android附近的人的实现

项目要做附近的人这功能，然后就研究了下：

（1） 首先要做的就是要获取到自己当前位置的经纬度

（ 2）然后就是上传自己的数据给服务器

（3） 服务器经过计算然后把符合项目定义的最大距离的附近的人的数据传到前台

（4）前台通过数据来展示

其中最主要的其实就是经纬度的距离的计算，这里我把我试过的俩个贴上来

public static double getDistance(double lat1,double longt1 , double lat2,double longt2
            ) {
        double PI = 3.14159265358979323; // 圆周率
        double R = 6371229; // 地球的半径

        double x, y, distance;
        x = (longt2 - longt1) * PI * R
                * Math.cos(((lat1 + lat2) / 2) * PI / 180) / 180;
        y = (lat2 - lat1) * PI * R / 180;
        distance = Math.hypot(x, y);

        return distance;
    }

还有一个比较复杂的方法，相比上边的更加精确

public static double computeDistance(double lat1, double lon1,
             double lat2, double lon2) {
             // Based on http://www.ngs.noaa.gov/PUBS_LIB/inverse.pdf
             // using the "Inverse Formula" (section 4)

             int MAXITERS = 20;
             // Convert lat/long to radians
             lat1 *= Math.PI / 180.0;
             lat2 *= Math.PI / 180.0;
             lon1 *= Math.PI / 180.0;
             lon2 *= Math.PI / 180.0;

             double a = 6378137.0; // WGS84 major axis
             double b = 6356752.3142; // WGS84 semi-major axis
             double f = (a - b) / a;
             double aSqMinusBSqOverBSq = (a * a - b * b) / (b * b);

             double L = lon2 - lon1;
             double A = 0.0;
             double U1 = Math.atan((1.0 - f) * Math.tan(lat1));
             double U2 = Math.atan((1.0 - f) * Math.tan(lat2));

             double cosU1 = Math.cos(U1);
             double cosU2 = Math.cos(U2);
             double sinU1 = Math.sin(U1);
             double sinU2 = Math.sin(U2);
             double cosU1cosU2 = cosU1 * cosU2;
             double sinU1sinU2 = sinU1 * sinU2;

             double sigma = 0.0;
             double deltaSigma = 0.0;
             double cosSqAlpha = 0.0;
             double cos2SM = 0.0;
             double cosSigma = 0.0;
             double sinSigma = 0.0;
             double cosLambda = 0.0;
             double sinLambda = 0.0;

             double lambda = L; // initial guess
             for (int iter = 0; iter <</span> MAXITERS; iter++) {
                 double lambdaOrig = lambda;
                 cosLambda = Math.cos(lambda);
                 sinLambda = Math.sin(lambda);
                 double t1 = cosU2 * sinLambda;
                 double t2 = cosU1 * sinU2 - sinU1 * cosU2 * cosLambda;
                 double sinSqSigma = t1 * t1 + t2 * t2; // (14)
                 sinSigma = Math.sqrt(sinSqSigma);
                 cosSigma = sinU1sinU2 + cosU1cosU2 * cosLambda; // (15)
                 sigma = Math.atan2(sinSigma, cosSigma); // (16)
                 double sinAlpha = (sinSigma == 0) ? 0.0 :
                     cosU1cosU2 * sinLambda / sinSigma; // (17)
                 cosSqAlpha = 1.0 - sinAlpha * sinAlpha;
                 cos2SM = (cosSqAlpha == 0) ? 0.0 :
                     cosSigma - 2.0 * sinU1sinU2 / cosSqAlpha; // (18)

                 double uSquared = cosSqAlpha * aSqMinusBSqOverBSq; // defn
                 A = 1 + (uSquared / 16384.0) * // (3)
                     (4096.0 + uSquared *
                      (-768 + uSquared * (320.0 - 175.0 * uSquared)));
                 double B = (uSquared / 1024.0) * // (4)
                     (256.0 + uSquared *
                      (-128.0 + uSquared * (74.0 - 47.0 * uSquared)));
                 double C = (f / 16.0) *
                     cosSqAlpha *
                     (4.0 + f * (4.0 - 3.0 * cosSqAlpha)); // (10)
                 double cos2SMSq = cos2SM * cos2SM;
                 deltaSigma = B * sinSigma * // (6)
                     (cos2SM + (B / 4.0) *
                      (cosSigma * (-1.0 + 2.0 * cos2SMSq) -
                       (B / 6.0) * cos2SM *
                       (-3.0 + 4.0 * sinSigma * sinSigma) *
                       (-3.0 + 4.0 * cos2SMSq)));

                 lambda = L +
                     (1.0 - C) * f * sinAlpha *
                     (sigma + C * sinSigma *
                      (cos2SM + C * cosSigma *
                       (-1.0 + 2.0 * cos2SM * cos2SM))); // (11)

                 double delta = (lambda - lambdaOrig) / lambda;
                 if (Math.abs(delta) <</span> 1.0e-12) {
                     break;
                 }
             }

             return  b * A * (sigma - deltaSigma);
}