Publish and Subscribe with Android Data Streams

Building Realtime Android Apps is Easy with PubNub

The purpose of this blog series is to show how easy it is to build realtime Android applications using PubNub. Why? We think the Android platform is awesome because it gives developers the power to release applications across a huge range of devices. And since Android is a Java-like platform, that means developers don’t have to reinvent the wheel.

Although there are definitely challenges, like managing compatibility across previous versions of the operating system, for example. But Android does give developers a unified development experience across billions of devices: phone, tablets, wearables, TV and Auto.

Android Continues to Grow…

Over the past five years, it’s been amazing to witness the worldwide growth of Android’s market share, from about 50% in 2011 to over 80% in 2015. Over that time, there have seen several major releases of the operating system, all of which have made us very hungry. Everything from Ice Cream Sandwich to the latest one, Marshmallow. Along with these updates, we’ve also seen the addition of new platforms as well, including Android AutoAndroid TV, and Android Wear.

screenshots of completed android app


PubNub is a global realtime data stream network that allows you to create applications that scale from one user to hundreds of millions of users, seamlessly. You may have previously heard of technologies like WebSocket and PubNub takes the essence of these technologies, adds dozens of value-added features, and deploys it across a global network that enables message delivery within just a quarter of a second. That’s 250ms, much of which is taken up by the last hop from the mobile data carrier to the device itself.

Can developers build realtime applications without PubNub? Yes, but they also then have to manage a secure and highly reliable global network that scales to massive audience sizes, not to mention creating dozens of SDKs to provide a unified API and connectivity to the full range of devices on the network. Might as well leave it to PubNub.

There are a few reasons why PubNub and Android go so well together. The rise of enterprise communication services like Slack, ride-hailing services like Uber and Lyft, as well as the growth of IoT (Internet of Things) applications means that user expectations are moving rapidly towards a continuously-updated, “realtime” model of applications. This means that users don’t want to click a “refresh button” or “pull down to refresh”, they want to see changes in the application as soon as they happen. Similarly, daily data updates just don’t cut it anymore – stakeholders now want to see information with low latency as soon as it becomes available. A static GIF of a map, graph or pie chart is a huge fail – it needs to be a dynamically updated SVG showing a timestamp of “less than 5 seconds ago.”

Series Overview

In this blog series, we’ll take a look at an Android Data Stream application with several features:

Here’s what we have in mind:

Screen capture of running application


The app uses Publish/Subscribe messaging for a realtime chat feature, Presence tracking for a buddy list, and Multiplexing to show the last message across a group of channels. In this case, the Login activity is just a dummy one to collect the username.

Publish/Subscribe messaging is the core of any realtime application. It allows devices to subscribe to named “channels.” When messages are published, they are delivered instantly to all connected devices. What happens if a device is disconnected or on an unreliable connection? PubNub has a number of features including Reconnection, History, Storage and Playback to allow devices to seamlessly catch up on a channel’s content. Publish/Subscribe data streams can transfer device positions, chat messages, or just about any kind of dynamic structured data you can think of; think JSON.

Presence tracking is a tremendously useful feature for apps in gaming, social, collaboration, ride-hailing, and IoT spaces. If you’re familiar with chat applications, you’ve seen the friendly “buddy list” before. PubNub generalizes this concept across all the applications of Publish/Subscribe messaging, making it easy to see which devices are online and connected to channels using its Presence API. This makes it easy to see which users are online for a chat application, which cars are available in the case of a ride-hailing app, or which sensors are currently transmitting or receiving in the case of an IoT app. As devices come online, leave or become disconnected from the network, PubNub sends the corresponding Presence events of join, leave, and timeout to your application, allowing it to respond instantly to dynamic channel membership.

Multiplexing and Channel Groups. What fun would an app be if it only had one channel? PubNub gives developers the ability to create an unlimited number of channels. Using one connection for each channel subscription would quickly become unwieldy. Similarly, it’s often useful to give a group of channels a “nickname” to allow for easier subscription. For instance, creating an alias for all the users on a given team, or all the component stocks of the Dow Jones or S&P 500 indexes. PubNub provides Multiplexing to allow one device connection to support dozens of channel subscriptions. For cases where it’s necessary to subscribe to hundreds or thousands of channels, PubNub provides a feature called Channel Groups to create a compound subscription.

One thing we should note is that this is just a tiny selection of features provided by the PubNub platform – in future blogs, we’ll talk about other features such as Mobile Push NotificationsHistory, Storage & PlaybackPubNub Access Manager,Encryption and Wildcard Subscribe.

PubNub Android API

PubNub plays well with Android because the PubNub Android SDK (part of the PubNub Java SDK family) is extremely robust and has been battle-tested over the years across a huge number of mobile and backend installations. The SDK is currently on its 4th major release, which features a number of improvements such as fluent API, increased performance, sync/async operation, server-side filtering, streamlined logging & debugging, and more.

The PubNub Java SDK is distributed via the Maven Central repository, so it’s easy to integrate with your application whether you’re using Maven or Gradle (hopefully Gradle!).

Getting Started with PubNub

The first things you’ll need before you can create a realtime application with PubNub are publish and subscribe keys from PubNub. If you haven’t already, you can create an account, get your keys and be ready to use the PubNub network in less than 60 seconds.

screenshot of creating a PubNub account
  • Step 2: create a new application, including publish and subscribe keys.
screenshot of PubNub admin portal

The publish and subscribe keys look like UUIDs and start with “pub-c-” and “sub-c-” prefixes respectively. Keep these handy – you’ll need to plug them in when initializing the PubNub object in your Android application.

Getting Started with Android Studio

If you’re building an Android app, chances are you’re using Android Studio. Don’t worry – it’s ok if you use Eclipse, EMACS or Vim, for that matter! We just include the initial steps here so you will get the rough idea.

Starting a new project is the same as you always would:

screenshot of creating a new project in Android Studio

Then, you’ll want to adding a PubNub dependency line to gradle:

screenshot of adding PubNub SDK dependency

Here’s the dependency line up close:

compile group: 'com.pubnub', name: 'pubnub', version: '4.0.5'

Be sure to check the PubNub developer site frequently so you don’t miss a new version update!

Or, if you’d like to jump into the sample app right away, you can download it from GitHub.

screenshot of github checkout from Android Studio

If you use the “clone project from GitHub” feature in Android Studio, the Git url for the sample app is:

Navigating the Sample Application

Once you’ve set up the sample application, you’ll want to update the publish and subscribe keys in the Constants class. These are the keys you created when you made a new account and PubNub application in previous steps. Make sure to update these keys, or the app won’t work!

screenshot of sample app in Android Studio

As with any Android app, there are 2 main portions of the project – the Android code (written in Java), and the resource files (written in XML).

The Java code contains 2 Activities, plus packages for each major feature: Pub/Sub messaging, Presence, and Multiplexing.

screenshot of Java class list in Android Studio

The resource XML files include layouts for each activity, fragments for the 3 tabs, list row layouts for each data type, and a menu definition with a single option for “logout.”

Whatever you need to do to modify this app, chances are you’ll just need to tweak some Java code or resources. In rare cases, you might add some additional dependencies in the build.gradle file, or modify permissions or behavior in the AndroidManifest.xml.

Running the Code

Running the code should be as easy as clicking the play button in the Android Studio toolbar. You can use a connected device or an AVD in the emulator to run the application. As you sign into the application from multiple devices, you can exchange chat messages in the Pub/Sub tab, the Presence tab will show an updated member list, and the Multi tab will show the latest message sent by each device to a random channel. Here’s what you’ll find:

screenshots of completed android app

Wrapping Up

Thanks so much for stopping by and checking out our sample app for the Android SDK. Hopefully this gives you an idea of what’s possible! In the next articles in the series, we’ll dive deeper into working with Publish/Subscribe messaging, Presence tracking, and Multiplexing and channel groups. Stay tuned, and please reach out anytime if you feel especially inspired or need any help!



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