开发那点事（十一）微信小程序地图聚合功能实现

写在前面的话

公司项目需求要在微信小程序上实现地图marker点聚合的功能，百度苦寻无果，故自己实现。

最终效果

功能演示

核心思路

marker标签中的callout属性用来显示聚合点的数量
点击聚合点时，以聚合点为中心放大地图，不需要再次请求后台接口
根据map组件scale缩放级别将地图分成一个一个的小格子，计算小格子中marker点的数量
由于小程序无法像网页端那样处理庞大的数据量，为了提高用户体验，地图状态为缩放或者范围缩小时缓存上次marker数据，无需请求后台接口

关键js文件

MapUtil.js （判断是否为缩放状态，根据后台接口数据格式化成地图聚合类型marker数据等）
ZjMarker.js（maker点基类，根据简单的参数构建单个marker及聚合marker）

具体实现

MapUtil.js

import {
  zjMarker
} from '../../utils/mapUtil/ZjMarker';
import {
  transformFromWGSToGCJ
} from '../WSCoordinate';
export class MapUtil {
  constructor(northeast, southwest, scale) {
    this.northeast = northeast;
    this.southwest = southwest;
    this.scale = scale;
    console.log('初始化mapUtil成功');
    console.log(this.northeast, 'northeast');
  }
  //设置初始化范围
  setInitData(northeast, southwest, scale) {
    this.northeast = northeast;
    this.southwest = southwest;
    this.scale = scale;
    console.log('刷新mapUtil成功');
  }
  //判断是否为缩放，
  checkRefresh(northeast, southwest) {
    console.log('检测是否可以刷新接口');
    console.log(this.northeast, 'northeast');
    console.log(northeast, 'currentNortheast');
    let result = true;
    if (this.northeast.latitude > northeast.latitude) {
      console.log('东北纬度缩小');
    }
    if (this.southwest.latitude < southwest.latitude) {
      console.log('西南纬度增高');
    }
    if (this.northeast.longitude > northeast.longitude) {
      console.log('东北经度增大');
    }
    if (this.southwest.longitude < southwest.longitude) {
      console.log('西南经度缩小');
    }
    if (this.northeast.latitude > northeast.latitude && this.southwest.latitude < southwest.latitude &&
      this.northeast.longitude > northeast.longitude && this.southwest.longitude < southwest.longitude) {
      console.log('地图缩放，不请求接口');
      result = false
    }
    return result;
  }
  //根据东北 西南经纬度 以及后台返回标记点 格式化成小程序marker点
  getFortMatMarkerList(northeast, southwest, scale, backendMarkerList) {
    //屏幕中显示的经度的长度和纬度的长度
    let mapWidth = southwest.longitude - northeast.longitude;
    let mapHeight = northeast.latitude - southwest.latitude;
    //将屏幕中地图分割的横向 格子数和 纵向格子数
    let widthSize = scale;
    let heightSize = widthSize + parseInt(scale / 2);
    //计算每个格子的经纬度的长度
    let unitWidth = mapWidth / widthSize;
    let unitHeight = mapHeight / heightSize;
    let pointData = {};
    backendMarkerList.forEach(latLng => {
      //如果点在显示范围内
      if (latLng.latitude < northeast.latitude && latLng.latitude > southwest.latitude &&
        latLng.longitude < northeast.longitude && latLng.longitude > southwest.longitude) {
        let relativeX = latLng.longitude - northeast.longitude;
        let relativeY = latLng.latitude - southwest.latitude;
        //计算出这个点，处于哪个格子
        let x = parseInt(Math.floor(relativeX / unitWidth));
        let y = parseInt(Math.floor(relativeY / unitHeight));
        if (x < 0 || y < 0) {
          console.log('点位不在格子内', '失败');
        }
        //生成单元格点位数据
        let pointKey = x + ',' + y;
        if (pointData[pointKey] == undefined) {
          pointData[pointKey] = [];
        }
        pointData[pointKey].push(latLng);
      }
    });
    let resultMapArray = [];
    for (let y = 0; y < heightSize; y++) {
      for (let x = 0; x < widthSize; x++) {
        let pointKey = x + ',' + y;
        //筛选没有充电站点位的格子
        if (pointData[pointKey] != undefined) {
          let markerItem = {};
          //聚合点与单点共存 , 长度等于一 不聚合点
          if (pointData[pointKey].length == 1) {
            let iconPath = pointData[pointKey][0].ScanAndCharge == 1 ? '/img/scanMarkerIcon.png' : '/img/markerIcon.png';
            markerItem = new zjMarker(pointData[pointKey][0].longitude, pointData[pointKey][0].latitude, pointData[pointKey][0].StationID, {
              iconPath: iconPath
            })
            //长度大于一 聚合点
          } else if (pointData[pointKey].length > 1) {
            let iconPath = pointData[pointKey][0].ScanAndCharge == 1 ? '/img/cluScanMarkerIcon.png' : '/img/cluMarkerIcon.png';
            markerItem = new zjMarker(pointData[pointKey][0].longitude, pointData[pointKey][0].latitude, pointData[pointKey][0].StationID, {
              type: 'cluster',
              iconPath: iconPath,
              num: pointData[pointKey].length
            })
          }
          resultMapArray.push(markerItem);
        }
      }
    }
    console.log(resultMapArray, 'resultMapArray');
    return resultMapArray;
  }
  //获取中心纬度
  getCenterLocation(northeast, southwest) {
    let mapWidth = southwest.longitude - northeast.longitude;
    let mapHeight = northeast.latitude - southwest.latitude;
    let longitude = northeast.longitude + mapWidth;
    let latitude = southwest.latitude + mapHeight;
    return {
      latitude: latitude,
      longitude: longitude
    }
  }
}

ZjMarker.js

//地图marker标记点基类 （单点`聚合）
export class zjMarker {
  constructor(longitude, latitude, id, options = {}) {
    this.longitude = longitude;
    this.latitude = latitude;
    this.id = id;
    this.width = options.width ? options.width : 30;
    this.height = options.height != undefined ? options.height : 36;
    let type = options.type == undefined ? 'single' : options.type;
    this.iconPath = options.iconPath == undefined ? '/img/markerIcon.png' : options.iconPath;
    if (type != 'single') {
      this.callout = {
        content: options.num, //文本
        color: '#000', //文本颜色
        borderRadius: 3, //边框圆角
        borderWidth: 0, //边框宽度
        bgColor: 'transparent', //背景色
        padding: 0, //文本边缘留白,
        display: 'ALWAYS',
        textAlign: 'center', //文本对齐方式。有效值: left, right, center,
        anchorY: 62 //可能需要根据各个手机做出相应的适配
      }
    }
  }
}

最后，在map组件中实现bindregionchange方法获取东北以及西南经纬度，根据经纬度范围判断是否需要请求后台接口重新获取点位信息

 if (mapUtil.checkRefresh(res.northeast, res.southwest)) {
                console.log('开始刷新接口');
                let location = mapUtil.getCenterLocation(res.northeast, res.southwest);
                that.loadMapData(location.latitude, location.longitude, markerList => {
                  markerList.forEach(item => {
                    item.longitude = item.StationLng;
                    item.latitude = item.StationLat;
                  });
                  oriMarkerList = markerList;
                  that.setData({
                    markerList: mapUtil.getFortMatMarkerList(res.northeast, res.southwest, scale, markerList)
                  });
                });
                mapUtil.setInitData(res.northeast, res.southwest, scale);
              } else {
                that.setData({
                  markerList: mapUtil.getFortMatMarkerList(res.northeast, res.southwest, scale, oriMarkerList)
                });
              }

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