我的 map 包含多个点，可以从用户经过的地方点击用户的位置，但是 the polyline is not shown on the roads, but shows a direct line from one marker to other .我希望我的多段线穿过马路:道路转弯时，它也应该转弯。

这是我的相关代码

 dataholder = FirebaseDatabase.getInstance().getReference("UserLocation");
 Log.d("onMapReady", "iam here");
 dataholder.addValueEventListener(new ValueEventListener() {

     @Override
     public void onDataChange(DataSnapshot dataSnapshot) {
         Log.d("data",String.valueOf(dataSnapshot.getValue()));
         System.out.println(dataSnapshot.getValue());
         for (DataSnapshot a : dataSnapshot.getChildren()) {
             MapData mapData = a.getValue(MapData.class);
             arrayList.add(mapData);
             lati.add(arrayList.get(i).getLatituide());
             longit.add(arrayList.get(i).getLongitude());
             Log.d("mapi","i am in loop");
             mMap = googleMap;
             Double lat = Double.parseDouble(lati.get(i));
             Double longi = Double.parseDouble(longit.get(i));
             sydney = new LatLng(longi, lat);
             points.add(sydney);
             MarkerOptions mop = new MarkerOptions();
             mop.position(sydney);
             mop.title("check");
             mMap.addMarker(mop);
             Log.d("latitude", String.valueOf(lat));
             Log.d("longitude", String.valueOf(longi));
             // Add a marker in Sydney and move the camera
             mMap.addMarker(new MarkerOptions().position(sydney).title("check"));
             mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));

             i++;
         }

    line.addAll(points).width(5).color(Color.RED);
    line.geodesic(true);
    mMap.addPolyline(line);

    mMap.setOnMarkerClickListener(new GoogleMap.OnMarkerClickListener() {
        @Override
        public boolean onMarkerClick(Marker marker) {
            Toast.makeText(getApplicationContext(),marker.getTitle().toString(),Toast.LENGTH_LONG).show();
            return false;
        }
    });

最佳答案

尝试使用Google Maps Roads API部分 Snap to Road哪个

returns the best-fit road geometry for a given set of GPS coordinates. This service takes up to 100 GPS points collected along a route, and returns a similar set of data with the points snapped to the most likely roads the vehicle was traveling along.

类似于 Google Maps Roads API Snap to Road 示例中的数据:

public class MainActivity extends AppCompatActivity implements OnMapReadyCallback {

    private GoogleMap mGoogleMap;
    private MapFragment mapFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mapFragment = (MapFragment) getFragmentManager()
                .findFragmentById(R.id.map_fragment);
        mapFragment.getMapAsync(this);
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mGoogleMap = googleMap;

        List<LatLng> sourcePoints = new ArrayList<>();
        sourcePoints.add(new LatLng(-35.27801,149.12958));
        sourcePoints.add(new LatLng(-35.28032,149.12907));
        sourcePoints.add(new LatLng(-35.28099,149.12929));
        sourcePoints.add(new LatLng(-35.28144,149.12984));
        sourcePoints.add(new LatLng(-35.28194,149.13003));
        sourcePoints.add(new LatLng(-35.28282,149.12956));
        sourcePoints.add(new LatLng(-35.28302,149.12881));
        sourcePoints.add(new LatLng(-35.28473,149.12836));

        PolylineOptions polyLineOptions = new PolylineOptions();
        polyLineOptions.addAll(sourcePoints);
        polyLineOptions.width(5);
        polyLineOptions.color(Color.BLUE);
        mGoogleMap.addPolyline(polyLineOptions);

        mGoogleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(sourcePoints.get(0), 15));

        List<LatLng> snappedPoints = new ArrayList<>();
        new GetSnappedPointsAsyncTask().execute(sourcePoints, null, snappedPoints);
    }


    private String buildRequestUrl(List<LatLng> trackPoints) {
        StringBuilder url = new StringBuilder();
        url.append("https://roads.googleapis.com/v1/snapToRoads?path=");

        for (LatLng trackPoint : trackPoints) {
            url.append(String.format("%8.5f", trackPoint.latitude));
            url.append(",");
            url.append(String.format("%8.5f", trackPoint.longitude));
            url.append("|");
        }
        url.delete(url.length() - 1, url.length());
        url.append("&interpolate=true");
        url.append(String.format("&key=%s", <your_Google_Maps_API_key>);

        return url.toString();
    }


    private class GetSnappedPointsAsyncTask extends AsyncTask<List<LatLng>, Void, List<LatLng>> {

        protected void onPreExecute() {
            super.onPreExecute();
        }

        protected List<LatLng> doInBackground(List<LatLng>... params) {

            List<LatLng> snappedPoints = new ArrayList<>();

            HttpURLConnection connection = null;
            BufferedReader reader = null;

            try {
                URL url = new URL(buildRequestUrl(params[0]));
                connection = (HttpURLConnection) url.openConnection();
                connection.setRequestMethod("GET");
                connection.connect();

                InputStream stream = connection.getInputStream();

                reader = new BufferedReader(new InputStreamReader(stream));
                StringBuilder jsonStringBuilder = new StringBuilder();

                StringBuffer buffer = new StringBuffer();
                String line = "";

                while ((line = reader.readLine()) != null) {
                    buffer.append(line+"\n");
                    jsonStringBuilder.append(line);
                    jsonStringBuilder.append("\n");
                }

                JSONObject jsonObject = new JSONObject(jsonStringBuilder.toString());
                JSONArray snappedPointsArr = jsonObject.getJSONArray("snappedPoints");

                for (int i = 0; i < snappedPointsArr.length(); i++) {
                    JSONObject snappedPointLocation = ((JSONObject) (snappedPointsArr.get(i))).getJSONObject("location");
                    double lattitude = snappedPointLocation.getDouble("latitude");
                    double longitude = snappedPointLocation.getDouble("longitude");
                    snappedPoints.add(new LatLng(lattitude, longitude));
                }

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            } finally {
                if (connection != null) {
                    connection.disconnect();
                }
                try {
                    if (reader != null) {
                        reader.close();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

            return snappedPoints;
        }

        @Override
        protected void onPostExecute(List<LatLng> result) {
            super.onPostExecute(result);

            PolylineOptions polyLineOptions = new PolylineOptions();
            polyLineOptions.addAll(result);
            polyLineOptions.width(5);
            polyLineOptions.color(Color.RED);
            mGoogleMap.addPolyline(polyLineOptions);

            LatLngBounds.Builder builder = new LatLngBounds.Builder();
            builder.include(result.get(0));
            builder.include(result.get(result.size()-1));
            LatLngBounds bounds = builder.build();
            mGoogleMap.animateCamera(CameraUpdateFactory.newLatLngBounds(bounds, 10));

        }
    }

}

并且不要忘记在 Google APIs Console 中为您的项目添加 Google Maps Roads API 支持。 (选择你的项目，然后选择 Dashboard，然后按“+ ENABLE APIS AND SERVICES”按钮，然后在左侧“Filter by”选择“Maps”，然后按“Google Maps Roads API”，最后按“ENABLE”按钮").

你应该得到这样的东西:

其中:蓝色折线 - 用于源点，红色折线 - 用于捕捉点。

请记住，每个用户 (IP) 每天有 100 个 GPS 点和 2500 个请求以及每秒 10 个请求的限制。并且您还需要更优雅的解决方案来下载捕捉点 JSON。

关于java - 折线不在路上 : it goes straight from one point to other，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47329243/