绘制箭线的工具CArrowTool在OnLButtonDown中实际生成箭线对象，并记录箭线所连的开始节点，箭线的终节点确定在后面说明。

2. 2图元联动操作

2．2．1删除节点及箭线

void CDrawView::OnEditClear()

{

    CDrawDoc* pDoc=(CDrawDoc*)GetDocument();

    POSITION pos = m_selection.GetHeadPosition();

    while (pos != NULL)

    {

        CDrawObj* pObj = m_selection.GetNext(pos);

        GetDocument()->Remove(pObj);  //删除节点

        CDrawNode* pDrawCircle=(CDrawNode*)pObj;

        nIndex=pDrawCircle->GetObjIndex();//获取节点编号，若不是节点对象，返回0

        if(nIndex)      

        {

            pDoc->m_nIndex=nIndex;

            pos=GetDocument()->m_objects.GetHeadPosition();

            int i=0;

            int num=pDoc->m_objects.GetCount();

            m_num=pDoc->m_nIndex;

            while(i<num)

            {//序号位于被删除节点之后的所有节点序号减1

            CDrawNode* pDrawCircle=(CDrawNode*)pDoc->m_objects.GetNext(pos);

                if(pDrawCircle->GetObjIndex()>m_num)

                {

                    pDrawCircle->SetCircleIndex(m_num);

                    m_num++;

                }