从我的位置到android中的目标位置的距离计算

Question

我必须做一个项目,我需要计算从我的位置到目的地的距离,并在textview中显示它.请注意,当我的位置发生变化时,这个距离会更新.是否可以制作这种类型的项目？

[注意:没有实施谷歌地图我必须做它.目的地lon,lat是已知的.只需要找到我的位置并进行计算]

Answer 1

检查google android dev页面上的文档,了解如何监听位置变化.http://developer.android.com/guide/topics/location/obtaining-user-location.html

您可以使用此功能确定当前(起始)点与目标点之间的距离.

 /**
 * using WSG84
 * using the Metric system
 */
public static float getDistance(double startLati, double startLongi, double goalLati, double goalLongi){
    float[] resultArray = new float[99];
    Location.distanceBetween(startLati, startLongi, goalLati, goalLongi, resultArray);
    return resultArray[0];
}

Answer 2

Location.distanceBetween会给两点之间的直线距离.如果你想要两个地理点之间的PATH距离,那么你可以使用这个类来做到这一点:

public class GetDistance {

public String GetRoutDistane(double startLat, double startLong, double endLat, double endLong)
{
  String Distance = "error";
  String Status = "error";
  try {
      Log.e("Distance Link : ", "http://maps.googleapis.com/maps/api/directions/json?origin="+ startLat +","+ startLong +"&destination="+ endLat +","+ endLong +"&sensor=false");
        JSONObject jsonObj = parser_Json.getJSONfromURL("http://maps.googleapis.com/maps/api/directions/json?origin="+ startLat +","+ startLong +"&destination="+ endLat +","+ endLong +"&sensor=false"); 
        Status = jsonObj.getString("status");
        if(Status.equalsIgnoreCase("OK"))
        {
        JSONArray routes = jsonObj.getJSONArray("routes"); 
         JSONObject zero = routes.getJSONObject(0);
         JSONArray legs = zero.getJSONArray("legs");
         JSONObject zero2 = legs.getJSONObject(0);
         JSONObject dist = zero2.getJSONObject("distance");
         Distance = dist.getString("text");
        }
        else
        {
            Distance = "Too Far";
        }
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
return Distance;


} 

}

这将为您提供两点之间的路径/道路的距离或长度.

这是解析JSON api的parser_Json类

 public class parser_Json {

public static JSONObject getJSONfromURL(String url){

    //initialize
    InputStream is = null;
    String result = "";
    JSONObject jArray = null;

    //http post
    try{
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(url);
        HttpResponse response = httpclient.execute(httppost);
        HttpEntity entity = response.getEntity();
        is = entity.getContent();

    }catch(Exception e){
        Log.e("log_tag", "Error in http connection "+e.toString());
    }

    //convert response to string
    try{
        BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        result=sb.toString();
    }catch(Exception e){
        Log.e("log_tag", "Error converting result "+e.toString());
    }

    //try parse the string to a JSON object
    try{
            jArray = new JSONObject(result);
    }catch(JSONException e){
        Log.e("log_tag", "Error parsing data "+e.toString());
    }

    return jArray;
}

 public static InputStream retrieveStream(String url) {

        DefaultHttpClient client = new DefaultHttpClient(); 

        HttpGet getRequest = new HttpGet(url);

        try {

           HttpResponse getResponse = client.execute(getRequest);
           final int statusCode = getResponse.getStatusLine().getStatusCode();

           if (statusCode != HttpStatus.SC_OK) { 

              return null;
           }

           HttpEntity getResponseEntity = getResponse.getEntity();
           return getResponseEntity.getContent();

        } 
        catch (IOException e) {
           getRequest.abort();

        }

        return null;

     }

}