Koin sharedViewModel with SavedStateHandle

Question

I have single activity application and number of fragments. Some of these fragments are using my viewmodel, typically like this:

private val myViewModel: MyViewModel by sharedViewModel()

What if I want to have the model both shared and keep its state with SavedStateHandle? I cannot figure out if this is supported and if so, how it needs to be used (declaring viewmodel as stateViewModel in hosting activity is not working).

Answer 1

Update: as koin 2.1.6 is around, they introduced org.koin.androidx.viewmodel.ext.android.stateSharedViewModel that you can use in your fragments.

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Ok after an hour of digging Koin samples and figuring out a few gotchas:

1. Assuming your view model is something similar to this:

class SavedStateViewModel(val handle: SavedStateHandle, val service: SimpleService) 

2. ...and your DI looks like this:

viewModel { (handle: SavedStateHandle) -> SavedStateViewModel(handle, get()) }

3. Your shared state view model can be consumed in your fragments like this:

val sharedSaved: SavedStateViewModel by sharedViewModel()

4. (important!) You need this declaration in your activity:

lateinit var savedVm: SavedStateViewModel

5. (important) You need to call this right after super.onCreate(savedInstanceState) in your activity:

savedVm  = getStateViewModel() 

It is important not to use lazy version for the above (stateViewModel).