Real-Time Chat App Project for Android with Firebase Messaging and Media Sharing

A chat app is the clearest way to demonstrate realtime client–server engineering on Android: every message, presence change and typing event must travel from one phone to a cloud backend and back to another phone with no manual refresh. Most student chat projects fake this with polling or a local database, which collapses the moment two real devices are involved. This project does it properly — a native Android app written in Kotlin, backed entirely by Firebase: Cloud Firestore streams every message the instant it is written, Firebase Cloud Messaging wakes the app with a push notification when it is closed, and Cloud Storage handles image, video and document uploads with progress feedback. Students learn authentication, NoSQL data modelling, security rules, background services and push infrastructure — the exact stack behind production messaging apps. Because the backend is Firebase rather than a self-hosted server, the project is genuinely demoable in a viva on two physical phones.

1. The user signs in with phone OTP or Google; Firebase Authentication returns a UID that identifies them in every security rule.
2. Chat rooms and messages are stored as Firestore documents — one rooms collection, a messages subcollection per room, and a presence document per user.
3. Each open conversation attaches a Firestore snapshot listener; any write to the messages subcollection is pushed to all listeners within the sync window.
4. Media is uploaded to Cloud Storage under a per-user path; the download URL is written into the message document, so receivers stream it on demand.
5. When the app is backgrounded, a Cloud Function (or the client write path) triggers an FCM push carrying the sender name and message preview.
6. Typing state and presence are written as lightweight Firestore documents with a short TTL-style refresh, and rendered as "typing..." and presence dots in the UI.
7. Security rules enforce that only authenticated room members can read or write their rooms, and uploads are capped per file size.

Tech stack:

• Kotlin, Android SDK with Jetpack components
• Firebase Authentication (phone OTP, Google sign-in)
• Cloud Firestore (realtime database and listeners)
• Firebase Cloud Messaging (push notifications)
• Cloud Storage for Firebase (media uploads)
• Android Studio (build and debugging)

• [1-1 and group chats] Private conversations and group rooms with named members, per-room message history and unread counters — the two conversation models every messaging app needs.
• [Realtime message sync] Firestore snapshot listeners push new messages to all participants instantly; no polling, no pull-to-refresh, with the sync-event flow visible in the demo.
• [Media sharing] Images, video clips and documents (PDF and others) upload to Cloud Storage with an in-bubble progress bar, then render inline as media or document bubbles.
• [Push notifications] Firebase Cloud Messaging delivers a notification with the sender name and message preview when the app is in the background or closed.
• [Typing indicator and online presence] A per-user typing flag and online/last-seen presence, synced through Firestore, so the UI shows "typing..." and green presence dots live.
• [Read receipts and timestamps] Double-tick read receipts that turn accent-coloured on read, plus per-message timestamps in every bubble.
• [Phone and Google sign-in] Firebase Authentication with phone-OTP and Google sign-in; every Firestore rule is keyed to the authenticated UID.

• Complete Kotlin Android Studio project source code
• Firestore data model, security rules and Storage rules
• Firebase console setup guide (project creation to first push notification)
• Project report PDF (architecture, data model, Firebase service design, testing)
• PPT presentation for final review
• Viva Q&A preparation document (Firestore listeners, FCM flow, security rules, offline behaviour)