Saved state

A destination can store state in four places. The table shows whether each place keeps the state after each event.

Stored in	Destination covered by another destination	Configuration change	Process death
remember	lost	lost	lost
rememberSaveable	kept	kept	kept
a ViewModel property	kept	kept	lost
the ViewModel’s SavedStateHandle	kept	kept	kept

Covered destinations

With the default scenes, a destination is removed from the composition when another destination is opened on top of the destination. While a covered destination is on the backstack, Enro keeps the destination’s rememberSaveable state and ViewModel. Enro restores both when the destination is displayed again. State stored with remember is lost.

Use rememberSaveable for UI state that must be restored when the user returns to the destination: text in a field, a scroll position, a selected tab.

The backstack

rememberNavigationContainer saves the container’s backstack with rememberSaveable. After a configuration change or process death, rememberNavigationContainer restores the saved backstack and ignores the backstack argument.

Each NavigationKey on the backstack is written to saved state, so a NavigationKey must be @Serializable.

In a ViewModel

A ViewModel is retained while the ViewModel’s destination is on the backstack, including across configuration changes. A ViewModel is not restored after process death. For state that must be restored after process death, pass a SavedStateHandle to the ViewModel:

class CountersViewModel(
    private val savedStateHandle: SavedStateHandle,
) : ViewModel() {
    // A ViewModel property is lost on process death.
    private val _inMemory = MutableStateFlow(0)
    val inMemory: StateFlow<Int> = _inMemory.asStateFlow()

    // A SavedStateHandle value is restored after process death.
    val saved: StateFlow<Int> = savedStateHandle.getStateFlow("saved", 0)

    fun increment() {
        _inMemory.update { it + 1 }
        savedStateHandle["saved"] = saved.value + 1
    }
}

createSavedStateHandle() creates a SavedStateHandle scoped to the destination:

var remembered by remember { mutableIntStateOf(0) }
var saveable by rememberSaveable { mutableIntStateOf(0) }
// createSavedStateHandle() creates a SavedStateHandle scoped to this destination.
val viewModel = viewModel<CountersViewModel> {
    createEnroViewModel { CountersViewModel(createSavedStateHandle()) }
}

Per platform

• Android: the Activity saves the state, so all three columns of the table apply. To test process death, turn on “Don’t keep activities” in Developer Options, send the app to the background and return to the app.
• Web: state is kept while the page is loaded. After a full page reload, the app has only the URL; see Web.

See also

• Saved State recipe — one counter for each row of the table.
• Saveable Back Stack recipe.
• Navigation Handles → Saved state.