Android: Using Volley

Android docs

0) Download Volley
2) File > New > Import module (Volley)
1)  En el build.gradle de la app

dependencies {
    compile project(":volley")
    compile 'com.google.code.gson:gson:2.6.2'
    ...
}

4) Server class

public class Server {

    private RequestQueue mRequestQueue;
    private Context context;

    private static class Holder {
        static final Server INSTANCE = new Server();
    }

    public static Server getInstance() {
        return Holder.INSTANCE;
    }

    private Server() {

    }

    public void initialize(Context context) {
        this.context = context;

        // Instantiate the cache
        Cache cache = new DiskBasedCache(context.getCacheDir(), 1024 * 1024); // 1MB cap

        // Set up the network to use HttpURLConnection as the HTTP client.
        Network network = new BasicNetwork(new HurlStack());

        // Instantiate the RequestQueue with the cache and network.
        mRequestQueue = new RequestQueue(cache, network);

        // Start the queue
        mRequestQueue.start();
    }

    public void getHoroscope(Response.Listener responseListener, Response.ErrorListener errorListener) {

        String url = "https://volley-test.herokuapp.com/volley";

        JsonObjectRequest jsObjRequest = new JsonObjectRequest
                (Request.Method.GET, url, null, new Response.Listener() {

                    @Override
                    public void onResponse(JSONObject response) {
                        Log.d("Server", "Response: " + response.toString());
                    }
                }, new Response.ErrorListener() {

                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Log.d("Server", "Error: " + error.toString());
                    }
                });

        mRequestQueue.add(jsObjRequest);
    }
}

5) GsonRequest class

public class GsonRequest extends Request {
    private final Gson gson = new Gson();
    private final Class clazz;
    private final Map headers;
    private final Response.Listener listener;

    /**
     * Make a GET request and return a parsed object from JSON.
     *
     * @param url URL of the request to make
     * @param clazz Relevant class object, for Gson's reflection
     * @param headers Map of request headers
     */
    public GsonRequest(String url, Class clazz, Map headers,
                       Response.Listener listener, Response.ErrorListener errorListener) {
        super(Method.GET, url, errorListener);
        this.clazz = clazz;
        this.headers = headers;
        this.listener = listener;
    }

    @Override
    public Map getHeaders() throws AuthFailureError {
        return headers != null ? headers : super.getHeaders();
    }

    @Override
    protected void deliverResponse(T response) {
        listener.onResponse(response);
    }

    @Override
    protected Response parseNetworkResponse(NetworkResponse response) {
        try {
            String json = new String(
                    response.data,
                    HttpHeaderParser.parseCharset(response.headers));
            return Response.success(
                    gson.fromJson(json, clazz),
                    HttpHeaderParser.parseCacheHeaders(response));
        } catch (UnsupportedEncodingException e) {
            return Response.error(new ParseError(e));
        } catch (JsonSyntaxException e) {
            return Response.error(new ParseError(e));
        }
    }
}

6) Performing a GsonRequest

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