AndroidAutoSurfaceHolder

Holds and manages shared state for Android Auto map rendering.

This class acts as a shared holder between the phone app (where MapController lives) and the Android Auto module (where MapView is created for Android Auto).

Purpose

• Bridge: Connects phone app's MapController to Android Auto's SurfaceCallback

• Shared State: Allows Android Auto module to access MapController without depending on app

• MSDK-ready: Uses interfaces instead of concrete implementations

Threading

All setter and getter methods on this class's own fields must be called from the main thread. The fields are plain var references without synchronization, relying on single-thread access for correctness.

Note: The reference to this holder (stored in AndroidAutoStateHolder.holder) is marked @Volatile and may be read from binder threads via the AndroidAutoSurfaceManager facade. This is safe because the reference itself is volatile, and the holder's fields are only mutated from the main thread (typically well before AA binder threads read them).

Architecture

Phone App (MainActivity/MainViewModel)
   ↓ setMapController() - shares MapController when phone map initializes
AndroidAutoSurfaceHolder (shared singleton via Hilt or manual injection)
   ↓ getMapController() - Android Auto retrieves to initialize AA MapView
Android Auto Module (AndroidAutoSurfaceCallback)

Flow

1. Phone app launches, MapViewComposable initializes

2. MainViewModel creates a MapControllerAdapter wrapping MapViewModel

3. MainViewModel calls setMapController(adapter) to share it

4. Android Auto connects, SurfaceCallback creates fresh MapView

5. SurfaceCallback calls getMapController() to initialize AA MapView

6. AA MapView uses the MapController for state and camera control

7. On disconnect, AA MapView is destroyed

Implementation Notes

This class implements MapStateProvider to provide a standard interface for Android Auto to access the map controller and cached position.

See also