[Android]LiveDataのActive/InActiveの挙動

LiveDataの挙動

Home画面にいって（アプリが裏に行く）、アプリを起動してもLiveDataは発火しない。Home画面でアプリが裏にいる時に、データに更新があって再度アプリが起動すると発火する。

EventObserverの挙動

EventObserverの話が以下記事にある。

LiveData with SnackBar, Navigation and other events (the SingleLiveEvent case)

2021 Update: This guidance is deprecated in favor of the official guidelines.

medium.com

コメントのMykola Morgunさんと記事作成者のやり取りで

I’m new to Android and after reading this a few times I don’t really get what’s wrong with “Bad: 1. Using LiveData for events”.
I have written a few simple apps for training where I use this (and right now I specificaally made an app with the 2nd activity being launched from LiveData) and there’s no such scenario where LiveData fires twice. 
Maybe I did not enough testing and there is some specific lifecycle scenario where this emerges?

Navigate using LiveData, press back, rotate phone. It will navigate again.

と記載があり、EventObserverは端末が回転した時に発火させないようにする時に使いそう。