android - 如何计算android中的步行距离？

Question

我正在开发如下所示的计步器应用

到目前为止，我找到了如下解决方案:

private void GetDistance(GeoPoint src, GeoPoint dest) {

    StringBuilder urlString = new StringBuilder();
    urlString.append("http://maps.googleapis.com/maps/api/directions/json?");
    urlString.append("origin=");//from
    urlString.append( Double.toString((double)src.getLatitudeE6() / 1E6));
    urlString.append(",");
    urlString.append( Double.toString((double)src.getLongitudeE6() / 1E6));
    urlString.append("&destination=");//to
    urlString.append( Double.toString((double)dest.getLatitudeE6() / 1E6));
    urlString.append(",");
    urlString.append( Double.toString((double)dest.getLongitudeE6() / 1E6));
    urlString.append("&mode=walking&sensor=true");
    Log.d("xxx","URL="+urlString.toString());

    // get the JSON And parse it to get the directions data.
    HttpURLConnection urlConnection= null;
    URL url = null;

    url = new URL(urlString.toString());
    urlConnection=(HttpURLConnection)url.openConnection();
    urlConnection.setRequestMethod("GET");
    urlConnection.setDoOutput(true);
    urlConnection.setDoInput(true);
    urlConnection.connect();

    InputStream inStream = urlConnection.getInputStream();
    BufferedReader bReader = new BufferedReader(new InputStreamReader(inStream));

    String temp, response = "";
    while((temp = bReader.readLine()) != null){
        //Parse data
        response += temp;
    }
    //Close the reader, stream & connection
    bReader.close();
    inStream.close();
    urlConnection.disconnect();

    //Sortout JSONresponse 
    JSONObject object = (JSONObject) new JSONTokener(response).nextValue();
    JSONArray array = object.getJSONArray("routes");
        //Log.d("JSON","array: "+array.toString());

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

    String summary = routes.getString("summary");
        //Log.d("JSON","summary: "+summary);

    JSONArray legs = routes.getJSONArray("legs");
        //Log.d("JSON","legs: "+legs.toString());

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

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

            String sDistance = distance.getString("text");
            int iDistance = distance.getInt("value");

}

我决定用GPS的方式来实现。但是，实现这个的“常用方法”是什么？是否只是在 30 秒获取 gps lat，lan，然后计算差异？例如获取 GPS 数据的间隔时间是多长。

感谢帮助

Answer 1

您可以使用计算距离的方法来代替调用 google api。

public double getDistance(double lat1, double lon1, double lat2, double lon2) {
    double latA = Math.toRadians(lat1);
    double lonA = Math.toRadians(lon1);
    double latB = Math.toRadians(lat2);
    double lonB = Math.toRadians(lon2);
    double cosAng = (Math.cos(latA) * Math.cos(latB) * Math.cos(lonB-lonA)) +
                (Math.sin(latA) * Math.sin(latB));
    double ang = Math.acos(cosAng);
    double dist = ang *6371;
    return dist;
}

这将减少一次 API 调用并快速找到两个位置之间的距离。