通过ProcessID获取窗口句柄

HWND g_hwnd;
int g_nFound;

BOOL CALLBACK FindHwndFromPID( HWND hwnd, LPARAM lParam) :

HWND GetHwndFromPID ( DWORD dwProcessId)
{
g_hwnd = NULL;
g_nFound = 0;

EnumWindows ( FindHwndFromPID, ( LPARAM) dwProcessId));

if ( g_hwnd) // we found one...
return ( g_hwnd);

// nothing found :-(

return (NULL);
}

BOOL CALLBACK FindHwndFromPID( HWND hwnd, LPARAM lParam)
{
DWORD dwPID2Find = ( DWORD) lParam;
DWORD dwPID = 0;

if ( GetWindowThreadProcessId ( hwnd, &dwPID))
{
if ( dwPID == dwPID2Find)
{
g_hwnd = hwnd;

return ( FALSE);
}
}

return ( TRUE);
}

使用方法：
HWND hwnd = GetHwndFromPID(GetCurrentProcessId());