I have LazyColumn with swipe-to-delete. When I swipe an item, it is deleted by viewModel. The problem is that if I swipe the item away, the LazyColumn doesn't update the position of other items (as shown in GIF).
Here's my code implementation:
@ExperimentalMaterialApi
@Composable
fun Screen() {
val livedata = viewModel.itemsLiveData.observeAsState()
val stateList = remember { mutableStateListOf<Data>() }
stateList.addAll(livedata.value!!)
SwipableLazyColumn(stateList)
}
@ExperimentalMaterialApi
@Composable
fun SwipableLazyColumn(
stateList: SnapshotStateList<Data>
) {
LazyColumn {
items(items = stateList) { item ->
val dismissState = rememberDismissState()
if (dismissState.isDismissed(EndToStart) || dismissState.isDismissed(StartToEnd)) {
viewModel.swipeToDelete(item)
}
SwipeToDismiss(
state = dismissState,
directions = setOf(StartToEnd, EndToStart),
dismissThresholds = {
FractionalThreshold(0.25f)
},
background = {},
dismissContent = {
MyData(item)
}
)
}
}
}
I use SnapshotStateList
as it's suggested here . Although I don't use swapList
because it clears out all items
ViewModel :
class MyViewModel @Inject internal constructor(
private val itemRepository: ItemRepository
) : BaseViewModel(), LifecycleObserver {
private val itemsList = mutableListOf<MyData>()
private val _itemsLiveData = MutableLiveData<List<MyData>>()
val itemsLiveData: LiveData<List<MyData>> = _itemsLiveData
init {
loadItems()
}
private fun loadItems() {
viewModelScope.launch {
itemRepository.getItems().collect {
when (it) {
is Result.Success -> onItemsLoaded(it.data)
is Result.Error -> {
onItemsLoaded(emptyList())
}
}
}
}
}
private fun onItemsLoaded(itemsList: List<MyData>) {
itemsList.clear()
itemsList.addAll(notifications)
_itemsLiveData.value = if (itemsList.isNotEmpty()) {
itemsList
} else {
null
}
}
fun swipeToDelete(item: MyData) {
if (itemsList.size == 0) return
viewModelScope.launch {
when (
val result =
itemRepository.deletelItem(item)
) {
is Result.Success -> {
onItemDeleted(item)
}
is Result.Error -> {
showSnackBar(
"error"
)
}
}
}
}
private fun onItemDeleted(item: MyData) {
itemsList.remove(item)
_itemsLiveData.value = itemsList
}
}
You need to provide key
for the LazyColumn
's items
.
By default, each item's state is keyed against the position of the item in the list. However, this can cause issues if the data set changes, since items which change position effectively lose any remembered state.
Example
LazyColumn {
items(
items = stateList,
key = { _, listItem ->
listItem.hashCode()
},
) { item ->
// As it is ...
}
}
You should refresh your list inside viemodel(delete item) and return modified list right here
var tempList = itemList
ItemList.clear()
ItemList.addAll(tempList)
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