ArcEngine-长度量算

在使用ArcGIS的过程中，我们会发现在右上角有个长度量算的工具，对于随意在地图上选择的两点进行量算并给出实际距离。那么到底是怎么实现的呢，本文附上实现的源代码，有错误或者更好地优化的方案请进行纠正，努力才会让目标离我们更近些。

 //长度量算工具代码
        private IHookHelper m_hookHelper;
        private IGraphicsContainer pGraphicContainer;
        private IMap pMap;
        private IActiveView pActiveView;
        private IDisplayFeedback pDisplayFeedback;
        private IScreenDisplay pScreenDisplay = null;
        IPoint pPointStd;
        IPoint pPoint;
        IPoint pPointLast;
        IProximityOperator pProximity;
        public double measureDistance = 0;
        public double DistanceSegment = 0;
        INewLineFeedback pNewLineFeedback = null;
        public DistancePointsTool()
        {
            base.m_category="SpatailAnalyst";
            base.m_caption="长度量算";
            base.m_message="长度量算";
            base.m_toolTip="长度量算";
            base.m_name="长度量算";
        }
        public override void OnCreate(object hook)
        {
            if (m_hookHelper==null)
                m_hookHelper=new HookHelperClass();
            m_hookHelper.Hook=hook;
            pActiveView=m_hookHelper.ActiveView;
            pMap=pActiveView.FocusMap;
            pGraphicContainer=pMap as IGraphicsContainer;
            pDisplayFeedback=null;
            pScreenDisplay=pActiveView.ScreenDisplay;
        }
        //重载鼠标点击事件
        protected override void OnMouseDown(int Button,int shift,int X,int Y)

 {
    //产生一个当前点击的点对象
            if (Button==1)
            {
                //判断该点是否为第一个点
                if (pDisplayFeedback==null)
                {
                    pPointStd=new PointClass();
                    pPointStd.SpatialReference=pMap.SpatialReference;
                    pPointStd=pActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(X,Y);
                    pDisplayFeedback=new NewLineFeedbackClass();
                    pDisplayFeedback.Display=pScreenDisplay;
                    pNewLineFeedback=pDisplayFeedback as INewLineFeedback;
                    pNewLineFeedback.Start(pPointStd);
                    pPointLast=pPointStd;
                    pProximity=pPointStd as IProximityOperator;
                }
                else{
                    pNewLineFeedback=pDisplayFeedback as INewLineFeedback;
                    pNewLineFeedback.AddPoint(pPoint);
                    IProximityOperator pProximity=pPointLast as IProximityOperator;
                    DistanceSegment=pProximity.ReturnDistance(pPoint);
                    measureDistance+=pProximity.ReturnDistance(pPoint);
                    pPointLast =pPoint;
                }
            }
        }
        //重载鼠标移动事件
        public override void OnMouseMove(int Button,int shift,int X,int Y)
{
            pPoint =new PointClass();
            pPoint.SpatialReference=pMap.SpatialReference;
            pPoint=pActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(X,Y);
            if(pNewLineFeedback!=null)
            {

                    pNewLineFeedback.MoveTo(pPoint);
                }
            }
        //重载鼠标双击事件，距离量测结束
        public override void onDblClick()
        {
            base.onDblClick();
            IGeometry pGeometry=null;
            string LengthUnits=null;
            if (pNewLineFeedback!=null)
            {
                pGeometry=pNewLineFeedback.Stop();
                pNewLineFeedback=null;
                IElement pElement=null;
                ISimpleLineSymbol pSimpleLineSymbol=new SimpleLineSymbolClass();
                pSimpleLineSymbol.Width=2;
                pSimpleLineSymbol.Style=esriSimpleLineStyle.esriSLSSolid;

                ISimpleFillSymbol pSimpleFillSymbol=new SimpleFillSymbolClass();
                pSimpleFillSymbol.Style=esriSimpleFillStyle.esriSFSSolid;
                pSimpleFillSymbol.Outline= pSimpleLineSymbol;
                ILineElement pLineElement=new LineElementClass();
                pLineElement.Symbol=pSimpleLineSymbol;
                pElement=pLineElement as IElement;
                pElement=pLineElement as IElement;
                pElement.Geometry=pGeometry;
                IGraphicsContainer pGraphicsContainer=pActiveView.FocusMap as IGraphicsContainer;
                pGraphicsContainer.AddElement(pElement,0);
                pActiveView.PartialRefresh(esriViewDrawPhase.esriViewGraphics,null,null);
                pGraphicsContainer.DeleteElement(pElement);
                MessageBox.Show("\n线段长度："+DistanceSegment.ToString()+"\n总长度："+measureDistance.ToString()+"\n地图单位："+LengthUnits,"长度量算");
                measureDistance=0;
                DistanceSegment=0;
                pNewLineFeedback=null;
                pDisplayFeedback=null;
            }
        }