Implementation Double back key pressed to exit Using Rx

rx_double_back_key_to_exit.kt

data class BackKeyPressedTimePair(val prev: Long, val curr: Long)
private var backSubject = PublishSubject.create<Boolean>()


// onBackPressed()
backSubject.throttleFirst(100, TimeUnit.MILLISECONDS)
        .observeOn(uiScheduler)
        .filter { isAvailable }
        .map {
          // if there is BottomSheet, hide that.
            if (delayTimeSheetHolder?.isShowing == true) {
                delayTimeSheetHolder?.hide()
                true
            } else if (bgmSheetHolder?.isShowing == true) {
                bgmSheetHolder?.hide()
                true
            } else {
                false
            }
        }
        .filter { !it }
        .map { BackKeyPressedTimePair(0, System.currentTimeMillis()) }
        .scan { old, new -> BackKeyPressedTimePair(old.curr, new.curr) } // pairing old and new pressed time
        .map { it.curr - it.prev }
        .doOnNext {
          // Toast message once
            if (it > 1000L) {
                showToast(R.string.double_tap_back_key_to_finish)
            }
        }
        .filter { it < 1000L }
        .take(1)
        .compose { bindUntilViewDestroy(it) }
        .subscribe {
          // if there is ad to show when exit, shows that.
            if (hasAd && !isInterstitialOpened) {
                if (ggInterstitial?.isLoaded == true) {
                    ggInterstitial?.show()
                } else if (fbInterstitial?.isAdLoaded == true) {
                    fbInterstitial?.show()
                } else {
                    finish()
                }
            } else {
              finish()
            }
        }
        .addTo(disposableBag)