Rotation will cause stale fragments in ChildFragmentManager

[zjn0505]

Open app, rotate several times.
Fragments added in ChildFragmentManager will be 3 * rotation.
Could be leak, also too large savedInstance issue.

[zjn0505]

https://stackoverflow.com/a/40245070/5292852

[zjn0505]

Maybe check an example, see how fm behave.

[zjn0505]

Checked ViewPager2 1.0.0, the scroll is not natural, and buggy on What if nested scroll.