Safety Lock

Safety lock is a feature that allows the UI to disable or change certain functionality depending on whether or not it's safe for the driver to do so. For example, while driving it is commonly considered unsafe for the driver to be typing, and so a frontend that allows text input may disable its input field when safety lock is enabled.

Safety lock can be configured per IVI instance, allowing safety lock to be enabled on the driver display without impacting passenger displays. This allows frontend plugins to remain agnostic as to whether the display is for a driver or passenger and simply use the service information as provided.

Note: Configuring services per IVI instance is still under development and will be delivered in an upcoming release.

Using safety lock

The main interface for safety lock is the SafetyLockService, found in platform_safetylock_api_service_safetylock. It exposes an observable Boolean isSafetyLockEnabled to indicate whether safety lock is currently enabled.

The service has multiple instances to allow enabling safety lock on one display (for the driver) without enabling it on others (such as for the passenger). The service implementation can either determine this internally based on its IviInstanceId or the service may be configured to only be deployed in certain IVI instances. As the final product configures which plugins are available in which IVI instance, the internal logic of a frontend or service plugin cannot make assumptions on whether the SafetyLockService is accessible to them. SafetyLockService should therefore be accessed through createApiOrNull instead of createApi, allowing the plugin to gracefully handle the scenario where the SafetyLockService is not available with a null-check. This can be done as shown in the following Kotlin example:

1val isSafetyLockEnabled: LiveData<Boolean> =
2 SafetyLockService.createApiOrNull(lifecycleOwner, iviServiceProvider)
3 ?.isSafetyLockEnabled
4 ?: ImmutableLiveData(false)

Note that createApiOrNull means that ?.isSafetyLockEnabled may return null. ?: ImmutableLiveData(false) is added here in order to assign a value of type LiveData<Boolean> instead of a nullable LiveData<Boolean>? that has to be checked for null in usage.

In frontends

The most common use-case for safety lock is in frontends which update the contents of fragment layouts depending on whether safety lock is enabled. To facilitate this use-case, FrontendViewModel exposes a LiveData<Boolean> isSafetyLockEnabled that is linked to the service. This allows XML layouts to directly use it in data binding without having to manually set up a service connection.

For example, a frontend that has a ViewModel like:

1class MyViewModel(panel: MyPanel) : FrontendViewModel<MyPanel>(panel) {
2 fun onButtonClicked() {
3 // Do something
4 }
5}

can be used to enable or disable a button depending on the safety lock state in an XML layout as follows:

1<Button
2 android:text="@string/my_button_text"
3 android:onClick="@{viewModel.onButtonClicked()}"
4 android:enabled="@{viewModel.isSafetyLockEnabled}" />

In frontend logic that is outside of a ViewModel's scope, the safety lock state can be accessed directly from the service.

In services

Though not as common as usage in frontends, business logic that lives in services may also want to adjust its output depending on whether safety lock is active. Similarly to frontend logic, services can also access the safety lock state through SafetyLockService.createApiOrNull.

Note however that only services with multiple instances (configured through @IviService(multipleInstances = true)) can access SafetyLockService, as SafetyLockService is itself a service with multiple instances. Global services that have a single instance for all displays cannot take safety lock state into account as they facilitate various displays that can have different safety lock states. If you have a global service that needs this information, it is an indicator that the service should perhaps not be global as it requires instance-specific information and thus should itself be a service with multiple instances.

Specifying safety lock criteria

The exact criteria for enabling safety lock depends on the service implementation. Common criteria include the vehicle's speed based or the gear stick position.

The stock implementation monitors the vehicle's speed through VehicleDrivingStateService and enables safety lock depending on the drivingState. The stock implementation of that service in turn considers the state to be DrivingState.DRIVING when the speed reported by NavKit 2 exceeds 5 kilometers an hour.

To change the stock behaviour, the service plugin safetyLockServiceHost can be replaced with a custom one, implemented as seen fit. The pages Create an IVI Service and Configure the Runtime Deployment of the IVI System describe this in further detail.