Is there callback received based on periodic subscription or only on change in subscribe() interface in android VHAL?
Tags: android, hal, asynccallback, androidbinder
Published: 2023-09-01 15:06:45

Is there callback received based on periodic subscription or only on change in subscribe() interface in Android VHAL?
---------------------------------------------------------------------------------------------------------------------

In the world of Android development, working with Vehicle Hardware Abstraction Layer (VHAL) can be both exciting and challenging. VHAL provides a standardized interface for communicating with vehicle hardware components, allowing developers to create innovative automotive applications. However, when it comes to receiving callbacks in Android VHAL, there is often confusion regarding whether callbacks are received based on periodic subscription or only on changes in the subscribe() interface.

Let's dive into this topic and shed some light on how callbacks work in Android VHAL.

When subscribing to VHAL interfaces, developers can register their interest in specific events or data updates by implementing the appropriate callback methods. These callbacks are essential for receiving real-time information from vehicle sensors, control units, and other hardware components.

Now, the question arises: are these callbacks triggered periodically, providing a stream of data, or are they only triggered when there is a change in the subscribe() interface?

The answer is that it depends on the specific VHAL interface implementation. Some VHAL interfaces provide periodic callbacks, allowing developers to receive a continuous stream of data at a predefined interval. This is particularly useful for applications that require real-time updates, such as speedometers or fuel consumption monitors.

However, not all VHAL interfaces follow the periodic callback approach. In some cases, callbacks are triggered only when there is a change in the subscribe() interface. This means that the callback will be invoked when there is a modification in the subscribed data or event. For example, if you subscribe to the vehicle's engine RPM, the callback will be triggered whenever there is a change in the RPM value.

It's important to note that the behavior of callbacks in Android VHAL is determined by the VHAL implementation provided by the vehicle manufacturer. Therefore, it's crucial for developers to refer to the specific documentation or resources provided by the manufacturer to understand the callback behavior for a particular VHAL interface.

So, to summarize, callbacks in Android VHAL can be received based on periodic subscription or only on changes in the subscribe() interface. It varies depending on the VHAL interface implementation. Some interfaces provide periodic callbacks, while others trigger callbacks only when there is a change in the subscribed data or event.

Now that you have a better understanding of how callbacks work in Android VHAL, go ahead and create amazing automotive applications with confidence!

### References:

*   Android Open Source Project: [https://source.android.com/devices/automotive](https://source.android.com/devices/automotive)
*   Android VHAL Documentation: [https://developer.android.com/reference/android/hardware/automotive/vehicle/package-summary](https://developer.android.com/reference/android/hardware/automotive/vehicle/package-summary)