PresenceMaintainer.kt

open class PresenceMaintainer(
 networkingModule: NetworkingModule,
) : Application.ActivityLifecycleCallbacks {
 internal val presenceService =
 networkingModule.createSecureServiceEndpoint(PresenceService::class.java)
 private val foregroundSubject = PublishSubject.create<Boolean>()
 private val polling = presenceService.sendHeartbeat()
 .subscribeOn(Schedulers.io())

private var connected by Delegates.observable(false) { … }

init {
 foregroundSubject
 .debounce(TIMEOUT, TimeUnit.SECONDS)
 .distinctUntilChanged()
 .switchMap {
 if (it && connected) polling.toObservable<Unit>() else Observable.never()
 }
 .subscribe()
 }

override fun onActivityPaused(activity: Activity?) {
 foregroundSubject.onNext(false)
 }

override fun onActivityResumed(activity: Activity?) {
 foregroundSubject.onNext(true)
 }

override fun onActivityStarted(activity: Activity?) = Unit
 override fun onActivityDestroyed(activity: Activity?) = Unit
 override fun onActivitySaveInstanceState(activity: Activity?, outState: Bundle?) = Unit
 override fun onActivityStopped(activity: Activity?) = Unit
 override fun onActivityCreated(activity: Activity?, savedInstanceState: Bundle?) = Unit
}