I started diving into AOSP development recently and I am following some code labs originally written in Java on how to customize the SystemUI (for Automotive AOSP).

I have checked that parts of CarSystemUI are now using Kotlin, and I wanted to redo this code lab.

I followed the tutorial and added the codelab_layout.xml. I then updated the sysui_overlay_window.xml and added this ViewStub:

<ViewStub android:id="@+id/codelab_stub"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout="@layout/codelab_layout"/>

Which declares the codelab_stub id.

The puzzle is that in the next step I am supposed to add a view controller. In Java the code lab asks to add:

@SysUISingleton
public class CodeLabViewControllerJava extends OverlayViewController {

    @Inject
    public CodeLabViewControllerJava(
            OverlayViewGlobalStateController overlayViewGlobalStateController) {
        super(R.id.codelab_stub, overlayViewGlobalStateController);
    }
}

which compiles just fine. However, if I add a view controller in Kotlin like:

@SysUISingleton
class CodeLabViewControllerKotlin @Inject constructor(
    overlayViewGlobalStateController: OverlayViewGlobalStateController
) : OverlayViewController(R.id.codelab_stub, overlayViewGlobalStateController)

I get the following compilation error:

CodeLabViewControllerKotlin.kt:12:32: error: unresolved reference: codelab_stub
) : OverlayViewController(R.id.codelab_stub, overlayViewGlobalStateController) {
                               ^

which is baffling to me, since the Java code compiles without any problem.

Any idea why this is happening?

PS: If I replace R.id.codelab_stub with a hardcoded Int, the Kotlin code compiles fine.