RxJava + Fast Android Networking

Big news: Fast Android Networking now supports RxJava.

Let’s explore why RxJava support is important.

What is RxJava?

RxJava is used for reactive programming. In reactive programming, the consumer reacts to the data as it comes in. Reactive programming allows for event changes to propagate to registered observers.

The main components: observables, observers, and subscriptions

RxJava provides Observables and Observers. Observables can send out values. Observers watch Observables by subscribing to them.
Observers are notified when an Observable emits a value and when the Observable says an error has occurred. They are also notified when the Observable sends the information confirming that it no longer has any values to emit.

The corresponding functions are onNext, onError, and onCompleted() from the Observer interface. An instance of Subscription represents the connection between an observer and an observable. We can call unsubscribe() on this instance to remove the connection.

Let’s understand this better by exploring an example:

Observable<String> observable = Observable.just("Cricket", "Football");

This is an Observable which emits strings and it can be observed by an Observer.

Let’s create an Observer:

Observer<String> observer = new Observer<String>() {
public void onCompleted() {


public void onError(Throwable e) {


public void onNext(String response) {
        Log.d(TAG, "response : " + response);

Now, we have to connect both Observable and Observer with a subscription. Only then can it actually do anything:


This will cause the following output, one line at a time:


This means the Observable emits two strings, one by one, which are observed by Observer.

Using RxJava with Fast Android Networking

If you aren’t yet familiar with Fast Android Networking, you can learn more about it here.

By using RxJava with Fast Android Networking, you can do many things like:

  1. Chaining requests
  2. Combining many requests and getting the combined response
  3. Cancelling the Network call when an activity is destroyed
  4. Using operators to filter out the response from Network, which you can then show to users
  5. Setting the thread on which we need a response from the server
  6. Proper Error handling

…and much more. Trust me, RxJava is an Art and endless possibilities await those who can master it. So let’s start mastering it by learning how to use it with the network layer.

To use RxJava in Fast Android Networking, you need to compile this.

compile 'com.amitshekhar.android:rx-android-networking:1.0.1'

If you are using RxJava2, then compile

compile 'com.amitshekhar.android:rx2-android-networking:1.0.1'

And Check here for RxJava2

Then initialize it in the onCreate() Method of the application class:


Make sure you have provided the internet permission in manifest.

Show me the code

I will try to give you a more friendly introduction to RxJava Operators, with plenty of complete code samples that you can actually compile and modify.

The below examples are based on RxJava one.

Example Using Map Operator

Use Case : Assume that we get ApiUser Object from server Api and our android client database accepts User Object. So after getting ApiUser from server, we are converting it into User Object using Map operator.

Example Using Zip Operator : Combining two network requests

Use Case : Let say we get the list of football fans from one network call, and from another we get the list of cricket fans and then we have to find the user who loves both cricket and football. Here we are using Zip Operator to get the result of network call in one common method to apply our logic to find those who loves both.

Example using flatMap and filter operator.

Use Case : Let say our server return the list of my friends , but we need to filter out only who those friends who is also following me. Here comes the filter operator to do so.

Another example using flatMap operator.

Use Case : Assume one api endpoint returns us the list of user and another returns the user detail corresponding to each user. Here we are using flatMap operator to do so.

There are plenty more examples here.

Thanks for reading this article.

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Amit Shekhar

Amit Shekhar

Co-Founder at Mindorks | Learning is a journey, let’s learn together