ViewPager中当前显示的片段的保存状态

Question

I'm currently working with a TabLayout that makes use of a ViewPager to display three different instances of a Fragment. These are the 'master' fragments in my master-detail flow.

When the user rotates the screen, the application will display two fragments, the master and detail fragment. What i've been trying to achieve is to display the same master fragment when rotating from portrait to landscape mode. So if i'm currently looking at the second instance of 'MyFragment' that lives in the second tab, I want to have that same instance in my master fragment on screen rotation.

I've been looking at different solutions surrounding the Fragment lifecycle but none of them work with my specific scenario. Any advice for this problem would be greatly appreciated!

If the problem isn't clear enough and code is needed, i'll edit this post with the neccessary code.

Answer 1

Device re-orientation is a destructive process, as in it destroys the Activity currently shown on screen, and since their lifecycles are tied, any fragments attached to that Activity as well. To restore the UI state, then what I would do is persist that information as flags/fields in a ViewModel instance. So when the device re-orients and the Activity/Fragments are recreated, you can retrieve the VideModel and check it's fields to know which fragment should be shown initially.