VC 中使用 COM 接口的一般步骤

1.在“stdafx.h”中，在   #include <afxwin.h>         // MFC 核心和标准组件   #include <afxext.h>         // MFC 扩展   #include <afxdisp.h>        // MFC 自动化类   前面加上   #include <afx.h>   #include <wininet.h>      这两个头文件顺序不可颠倒   即：   #include <afx.h>   #include <wininet.h>     #include <afxwin.h>         // MFC 核心和标准组件   #include <afxext.h>         // MFC 扩展   #include <afxdisp.h>        // MFC 自动化类

2.使用 CoInitialize(NULL)  和  CoUninitialize() 初始化和终止 COM 使用环境。

3.在使用了 ATL COM 接口的源文件头部，包含声明该 ATL COM 接口的头文件即可。    IActiveDesktop ＝》#include <shlobj.h>

一个使用 ATL COM 的例子：BOOL CSystemSet::SetWallPaper(CString strImaglePath, DWORD dwStyle){ CoInitialize(NULL);

 BOOL bRet = FALSE; HRESULT hr = S_FALSE; IActiveDesktop* pIAD = NULL;

 hr = CoCreateInstance(CLSID_ActiveDesktop,  NULL, CLSCTX_INPROC_SERVER,    IID_IActiveDesktop, (void**) &pIAD ); if (SUCCEEDED(hr)) {  BOOL bActiveDesktop = FALSE;

  COMPONENTSOPT co;  co.dwSize = sizeof(co);  if (SUCCEEDED(pIAD->GetDesktopItemOptions(&co, 0)))  {   if (!co.fActiveDesktop || !co.fEnableComponents)   {    co.fActiveDesktop = TRUE;    co.fEnableComponents = TRUE;    if (SUCCEEDED(pIAD->SetDesktopItemOptions(&co, 0)))     bActiveDesktop = TRUE;   }   else    bActiveDesktop = TRUE;  }  if (bActiveDesktop)  {   WCHAR wszWallpaper [MAX_PATH];   ZeroMemory(wszWallpaper, sizeof(wszWallpaper));

   #if defined(_UNICODE)   CopyMemory(wszWallpaper, strImaglePath.GetBuffer(0),     min(MAX_PATH * sizeof(TCHAR), (strImaglePath.GetLength() + 1) * sizeof(TCHAR)));   #else   MultiByteToWideChar(CP_ACP, 0, strImaglePath, -1, wszWallpaper, MAX_PATH);   #endif

   WALLPAPEROPT wpo;   wpo.dwSize = sizeof(wpo);   wpo.dwStyle = dwStyle;   if (SUCCEEDED(hr = pIAD->SetWallpaper(wszWallpaper, 0)) &&    SUCCEEDED(hr = pIAD->SetWallpaperOptions(&wpo, 0)) &&    SUCCEEDED(hr = pIAD->ApplyChanges(AD_APPLY_ALL)) &&    SUCCEEDED(hr = pIAD->GetWallpaper(wszWallpaper, MAX_PATH, 0)))   {    bRet = TRUE;   }  }  pIAD->Release(); }

 CoUninitialize(); return bRet;}