ActivityProvider.kt

class ActivityProvider : Application.ActivityLifecycleCallbacks {

    private var _currentActivity = WeakReference<ComponentActivity>(null)
    val currentActivity
        get() = _currentActivity.get()

    fun init(application: Application) = application.registerActivityLifecycleCallbacks(this)

    override fun onActivityCreated(activity: Activity, bundle: Bundle?) {}

    override fun onActivityStarted(activity: Activity) {
        (activity as? ComponentActivity)?.let {
            _currentActivity = WeakReference(it)
        }
    }

    override fun onActivityResumed(activity: Activity) {
        (activity as? ComponentActivity)?.let {
            _currentActivity = WeakReference(it)
        }
    }

...
}