Android Tweets

An Android app that lets you pick any location on a map and see Mastodon posts tagged with #Android and your chosen city. Originally a GWU course project; modernized from 2020-era patterns to current Android best practices.

---

Running the app

Prerequisites

Tool	Version
Android Studio	Hedgehog (2023.1) or newer
JDK	17 (bundled with Android Studio)
Android SDK	API 35 (install via SDK Manager)
Emulator or device	API 23+

No API keys, cloud accounts, or secrets are required.

Steps

1. Clone the repo

   git clone https://github.com/bushidocodes/Android-Tweets.git
   cd Android-Tweets

2. Open in Android Studio File → Open → select the Android-Tweets directory.

3. Sync Gradle Android Studio will prompt you to sync. Let it finish — it downloads dependencies on first run (~200 MB including the OSMDroid tile library).

4. Run Select a device or emulator (API 23+) and press Run (▶).

Logging in

The app uses local authentication — no Firebase, no account needed.

• Email: any address containing @ (e.g. demo@demo.com)
• Password: any string ≥ 6 characters (e.g. demo123)

Using the map

• Long-press anywhere on the OpenStreetMap map to drop a pin. The app reverse-geocodes the tap to a city name and the confirm button turns green.
• Tap the green confirm button to load posts.
• Tap the location crosshair (top-left) to jump to your device's current GPS position.

The posts screen

Shows Mastodon posts from mastodon.social tagged with both #Android and #<city> (e.g. #android + #london). If the city has no co-tagged posts the feed falls back to global #Android posts.

---

Architecture

LoginFragment
    └─ AuthViewModel          local email/password validator
MapsFragment
    └─ MapsViewModel          Geocoder (Android OS), LocationSelection state
TweetsFragment
    ├─ MapsViewModel          reads selected address (activity-scoped)
    └─ TweetsViewModel        Mastodon API via Retrofit + kotlinx.serialization

All three screens share a single MainActivity shell wired through the Jetpack Navigation Component. The address selected on the map travels to the tweets screen via an activity-scoped MapsViewModel — no Intent extras, no argument bundles.

Key libraries

Purpose	Library
Maps	OSMDroid (OpenStreetMap, no key needed)
Networking	Retrofit 2 + OkHttp + kotlinx.serialization
Social feed	Mastodon public API
Images	Coil
UI	Material 3 (Theme.Material3.DayNight)
Navigation	Jetpack Navigation Component
Async	Kotlin Coroutines + StateFlow

---

Tests

./gradlew testDebugUnitTest

39 unit tests across 5 classes:

Class	What it covers
AuthViewModelTest	Local validation (success, failure, state isolation)
MappersTest	DTO → Tweet HTML stripping, entity decoding
TweetsViewModelTest	City-filter → fallback → error propagation
MastodonApiServiceTest	HTTP parsing, unknown fields, URL params
TweetTest	Data class, no-arg constructor

---

CI

GitHub Actions runs on every push to master and every pull request:

JDK 17 + Gradle cache
  → ./gradlew testDebugUnitTest
  → ./gradlew lintDebug
  → ./gradlew assembleDebug

Test reports and the debug APK are uploaded as workflow artifacts.

---

Project history

This started as a GWU CSCI 4237 course project (Fall 2020). The original used Twitter v1.1 geo-search, Firebase Auth, Google Maps, Anko doAsync, and Activity-based navigation with manual onSaveInstanceState — all replaced during this modernization pass:

Before	After
Twitter API (paywalled)	Mastodon public hashtag timeline
Firebase Auth	Local validator (no cloud needed)
Google Maps SDK (API key)	OSMDroid / OpenStreetMap (no key)
FusedLocationProviderClient	Platform LocationManager
Anko doAsync	viewModelScope + Coroutines
3 Activities + Intent extras	Navigation Component + 3 Fragments
AppCompat theme	Material 3 (Theme.Material3.DayNight)
Picasso	Coil
2 placeholder tests	39 unit tests across 5 classes