer interface!");

                            return 0;

                     }

              }

              IConnectionPoint *pIConnPt = NULL;

              if(pIConnPtCont!=NULL)

              {

                     hr = pIConnPtCont->FindConnectionPoint (DIID__IConnectionObjEvents, &pIConnPt);

                     if(FAILED(hr))

                     {

                            AfxMessageBox("Can't get IConnectionPoint interface!");

                            return 0;

                     }

              }

              printf("Get IConnectionPoint interface!\n");

 

 

              CComObject<CMyEvent> *pEvent = NULL;

              CComObject<CMyEvent>::CreateInstance(&pEvent);

              ASSERT(pEvent);

              // give this pointer to the server

              pIUnknown = NULL;

              hr = pEvent->QueryInterface(__uuidof(IUnknown), (void **) &pIUnknown);

              if (FAILED(hr))

              {

                     AfxMessageBox("pEvent->QueryInterface() fail!");

                     return 0;

              }

              hr = pIConnPt->Advise(pIUnknown, &dwMyEvt);

              if (FAILED(hr))

              {

                     AfxMessageBox("pIConnPt->Advise() faile!");

                     return 0;

              }

              // Do some work

              pIConnectionObj->DoClick();       //DoClick()在server端定义，在client端实现

              hr = pIConnPt->Unadvise( dwMyEvt );

              if (FAILED(hr))

              {

                     AfxMessageBox("pIConnPt->Unadvise() faile");

                     return 0;

              }

              pEvent->Release();

              pIConnPt->Release();

              pIConnPtCont->Release();

              pIConnectionObj->Release();

              pIUnknown->Release();

              CoUninitialize();

       }