Probably it is a well-known topic, but I didn't find any "universal" solution.
The main problems are two:
fragment is put to backstack, onSavedInstanceState is never calledfragment's views in onCreate?And at this point my question is: since the fragment lifecycle goes through onCreateView every resume, and since we can't instantiate views in onCreate; why do we have to re-create views every time the fragment is shown? There must be a way as in the Activity with onCreate.
We might avoid by adding a class-scoped boolean and check if it has a value, but it means adding an if and this can't be the best solution. Another solution might be this one, but it is also a workaround and it also has some limitations.
Is there a built-in (or a standard) solution that solve this problem?
I'm unclear on the meaning of the title of your question - but I can answer these three points:
When a fragment is put to backstack, onSavedInstanceState is never called
onSavedInstanceState is called when saving state - just adding to the backstack is not causing that to happen - it happens when pausing the fragment if there is some UI showing. Actually a good answer addressing this problem exists here (link)
Why can't you instantiate fragment's views in onCreate?
A fragment is resumed from the onPostResume method of an Activity, only at this point can you safely touch the views of a fragment. (Inside the fragment you can use onViewsCreated)
why do we have to re-create views every time the fragment is shown
This can be avoided by retaining your fragment instances (although there are drawbacks). You can retain by using:
setRetainInstance(true)