cesium面积测量

使用方法新建一个文件measureArea.js将下面代码贴上去

// DrawPolygon
/*
绘制面(面积测量)
 */
 
class measureArea {
  constructor(arg) {
    this.objId = Number(
      new Date().getTime() + "" + Number(Math.random() * 1000).toFixed(0)
    );
    this.viewer = arg.viewer;
    this.Cesium = arg.Cesium;
    this.callback = arg.callback;
    this._polygon = null; //活动面
    this._polygonLast = null; //最后一个面
    this._positions = []; //活动点
    this._entities_point = []; //脏数据
    this._entities_polygon = []; //脏数据
    this._polygonData = null; //用户构造面
  }
 
  //返回最后活动面
  get polygon() {
    return this._polygonLast;
  }
 
  //返回面数据用于加载面
  getData() {
    return this._polygonData;
  }
 
  //加载面
  loadPolygon(data) {
    var $this = this;
    return this.viewer.entities.add({
      polygon: {
        hierarchy: new $this.Cesium.PolygonHierarchy(data),
        clampToGround: true,
        show: true,
        fill: true,
        material: $this.Cesi