JSON with value - App List Null

I'm creating an App, where it will display some information from an external database using a JSON file so that I can display this information in the App. But when I run the code, the list in my app returns null and void. I would like to know where I am failing to build my Code.

public class PontosActivity extends AppCompatActivity {

private String TAG = PontosActivity.class.getSimpleName();

private ListView lstPontos;

private static String url = "http://mpeprojeto.com/pontos";

ArrayList<HashMap<String, String>> pontosList;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_pontos);


    pontosList = new ArrayList<>();

    lstPontos = (ListView) findViewById(R.id.listPontos);

    new GetPontos().execute();


}

private class GetPontos extends AsyncTask<Void, Void, Void> {

    @Override
    protected Void doInBackground(Void... voids) {
        HttpHandler sh = new HttpHandler();

        // Making a request to url and getting response
        String jsonStr = sh.makeHttpHandler(url);

        if (jsonStr != null) {
            try {
                JSONObject jsonObj = new JSONObject(jsonStr);

                // Getting JSON Array node
                JSONArray pontos = jsonObj.getJSONArray("pontos");

                // looping through All Contacts
                for (int i = 0; i < pontos.length(); i++) {
                    JSONObject c = pontos.getJSONObject(i);

                    String data = c.getString("datar");
                    String hora = c.getString("horar");
                    String lat = c.getString("latr");
                    String longt = c.getString("longtr");

                    // tmp hash map for single contact
                    HashMap<String, String> ponto = new HashMap<>();

                    // adding each child node to HashMap key => value
                    ponto.put("datar", data);
                    ponto.put("horar", hora);
                    ponto.put("latr", lat);
                    ponto.put("longtr", longt);

                    // adding contact to contact list
                    pontosList.add(ponto);
                }
            } catch (final JSONException e) {
                Log.e(TAG, "Json parsing error1: " + e.getMessage());
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(getApplicationContext(),
                                "Json parsing error2: " + e.getMessage(),
                                Toast.LENGTH_LONG)
                                .show();
                    }
                });

            }
        } else {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(getApplicationContext(),
                            "Avalie novamente seus ultimos pontos, pois não foi encontrado nenhum!",
                            Toast.LENGTH_LONG)
                            .show();
                }
            });

        }

        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);
        // Dismiss the progress dialog
        if(result!=null) {
            ListAdapter adapter = new SimpleAdapter(
                    PontosActivity.this, pontosList,
                    R.layout.activity_listpontos, new String[]{"Data:", "Hora:",
                    "Latitude:", "Longitude:"}, new int[]{R.id.dataPonto,
                    R.id.horaPonto, R.id.latitudePonto, R.id.longitudePonto});
            adapter.notifyAll();
            lstPontos.setAdapter(adapter);
        }
        else
        {
            Toast.makeText(getApplicationContext(), "Nenhum Ponto Registrado", Toast.LENGTH_LONG).show();
        }
    }


}

JSON file:

{
"pontos": [
    {
            "datar": "14/11/2016",
            "horar": "20:37:001",
            "latr": "-22.778899",
            "longtr": "-47.554477"
    },
    {

        "datar": "14/11/2016",
            "horar": "20:39:001",
            "latr": "-22.748596",
            "longtr": "-47.858532"

     }
    ]
    }

HttpHandler:

public class HttpHandler {

private static final String TAG = HttpHandler.class.getSimpleName();

public String makeHttpHandler(String reqUrl){
    String resposta = null;

    try{
        URL url = new URL(reqUrl);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");
        InputStream is = new BufferedInputStream(connection.getInputStream());
        resposta = convertStreamToString(is);
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    return resposta;
}

XML:

<TextView
    android:id="@+id/dataPonto"
    android:layout_width="67dp"
    android:layout_height="wrap_content"
    android:layout_marginLeft="5dp"
    android:layout_marginTop="5dp"
    android:text="" />

<TextView
    android:id="@+id/horaPonto"
    android:layout_width="67dp"
    android:layout_height="wrap_content"
    android:layout_marginLeft="5dp"
    android:text=""
    android:layout_alignParentTop="true" />

<TextView
    android:id="@+id/latitudePonto"
    android:layout_width="67dp"
    android:layout_height="wrap_content"
    android:layout_marginLeft="5dp"
    android:layout_marginTop="5dp"
    android:text="" />

<TextView
    android:id="@+id/longitudePonto"
    android:layout_width="67dp"
    android:layout_height="wrap_content"
    android:layout_marginLeft="5dp"
    android:text=""/>