public class Login extends AppCompatActivity {
TextView tvsesion;
private EditText email,password;
private Button sign_in_register;
private RequestQueue requestQueue;
private static final String URL = "http://xxxxxxxxxx/WebService/user_control.php";
private StringRequest request;
Context ctx;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);
    ctx=this;


    Toolbar toolbar = (Toolbar)findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    tvsesion = (TextView)findViewById(R.id.tvsesion);
    email = (EditText)findViewById(R.id.txusuario);
    password = (EditText)findViewById(R.id.txpass);
    sign_in_register = (Button) findViewById(R.id.login);

    comprobarPreferencias();

    String font_path = "font/Harabara Mais Demo.otf";
    Typeface TF = Typeface.createFromAsset(getAssets(),font_path);
    tvsesion.setTypeface(TF);

    requestQueue = Volley.newRequestQueue(this);


    sign_in_register.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            final String nombre = email.getText().toString();
            String contraseña = password.getText().toString();

            PreferenciasFragment.setString(ctx, PreferenciasFragment.getKeyNombreEd(), nombre);
            PreferenciasFragment.setString(ctx, PreferenciasFragment.getKeyContraseñaEd(),  contraseña);

            request = new StringRequest(Request.Method.POST, URL, new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {

                    try {
                        JSONObject jsonObject = new JSONObject(response);
                        if(jsonObject.names().get(0).equals("success")){
                            Toast.makeText(getApplicationContext(),"CORRECTO!"+jsonObject.getString("success"),Toast.LENGTH_SHORT).show();
                            startActivity(new Intent(getApplicationContext(),Drawer.class));
                        }
                        else {
                            Toast.makeText(getApplicationContext(), "Error:" +jsonObject.getString("error"), Toast.LENGTH_SHORT).show();
                        }

                    } catch (JSONException e) {
                        e.printStackTrace();
                    }


                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {

                }
            }){
                @Override
                protected Map<String, String> getParams() throws AuthFailureError {
                    HashMap<String,String> hashMap = new HashMap<String, String>();
                    hashMap.put("email",email.getText().toString());
                    hashMap.put("password",password.getText().toString());

                    return hashMap;
                }
            };

            requestQueue.add(request);
        }
    });
}

<?php
include_once 'connection.php';
class User {

    private $db;
    private $connection;

    function __construct() {
        $this -> db = new DB_Connection();
        $this -> connection = $this->db->getConnection();
    }

    public function does_user_exist($email,$password)
    {
        $query = "Select * from usuarios where usuario='$email' and contrasena = '$password' ";
        $result = mysqli_query($this->connection, $query);
        if(mysqli_num_rows($result)>0){
            $json['success'] = ' Bienvenido '.$email;
            echo json_encode($json);

            mysqli_close($this -> connection);
        }
        else{
            $query = "insert into USERS (email, password) values ( '$email','$password')";
            $inserted = mysqli_query($this -> connection, $query);
            if($inserted == 1 ){
                $json['success'] = 'Acount created';
            }else{
                $json['error'] = ' Usuaio o Contraseña incorrectos';
            }
            echo json_encode($json);
            mysqli_close($this->connection);
        }

    }


}


$user = new User();
if(isset($_POST['email'],$_POST['password'])) {
    $email = $_POST['email'];
    $password = $_POST['password'];

    if(!empty($email) && !empty($password)){

        $encrypted_password = md5($password);
        $user-> does_user_exist($email,$password);

    }else{
        echo json_encode("you must type both inputs");
    }

}

public class FragmentNuevas extends Fragment {

private OnFragmentInteractionListener mListener;
ArrayList<Product> arrayList;
ListView lv;
ProgressDialog pdialog = null;
Context context = null;

public FragmentNuevas() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_fragment_nuevas, container, false);

    lv = (ListView)view.findViewById(R.id.listView);
    arrayList = new ArrayList<>();
    context = getActivity();

    getActivity().runOnUiThread(new Runnable() {
        @Override
        public void run() {
            pdialog = ProgressDialog.show(context, "", "Buscando Noticias...", true);
            new ReadJSON().execute("http://xxxxxxxxxx/WebService/consultanuevas.php");
        }
    });

    /*lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
            Product selectedProduct = arrayList.get(position);

            Intent intent = new Intent(getActivity().getApplicationContext(), Nuevas.class);
            intent.putExtra("nombre", selectedProduct.getName());
            intent.putExtra("fecha", selectedProduct.getFecha());
            intent.putExtra("observaciones", selectedProduct.getPrice());
            intent.putExtra("folio", selectedProduct.getImage());
            startActivity(intent);
        }
    });*/

    // Inflate the layout for this fragment
    return view;
}

class ReadJSON extends AsyncTask<String, Integer, String> {
    @Override
    protected String doInBackground(String... params) {
        return readURL(params[0]);
    }
    @Override
    protected void onPostExecute(String content) {

        pdialog.dismiss();
        try {
            JSONArray jsonarray = new JSONArray(content);
            for(int i =0;i<jsonarray.length(); i++){
                JSONObject productObject = jsonarray.getJSONObject(i);
                arrayList.add(new Product(
                        productObject.getString("nombre"),
                        productObject.getString("observaciones"),
                        productObject.getString("fecha"),
                        productObject.getString("folio"),
                        productObject.getString("lugar"),
                        productObject.getString("estado"),
                        productObject.getString("asunto")

                ));
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
        CustomListAdapter adapter = new CustomListAdapter(
                getActivity(), R.layout.custom_list_layout, arrayList
        );
        lv.setAdapter(adapter);
    }
}

private static String readURL(String theUrl) {
    StringBuilder content = new StringBuilder();
    try {
        // create a url object
        URL url = new URL(theUrl);
        // create a urlconnection object
        URLConnection urlConnection = url.openConnection();
        // wrap the urlconnection in a bufferedreader
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
        String line;
        // read from the urlconnection via the bufferedreader
        while ((line = bufferedReader.readLine()) != null) {
            content.append(line + "n");
        }
        bufferedReader.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return content.toString();
}

// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
    if (mListener != null) {
        mListener.onFragmentInteraction(uri);
    }
}

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    if (context instanceof OnFragmentInteractionListener) {
        mListener = (OnFragmentInteractionListener) context;
    } else {
        throw new RuntimeException(context.toString()
                + " must implement OnFragmentInteractionListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mListener = null;
}

/**
 * This interface must be implemented by activities that contain this
 * fragment to allow an interaction in this fragment to be communicated
 * to the activity and potentially other fragments contained in that
 * activity.
 * <p>
 * See the Android Training lesson <a href=
 * "http://developer.android.com/training/basics/fragments/communicating.html"
 * >Communicating with Other Fragments</a> for more information.
 */
public interface OnFragmentInteractionListener {
    // TODO: Update argument type and name
    void onFragmentInteraction(Uri uri);
}

<?php
      link=mysqli_connect("localhost","xxxxxx","xxxxx","xxxxxxxx") or die("Error en la conexion" . mysqli_error($link));

$resultado = mysqli_query($link,"SELECT * FROM solicitudes WHERE estado = 'Pendiente' ORDER BY folio DESC");
while ($row = mysqli_fetch_assoc($resultado)) {
$arr[] = $row;

}

echo json_encode($arr);