如何从给定数据中找到当前位置的最近位置。

Question

我有位置地址列表。从我目前的位置，我需要到最近的地方，并在地图上显示它。我怎样才能从当前位置到达最近的地方。首先，我会得到我当前的位置lat，然后我将如何到达最近的位置。

谢谢

Answer 1

首先获取您当前的location Lattitude＆amp; Longitude，然后获取每个位置的Lattitude & Longitude，并使用Location类的distanceTo方法找出每个地点与当前位置的距离，然后查找最少距离从你的清单。

Answer 2

一步一步，

如何获取某个位置的最近位置列表。

第1步：转到API控制台获取Place API

https://code.google.com/apis/console/

并在服务标签上选择

地点服务上的

现在选择API Access选项卡并获取API KEY

现在您有一个用于获取地点的API密钥

---

现在正在编程

*步骤2 * ：首先创建一个名为 Place.java 的类。此类用于包含Place api提供的场所属性。

package com.android.code.GoogleMap.NearsetLandmark;

import java.util.logging.Level;
import java.util.logging.Logger;
import org.json.JSONException;
import org.json.JSONObject;


public class Place {
    private String id;
    private String icon;
    private String name;
    private String vicinity;
    private Double latitude;
    private Double longitude;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getIcon() {
        return icon;
    }

    public void setIcon(String icon) {
        this.icon = icon;
    }

    public Double getLatitude() {
        return latitude;
    }

    public void setLatitude(Double latitude) {
        this.latitude = latitude;
    }

    public Double getLongitude() {
        return longitude;
    }

    public void setLongitude(Double longitude) {
        this.longitude = longitude;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getVicinity() {
        return vicinity;
    }

    public void setVicinity(String vicinity) {
        this.vicinity = vicinity;
    }

    static Place jsonToPontoReferencia(JSONObject pontoReferencia) {
        try {
            Place result = new Place();
            JSONObject geometry = (JSONObject) pontoReferencia.get("geometry");
            JSONObject location = (JSONObject) geometry.get("location");
            result.setLatitude((Double) location.get("lat"));
            result.setLongitude((Double) location.get("lng"));
            result.setIcon(pontoReferencia.getString("icon"));
            result.setName(pontoReferencia.getString("name"));
            result.setVicinity(pontoReferencia.getString("vicinity"));
            result.setId(pontoReferencia.getString("id"));
            return result;
        } catch (JSONException ex) {
            Logger.getLogger(Place.class.getName()).log(Level.SEVERE, null, ex);
        }
        return null;
    }

    @Override
    public String toString() {
        return "Place{" + "id=" + id + ", icon=" + icon + ", name=" + name + ", latitude=" + latitude + ", longitude=" + longitude + '}';
    }

}

现在创建一个名为 PlacesService

的类

package com.android.code.GoogleMap.NearsetLandmark;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;


public class PlacesService {

    private String API_KEY;

    public PlacesService(String apikey) {
        this.API_KEY = apikey;
    }

    public void setApiKey(String apikey) {
        this.API_KEY = apikey;
    }

    public List<Place> findPlaces(double latitude, double longitude,String placeSpacification) 
    {

        String urlString = makeUrl(latitude, longitude,placeSpacification);


        try {
            String json = getJSON(urlString);

            System.out.println(json);
            JSONObject object = new JSONObject(json);
            JSONArray array = object.getJSONArray("results");


            ArrayList<Place> arrayList = new ArrayList<Place>();
            for (int i = 0; i < array.length(); i++) {
                try {
                    Place place = Place.jsonToPontoReferencia((JSONObject) array.get(i));

                    Log.v("Places Services ", ""+place);


                    arrayList.add(place);
                } catch (Exception e) {
                }
            }
            return arrayList;
        } catch (JSONException ex) {
            Logger.getLogger(PlacesService.class.getName()).log(Level.SEVERE, null, ex);
        }
        return null;
    }
//https://maps.googleapis.com/maps/api/place/search/json?location=28.632808,77.218276&radius=500&types=atm&sensor=false&key=api key
    private String makeUrl(double latitude, double longitude,String place) {
         StringBuilder urlString = new StringBuilder("https://maps.googleapis.com/maps/api/place/search/json?");

        if (place.equals("")) {
                urlString.append("&location=");
                urlString.append(Double.toString(latitude));
                urlString.append(",");
                urlString.append(Double.toString(longitude));
                urlString.append("&radius=1000");
             //   urlString.append("&types="+place);
                urlString.append("&sensor=false&key=" + API_KEY);
        } else {
                urlString.append("&location=");
                urlString.append(Double.toString(latitude));
                urlString.append(",");
                urlString.append(Double.toString(longitude));
                urlString.append("&radius=1000");
                urlString.append("&types="+place);
                urlString.append("&sensor=false&key=" + API_KEY);
        }


        return urlString.toString();
    }

    protected String getJSON(String url) {
        return getUrlContents(url);
    }

    private String getUrlContents(String theUrl) 
    {
        StringBuilder content = new StringBuilder();

        try {
            URL url = new URL(theUrl);
            URLConnection urlConnection = url.openConnection();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()), 8);
            String line;
            while ((line = bufferedReader.readLine()) != null) 
            {
                content.append(line + "\n");
            }

            bufferedReader.close();
        }

        catch (Exception e)
        {

            e.printStackTrace();

        }

        return content.toString();
    }
}

现在创建一个新的活动，您可以在其中获取最近的地点列表。

/ **  *  * /

    public class CheckInActivity extends ListActivity{


@Override
protected void onCreate(Bundle arg0) {
    // TODO Auto-generated method stub
    super.onCreate(arg0);

    new GetPlaces(this, getListView()).execute();

}




class GetPlaces extends AsyncTask<Void, Void, Void>{

        private ProgressDialog dialog;
        private Context context;
        private String[] placeName;
        private String[] imageUrl;
        private ListView listView;

        public GetPlaces(Context context, ListView listView) {
            // TODO Auto-generated constructor stub
            this.context = context;
            this.listView = listView;
        }

        @Override
        protected void onPostExecute(Void result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
            dialog.dismiss();

            listView.setAdapter(new ArrayAdapter<String>(context, android.R.layout.simple_expandable_list_item_1,placeName));
        }

        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();
            dialog = new ProgressDialog(context);
            dialog.setCancelable(true);
            dialog.setMessage("Loading..");
            dialog.isIndeterminate();
            dialog.show();
        }

        @Override
        protected Void doInBackground(Void... arg0) {
            // TODO Auto-generated method stub
            PlacesService service = new PlacesService("AIzaSyDIRAipDcVMf1FGYHEGDRzvLv0SFH46uRQ");
              List<Place> findPlaces = service.findPlaces(28.632808,77.218276,"hospital");  // hq for hospital
                                                                                        // atm for ATM

                placeName = new String[findPlaces.size()];
                imageUrl = new String[findPlaces.size()];

              for (int i = 0; i < findPlaces.size(); i++) {

                  Place placeDetail = findPlaces.get(i);
                  placeDetail.getIcon();

                System.out.println(  placeDetail.getName());
                placeName[i] =placeDetail.getName();

                imageUrl[i] =placeDetail.getIcon();

            }
            return null;
        }

    }

}

Answer 3

您的当前位置纬度是经度，因此请使用此公式找出当前位置与位置地址地理位置列表之间的距离，并显示最短距离的地址。

private double distance(double lat1, double lon1, double lat2, double lon2) {
        // haversine great circle distance approximation, returns meters
        double theta = lon1 - lon2;
        double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2))
                + Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2))
                * Math.cos(deg2rad(theta));
        dist = Math.acos(dist);
        dist = rad2deg(dist);
        dist = dist * 60; // 60 nautical miles per degree of seperation
        dist = dist * 1852; // 1852 meters per nautical mile
        return (dist);
    }

    private double deg2rad(double deg) {
        return (deg * Math.PI / 180.0);
    }

    private double rad2deg(double rad) {
        return (rad * 180.0 / Math.PI);
    }