代碼如下：

import 'dart:math';

void main() {
  print("distance between two point is : ${getDistance(
      119.9831030000, 30.2340350000, 119.9809580000, 30.2320980000)}");
}

getDistance(double lat1, double lng1, double lat2, double lng2) {
  double radLat1 = rad(lat1);
  double radLat2 = rad(lat2);
  double a = radLat1 - radLat2;
  double b = rad(lng1) - rad(lng2);
  double s = 2 *
      asin(sqrt(pow(sin(a / 2), 2) +
          cos(radLat1) * cos(radLat2) * pow(sin(b / 2), 2)));
  return s * 6378138.0;
}

double rad(double d) {
  return d * pi / 180.0;
}

選取兩點作為例子：

1. 贊成樂山紅葉北門（Latitude: 119.9831030000, Longitude: 30.2340350000）
2. 閑林街道辦事處（Latitude: 119.9809580000, Longitude: 30.2320980000）
   運行結果：

distance between two point is : 261.9676660067193

從一個測經(jīng)緯度距離的網(wǎng)站測試的結果如下:

image.png