package com.fh.util;

import java.util.HashMap;
import java.util.Map;

public class MapDistance {  
      
    private static double EARTH_RADIUS = 6378.137;  
  
    private static double rad(double d) {  
        return d * Math.PI / 180.0;  
    }
    
    /**
     * 根据两个位置的经纬度，来计算两地的距离（单位为KM）
     * 参数为String类型
     * @param lat1 用户经度
     * @param lng1 用户纬度
     * @param lat2 商家经度
     * @param lng2 商家纬度
     * @return
     */
    public static String getDistance(String lat1Str, String lng1Str, String lat2Str, String lng2Str) {
        Double lat1 = Double.parseDouble(lat1Str);
        Double lng1 = Double.parseDouble(lng1Str);
        Double lat2 = Double.parseDouble(lat2Str);
        Double lng2 = Double.parseDouble(lng2Str);
        double patm = 2;
        double radLat1 = rad(lat1);
        double radLat2 = rad(lat2);
        double difference = radLat1 - radLat2;
        double mdifference = rad(lng1) - rad(lng2);
        double distance = patm * Math.asin(Math.sqrt(Math.pow(Math.sin(difference / patm), patm)
                + Math.cos(radLat1) * Math.cos(radLat2)
                * Math.pow(Math.sin(mdifference / patm), patm)));
        distance = distance * EARTH_RADIUS;
        String distanceStr = String.valueOf(distance);
        return distanceStr;
    }
    
    /**
     * 获取当前用户一定距离以内的经纬度值
     * 单位米 return minLat
     * 最小经度 minLng
     * 最小纬度 maxLat
     * 最大经度 maxLng
     * 最大纬度 minLat
     */
    public static Map getAround(String latStr, String lngStr, String raidus) {
        Map map = new HashMap();
        
        Double latitude = Double.parseDouble(latStr);// 传值给经度
        Double longitude = Double.parseDouble(lngStr);// 传值给纬度

        Double degree = (24901 * 1609) / 360.0; // 获取每度
        double raidusMile = Double.parseDouble(raidus);
        
        Double mpdLng = Double.parseDouble((degree * Math.cos(latitude * (Math.PI / 180))+"").replace("-", ""));
        Double dpmLng = 1 / mpdLng;
        Double radiusLng = dpmLng * raidusMile;
        //获取最小经度
        Double minLat = longitude - radiusLng;
        // 获取最大经度
        Double maxLat = longitude + radiusLng;
        
        Double dpmLat = 1 / degree;
        Double radiusLat = dpmLat * raidusMile;
        // 获取最小纬度
        Double minLng = latitude - radiusLat;
        // 获取最大纬度
        Double maxLng = latitude + radiusLat;
        
        map.put("minLat", minLat+"");
        map.put("maxLat", maxLat+"");
        map.put("minLng", minLng+"");
        map.put("maxLng", maxLng+"");
        
        return map;
    }
    
    public static void main(String[] args) {
        //济南国际会展中心经纬度：117.11811  36.68484
        //趵突泉：117.00999000000002  36.66123
        System.out.println(getDistance("116.97265","36.694514","116.597805","36.738024"));
        
        System.out.println(getAround("117.11811", "36.68484", "13000"));
        //117.01028712333508(Double), 117.22593287666493(Double),
        //36.44829619896034(Double), 36.92138380103966(Double)
        
    }
    
}

41.784600476700476
{minLng=117.001301883613, maxLat=36.941095784459634, minLat=36.42858421554037, maxLng=117.234918116387}