Intro

Android automotive CAR API usage example.

The example is based on the use of android.car.hardware.CarPropertyManager and shows how to work with SYSTEM (speed, transfer, etc.) and VENDOR custom properties that belong to all possible permission protection levels:

• normal
• dangerous
• signature|privileged

Project support both gradle and AOSP (Android.bp) builds.

How to use CAR API

To use and test the CAR API, the following is done in the project:

1. Add android.car library (to gradle, to Android.bp).

2. Add permissions to AndroidManifest.xml.

3. Request dangerous permissions in runtime in onCreate() in MainActivity.java.

4. Use CarPropertyManager API in MainActivity.java:

   • listeners: registerCallback()
   • getters: getIntProperty()
   • setters: setBooleanProperty

Where to test app

• AOSP Android Automotive Emulator (e.g aosp_car_x86-userdebug product)
• NCAR - Android Automotive Project (is used for testing VENDOR properties supported by custom VHAL)
• Polestar2 Emulator

To change car speed, gear, location, etc. use AVD Extended Controls:

How to run app

Start CarApiHelloWorldApp app via ADB ActivityManager:

$ am start -n com.example.carapihelloworld/.MainActivity

Or manually through the app list if it is part of the entire AOSP build (e.g. NCAR - Android Automotive Project)

Logcat output examples

After compiling and running this project, the following logcat messages are expected:

2022-02-14 17:29:18.154 4979-4979/com.example.carapihelloworld D/CarApiHelloWorld: Test CarPropertyManager getters:
2022-02-14 17:29:18.155 4979-4979/com.example.carapihelloworld D/CarApiHelloWorld: GEAR_SELECTION: getIntProperty(289408000, 0)=4
2022-02-14 17:29:18.156 4979-4979/com.example.carapihelloworld D/CarApiHelloWorld: VENDOR_TEST_COUNTER: getIntProperty(557842433, 0)=4
2022-02-14 17:29:18.156 4979-4979/com.example.carapihelloworld D/CarApiHelloWorld: Test CarPropertyManager callbacks:
2022-02-14 17:29:18.282 4979-4979/com.example.carapihelloworld D/CarApiHelloWorld: GEAR_SELECTION: onChangeEvent(4)
2022-02-14 17:29:18.282 4979-4979/com.example.carapihelloworld D/CarApiHelloWorld: PERF_VEHICLE_SPEED: onChangeEvent(0.0)
2022-02-14 17:29:18.282 4979-4979/com.example.carapihelloworld D/CarApiHelloWorld: EV_BATTERY_LEVEL: onChangeEvent(150000.0)
2022-02-14 17:29:18.283 4979-4979/com.example.carapihelloworld D/CarApiHelloWorld: FUEL_DOOR_OPEN: onChangeEvent(false)
2022-02-14 17:29:18.283 4979-4979/com.example.carapihelloworld D/CarApiHelloWorld: VENDOR_TEST_COUNTER: onChangeEvent(4)

Examples of permissions error messages:

2021-11-01 03:16:36.840 26840-26840/com.example.carapihelloworld E/CarApiHelloWorld: FUEL_DOOR_OPEN: setBooleanProperty(), Exception: permission is null

2021-11-02 13:13:55.293 2642-2642/com.example.carapihelloworld E/CarApiHelloWorld: FUEL_DOOR_OPEN: setBooleanProperty(), Exception: requires android.car.permission.CONTROL_CAR_ENERGY_PORTS