计算两个地理点之间的最短路径？

Question

我是 Java 和 Android 的新手。我需要找到两个 goepoint 之间的最短路径。 我整天都在寻找答案，我刚刚得到了这个代码：

var directionDisplay;
  var directionsService = new google.maps.DirectionsService();
  var map;

  function initialize() {
    directionsDisplay = new google.maps.DirectionsRenderer();
    var chicago = new google.maps.LatLng(41.850033, -87.6500523);
    var myOptions = {
      zoom:7,
      mapTypeId: google.maps.MapTypeId.ROADMAP,
      center: chicago
    }
    map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);
    directionsDisplay.setMap(map);
  }

  function calcRoute() {
    var start = document.getElementById("start").value;
    var end = document.getElementById("end").value;
    var request = {
        origin:start, 
        destination:end,
        travelMode: google.maps.DirectionsTravelMode.DRIVING
    };
    directionsService.route(request, function(response, status) {
      if (status == google.maps.DirectionsStatus.OK) {
        routePath = result.routes[0].overview_path;
        for(var a = 0; a< routePath.length; a++){
          // Your vector layer to render points with line
        }
        directionsDisplay.setDirections(response);
      }
    });
  }

主要代码在这里：

      directionsService.route(request, function(response, status) {
              if (status == google.maps.DirectionsStatus.OK) {
                routePath = result.routes[0].overview_path;
                for(var a = 0; a< routePath.length; a++){
                  // Your vector layer to render points with line
                }
                directionsDisplay.setDirections(response);
              }
            });

问题是我想在 Android 中实现这段代码。但我不知道怎么做。 有没有人知道如何更改代码以便我可以在 Android 中使用它？

这里是链接来源This

Answer 1

有两种方法可以找到两个 GeoPoint 之间的距离：

1. 这不使用互联网连接并使用一些数学方法来计算两点之间的最短距离。

   /**** Method for Calculating distance between two locations ****/
   public float DistanceBetweenPlaces(double lat1, double lon1, double lat2, double lon2, Context cont) {
       float[] results = new float[1];
       Location.distanceBetween(lat1, lon1, lat2, lon2, results);
       return results[0];
   }
   

2. 这使用互联网连接并使用 Google Maps API 来检测两点之间的确切距离。实现它的代码如下：

   /**** Class for calculating the distance between two places ****/
   public class CalculateDistance {
        String distance;
        public void calculate_distance(String src_lat, String src_lng, String dest_lat, String dest_lng) {
            distance = getdistance(makeUrl(src_lat, src_lng, dest_lat, dest_lng));
        }
   
   /**** Method for make URL ****/
   private String makeUrl(String src_lat, String src_lng, String dest_lat, String dest_lng) {
       StringBuilder urlString = new StringBuilder();
       urlString.append("http://maps.googleapis.com/maps/api/distancematrix/json?");
       urlString.append("origins="); // from
       urlString.append(src_lat);
       urlString.append(",");
       urlString.append(src_lng);
       urlString.append("&destinations="); // to
       urlString.append(dest_lat);
       urlString.append(",");
       urlString.append(dest_lng);
       urlString.append("&sensor=true&mode=driving");
       return urlString.toString();
   }
   
   /**** Method for getting the distance between the two places ****/
   private String getdistance(String urlString) {
        URLConnection urlConnection = null;
        URL url = null;
        try {
             url = new URL(urlString.toString());
             urlConnection = url.openConnection();
             BufferedReader in = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
   
             String line;
             StringBuffer sb = new StringBuffer();
             // take Google's legible JSON and turn it into one big string.
             while ((line = in.readLine()) != null) {
                   sb.append(line);
             }
             // turn that string into a JSON object
             JSONObject distanceMatrixObject = new JSONObject(sb.toString());
             // now get the JSON array that's inside that object
             if (distanceMatrixObject.getString("status").equalsIgnoreCase("OK")) {
                   JSONArray distanceArray = new JSONArray(distanceMatrixObject.getString("rows"));
                   JSONArray elementsArray = new JSONArray(distanceArray.getJSONObject(0).getString("elements"));
                   JSONObject distanceObject = new JSONObject(elementsArray.getJSONObject(0).getString("distance"));
                   return distanceObject.getString(("text"));
             }
        return null;
        } catch (Exception e) {
             return null;
             e.printStackTrace();
        }
     }
   }