مشکل در پروژه note

سلام دوستان در مراحل اولیه پروژه نوت یه مشکلی برام پیش اومده که وقتی برنامه رو run  می کنم اون فیلدی رو که می خوام برام نمایش نمی ده و خطا می ده بدین صورت :

 public class WebService {

    public static String readUrl(String url) {
        try {
            HttpClient client = new DefaultHttpClient();
            HttpPost method = new HttpPost(url);
            HttpResponse response = client.execute(method);
            InputStream inputStream = response.getEntity().getContent();
            String result = convertInputStreamToString(inputStream);
            return result;
        }
        catch (ClientProtocolException e) {
            e.printStackTrace();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }


    private static String convertInputStreamToString(InputStream inputStream) {
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            StringBuilder builder = new StringBuilder();
            String line = "";

            while ((line = reader.readLine()) != null) {
                builder.append(line);
            }

            return builder.toString();
        }
        catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
}

 public class NotesActivity extends Activity {

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        String result = WebService.readUrl("http://192.168.1.7/note-server/");
        if (result != null) {
            try {
                JSONArray tasks = new JSONArray(result);
                for (int i = 0; i < tasks.length(); i++) {
                    JSONObject task = tasks.getJSONObject(i);
                    Log.i("LOG", task.getString("task_title"));
                }

            }
            catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

 08-05 18:33:28.624: I/global(1381): Default buffer size used in BufferedReader constructor. It would be better to be explicit if an 8k-char buffer is required.
08-05 18:33:28.634: W/System.err(1381): org.json.JSONException: No value for task_title
08-05 18:33:28.634: W/System.err(1381): 	at org.json.JSONObject.get(JSONObject.java:354)
08-05 18:33:28.634: W/System.err(1381): 	at org.json.JSONObject.getString(JSONObject.java:510)
08-05 18:33:28.634: W/System.err(1381): 	at com.hadi.app.notes.NotesActivity.onCreate(NotesActivity.java:24)
08-05 18:33:28.634: W/System.err(1381): 	at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-05 18:33:28.634: W/System.err(1381): 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
08-05 18:33:28.634: W/System.err(1381): 	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
08-05 18:33:28.644: W/System.err(1381): 	at android.app.ActivityThread.access$2300(ActivityThread.java:125)
08-05 18:33:28.644: W/System.err(1381): 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
08-05 18:33:28.644: W/System.err(1381): 	at android.os.Handler.dispatchMessage(Handler.java:99)
08-05 18:33:28.644: W/System.err(1381): 	at android.os.Looper.loop(Looper.java:123)
08-05 18:33:28.644: W/System.err(1381): 	at android.app.ActivityThread.main(ActivityThread.java:4627)
08-05 18:33:28.644: W/System.err(1381): 	at java.lang.reflect.Method.invokeNative(Native Method)
08-05 18:33:28.644: W/System.err(1381): 	at java.lang.reflect.Method.invoke(Method.java:521)
08-05 18:33:28.644: W/System.err(1381): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
08-05 18:33:28.644: W/System.err(1381): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
08-05 18:33:28.644: W/System.err(1381): 	at dalvik.system.NativeStart.main(Native Method)