Question

我想计算两个位置之间的距离（即用户的当前位置和目的地位置）。我在我的数据库和当前位置有目的地位置的纬度和经度（我通过位置管理器类找到）。我需要在列表视图中显示该计算的距离。如果我通过位置类的任何数学公式或 DistanceTo（）和DistanceBetween（）方法计算它，那么我就不会在地图上获得准确的距离。如果我通过Google的距离矩阵API计算距离，那么它需要花费太多时间来计算距离并加载列表。（因为有很多目的地位置有一个当前位置的用户）请有人建议我最好的计算方法.. 我在最近几天遇到了这个问题。帮助我提前谢谢......

Answer 1

最后经过大量的谷歌搜索我完成了我的任务。我通过异步任务尝试了它。这是我的代码..

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;

    }


 }

参考链接是 -

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

我不善于解释，但我正在努力。希望它能帮助像我这样的其他人，因为我遇到了这个任务。

Answer 2

试试这个。我在旧的应用程序中添加它。它对我有用。通过Initialize R=Radius的方式。仔细阅读this文章

 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。只需几行代码即可完成此任务：

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);

我们如何计算当前位置与android中许多目标位置之间的距离？

3 个答案: