背景：
某项目要做一个公交换乘查询。以最简单的情况为例，即只需乘坐一次车，不需换乘即可到达。线路A包含若干个站点（A0,A1,A2,...,An），其中A0为线路起始站点，An为终止站点。已获取出发的站点（As，其中0<=s<n）、到达的点（Ae，其中0<e<=n，且s<e），以及线路（一个Polyline对象，包含Paths个数为1）。
As、Ae位于站点图层中，其坐标在空间上可能位于线路Polyline上，也可能与线路稍有偏差，不落在线上。
在进行乘车线路展示时，需要截取该线路位于出发站点As、到达站点Ae之间的Polyline的一段。
代码如是：
/** * 使用两点（可能在线上，也可在线外）切割一条Polyline，截取两点之间的Polyline * @param {[type]} firstPoint [第一个切割点] * @param {[type]} secondPoint [第二个切割点] * @param {[type]} targetPolyline [被切割的Polyline] * @return {[type]} [Polyline] */ getCutLine: function(firstPoint,secondPoint,targetPolyline) { console.log("firstPoint : ",firstPoint," secondPoint : ",secondPoint," targetPolyline : ",targetPolyline); //获取与两个切割点最近的目标Polyline上的点 var firstNearestPoint = geometryEngine.nearestCoordinate(targetPolyline,firstPoint).coordinate; var secondNearestPoint = geometryEngine.nearestCoordinate(targetPolyline,secondPoint).coordinate; console.log("firstNearestPoint : ",firstNearestPoint," secondNearestPoint : ",secondNearestPoint); //构造第一条切割线 var firstFromX = firstNearestPoint.x + 1; var firstFromY = firstNearestPoint.y + 1; var firstToX = firstNearestPoint.x - 1; var firstToY = firstNearestPoint.y - 1; var firstFromPoint = new esri.geometry.Point(firstFromX, firstFromY, this.map.spatialReference); var firstToPoint = new esri.geometry.Point(firstToX, firstToY, this.map.spatialReference); var firstCuttingLine = new esri.geometry.Polyline(this.map.spatialReference); firstCuttingLine.addPath([firstFromPoint, firstNearestPoint, firstToPoint]); //构造第二条切割线 var secondFromX = secondNearestPoint.x + 1; var secondFromY = secondNearestPoint.y + 1; var secondToX = secondNearestPoint.x - 1; var secondToY = secondNearestPoint.y - 1; var secondFromPoint = new esri.geometry.Point(secondFromX, secondFromY, this.map.spatialReference); var secondToPoint = new esri.geometry.Point(secondToX, secondToY, this.map.spatialReference); var secondCuttingLine = new esri.geometry.Polyline(this.map.spatialReference); secondCuttingLine.addPath([secondFromPoint, secondNearestPoint, secondToPoint]); //第一次切割之后的结果（使用第一条切割线，切得两条Polyline） var firstCutResult = geometryEngine.cut(targetPolyline,firstCuttingLine); //两次切割之后的结果集（三条Polyline） var lineSegments=[]; //使用第二条切割线，对第一次切割之后的结果进行切割 firstCutResult.forEach(function(aLine){ var cutLines = geometryEngine.cut(aLine,secondCuttingLine); cutLines.forEach(function(aLineSegment){ lineSegments.push(aLineSegment); }); }); console.log(lineSegments); //要返回的结果（为传入的Polyline的一段。默认为结果集中的第一条记录） var lineSegment = lineSegments[0]; //结果段长度 var pathLength = lineSegment.paths[0].length; //首末两个点 var fromPoint = lineSegment.paths[0][0]; var toPoint = lineSegment.paths[0][pathLength-1]; /** * 取首末两点，与两个切割点求距离平方和（以下简称距离） * 正反方向两次距离计算，取二者较小者 **/ var minDistance1 = Math.pow((firstPoint.x-fromPoint[0]),2)+Math.pow((firstPoint.y-fromPoint[1]),2)+ Math.pow((secondPoint.x-toPoint[0]),2)+Math.pow((secondPoint.y-toPoint[1]),2); var minDistance2 = Math.pow((firstPoint.x-toPoint[0]),2)+Math.pow((firstPoint.y-toPoint[1]),2)+ Math.pow((secondPoint.x-fromPoint[0]),2)+Math.pow((secondPoint.y-fromPoint[1]),2); var minDistance = (minDistance1<=minDistance2)?minDistance1:minDistance2; console.log("PathLength : ",pathLength,"MinDistance1 : ",minDistance1,"MinDistance2 : ",minDistance2,"MinDistance : ",minDistance); //循环结果集中的每一条记录，分别计算距离 lineSegments.forEach(function(aSegment,nIndex){ if(0<nIndex){ //跳过第一个 var tempPathLength = aSegment.paths[0].length; var tempFromPoint = aSegment.paths[0][0]; var tempToPoint = aSegment.paths[0][tempPathLength-1]; var tempMinDistance1= Math.pow((firstPoint.x-tempFromPoint[0]),2)+Math.pow((firstPoint.y-tempFromPoint[1]),2)+ Math.pow((secondPoint.x-tempToPoint[0]),2)+Math.pow((secondPoint.y-tempToPoint[1]),2); var tempMinDistance2 = Math.pow((firstPoint.x-tempToPoint[0]),2)+Math.pow((firstPoint.y-tempToPoint[1]),2)+ Math.pow((secondPoint.x-tempFromPoint[0]),2)+Math.pow((secondPoint.y-tempFromPoint[1]),2); console.log("TempPathLength : ",tempPathLength," TempMinDistance1 : ",tempMinDistance1," TempMinDistance2 : ",tempMinDistance2); //若当前距离小于最小距离，则将当前结果记录保存为备选返回记录 if(tempMinDistance1<minDistance||tempMinDistance2<minDistance){ console.log("aSegment : ",aSegment); lineSegment = aSegment; } } }); console.log("LineSegment : ",lineSegment); return lineSegment; }示例：
换乘结果展示：
完整的线路：
