First of all, I have looked at similar questions (for example, this one: Android RecyclerView ItemTouchHelper revert swipe and restore view holder). This already helped a great deal, until I - more or less, accidentally - noticed my current (and hopefully, final) issue with this screen of mine.
Let's start with the setup:
I have a fragment with a RecyclerView filled with some CardView items (it's a little fancier, but that's what is important right now). I also created an ItemTouchHelper with the implementation of SimpleCallback (nothing in onMove()) to make swiping the items (right) possible. For the record: I am using API 27 right now.
So far, so good.
What I want to achieve:
I want to be able to swipe the items to be notified through the onSwiped() method of my SimpleCallback implementation. Also, I do NOT want the items to disappear, be removed, or otherwise taken out of my list of items in the RecyclerView. I just want to swipe them and have them return to their original position afterward (and yes, I know that it is sort of assumed that swiped items get removed). I am using the notifyItemChanged() method of my adapter in the onSwiped() method (also tried using notifyDataSetChanged()).
The problem:
Funnily enough, that works (mostly thanks to the aforementioned question) - until I hit that "app switch" button (don't know if there's actually one official name for it) and send the app to the background. Once I put it in the foreground again and start swiping, the items will not (visually) return. They are still on the list, and if I scroll or click the "app switch" button again, they will be displayed properly again (but won't return on swiping). Same if I navigate back one screen and come back to the list.
That makes me think something happens when I send the app to the background and recover it. Something different than navigating to that screen (in which case everything works as intended) - which I thought would more or less produce the same results. Any ideas what I might be overlooking here?
After some testing, I finally found the source of the issue:
I had both the RecyclerView and its Adapter initialised through onStart() of the Fragment and not onViewCreated(). After changing that, I got the proper results I wanted.
Lesson learned: Set your RecyclerView's Adapter as early as possible, unless you want to deal with sometimes strange issues.