Android Automotive CarPropertyManager: Get Vehicle Information

Chapter 1: Introduction to Android CarPropertyManager

Android CarPropertyManager is a key class for managing car-related properties in Android. This class is designed to handle a myriad of modifiable properties and functions in vehicles. In this chapter, we focus on understanding the purpose of Android CarPropertyManager and learning the fundamental concepts.

1. Purpose of CarPropertyManager

The CarPropertyManager provides the capability to get or set specific properties related to cars. For instance, applications can utilize information such as media volume, air conditioner temperature, vehicle speed, and fuel level. Additionally, it is also possible to alter some system settings.

2. Understanding Properties

Car properties are divided into the following three types:

• Static properties: These are fixed properties of cars, and no additional access permissions are required.
• Dynamic properties: These are mutable properties of cars, and access permissions may be needed when reading or writing to the property.
• Real-time dynamic properties: These properties change frequently depending on the car's configuration or driving conditions. They can receive notifications of events in advance and are valid for a certain period of time.

3. Setting up and using CarPropertyManager

The procedure for utilizing Android CarPropertyManager is as follows:

1. Require car features using the uses-feature tag in AndroidManifest.xml to use car features.
2. Initialize the Car object through Activity and obtain an instance of CarPropertyManager from this object.
3. Before reading or setting a property, you can perform operations such as registering or setting a property listener to observe changes in the value of a specific property.
4. Get or change the property value.
5. When the task is finished, clean up all operations and unregister the listener.

You have now understood the basic concepts of Android CarPropertyManager. In the next chapter, we will delve into how to read and write property values through CarPropertyManager.

Chapter 2: Utilizing Android CarPropertyManager to Read and Write Properties

This chapter delves into the diverse methods of reading and writing car property values using Android's CarPropertyManager.

2.1. Acquiring a CarPropertyManager Instance

One can acquire a CarPropertyManager instance via a Car object. The said Car object can be initialized merely by using a Context object.

Car car = Car.createCar(context);
CarPropertyManager carPropertyManager = (CarPropertyManager) car.getCarManager(Car.PROPERTY_SERVICE);

2.2. Reading Properties

To obtain a property value, the property key must first be identified. This key is defined as an integer constant supplied by CarPropertyManager.

int propertyKey = CarPropertyManager.PROPERTY_EXAMPLE;

Following this, the property value can be retrieved using the getProperty() method.

Java

CarPropertyValue<?> carPropertyValue = carPropertyManager.getProperty(propertyKey);

As a variety of value types can be returned, the CarPropertyValue is declared using a wildcard such as <?>. The returned value can then be cast to the necessary type.

int value = (int) carPropertyValue.getValue();

2.3. Writing Properties

To set a property value, the property key must first be identified. Following this, a value object must be created and the property key and new value set.

int propertyKey = CarPropertyManager.PROPERTY_EXAMPLE;
int newValue = 10;
CarPropertyValue<?> newCarPropertyValue = new CarPropertyValue<>(propertyKey, newValue);

The operation to change status must be performed within a try-catch block, and a CarNotConnectedException could potentially occur.

try {
 carPropertyManager.setProperty(newCarPropertyValue);
} catch (CarNotConnectedException e) {
 e.printStackTrace();
}

2.4. Detecting Property Changes Using the Event Service

To receive notifications regarding changes in the value of a specific property, the CarPropertyEventService feature can be used. To do so, a CarPropertyEventListener object must first be created with the property key that one wishes to listen to.

CarPropertyEventListener carPropertyEventListener = new CarPropertyEventListener() {
 @Override
 public void onChangeEvent(CarPropertyValue<?> propertyValue) {
 // Write code to handle value changes here.
 }
 @Override
 public void onErrorEvent(int propertyKey, int zone) {
 // Write code to handle errors here.
 }
};

Changes in the value of the property key can be subscribed to using the created EventListener.

carPropertyManager.registerListener(carPropertyEventListener, propertyKey, CarPropertyManager.SENSOR_RATE_NORMAL);

An event is now triggered whenever the property changes. If required, the observer can be removed by unregistering.

carPropertyManager.unregisterListener(carPropertyEventListener, propertyKey);

We have now covered reading and writing car properties using Android's CarPropertyManager. In the ensuing chapter, we will examine in greater detail how to process real-time property data using CarPropertyManager.

Chapter 3: Processing Real-Time Vehicle Property Data

This chapter delves into processing real-time vehicle property data, which can enhance the user experience of your application and enable immediate access to the information required.

3.1. Preparation for Real-Time Data Processing

Prior to processing real-time vehicle property data, the following preparation steps need to be completed.

• Acquire an instance of Android CarPropertyManager. (Refer to Chapter 2.1)
• Identify the property key and create an event listener. (Refer to Chapter 2.4)

Following the completion of the preparation steps as outlined in the referenced sections, the processing of real-time vehicle property data can commence.

3.2. Vehicle Property Data Processing Strategies

When processing real-time vehicle property data, consider the following strategies for efficient user experience and performance.

• Synchronize property values at an optimized UI update interval to avoid inefficient constant updates.
• Unregister listeners when not needed to minimize resource usage.
• Optimize the real-time representation of data using UI components with low latency.

3.3. Real-Time Vehicle Property Data Processing Example

The following example code demonstrates the implementation of a CarPropertyEventListener that receives and displays vehicle speed in real time.

CarPropertyEventListener carSpeedEventListener = new CarPropertyEventListener() {
 @Override
 public void onChangeEvent(CarPropertyValue<?> propertyValue) {
 if (propertyValue.getPropertyKey() == CarPropertyManager.PROPERTY_SPEED) {
 float speedInMetersPerSecond = (float) propertyValue.getValue();
 float speedInKilometersPerHour = speedInMetersPerSecond * 3600 / 1000;
 updateSpeedDisplay(speedInKilometersPerHour);
 }
 }
 @Override
 public void onErrorEvent(int propertyKey, int zone) {
 // Code to handle errors goes here.
 }
};
carPropertyManager.registerListener(carSpeedEventListener, CarPropertyManager.PROPERTY_SPEED, CarPropertyManager.SENSOR_RATE_NORMAL);

In the above example, the speed data is processed by invoking the updateSpeedDisplay() method whenever the vehicle speed changes and updating the UI.

3.4. Finishing Real-Time Vehicle Property Processing

Upon completion of the real-time vehicle property data processing, the following tasks need to be performed to ensure resource release and cleanup.

• Unregister event listeners related to the property. (Refer to the bottom code example in Chapter 2.4)
• Disconnect the Car object at application termination.

car.disconnect();

With this, we have covered how to process real-time vehicle property data using Android's CarPropertyManager. The guide is intended to help you gain a deep understanding of CarPropertyManager and to use it to develop car-related applications.