VC+MapX 在临时图层中添加点图元,该如何解决

        //创建点图元    CMapXPoint point;    point.Set(m_dMapXX,m_dMapXY);    //创建图元样式    CMapXStyle style;    style.SetSymbolType(miSymbolTypeBitmap);    style.SetSymbolBitmapName(_T("camera.bmp"));    //设置MapX不进行自动更新    m_ctrlMapX.SetAutoRedraw(FALSE);    //设置图层可写    pLayer->SetEditable(TRUE);    //创建特征对象    VARIANT varPoint;    VARIANT varStyle;    varPoint.vt = VT_DISPATCH;    varPoint.pdispVal = point.m_lpDispatch;    varStyle.vt = VT_DISPATCH;    varStyle.pdispVal = style.m_lpDispatch;    CMapXFeatureFactory factory;    CMapXFeature feature = factory.CreateSymbol(varPoint,varStyle);    //添加到图层    pLayer->AddFeature(feature);    pLayer->Refresh();    //设置MapX进行自动更新    m_ctrlMapX.SetAutoRedraw(TRUE);    //设置图层不可写    pLayer->SetEditable(FALSE);