Access scoped viewModel from TopAppBar in jetpack compose - android-jetpack-compose

Question

Folks I am stuck engineering a proper solution to access a viewModel scoped to a nav graph , from a button that exists in the TopAppBar in a compose application
Scaffold{
TopAppBar-> Contains the Save Button
Body->
BioDataGraph() -> Contains 5 screens to gather biodata information , and a viewmodel scoped to the graph
}
}
My BioDataViewModel looks like this
class BioDataViewModel{
fun gatherPersonalInformation()
fun gatherPhotos()
...
fun onSaveEverything()
}
The issue i came across is as i described above , how should i go about access the BioDataViewModel , such that i can invoke onSaveEverything when save is clicked in the TopAppBar.
What I have tried
private val performSave by mutableStateOf(false)
Scaffold(
topBar = {
TopAppBar(currentDestination){
//save is clicked.
performSave = true
}
})
{
NavHost(
navController = navController,
startDestination = homeNavigationRoute,
modifier = Modifier
.padding(padding)
.consumedWindowInsets(padding),
) {
composable(route = bioDataRoute) {
val viewModel = hiltViewModel<BioDataViewModel>()
if (performSave){
viewModel.onSaveEverything()
}
BioDataScreen(
viewModel
)
}
}
}
The problem with the approach above is that how and when should i reset the state of performSave ? . Because if i do not set it to false; on every recomposition onSaveEverything would get called.
What would be the best way to engineer a solution for this ? . I checked to see if a similar situation was tackled in jetpack samples , but i found nothing there .

Answer 1

I'm not sure if I understand you correctly, but you can define the BioDataViewModel in activity level, and you can access it in the TopAppBar like this
class MyActivity: ComponentActivity() {
// BioDataViewModel definition here
private val viewModel: BioDataViewModel by viewModels()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
Scaffold(
topBar = {
TopAppBar(currentDestination) {
//save is clicked.
viewModel.onSaveEverything() // call onSaveEverything here
}
})
{
...
...
}
...
...
Edit:
If you want to have the same instance of ViewModel from activity and NavGraph level, you can consider this, a reference from my other answer.
You can define the ViewModelStoreOwner in the navigation graph level.
NavHost(
navController = navController,
startDestination = homeNavigationRoute,
modifier = Modifier
.padding(padding)
.consumedWindowInsets(padding),
) {
val viewModelStoreOwner = checkNotNull(LocalViewModelStoreOwner.current) {
"LocalViewModelStoreOwner not available"
}
composable(route = bioDataRoute) {
val viewModel = hiltViewModel<BioDataViewModel>(viewModelStoreOwner)
if (performSave){
viewModel.onSaveEverything()
}
BioDataScreen(
viewModel
)
}
}