Case 05

Rebook

Google Sign-In and live data sync on Android

DESIGNOPERATE

A native Android marketplace for second-hand books, using Google Sign-In and Firebase for live listing updates.

The problem

Students wanted a simple place to buy and sell textbooks, without me running a login server and a sync backend to support it.

Where it could go wrong

What is exposed

mobile identity
listing ownership
offline data

Checks in place

Google Sign-In
Firebase Authentication
realtime synchronization

Result

low-friction onboarding
live listing updates
offline persistence

How I built it

Firebase Authentication with Google Sign-In handles identity. Firebase Realtime Database keeps listings in sync and works offline. Material components handle navigation, with multidex for older devices.

AndroidJavaFirebase AuthRealtime DatabaseGoogle Sign-In

What it does

Google Sign-In
Firebase Authentication
Realtime listing sync
Offline persistence

What I would improve

Document and test database security rules
Add ownership validation for listing mutations
Introduce abuse reporting and moderation controls

Code

View repository