LiveData input and output to the ReactiveStreams spec.
public static LiveData<T> fromPublisher (Publisher<T> publisher)
When the LiveData becomes active, it subscribes to the emissions from the Publisher.
When the LiveData becomes inactive, the subscription is cleared. LiveData holds the last value emitted by the Publisher when the LiveData was active.
Therefore, in the case of a hot RxJava Observable, when a new LiveData
added, it will automatically notify with the last value held in LiveData,
which might not be the last value emitted by the Publisher.
Note that LiveData does NOT handle errors and it expects that errors are treated as states in the data that's held. In case of an error being emitted by the publisher, an error will be propagated to the main thread and the app will crash.
public static Publisher<T> toPublisher (LifecycleOwner lifecycle, LiveData<T> liveData)
By using a good publisher implementation such as RxJava 2.x Flowables, most consumers will
be able to let the library deal with backpressure using operators and not need to worry about
ever manually calling
On subscription to the publisher, the observer will attach to the given
Subscription.request(long) is called on the subscription object, an observer will be
connected to the data stream. Calling request(Long.MAX_VALUE) is equivalent to creating an
unbounded stream with no backpressure. If request with a finite count reaches 0, the observer
will buffer the latest item and emit it to the subscriber when data is again requested. Any
other items emitted during the time there was no backpressure requested will be dropped.