Android collectAsStateWithLifecycle()不收集内部可组合

Question

我正在使用composeLazyColumn与viewModel更新列表项，通过在我的viewModel:

data class ContactsListUiState(
val contacts: MutableList<Contact>
)
@HiltViewModel
class ContactsViewModel @Inject constructor(savedStateHandle: SavedStateHandle) : ViewModel() {
private val _contactsListUiState = MutableStateFlow(ContactsListUiState(mutableListOf()))
val contactsListUiState: StateFlow<ContactsListUiState> = _contactsListUiState.asStateFlow()
private fun updateContactsList(newContacts: MutableList<Contact>) {
_contactsListUiState.update{ currentState ->
currentState.copy(
contacts = newContacts
)
}
}

使我的updateContactsList()函数更新stateFlow，我应该在MainActivity内的可组合函数中收集collectAsStateWithLifecycle()的联系人列表

@OptIn(ExperimentalLifecycleComposeApi::class, ExperimentalFoundationApi::class)
@Composable
fun ContactsListScreen(
navController: NavController,
modifier: Modifier = Modifier
) {
Log.d("ViewModel", "ContactsListScreen recomposed")
val uiState by contactsViewModel.contactsListUiState.collectAsStateWithLifecycle()
Box(modifier = modifier) {
val listState = rememberLazyListState()
val scope = rememberCoroutineScope()
Column {
TextField(
value = searchText,
singleLine = true,
onValueChange = {
searchText = it
Log.d("MainActivity", "calling filter with $it")
contactsViewModel.filterContactsByString(it)
},
leadingIcon = if (searchText.isNotBlank()) searchLeadingIcon else null,
trailingIcon = if (searchText.isBlank()) searchTrailingIcon else null,
modifier = Modifier
.fillMaxWidth()
.background(Color.White)
)
LazyColumn(
Modifier.fillMaxWidth(),
state = listState,
contentPadding = PaddingValues(bottom = 80.dp)
) {                      
items(uiState.contacts) { contact ->
ContactListItem(
navController,
contact = contact,
modifier = Modifier.fillMaxWidth()
)
Divider(thickness = 0.5.dp, color = colorResource(id = R.color.blue))
}
}
...

其中contactsListViewModel声明在我使用hill注入的活动的顶部:

@AndroidEntryPoint
class MainActivity : ComponentActivity(), LoaderManager.LoaderCallbacks<Cursor> {
private val contactsViewModel: ContactsViewModel by viewModels()

出于某种原因，uiState.contacts在可组合函数中是空的，但当我在viewModel函数中记录它时，它确实包含了项目，因此我的列表保持空。

有什么地方出了问题吗?

感谢

Answer 1

请使用SnapshotStatelist/(mutableStateListOf())代替普通列表(mutableList)。

private val _contactsListUiState = MutableStateFlow(ContactsListUiState(mutableStateListOf()))

也请查看这篇文章这篇和这篇