onBackPressed with rxjava :: in presenter

onback.kt

private val backButtonSubject: Subject<Long> = BehaviorSubject.createDefault(0L).toSerialized()

private val backButtonSubjectDisposable =
        compositeDisposable.add(backButtonSubject.toFlowable(BackpressureStrategy.BUFFER)
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())  // need compose
                .buffer(2, 1)
                .map { it[0] to it[1] }
                .subscribe({ value ->
                    if (value.second - value.first < 2000) getView()?.finishView()
                    else getView()?.showBackButtonToast()
                },{ getView()?.showErrorToast() })
        )

override fun onBackPressed() = backButtonSubject.onNext(System.currentTimeMillis())