2010-11-27 202 views

回答

3

距離的計算是基於LatLong網數學這樣的:

距離

這裏使用了「半正矢」的公式計算出兩點間的大圓距離 - 也就是,在地球的距離最短表面 - 給點之間的「烏鴉飛」距離(忽略任何山丘!)。

半正矢式:

R = earth’s radius (mean radius = 6,371km) 
Δlat = lat2− lat1 
Δlong = long2− long1 
a = sin²(Δlat/2) + cos(lat1).cos(lat2).sin²(Δlong/2) 
c = 2.atan2(√a, √(1−a)) 
d = R.c 

(注意,角度需要在弧度傳遞給三角函數)。 的JavaScript:

var R = 6371; // km 
var dLat = (lat2-lat1).toRad(); 
var dLon = (lon2-lon1).toRad(); 
var a = Math.sin(dLat/2) * Math.sin(dLat/2) + 
     Math.cos(lat1.toRad()) * Math.cos(lat2.toRad()) * 
     Math.sin(dLon/2) * Math.sin(dLon/2); 
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); 
var d = R * c; 
7

分步實施,

谷歌的地方API用於通過anloaction的標誌性建築附近訪問

步驟1:轉到API控制檯獲取Place API

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

,並在地方服務

enter image description here

現在選擇API訪問選項卡中選擇服務選項卡

Service

,並得到了API KEY

enter image description here

現在你有一個API密鑰對編程讓地方


現在

*步驟2 *:首先創建一個名爲Place.java類。該類用於包含由Place API提供的地點屬性。

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 + '}'; 
    } 

} 

現在創建一個名爲地方信息

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=apikey 
    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(); 
    } 
} 

要獲得最近的地方名單現在創建一個新的活動類。

/** * * /

package com.android.code.GoogleMap.NearsetLandmark; 

     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("paste your place api key"); 
       List<Place> findPlaces = service.findPlaces(28.632808,77.218276,"hospital"); // hospiral 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; 
     } 

    } 

} 
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