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After looking more into this issue, ViewModels are persisted using retained fragments. After adding retained fragments to the sample app, we can observe that retained fragments are not able to survive landscape lock and unlock scenario either.

Hey, currently I can't reproduce your issue.
Link you provided doesn't work, in my simple test project I don't observe described issue.
Could you please say reupload your project somewhere else?
Could you please say what kind of lockscreen, do you use? (it may effect issue)
Could you reproduce this behavior on other devices?

Hey,

Sorry about the repo link, here is the public one: https://github.com/karmazindmitriy/viewmodelscoping, git@github.com:karmazindmitriy/viewmodelscoping.git

Tested on:
1. Device: NEXUS 5X, API level: 24, lock method: PIN / PATTERN / SWIPE / PASSWORD. Can reproduce by unlocking with any of the unlocking methods. Can also reproduce by unlocking with fingerprint.

2. Device: NEXUS 5X, API level: 27, lock method: PIN / PATTERN / PASSWORD . Can reproduce only when unlocking the device with a fingerprint. Unlocking with PIN / PATTERN / PASSWORD works fine.

3. Device: Pixel, API level: 27, lock method: PIN (haven't tested other) + fingerprint. Can reproduce only when unlocking the device with a fingerprint. Unlocking with PIN / PATTERN / PASSWORD works fine.

Hope this is helpful, please let me know if you need any other info.

Thanks, yep, I was able to reproduce it.

Oh, another instance when platform doesn't call onSaveInstanceState, but calls onStop and onRetainNonConfiguration, so fragments are confused, we are going to fix fragments so they work around this behavior.

Are you referring to the first `onStop` that happens right after unlock (line 12 in screenshot)?

yep

Hello, I Have notice the same issue when using ViewModel, here is the scenario:

1) open ActivityA
-gets ViewModel with reference: TestViewModel@e71fab8
2) rotate device
-gets ViewModel with reference: TestViewModel@e71fab8
3) open ActivityB
4) rotate device
5) press back (finish Activity B)
6) Activity A comes back from stack
-gets ViewModel with reference: TestViewModel@260072e

I have tested with two kinds of ViewModel, with factory and default creation method:
ViewModelProviders.of(this).get(TestViewModel::class.java)
ViewModelProviders.of(this, factory).get(DashboardViewModel::class.java)

Both Activities extends AppCompatActivity class.

I have made some research and find case when this issue do not happend:

1) open ActivityA (vertical)
-gets ViewModel with reference: TestViewModel@e71fab8
2) rotate device (horizontal)
-gets ViewModel with reference: TestViewModel@e71fab8
3) open ActivityB (horizontal)
4) rotate device (vertical)
5) rotate device (horizontal)
6) press back (finish Activity B)
7) Activity A comes back from stack (horizontal)
-gets ViewModel with reference: TestViewModel@e71fab8


So when I rotate device twice on Activity B and press back the Activity A do not recreate ViewModel, mayeby it is becouse it has the same orientation as befor putting it in activities stack.

This behavior is due to FragmentActivity.onDestroy() calling into mViewModelStore.clear() if mRetaining is false. This is the case when the device is rotated and the affected activity is in the background (and probably in other conditions outlined above as well). It is not the case if the configuration changes when the activity is in the front.

Since the view model store has ben cleared, a new view model will be created for the affected activity after a configuration change in the background.

The behavior can be observed easily using a break point in ViewModelStore.clear()