A Guide to Develop Vehicle-Connected Apps on AOSP Android Automotive OS

Chapter 1: Introduction to Android Automotive OS

Android Automotive OS is a car-specific operating system developed by Google, based on the AOSP (Android Open Source Project). This operating system provides features optimized for integrating with vehicle components, which are different from the traditional smartphone-based Android OS.

Android Automotive OS comes with various vehicle APIs that provide information such as vehicle cameras, vehicle data, driving data, GPS location, and local media. This enables developers to easily implement vehicle-specific features such as collision warnings and lane departure warnings.

To simplify the integration between vehicle attributes and apps, Android Automotive OS supports Android Car API and VHAL (Vehicle Hardware Abstraction Layer). These two technologies play a crucial role in simplifying the development process of apps that can access and control vehicle attributes, allowing for application development based on vehicle information.

In the next chapter, we will explain the concepts of Android Car API and VHAL, and how to access vehicle attributes using these technologies.

Chapter 2: Understanding the Concepts of Android Car API and VHAL

To obtain vehicle attributes necessary for automotive application development, Android Automotive OS offers two core technologies: Android Car API and VHAL. In this chapter, we will take an in-depth look at these two technologies.

Android Car API

Android Car API is an interface developed by Google that provides a way to bring vehicle information and functions into an application. Through this, developers can control various vehicle-related information and features such as vehicle speed, fuel consumption, door locking and unlocking, and more. The Android Car API consists of the following main services:

• CarPropertyManager: Retrieves or sets the values of vehicle properties, such as headlight status and outside temperature.
• CarInfoManager: Provides unique information about the vehicle, such as the vehicle manufacturer and model name.
• CarUxRestrictionsManager: A service that manages regulations for UX elements that may be restricted or unavailable during driving, such as smartphone messaging capabilities.

VHAL (Vehicle Hardware Abstraction Layer)

VHAL is an interface that abstracts the communication between vehicle hardware and software, enabling it to provide the same API for various vehicle models. As a result, when developing applications that access vehicle attributes using VHAL, it is possible to write consistent code regardless of vehicle manufacturers and models.

VHAL is a type of HAL (Hardware Abstraction Layer) that provides a familiar programming interface for vehicle networks and electronic control units (ECU) in different vehicles. This allows developers to focus on application development while being isolated from the complexities of the operating system and hardware.

Now that we understand the concepts of Android Car API and VHAL, we will take a look at the actual application development process that connects to vehicle attributes in the next chapter.

Chapter 3: Application Development Process Integrating Vehicle Attributes

In this chapter, we will examine the step-by-step process of developing an application using vehicle attributes in Android Automotive OS.

Step 1: Enable Android Car API Service Usage

To use the Android Car API in your application, add the following permission to the AndroidManifest.xml file:

<uses-permission android:name="com.google.android.permission.CAR"/>

Step 2: Select the Car API Service to Use for Vehicle Attributes

Determine the Car API service that suits the vehicle attribute you want to develop. As previously described, select an appropriate service based on the purpose and functionality provided by each service.

Step 3: Connect to the Vehicle Service

To connect to the Car API service, obtain the Car object using the existing getSystemService() method:

private Car mCar;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    mCar = Car.createCar(this);
}

Step 4: Create a Vehicle Service Manager Object

Create a manager object for the chosen vehicle service as follows:

private CarPropertyManager mCarPropertyManager;

@Override
public void onCarConnected(Car car) {
    mCarPropertyManager = (CarPropertyManager) car.getCarManager(Car.PROPERTY_SERVICE);
}

Step 5: Read and Control Vehicle Attributes

Read or control the values of vehicle attributes through the manager object. For example, to obtain the outside temperature, you can write the following:

int propertyId = VehiclePropertyIds.ENV_OUTSIDE_TEMPERATURE;
float outsideTemperature = mCarPropertyManager.getFloatProperty(propertyId, 0);

By following this approach, you can access various vehicle attributes and effectively utilize vehicle-related information and features required for application functionality. This allows developers to implement vehicle-application integration.

In the final chapter, we will examine a practical example of vehicle attribute connection app development.

Chapter 4: Developing a Vehicle Attribute Connection App with a Practical Example

In this chapter, we will learn how to develop an application connected to vehicle attributes through a practical example. We will create a simple application that reads the outside temperature of a vehicle.

Application Setup and Initialization

Add the following permission to the AndroidManifest.xml file:

<uses-permission android:name="com.google.android.permission.CAR"/>

In the MainActivity.java file, create a Car object and write code to get the CarPropertyManager object each time the vehicle is connected:

public class MainActivity extends AppCompatActivity {

    private Car mCar;
    private CarPropertyManager mCarPropertyManager;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        mCar = Car.createCar(this, mCarServiceConnection);
    }

    private CarServiceConnection mCarServiceConnection = new CarServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            mCarPropertyManager = (CarPropertyManager) mCar.getCarManager(Car.PROPERTY_SERVICE);
            readOutsideTemperature();
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            mCarPropertyManager = null;
        }
    };
}

Reading the Outside Temperature Value

Create the readOutsideTemperature() method to obtain the outside temperature value of the vehicle and display it in a TextView:

private void readOutsideTemperature() {
    int propertyId = VehiclePropertyIds.ENV_OUTSIDE_TEMPERATURE;
    float outsideTemperature = mCarPropertyManager.getFloatProperty(propertyId, 0);
    TextView temperatureTextView = findViewById(R.id.temperatureTextView);
    temperatureTextView.setText(getString(R.string.outside_temperature, outsideTemperature));
}

This allows you to create a simple application that reads the outside temperature when connected to a vehicle and displays it in a TextView.

Note that this application should only be executed on vehicles running Android Automotive OS. Although there are ways to serve or test using a simulator, it is best to verify the operation and accuracy with a real vehicle.

Through this simple example using vehicle attributes, we have explored how to develop applications connected to vehicles using the Android Car API and VHAL. You should now be able to develop a variety of applications that provide multiple vehicle-related features using the concepts we have learned.