未为列表类型激发StateFlow集合

Question

@HiltViewModel
class HistoryViewModel @Inject constructor(private val firebaseRepository: FirebaseRepository) :
ViewModel() {
private val translateList: MutableList<Translate> = mutableListOf()
private val _translateListState: MutableStateFlow<List<Translate>> =
MutableStateFlow(translateList)
val translateListState = _translateListState.asStateFlow()
init {
listenToSnapshotData()
}
private suspend fun addItemToList(translate: Translate) {
Log.d("customTag", "item added adapter $translate")
translateList.add(translate)
_translateListState.emit(translateList)
}
private suspend fun removeItemFromList(translate: Translate) {
Log.d("customTag", "item removed adapter $translate")
val indexOfItem = translateList.indexOfFirst {
it.id == translate.id
}
if (indexOfItem != -1) {
translateList.removeAt(indexOfItem)
_translateListState.emit(translateList)
}
}
private suspend fun updateItemFromList(translate: Translate) {
Log.d("customTag", "item modified adapter $translate")
val indexOfItem = translateList.indexOfFirst {
it.id == translate.id
}
if (indexOfItem != -1) {
translateList[indexOfItem] = translate
_translateListState.emit(translateList)
}
}
private fun listenToSnapshotData() {
viewModelScope.launch {
firebaseRepository.translateListSnapshotListener().collect { querySnapshot ->
querySnapshot?.let {
for (document in it.documentChanges) {
val translateData = document.document.toObject(Translate::class.java)
when (document.type) {
DocumentChange.Type.ADDED -> {
addItemToList(translate = translateData)
}
DocumentChange.Type.MODIFIED
-> {
updateItemFromList(translate = translateData)
}
DocumentChange.Type.REMOVED
-> {
removeItemFromList(translate = translateData)
}
}
}
}
}
}
}
}

这里数据正确地出现在listenToSnapshotData函数中的querySnapshot中。并发布它正确地调用相应的函数来更新列表
但在这条线之后，_translateListState.emit(translateList)流没有进入相应的collectLatest

private fun observeSnapShotResponse() {
lifecycleScope.launch {
repeatOnLifecycle(Lifecycle.State.STARTED) {
historyViewModel.translateListState.collectLatest {
Log.d("customTag", "calling submitList from fragment")
translateListAdapter.submitList(it)
}
}
}
}

从片段调用submitList在开始时被调用一次，但作为&当在列表视图模型中修改数据时，回调不会到达collectLatest

Answer 1

这来自StateFlow文档：

状态流中的值使用Any.equals比较进行合并，方法与distinctUntilChanged运算符类似。它用于合并MutableStateFlow中对值的传入更新，并在新值等于以前发出的值时抑制向收集器发出值。

您一直在尝试发出List的同一个实例，但由于文档中所写的内容，该实例无效。每次都必须创建列表的新实例。