LaunchedEffect not triggering when adding a new profile in Jetpack Compose

Question

I'm working on a Jetpack Compose app where users can manage login profiles. The profiles are stored in a Room database, and the UI shows the profiles in a dropdown menu. The LaunchedEffect block in my LoginScreen is supposed to react to changes in the profile list (profiles), which is exposed as a StateFlow from the LoginViewModel.

When I edit or delete a profile, the LaunchedEffect is triggered, and the logs confirm that the updated profile list is fetched. However, when I add a new profile, the LaunchedEffect does not trigger.

view model code:

private val _profiles = MutableStateFlow<List<LoginProfile>>(emptyList())
val profiles: StateFlow<List<LoginProfile>> = _profiles

init {
    fetchProfiles()
}

fun fetchProfiles() {
    viewModelScope.launch {
        val currentProfiles = database.loginProfileDao().getAllProfiles()
        _profiles.value = currentProfiles
        Log.d("Profile_Test", "Profiles fetched from DB: $_profiles")
    }
}

fun saveProfileToDatabase(profile: LoginProfile) {
    viewModelScope.launch {
        database.loginProfileDao().insertProfile(profile)
        fetchProfiles()
    }
}

UI Code:

@Composable
fun ProfileDropdown(loginViewModel: LoginViewModel) {
    var expanded by remember { mutableStateOf(false) }
    var selectedItem by remember { mutableStateOf<LoginProfile?>(null) }

    val profiles = loginViewModel.profiles.collectAsState().value

    LaunchedEffect(profiles) {
        Log.d("Profile_Test", "Launched Effect: $profiles")
        if (profiles.isNotEmpty() && selectedItem != profiles.last()) {
            selectedItem = profiles.last()
            loginViewModel.selectedProfile.value = profiles.last()
        } else if (profiles.isEmpty()) {
            selectedItem = null
            loginViewModel.selectedProfile.value = null
        }
    }

    ExposedDropdownMenuBox(
        expanded = expanded,
        onExpandedChange = { expanded = !expanded }
    ) {
        OutlinedTextField(
            value = selectedItem?.name ?: "Select Profile",
            onValueChange = {},
            readOnly = true,
            trailingIcon = {
                ExposedDropdownMenuDefaults.TrailingIcon(expanded = expanded)
            }
        )
        DropdownMenu(
            expanded = expanded,
            onDismissRequest = { expanded = false }
        ) {
            profiles.forEach { profile ->
                DropdownMenuItem(
                    text = { Text(profile.name) },
                    onClick = {
                        selectedItem = profile
                        loginViewModel.selectedProfile.value = profile
                        expanded = false
                    }
                )
            }
        }
    }
}

Why is LaunchedEffect not triggering when a new profile is added, even though _profiles is updated? Is there something I'm missing in how StateFlow or LaunchedEffect works in Compose?

Any help or guidance would be greatly appreciated! Thanks!

tyg · Accepted Answer · 2024-11-27 12:46:15Z

2

You should let the Room database return the profiles in a Flow:

@Dao
interface LoginProfileDao {
    @Query(...)
    fun getAllProfiles(): Flow<List<LoginProfile>>
    
    // ...
}

Then you can simplify the view model accordingly: You do not need _profiles, fetchProfiles and the init block anymore. Just replace profiles with this:

val profiles: StateFlow<List<LoginProfile>> = database.loginProfileDao().getAllProfiles()
    .stateIn(
        scope = viewModelScope,
        started = SharingStarted.WhileSubscribed(5_000),
        initialValue = emptyList(),
    )

It takes the Room flow and converts it to a StateFlow. You don't need to call fetchProfiles() anymore because the flow is automatically updated when anything changes in the database.

Your composable can stay the same, although it looks suspicious why you use a LaunchedEffect there, that doesn't seem to be necessary and should be removed.

edited Nov 27, 2024 at 12:46

answered Nov 27, 2024 at 12:17

tyg

20.7k5 gold badges46 silver badges59 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

user28512479 Nov 27, 2024 at 12:43

I changed the room database to return a Flow like you suggested, and it works perfectly now. Thank you for your suggestion.

Collectives™ on Stack Overflow

LaunchedEffect not triggering when adding a new profile in Jetpack Compose

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related