EnumWindowsProc

BOOL CALLBACK EnumWindowsProc(HWND hWnd, LPARAM lParam)
进程回调函数，类似于窗口句柄的枚举

typedef struct
{
    	HWND	hWnd;
    	DWORD	dwProcessID;//可以根据需求修改，例如根据窗口名找到窗口
}EnumWindowsArg;
#define WINDOWNAME_BUFLEN 1000
wchar_t* g_szWindowNameBuf = NULL;
#define AUTOMARK_BACKGROUND_WINDOWNAME _T("WindowID")
CString g_sWindowName(AUTOMARK_BACKGROUND_WINDOWNAME);

BOOL CALLBACK EnumWindowsProc(HWND hWnd, LPARAM lParam)
{//根据进程id获得句柄
    EnumWindowsArg* pArg = (EnumWindowsArg*)lParam;//传入已知的进程id

	DWORD dwProcessID = 0;
	//根据句柄获得进程ID
	::GetWindowThreadProcessId(hWnd, &dwProcessID);
	if (dwProcessID == pArg->dwProcessID)//如果当前句柄的进程id等于传入的id
	{
        wmemset(g_szWindowNameBuf, 0, WINDOWNAME_BUFLEN);
		::GetWindowText(hWnd, g_szWindowNameBuf, WINDOWNAME_BUFLEN);//根据句柄获得窗口名

		if (g_sWindowName.CompareNoCase(g_szWindowNameBuf) == 0)
		{	
			pArg->hWnd = hWnd;//返回当前的句柄
			return FALSE;	// Found
		}
	}	
	return TRUE;	// Not found
}
HWND GetHwndByProcessID(DWORD dwProcessID)
{
	HWND hWnd = NULL;

	EnumWindowsArg ewa;
	ewa.dwProcessID = dwProcessID;
	ewa.hWnd = NULL;

	g_szWindowNameBuf = new wchar_t[WINDOWNAME_BUFLEN];//必须要开辟新空间

	EnumWindows(EnumWindowsProc, (LPARAM)& ewa);//调用回调函数，循环寻找等于当前进程id的句柄

	delete[] g_szWindowNameBuf;
	g_szWindowNameBuf = NULL;

	if (ewa.hWnd)//不为空则找到
	{
		hWnd = ewa.hWnd;
	}

	return hWnd;
}