MFC 更换背景图片的方法

void CRobotClientDlg::OnPaint() {if (IsIconic()){CPaintDC dc(this); // device context for paintingSendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);// Center icon in client rectangleint cxIcon = GetSystemMetrics(SM_CXICON);int cyIcon = GetSystemMetrics(SM_CYICON);CRect rect;GetClientRect(&rect);int x = (rect.Width() - cxIcon + 1) / 2;int y = (rect.Height() - cyIcon + 1) / 2;// Draw the icondc.DrawIcon(x, y, m_hIcon);}else{  //CDialog::OnPaint();把这个注释掉，不调用基类的OnPaint()   CPaintDC dc(this);       CDC memdc;       memdc.CreateCompatibleDC(&dc);//创建兼容DC       CBitmap bkg;       bkg.LoadBitmap(IDB_BG);//载入位图（这里用自己定义的位图ID）       BITMAP bkginfo;       bkg.GetBitmap(&bkginfo);//获取位图信息       memdc.SelectObject(&bkg);       RECT rect;       GetWindowRect(&rect);//获取对话框信息       dc.StretchBlt(0,0,rect.right-rect.left,rect.bottom-rect.top,&memdc,0,0,bkginfo.bmWidth,bkginfo.bmHeight,SRCCOPY);}}