Implement screen navigation

Apps often present a number of different screens, each possibly using different templates the user can navigate through as they interact with the interface.

The ScreenManager class provides a screen stack you can use to push screens that can be popped automatically when the user selects a Back button on the car screen or uses the hardware Back button available in some cars.

This code shows how to add a back action to a message template as well as an action to push a new screen when selected by the user:

val template = MessageTemplate.Builder("Hello world!")
     .setHeaderAction(Action.BACK)
     .addAction(
         Action.Builder()
             .setTitle("Next screen")
             .setOnClickListener { screenManager.push(NextScreen(carContext)) }
             .build())
     .build()

MessageTemplate template = new MessageTemplate.Builder("Hello world!")
    .setHeaderAction(Action.BACK)
    .addAction(
        new Action.Builder()
            .setTitle("Next screen")
            .setOnClickListener(
                () -> getScreenManager().push(new NextScreen(getCarContext())))
            .build())
    .build();

The Action.BACK object is a standard Action that automatically invokes ScreenManager.pop. This behavior can be overridden by using the OnBackPressedDispatcher instance available from the CarContext.

To promote safe driving, the screen stack can consist of no more than five screens. To learn more, see Template restrictions.