我们怎样才能计算出当前位置与android中的许多目标位置之间的距离？

Question

我想计算两个位置（即用户和目的地位置的当前位置）之间的距离。我有我的数据库和当前位置的目标位置的经度和纬度（我确实找到位置管理器类）。 我需要在列表视图中显示计算出的距离。 如果我计算它的任何数学公式或DistanceTo（）和DistanceBetween（）方法的位置类，然后我没有得到准确的距离作为超过地图。 如果我通过Google的距离矩阵API计算距离，那么它计算距离和加载列表需要花费太多时间（因为有很多目标位置和用户的当前位置） 请有人向我推荐最好的方式来计算它.. 我在这个问题从最近几天卡住..帮我 在此先感谢...

Answer 1

很多谷歌上搜索我已经做了我task.I尝试过通过异步任务.. 这里是我的代码后，最后..

public View getView(int position, View convertView, ViewGroup Parent) 
    { 
final ViewHolder holder=new ViewHolder(); 
View view=convertView; 
if (view==null) { 
    convertView= inflater.inflate(R.layout.layout_row, null); 
} 



holder.textdistance=(TextView) convertView.findViewById(R.id.textView_Distance); 

    holder.position = position; 


    if(data.size()<=0) 
    { 

    Toast.makeText(activity, "No data", Toast.LENGTH_LONG).show(); 
    } 
    else 
    { 
    **new ThumbnailTask(position, holder) 
    .executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, null);** 
    } 
return convertView; 



    } 
    //Thumbnail Class 
private static class ThumbnailTask extends AsyncTask { 
    private int mPosition; 
    private ViewHolder mHolder; 

    public ThumbnailTask(int position, ViewHolder holder) { 
     mPosition = position; 
     mHolder = holder; 
    } 



    /* (non-Javadoc) 
    * @see android.os.AsyncTask#doInBackground(Params[]) 
    */ 
    @Override 
    protected Object doInBackground(Object... params) { 
     // TODO Auto-generated method stub 
     String Distance="3"; 
     String uri="https://maps.googleapis.com/maps/api/distancematrix/json? origins=(Your source Addres like XYZ,South Delhi-110064),&mode=deriving&sensor=false&key=(Your API Key)"; 


      String result= GET(uri); 
      Log.d("result","res="+result); 

      try { 

        //jArray = new JSONObject(result); 
        JSONObject object = (JSONObject) new JSONTokener(result).nextValue(); 
        JSONArray array = object.getJSONArray("rows"); 
        // Log.d("JSON","array: "+array.toString()); 

       //Routes is a combination of objects and arrays 
       JSONObject rows = array.getJSONObject(0); 
        //Log.d("JSON","routes: "+routes.toString()); 
       JSONArray elements = rows.getJSONArray("elements"); 
       // Log.d("JSON","legs: "+legs.toString()); 

       JSONObject steps = elements.getJSONObject(0); 
        //Log.d("JSON","steps: "+steps.toString()); 

       JSONObject distance = steps.getJSONObject("distance"); 
       Log.d("JSON","distance: "+distance.toString()); 

        Distance = distance.getString("text"); 
        Log.d("final value","tot dis="+Distance); 
        JSONObject duration=steps.getJSONObject("duration"); 
       // MyDuration=duration.getString("text"); 


       } 
       catch(JSONException e) 
         { 
        Log.d("JSONEXCeption","my exce"+e.getMessage()); 
         } 
      return Distance; 
    } 



    @Override 
    protected void onPostExecute(Object result) { 
     // TODO Auto-generated method stub 
    mHolder.textdistance.setText(result.toString()); 
    } 


} 

//method to execute Url 

private static String GET(String url) 
    { 
    InputStream inputStream = null; 
    String result = ""; 
    try { 

    // create HttpClient 
    HttpClient httpclient = new DefaultHttpClient(); 

    // make GET request to the given URL 
    HttpResponse httpResponse = httpclient.execute(new HttpGet(url)); 


    // receive response as inputStream 
    inputStream = httpResponse.getEntity().getContent(); 



    // convert inputstream to string 
    if(inputStream != null) 
     result = convertInputStreamToString(inputStream); 

//  Log.i("Result",result); 

    else 
     result = "Did not work!"; 

} catch (Exception e) { 
    Log.d("InputStream", "hello"+e); 
} 

return result; 




    } 


private static String convertInputStreamToString(InputStream inputStream) throws IOException{ 
     BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream)); 
     String line = ""; 
     String result = ""; 
     while((line = bufferedReader.readLine()) != null) 
      result += line; 

     inputStream.close(); 
     return result; 

    } 


} 

参考链接为─

http://lucasr.org/2012/04/05/performance-tips-for-androids-listview/ https://developers.google.com/maps/documentation/distancematrix/

我不擅长爆炸但是我正在尽我所能。希望这会帮助像我这样的其他人，因为我陷入了这个任务。

Answer 2

试试这个。我加我的旧应用程序中。它适用于我。通过初始化R=Radius。阅读this文章仔细

public double CalculationByDistance(GeoPoint StartP, GeoPoint EndP) { 
     double lat1 = StartP.getLatitudeE6()/1E6; 
     double lat2 = EndP.getLatitudeE6()/1E6; 
     double lon1 = StartP.getLongitudeE6()/1E6; 
     double lon2 = EndP.getLongitudeE6()/1E6; 
     double dLat = Math.toRadians(lat2-lat1); 
     double dLon = Math.toRadians(lon2-lon1); 
     double a = Math.sin(dLat/2) * Math.sin(dLat/2) + 
     Math.cos(Math.toRadians(lat1)) * Math.cos(Math.toRadians(lat2)) * 
     Math.sin(dLon/2) * Math.sin(dLon/2); 
     double c = 2 * Math.asin(Math.sqrt(a)); 
     return Radius * c; 
    } 

Answer 3

如果有很多地方使用循环。只有几行代码来完成这件事：

Location l1=new Location("One"); 
l1.setLatitude(location.getLatitude()); 
l1.setLongitude(location.getLongitude()); 

Location l2=new Location("Two"); 
l2.setLatitude(Double.parseDouble(frnd_lat)); 
l2.setLongitude(Double.parseDouble(frnd_longi)); 

float distance_bw_one_and_two=l1.distanceTo(l2);