WM_ACTIVATE

范例1：实现效果，非激活状态下，则隐藏
void CGUIExp::OnActivate(UINT nState, CWnd* pWndOther, BOOL bMinimized)
{
    CDialogEx::OnActivate(nState, pWndOther, bMinimized);
    // TODO: Add your message handler code here
    if (WA_INACTIVE == nState)
    {
        ShowWindow(SW_HIDE);
    }
}