Volley - Part 2 - Application Model

Volley - Part 2 - Application Model - Lemberg Solutions Blog

Volley - Android HTTP client

Part 2 - Application Model

Do I need to instantiate request queue in each Service or Activity?

No

Should I create singleton wrapper?

Yes

Why ?

  • Request Queue creation is quite expensive
  • You will be able to access and cancel all your requests
  • You will be able to access and clear your cache

Let's create two class.

Request Proxy

  • wrapper for request queue
  • holds list of all application requests

Request Manager

  • singleton which hold Request Proxy

Put those two classes in the same package.

public class RequestProxy {

    private RequestQueue mRequestQueue;

    // package access constructor
    RequestProxy(Context context) {
    mRequestQueue = Volley.newRequestQueue(context.getApplicationContext());
    }
    public void login() {
        // login request
    }

    public void weather() {
        // weather request
    }
 }
public class RequestManager {

    private static RequestManager instance;
    private RequestProxy mRequestProxy;

    private RequestManager(Context context) {
        mRequestProxy = new RequestProxy(context);
    }
    public RequestProxy doRequest() {
        return mRequestProxy;
    }

    // This method should be called first to do singleton initialization
    public static synchronized RequestManager getInstance(Context context) {
        if (instance == null) {
            instance = new RequestManager(context);
        }
        return instance;
    }

    public static synchronized RequestManager getInstance() {
        if (instance == null) {
            throw new IllegalStateException(RequestManager.class.getSimpleName() +
                    " is not initialized, call getInstance(..) method first.");
        }
        return instance;
    }
}

Usage

Initialize RequestManager in application class

public class MyApplication extends Application {

    @Override
    public void onCreate() {
        super.onCreate();

        // RequestManager initialization
        RequestManager.getInstance(getApplicationContext());
    }
}

Now you can start your request as following.

RequestManager.getInstance().doRequest().login(..);
RequestManager.getInstance().doRequest().weather(..);

Original article.