I feel like I'm going crazy, but I can't find docs on how Compose + Hilt + AAC ViewModels can work t...

# compose

[Colton Idle]

I feel like I'm going crazy, but I can't find docs on how Compose + Hilt + AAC ViewModels can work together to pass arguments into a view model? I'm working on a typical list -> detail app, and I can't figure out how to pass an id from my NavHost to the new DetailScreen.

[Florian]

Did you follow this?
https://developer.android.com/jetpack/compose/navigation#nav-with-args

[Florian]

You can retrieve the arguments directly inside the ViewModel from the SavedStateHandle

[Colton Idle]

Yeah, that's what I was doing with fragments, but how do I pass the arg to the VM? The example only shows how to pass the arg to the composable

[Scott Kruse]

Dagger has assisted injection

[Colton Idle]

@Florian do you have any link to "retrieve the arguments directly inside the ViewModel from the SavedStateHandle"? I don't see that anywhere in the link.

[Colton Idle]

@Scott Kruse I'm using hilt and I know hilt provides fragment args via savedStateHandle without using assistedInjection, so that's why I'm asking if there's something like that for compose.

[Colton Idle]

Alright, I got it in case anyone else is wondering. It does end up working with SavedStateHandle (even though the first time I tried it I swear it didn't work). /shrug

My destination

composable("detail/{id}") { MyDetailScreen() }

Composable

@Composable
fun MyDetailScreen(
    vm: MyDetailViewModel = hiltViewModel(),
) {

ViewModel

@HiltViewModel
class MyDetailViewModel @Inject constructor(
    savedStateHandle: SavedStateHandle
) : ViewModel() {
    savedStateHandle.get<String>("id").orEmpty()

[Oleksandr Balan]

Does the same trick work with Koin?

[Florian]

@Colton Idle yes you just have to use the same id. I don't know why it's so badly documented.

[Florian]

you can also retrieve it as livedata

[Colton Idle]

I feel like it's documented well with fragments, but I was looking for this in compose and it seemed lacking.

[Colton Idle]

If anyone wants to add a star https://issuetracker.google.com/issues/196718064

[Dylan]

I had an issue related to SavedStateHandle too. Turns out after digging a lot into it, Ian Lake does mention that in a video from the Google I/O and also gives an example:

https://youtu.be/0z_dwBGQQWQ?t=987▾

One of the Jetpack Compose samples is also using SavedStateHandle .

https://github.com/android/compose-samples/blob/22eea87c898c8cc76e0c1042274e0962f0[…]java/androidx/compose/samples/crane/details/DetailsViewModel.kt

I really had a hard time figuring that out.

I should mention that I'm now trying to save some data to the SavedStateHandle , but it looks like the SavedStateHandle is not restored once my ViewModel is used again even though I'm using hiltViewModel(backStackEntry) in my nav graph. So I still haven't figured that part yet and I have to say documentation would help a lot.

[Florian]

I think the backstack entry and the viewmodel have different SavedStateHandles/SavedInstanceStates

[Dylan]

This clearly shows there's an issue with the documentation unfortunately.

[Florian]

I tried putting a value into the backstack entry of a destination and it didn't appear in that destination's ViewModel

[Florian]

but nav arguments do