Meshtastic-Android/feature/car

:feature:car

Overview

The :feature:car module provides the Android Auto integration built on androidx.car.app. MeshtasticCarAppService is a CarAppService registered in the MESSAGING category (androidx.car.app.category.MESSAGING); each host connection gets a MeshtasticCarSession that wires up state, alerts, and conversation shortcuts.

Target: Android only, google flavor only — the module is added via googleImplementation(projects.feature.car) in :androidApp, and FeatureCarModule is included from the google flavor's FlavorModule.

Templates Gating

Production ships notification-only Android Auto messaging (MessagingStyle notifications + ConversationShortcutManager). The full templated car app is gated:

• Build with -PenableCarTemplates=true to enable it (Internal/Closed Play tracks only).
• The Gradle property resolves the carTemplatesEnabled manifest placeholder — in this module's own build.gradle.kts/AndroidManifest.xml (a library resolves its own placeholders; the app's value does not override it) and again in :androidApp as defense-in-depth.
• The decisive host-side gate is automotive_app_desc's <uses name="template" />; the android:enabled="${carTemplatesEnabled}" service flag keeps the templated service unbindable in production.

Key Components

Service layer (service/)

• MeshtasticCarAppService — CarAppService; host validation (allowlist in release, ALLOW_ALL_HOSTS_VALIDATOR in debug), creates sessions.
• MeshtasticCarSession — per-connection Session; starts CarStateCoordinator, EmergencyHandler, and ConversationShortcutManager, tags the session in Crashlytics, and returns the first Screen.
• CarStateCoordinator — bridges repository flows (nodes, messages, connection state) into car presentation state (MessageSnapshot, NodeUi in model/CarUiModels.kt). Created per car session.
• ConversationShortcutManager — publishes dynamic shortcuts for active DMs/channels so Android Auto surfaces Meshtastic conversations and links notifications to conversations via LocusIdCompat (the notification/reply plumbing that also serves the notification-only production path).

Screens (screens/)

• HomeScreen — TabTemplate dashboard (messages / nodes / status tabs) fed by CarStateCoordinator.
• NodeDetailScreen — PaneTemplate detail for one node (signal, battery, last heard) with a message action.

Emergency alerts (alerts/)

• EmergencyHandler — observes incoming PortNum.ALERT_APP packets, maintains the active EmergencyAlert list, and triggers audio tones on the car head unit.

Util layer (util/)

• MessageFilter — decides which packets are displayable (text, non-blank, not emoji-only) and validates outgoing message byte length.
• CarScreenDataBuilder — pure functions converting domain models to car UI models; free of Car App Library types so they unit-test without Robolectric.
• NodeSubtitleFormatter — node subtitle text with signal colouring and responsive variants.
• PersonIconFactory — circular initial avatars for Person icons in MessagingStyle notifications and shortcut avatars.
• CrashlyticsCarTagger — sets the car_session Crashlytics custom key.

Key Dependencies

From feature/car/build.gradle.kts:

• core:common, core:data, core:database, core:domain, core:model, core:repository
• androidx.car.app, androidx.car.app.projected (+ androidx.car.app.testing for tests)
• koin.android, firebase.crashlytics (via Firebase BoM), kermit

Testing

Screen and flow tests run on the JVM via TestCarContext + mokkery + Robolectric (CarScreensTest) — the Desktop Head Unit cannot drive current Car App API levels. See TESTING.md for the full recipe.