android附近的人的實現，android實現

android附近的人的實現，android實現

項目要做附近的人這功能，然後就研究了下：

 （1） 首先要做的就是要擷取到自己當前位置的經緯度

（ 2）然後就是上傳自己的資料給伺服器

 （3） 伺服器經過計算然後把符合項目定義的最大距離的附近的人的資料傳到前台

  （4）前台通過資料來展示

   其中最主要的其實就是經緯度的距離的計算，這裡我把我試過的倆個貼上來

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

還有一個比較複雜的方法，相比上邊的更加精確

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);}