过滤坐标以获得listview中最接近的坐标

Question

现在我正在开发一个应用程序来绘制地图上的坐标作为标记，所有坐标都存储在数据库中并完成，现在我想用按钮和listview控件创建另一个活动，用户在点击按钮时从当前位置获取最近的坐标在列表视图中。我使用android位置服务获取当前位置纬度和经度，并使json api从数据库获取我的坐标。现在的问题是如何过滤坐标，从当前位置获取最接近的坐标并显示在列表视图中。

 public void getJSONString()
    {
        var request = HttpWebRequest.Create(string.Format(@"http://citysoftech.net/Coordinates/locations.php"));
        request.ContentType = "application/json";
        request.Method = "GET";
        var content = "";
        using (HttpWebResponse response = request.GetResponse() as HttpWebResponse)
        {
            if (response.StatusCode != HttpStatusCode.OK)
                Console.Out.WriteLine("Error fetching data. Server returned status code: {0}", response.StatusCode);
            using (StreamReader reader = new StreamReader(response.GetResponseStream()))
            {
                content = reader.ReadToEnd();
                if (string.IsNullOrWhiteSpace(content))
                {
                    Console.Out.WriteLine("Response contained empty body...");
                }
                else
                {
                    Console.Out.WriteLine("Response Body: \r\n {0}", content);
                }
                Assert.NotNull(content);
            }
        }
        Toast.MakeText(this, content, ToastLength.Short).Show();
        initializeMap(content); //calling map
    }

    /**
    *   
            try
            {
                JSONArray json = new JSONArray(content);
                for (int i = 0; i < json.Length(); i++)
                {
                    JSONObject obj = json.GetJSONObject(i);
                    String lati = obj.GetString("latitude");
                    String longi = obj.GetString("longitude");
                    Double.Parse(longi)))

            }
            catch (JSONException e)
            {
                e.StackTrace.ToString();
            }