Build a Real-Time In-App Chat in Android Using PubNub (Kotlin + MVVM) — Complete Tutorial Series

In this tutorial series, you’ll learn how to create a modern, scalable real-time in-app chat using Kotlin, the MVVM architecture, and **PubNub** — a robust platform built specifically for real-time communication.

This post is your go-to index for the entire series. I’ll update it with links as each part goes live. Bookmark it now!

Why PubNub?

PubNub is a real-time communication platform that removes the complexity of building low-latency messaging and presence systems. Here’s what it offers out of the box:

Core Features for Android (Kotlin)

• Real-Time Messaging — Send and receive messages across any number of devices instantly.
• Message Persistence — Store and retrieve message history.
• User Presence — Detect when users come online or go offline.
• Typing Indicators — Show “User is typing…” live updates.
• Channel Groups — Organize multiple chatrooms or group threads.
• Push Notifications — Integrate with FCM to alert users of new messages.
• Access Manager (PAM) — Control who can publish/subscribe to channels.
• File & Media Sharing — Send files or images directly within chat.
• Message Reactions & Metadata — Add context to any message.
• Low-Latency & Scalability — Designed to support millions of messages per second.

Tutorial Series Index

✅ = Live 🔄 = Coming Soon (links will be added as they’re published)

✅ 1. Introduction

What we’re building,why real-time chat matters, and why PubNub is a solid choice. Read Part 1

🔄 2. Project Setup (Kotlin + MVVM + PubNub SDK)

Create a new Android project, add MVVM structure, and connect to PubNub.

🔄 3. PubNub Initialization & Basic Messaging

Set up PubNub in the repository layer, and start sending/receiving basic text messages in real time.

🔄 4. Designing the Chat UI

Build a clean chat screen using RecyclerView, message bubbles, and input fields.

🔄 5. Implementing Message Sending

Capture user input, structure message payloads, and publish them through PubNub.

🔄 6. Subscribing & Receiving Messages

Listen for messages in real time and update the UI reactively using LiveData.

🔄 7. Chat History & Persistence

Fetch previous messages using PubNub’s history API and support pagination.

🔄 8. Presence & Typing Indicators

Show when users are online/offline and when they’re actively typing.

🔄 9. Reconnection & Error Handling

Handle network issues gracefully and ensure a reliable chat experience even under bad connectivity.

🔄 10. File & Image Sharing

Upload files, share image URLs in messages, and preview them in the chat window.

🔄 11. Push Notifications with FCM

Set up Firebase Cloud Messaging to alert users when messages arrive in the background.

🔄 12. Group Chat & Multi-Channel Support

Use PubNub’s channel and channel group system to manage multiple chat threads and rooms.

🔄 13. Security with Access Manager (PAM)

Implement user-level access control and protect your keys from unauthorized use.

🔄 14. Reactions, Metadata & Message Enrichment

Use PubNub’s objects and metadata features to add reactions, timestamps, and user info to messages.

🔄 15. Testing, Debugging & Wrapping Up

Final tweaks, testing best practices, and extending the app beyond chat (voice, bots, analytics).

Tech Stack

• Language: Kotlin
• Architecture: MVVM
• Platform: Android
• Libraries: PubNub SDK, LiveData, ViewModel, RecyclerView, FCM (optional)
• Extras: Firebase (optional), Glide, Retrofit (for media handling)

Stay Updated

Follow me on Medium or bookmark this series to stay updated as each part is released.

Are you ready to bring your Android app to life with chat? Let’s get started!