TaskObservable.kt

class TaskObservable<T>(private val task: Task<T>) : ObservableOnSubscribe<T> {

  override fun subscribe(emitter: ObservableEmitter<T>) {
    task
      .addOnSuccessListener { t ->
        if (!emitter.isDisposed) {
          emitter.onNext(t)
          emitter.onComplete()
        }
      }
      .addOnFailureListener { e ->
        if (!emitter.isDisposed) {
          emitter.onError(e)
        }
      }
  }
}