在谷歌地图中获取折线的长度

Question

我的主要目标是获得两点之间的距离。我正在尝试计算折线的起点/终点之间的距离(以英里为单位(。使用下面的代码，我能够绘制一条折线。但是，我不知道如何获得这条折线的总距离。

private String getDirectionsUrl(LatLng origin,LatLng dest){

// Origin of route
String str_origin = "origin="+origin.latitude+","+origin.longitude;
// Destination of route
String str_dest = "destination="+dest.latitude+","+dest.longitude;
// Sensor enabled
String sensor = "sensor=false";
// Building the parameters to the web service
String parameters = str_origin+"&"+str_dest+"&"+sensor;
// Output format
String output = "json";
// Building the url to the web service
String url = "https://maps.googleapis.com/maps/api/directions/"+output+"?"+parameters;
return url;
}
private String downloadUrl(String strUrl) throws IOException{
String data = "";
InputStream iStream = null;
HttpURLConnection urlConnection = null;
try{
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while( ( line = br.readLine()) != null){
sb.append(line);
}
data = sb.toString();
br.close();
}catch(Exception e){
Log.d("trDraw", e.toString());
}finally{
iStream.close();
urlConnection.disconnect();
}
return data;
}
private class DownloadTask extends AsyncTask<String, Void, String>{
// Downloading data in non-ui thread
@Override
protected String doInBackground(String... url) {
// For storing data from web service
String data = "";
try{
// Fetching the data from web service
data = downloadUrl(url[0]);
}catch(Exception e){
Log.d("Background Task",e.toString());
}
return data;
}
// Executes in UI thread, after the execution of
// doInBackground()
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
ParserTask parserTask = new ParserTask();
// Invokes the thread for parsing the JSON data
parserTask.execute(result);
}
}
private class ParserTask extends AsyncTask<String, Integer, List<List<HashMap<String,String>>> >{
// Parsing the data in non-ui thread
@Override
protected List<List<HashMap<String, String>>> doInBackground(String... jsonData) {
JSONObject jObject;
List<List<HashMap<String, String>>> routes = null;
try{
jObject = new JSONObject(jsonData[0]);
DirectionsJSONParser parser = new DirectionsJSONParser();
// Starts parsing data
routes = parser.parse(jObject);
}catch(Exception e){
e.printStackTrace();
}
return routes;
}
// Executes in UI thread, after the parsing process
@Override
protected void onPostExecute(List<List<HashMap<String, String>>> result) {
ArrayList<LatLng> points = null;
PolylineOptions lineOptions = null;
MarkerOptions markerOptions = new MarkerOptions();
// Traversing through all the routes
for(int i=0;i<result.size();i++){
points = new ArrayList<LatLng>();
lineOptions = new PolylineOptions();
// Fetching i-th route
List<HashMap<String, String>> path = result.get(i);
double lat;
double lng;
LatLng position = null;
// Fetching all the points in i-th route
for(int j=0;j<path.size();j++){
HashMap<String,String> point = path.get(j);
lat = Double.parseDouble(point.get("lat"));
lng = Double.parseDouble(point.get("lng"));
position = new LatLng(lat, lng);
points.add(position);
}
// Adding all the points in the route to LineOptions
lineOptions.addAll(points);
lineOptions.width(5);
lineOptions.color(Color.RED);
if(position == null){
Toast.makeText(getApplicationContext(), "Something went wrong", Toast.LENGTH_LONG).show();
}
else{
// Double totalDistance =  PolyUtil.distanceToLine(position ,driverStartLL, drivarDestinationLL);
// Log.i("trTotalCost", "polyDistance: " + totalDistance);
}
}
// Drawing polyline in the Google Map for the i-th route
mMap.addPolyline(lineOptions);
}
}
public class DirectionsJSONParser {
/**
* Receives a JSONObject and returns a list of lists containing latitude and longitude
*/
public List<List<HashMap<String, String>>> parse(JSONObject jObject) {
List<List<HashMap<String, String>>> routes = new ArrayList<List<HashMap<String, String>>>();
JSONArray jRoutes = null;
JSONArray jLegs = null;
JSONArray jSteps = null;
try {
jRoutes = jObject.getJSONArray("routes");
/** Traversing all routes */
for (int i = 0; i < jRoutes.length(); i++) {
jLegs = ((JSONObject) jRoutes.get(i)).getJSONArray("legs");
List path = new ArrayList<HashMap<String, String>>();
/** Traversing all legs */
for (int j = 0; j < jLegs.length(); j++) {
jSteps = ((JSONObject) jLegs.get(j)).getJSONArray("steps");
/** Traversing all steps */
for (int k = 0; k < jSteps.length(); k++) {
String polyline = "";
polyline = (String) ((JSONObject) ((JSONObject) jSteps.get(k)).get("polyline")).get("points");
List<LatLng> list = decodePoly(polyline);
/** Traversing all points */
for (int l = 0; l < list.size(); l++) {
HashMap<String, String> hm = new HashMap<String, String>();
hm.put("lat", Double.toString(((LatLng) list.get(l)).latitude));
hm.put("lng", Double.toString(((LatLng) list.get(l)).longitude));
path.add(hm);
}
}
routes.add(path);
}
}
} catch (JSONException e) {
e.printStackTrace();
} catch (Exception e) {
}
return routes;
}

}
private List<LatLng> decodePoly(String encoded) {
List<LatLng> poly = new ArrayList<LatLng>();
int index = 0, len = encoded.length();
int lat = 0, lng = 0;
while (index < len) {
int b, shift = 0, result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lat += dlat;
shift = 0;
result = 0;
do {
b = encoded.charAt(index++) - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
lng += dlng;
LatLng p = new LatLng((((double) lat / 1E5)),
(((double) lng / 1E5)));
poly.add(p);
}
return poly;
}

由于我试图用折线计算两点的距离，因此使用distanceOf(Location1, Location2);函数对我来说是没有用的，它可以给我尽可能短的距离。由于我使用的是折线，因此该方法根本行不通。

谢谢。

Answer 1

JSONArray array = jObject.getJSONArray("routes");
JSONObject routes = array.getJSONObject(0);
JSONArray legs = routes.getJSONArray("legs");
JSONObject steps = legs.getJSONObject(0);
JSONObject distance = steps.getJSONObject("distance");
Log.i("trJSON", "Distance String: " + distanceD.toString());
Double dist = Double.parseDouble(distanceD.getString("text").replaceAll("[^\.0123456789]","") );
Log.i("trJSON", "Distance Double: " + dist);

通过使用legs.getJSONObject(0)，我可以得到距离或持续时间steps。因此，在获得以英里为单位的距离串后，我只需将其转换为Double。

Answer 2

@grant，所以.forEach将帮助您:)