上一视图下一视图功能实现(C#+SuperMap Objects)

        //list 用于保存视图范围
        private List<SuperMapLib.soRect> m_extents = new List<SuperMapLib.soRect>();

        //视图存取list的最大限制数
        private int m_extentRecordsMax = 3;

        //当前显示视图在视图list中的index
        private int m_extentNowIndex = 0;

        //当前视图操作状态 next|last|other
        private String m_viewState = String.Empty;
        
        //上一视图
        private void btnLastView_Click(object sender, EventArgs e)
        {
            this.m_viewState="last";
            this.btnNextView.Enabled = true;
            if(this.m_extentNowIndex==0)
            {
            } 
            else if (this.m_extentNowIndex == 1)
            {
                this.m_extentNowIndex = this.m_extentNowIndex - 1;
                this.SuperMap1.ViewBounds = this.m_extents[this.m_extentNowIndex];
                this.SuperMap1.Refresh();
                this.btnLastView.Enabled = false;
            }

            else
            {
                this.m_extentNowIndex=this.m_extentNowIndex-1;
                this.SuperMap1.ViewBounds = this.m_extents[this.m_extentNowIndex];
                this.SuperMap1.Refresh();
            }
        }

        //下一视图
        private void btnNextView_Click(object sender, EventArgs e)
        {
            this.m_viewState = "next";
            this.btnLastView.Enabled = true;
            if (this.m_extentNowIndex == this.m_extents.Count - 1)
            {
            }
            else if (this.m_extentNowIndex == this.m_extents.Count - 2)
            {
                this.m_extentNowIndex = this.m_extentNowIndex + 1;
                this.SuperMap1.ViewBounds = this.m_extents[this.m_extentNowIndex];
                this.SuperMap1.Refresh();
                this.btnNextView.Enabled = false;
            }
            else
            {
                this.m_extentNowIndex = this.m_extentNowIndex + 1;
                this.SuperMap1.ViewBounds = this.m_extents[this.m_extentNowIndex];
                this.SuperMap1.Refresh();
            }
        }

        //地图绘制完成后动作
        private void SuperMap1_AfterMapDraw(object sender, AxSuperMapLib._DSuperMapEvents_AfterMapDrawEvent e)
        {
            if (this.m_viewState!="last"&& this.m_viewState!="next")
            {
                if (this.m_extents.Count < m_extentRecordsMax)
                {
                    this.m_extents.Add(this.SuperMap1.ViewBounds);
                    this.m_extentNowIndex = this.m_extents.Count - 1;
                    this.m_viewState = null;
                }
                else
                {
                    this.m_extents.Add(this.SuperMap1.ViewBounds);
                    this.m_extents.RemoveAt(0);
                    this.m_extentNowIndex = this.m_extents.Count - 1;
                    this.m_viewState = null;
                }
            }
        }