Lets_Go_Android_Client — Kotlin app for activity-based matching

Android client for the Lets Go platform. Users pick activities and timeframes, swipe through match cards, join event cards, and coordinate in an in-app chat—without sharing personal info. The app talks to the C++ gRPC server and stores lightweight local state for fast UI.

Stack: Kotlin · Jetpack Fragments/Navigation · WorkManager · gRPC/Protobuf client · Local databases (Room/SQLite) · Glide
Features: swipeable match cards · activity/timeframe selection · events as cards · private chat rooms · phone/Google login

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Product snapshots

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Highlights (skim me)

• Polished flows: phone/Google login → profile setup → activities & timeframes → swipe matches → chat.
• Responsive UI: swipeable cards with clear affordances, per-activity chips, and time-overlap visuals.
• Typed networking: generated gRPC stubs from shared .proto files (see Lets_Go_Protobuf).
• Smooth background work: WorkManager and dedicated workers for chat streaming, cleanup, and retries.
• Local persistence: small, focused databases for accounts, messages, icons, other users, and chat rooms.
• Privacy by design: in-app chat rooms so coordination doesn’t require exchanging personal details.

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How it works (client view)

Architecture at a glance

• UI layer: Activities + Fragments (matchScreenFragment, chatRoomFragment, etc.) with shared ViewModel utilities.
• Data layer: gRPC clients, repositories, and local databases (Room/SQLite) for offline reads and quick UI.
• Workers: background tasks for streaming, uploads, cleanup, and error handling.

Key flows

• Login & onboarding: fragments collect minimal info (name, birthday, pictures, categories), then confirm via SMS.
• Matching: client sends preferences (categories, distance, time windows); server returns a batch → rendered as cards.
• Chat: a background chat stream receives new messages (fan-out from server’s change stream) and writes to the local DB; UI observes DB for instant updates.

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Code tour (where to look)

UI & Navigation

• app/src/main/java/site/letsgoapp/letsgo/activities/ — top-level activities (entry points)
• app/src/main/java/site/letsgoapp/letsgo/applicationActivityFragments/ — main app screens
  • matchScreenFragment/, matchMadeScreenFragment/, chatRoomsListFragment/, chatRoomFragment/, profileScreenFragment/, selectLocationScreenFragment/, timeFrameTutorialFragment/
• app/src/main/java/.../loginActivityFragments/ — onboarding: phone/Google login, rules, verification
• app/src/main/res/navigation/ — NavGraph(s), transitions and destinations

Data & Networking

• app/src/main/java/.../gRPC/clients/ — gRPC client stubs/wrappers (generated from .proto)
• app/src/main/java/.../repositories/ — thin repos (e.g., chatRoomCommandsRPCs/) to isolate transport from UI
• app/src/main/java/.../standAloneObjects/ — chatStreamObject/, findMatchesObject/, loginFunctions/

Local databases (Room/SQLite)

• app/src/main/java/.../databases/
  • accountInfoDatabase/ → accountInfo/, accountPicture/
  • iconsDatabase/ → icons/
  • messagesDatabase/ → messages/, messageMimeTypes/, unsentSimpleServerCommands/
  • otherUsersDatabase/ → otherUsers/, chatRooms/, matches/

Workers & Utilities

• app/src/main/java/.../workers/ — chatStreamWorker/, chatStreamObjectWorkers/, cleanDatabaseWorker/, loginFunctionWorkers/, error_handling/
• app/src/main/java/.../utilities/ — date pickers, input filters, Glide config, shared ViewModel helpers
• app/src/main/res/ — layouts, drawables, animations, fonts, menus, colors, etc.

Tests

• app/src/androidTest/java/.../ — UI/instrumentation (fragments, fakes, stream object tests)
• app/src/test/java/.../ — unit tests + utilities

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Design choices (frontend)

• Fragments + NavGraph for structured flows and deep-link resilience.
• Local-first rendering: UI observes DB tables so lists/chat feel instant while network catches up.
• Background streaming via WorkManager keeps chat/live updates running with OS-friendly scheduling.
• Typed contracts (gRPC) reduce client/server drift and simplify data models.
• Defensive UX: clear error surfaces (retry, “trouble logging in”), block/report affordances, and guardrails during onboarding.

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Related

• Server (C++) — stateless hub, gRPC/Protobuf, MongoDB
  👉 Lets_Go_Server

• Desktop Admin (Qt) — admin/ops console for moderation, events, stats, and controls
  👉 Lets_Go_Interface

• Protobuf Files — protobuf files used to communicate between server and clients
  👉 Lets_Go_Protobuf

Status & compatibility

Portfolio reference of a completed app. SDK/Gradle versions are legacy; modern toolchains may require updates.

License

MIT