Using LiveData with Firebase Database on Kotlin

FirebaseLiveData.kt

class FirebaseLiveData(
        private val reference: DatabaseReference
) : LiveData<DataSnapshot>() {

    private var eventListener: ValueEventListener? = null

    override fun onActive() {
        super.onActive()
        logd("onActive $reference")
        eventListener = reference.addValueEventListener(FValueEventListener(
                onDataChange = { data ->
                    value = data
                },
                onError = { error ->
                    loge("FirebaseLiveData error", error.toException())
                }
        ))
    }

    override fun onInactive() {
        super.onInactive()
        logd("onInactive $reference")
        eventListener?.let {
            reference.removeEventListener(it)
        }
    }
}