E-Commerce App

Build a complete shopping experience: browse products, add to cart, check out, pay, and track orders. This is the canonical project for reinforcing Compose, clean architecture, Hilt, Room, Retrofit, and MVI state machines.

The user journey

Splash → Home (featured) → Category → Product detail → Add to cart
                                                             │
                                                             ▼
   Orders ← Confirmation ← Payment ← Checkout ← Cart ◄──────┘

Features (by milestone)

M1 — Skeleton (Week 1)

• Convention plugins (myapp.android.application, myapp.android.feature, myapp.android.compose)
• Material 3 theme + design tokens in :core:design
• Bottom navigation: Home, Categories, Cart, Orders, Profile
• Feature modules: :feature:home, :feature:catalog, :feature:product, :feature:cart, :feature:checkout, :feature:orders
• Empty state + loading + error composables in :core:ui

M2 — Data layer (Week 2)

• Retrofit with auth interceptor + token refresh
• Room schema for Product, Category, CartItem, Order, Address
• Repository interfaces in :core:domain, implementations in :core:data
• Dispatchers injected; Result<T> wrapper in :core:common
• Fake API with product fixtures for dev flavor

M3 — Primary flows (Week 3)

• Home: featured carousel + categories grid
• Catalog: paged product list with Paging 3
• Product detail: gallery, specs, reviews, add-to-cart
• Cart: quantity adjustments, remove, subtotal, move-to-wishlist

M4 — Checkout state machine (Week 4)

sealed interface CheckoutState {
    data object Initial : CheckoutState
    data class SelectAddress(val addresses: List<Address>, val selected: Address?) : CheckoutState
    data class SelectPayment(val address: Address, val methods: List<PaymentMethod>, val selected: PaymentMethod?) : CheckoutState
    data class Review(val address: Address, val payment: PaymentMethod, val cart: Cart) : CheckoutState
    data class Submitting(val snapshot: Review) : CheckoutState
    data class Failed(val snapshot: Review, val error: PaymentError) : CheckoutState
    data class Confirmed(val orderId: OrderId) : CheckoutState
}

Wire MVI from Module 04 — intents: SelectAddress, SelectPayment, Submit, Retry. Cover all transitions with reducer tests.

M5 — Production hardening (Week 5)

• Crashlytics with user.id, last.screen, checkout.state custom keys
• Baseline profile generator (Module 10) for home + product + checkout
• R8 tuned; Moshi rules; Retrofit interface rules
• Accessibility: TalkBack-complete flow from home to confirmation
• RTL: everything uses start/end padding; icons auto-mirrored
• Instrumentation tests for checkout happy path + retry

M6 — Ship (Week 6)

• GitHub Actions: PR validation + release pipeline (Module 17)
• Fastlane: internal + alpha + beta + production lanes
• Play Console: data safety declared, screenshots uploaded
• SBOM + license audit committed
• README with architecture diagram, screenshots, build badge

Architecture diagram

┌─────────────────────────────────────────────────────────────────────┐
│  :app                                                               │
│    MyApp, Hilt graph, NavHost, AppTheme                             │
├─────────────────────────────────────────────────────────────────────┤
│  :feature:home  :feature:catalog  :feature:product  :feature:cart   │
│  :feature:checkout (MVI)  :feature:orders  :feature:profile         │
├─────────────────────────────────────────────────────────────────────┤
│  :core:ui · :core:design · :core:domain · :core:data                │
│  :core:network · :core:database · :core:datastore · :core:common    │
│  :core:analytics · :core:testing                                    │
├─────────────────────────────────────────────────────────────────────┤
│  Retrofit + OkHttp + Auth interceptor + Certificate pinning        │
│  Room DB (source of truth for cart, offline products)              │
│  DataStore Proto (user prefs, auth token, recent searches)         │
└─────────────────────────────────────────────────────────────────────┘

Stretch goals (optional)

🔐

Biometric checkout

Require BiometricPrompt for orders over a threshold. Key stored in Keystore.

🏷️

Promo codes + flags

Firebase Remote Config flag gates promo UI. A/B test two checkout layouts.

📱

Tablet two-pane

Responsive: on Expanded window class, show catalog + detail side by side.

🌍

RTL + i18n

Translate to Arabic, Spanish, Hindi. Use pseudo-localization to catch bugs early.

🖼️

Shared element transitions

Product card → product detail with Compose 1.7 SharedTransitionLayout.

📊

Funnel analytics

Log home_view → product_view → add_to_cart → checkout_start → confirmed.

Testing strategy

1. 01

   Unit

   Every ViewModel, every use case, every mapper. MockK for repo interfaces. Turbine for StateFlow assertions.

2. 02

   Compose UI

   Screenshot tests with Paparazzi for every screen in light/dark/RTL/2x font variants. Node assertions for interactive flows.

3. 03

   Integration

   Room DAO tests with in-memory DB. Retrofit with MockWebServer. Hilt test rules to wire fakes.

4. 04

   End-to-end

   Espresso + Compose test for full checkout happy path + retry-on-payment-decline. Run on AVD in CI.

5. 05

   Macrobenchmark

   Cold start, home scroll frame timing, checkout completion time — all recorded as baseline.

Dependencies to learn / demonstrate

• Compose + Navigation Compose + Navigation type-safe routes (Module 03)
• Hilt for DI (Module 04)
• Room for offline-first products + cart (Module 05)
• Retrofit + Moshi + auth interceptor + cert pinning (Module 06, 16)
• Paging 3 for catalog (Module 06)
• Coil for images (Module 06)
• DataStore Proto for user prefs (Module 05)
• Firebase Crashlytics + Performance + Remote Config (Module 07, 18)
• Convention plugins + version catalog (Module 14)
• Baseline profile + Macrobenchmark (Module 10)
• Fastlane + GitHub Actions (Module 17)
• Paparazzi for visual regression (Module 09, 19)

Review rubric

When you submit this project for portfolio review, you'll be graded on:

Area	Excellent (5)	Pass (3)
Architecture	Clean 3-layer with typed errors, MVI for checkout	MVVM throughout, some logic in composables
Testing	≥ 80% domain coverage, Compose UI tests	50% coverage, some UI tests
Performance	Baseline profile + P95 cold start < 1.5s	No baseline profile, P95 < 2.5s
Accessibility	TalkBack-complete, WCAG AA contrast	Labels present, some gaps
Production readiness	Crashlytics, Fastlane, staged rollout, SBOM	Crashlytics only
Code quality	Detekt clean, ktlint clean, Konsist passes	Minor lint issues

Next

Once M6 is live, update your Career portfolio README, then start Project 2: Social Media App.