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If your project does not have a deep dependency on the paging3 library, I recommend implementing a simple paging library yourself to avoid all the weird features of paging3. The paging library needs the view layer and the model layer to work together. It doesn't make sense to encapsulate these together.
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| !simple paged list for jetpack compose |
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| // Model layer: remotePagingList() | |
| package com.fishhawk.lisu.data.network.base | |
| import kotlinx.coroutines.Dispatchers | |
| import kotlinx.coroutines.channels.Channel | |
| import kotlinx.coroutines.channels.awaitClose | |
| import kotlinx.coroutines.flow.Flow | |
| import kotlinx.coroutines.flow.callbackFlow | |
| import kotlinx.coroutines.flow.flowOn | |
| import kotlinx.coroutines.flow.receiveAsFlow | |
| import kotlinx.coroutines.launch | |
| sealed interface RemoteListAction<out T> { | |
| data class Mutate<T>(val transformer: (MutableList<T>) -> MutableList<T>) : RemoteListAction<T> | |
| object Reload : RemoteListAction<Nothing> | |
| object RequestNextPage : RemoteListAction<Nothing> | |
| } | |
| typealias RemoteListActionChannel<T> = Channel<RemoteListAction<T>> | |
| suspend fun <T> RemoteListActionChannel<T>.mutate(transformer: (MutableList<T>) -> MutableList<T>) { | |
| send(RemoteListAction.Mutate(transformer)) | |
| } | |
| suspend fun <T> RemoteListActionChannel<T>.reload() { | |
| send(RemoteListAction.Reload) | |
| } | |
| suspend fun <T> RemoteListActionChannel<T>.requestNextPage() { | |
| send(RemoteListAction.RequestNextPage) | |
| } | |
| class RemoteList<T>( | |
| private val actionChannel: RemoteListActionChannel<T>, | |
| val value: Result<PagedList<T>>?, | |
| ) { | |
| suspend fun mutate(transformer: (MutableList<T>) -> MutableList<T>) = | |
| actionChannel.mutate(transformer) | |
| suspend fun reload() = actionChannel.reload() | |
| suspend fun requestNextPage() = actionChannel.requestNextPage() | |
| } | |
| data class PagedList<T>( | |
| val list: List<T>, | |
| val appendState: Result<Unit>?, | |
| ) | |
| data class Page<Key : Any, T>( | |
| val data: List<T>, | |
| val nextKey: Key?, | |
| ) | |
| fun <Key : Any, T> remotePagingList( | |
| startKey: Key, | |
| loader: suspend (Key) -> Result<Page<Key, T>>, | |
| onStart: ((actionChannel: RemoteListActionChannel<T>) -> Unit)? = null, | |
| onClose: ((actionChannel: RemoteListActionChannel<T>) -> Unit)? = null, | |
| ): Flow<RemoteList<T>> = callbackFlow { | |
| val dispatcher = Dispatchers.IO.limitedParallelism(1) | |
| val actionChannel = Channel<RemoteListAction<T>>() | |
| var listState: Result<Unit>? = null | |
| var appendState: Result<Unit>? = null | |
| var value: MutableList<T> = mutableListOf() | |
| var nextKey: Key? = startKey | |
| onStart?.invoke(actionChannel) | |
| suspend fun mySend() { | |
| send( | |
| RemoteList( | |
| actionChannel = actionChannel, | |
| value = listState?.map { | |
| PagedList( | |
| appendState = appendState, | |
| list = value, | |
| ) | |
| }, | |
| ) | |
| ) | |
| } | |
| fun requestNextPage() = launch(dispatcher) { | |
| nextKey?.let { key -> | |
| appendState = null | |
| mySend() | |
| loader(key) | |
| .onSuccess { | |
| value.addAll(it.data) | |
| nextKey = it.nextKey | |
| listState = Result.success(Unit) | |
| appendState = Result.success(Unit) | |
| mySend() | |
| } | |
| .onFailure { | |
| if (listState?.isSuccess != true) | |
| listState = Result.failure(it) | |
| appendState = Result.failure(it) | |
| mySend() | |
| } | |
| } | |
| } | |
| var job = requestNextPage() | |
| launch(dispatcher) { | |
| actionChannel.receiveAsFlow().flowOn(dispatcher).collect { action -> | |
| when (action) { | |
| is RemoteListAction.Mutate -> { | |
| value = action.transformer(value) | |
| mySend() | |
| } | |
| is RemoteListAction.Reload -> { | |
| job.cancel() | |
| listState = null | |
| appendState = null | |
| value.clear() | |
| nextKey = startKey | |
| mySend() | |
| job = requestNextPage() | |
| } | |
| is RemoteListAction.RequestNextPage -> { | |
| if (!job.isActive) job = requestNextPage() | |
| } | |
| } | |
| } | |
| } | |
| launch(dispatcher) { | |
| Connectivity.instance?.interfaceName?.collect { | |
| if (job.isActive) { | |
| job.cancel() | |
| job = requestNextPage() | |
| } | |
| } | |
| } | |
| awaitClose { | |
| onClose?.invoke(actionChannel) | |
| } | |
| } |
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| // An example about how to use remotePagingList in repository. | |
| private val daoFlow: StateFlow<Result<NetworkDao>?> // NetworkDao describe interfaces provided by server | |
| suspend fun search( | |
| providerId: String, | |
| keywords: String, | |
| ) = daoFlow.filterNotNull().flatMapLatest { | |
| remotePagingList( | |
| startKey = 0, | |
| loader = { page -> | |
| it.mapCatching { dao -> dao.search(providerId, page, keywords) } | |
| .map { Page(it, if (it.isEmpty()) null else page + 1) } | |
| }, | |
| onStart = { providerMangaListActionChannels.add(it) }, | |
| onClose = { providerMangaListActionChannels.remove(it) }, | |
| ) | |
| } |
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| // An example about how to use remotePagingList in view model. | |
| private val _keywords = MutableStateFlow("") | |
| val keywords = _keywords.asStateFlow() | |
| private val _mangas = | |
| keywords | |
| .flatMapLatest { repository.search(it) } | |
| .stateIn(viewModelScope, SharingStarted.Eagerly, null) | |
| val mangas = | |
| _mangas | |
| .filterNotNull() | |
| .map { it.value } | |
| .stateIn(viewModelScope, SharingStarted.Eagerly, null) | |
| fun reload() { | |
| viewModelScope.launch { | |
| _mangas.value?.reload() | |
| } | |
| } | |
| fun requestNextPage() { | |
| viewModelScope.launch { | |
| _mangas.value?.requestNextPage() | |
| } | |
| } |
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| // An heavily simplified example about how to use manga in compose with a lot of. | |
| // There are potential performance issues that can be solved by reducing the frequency of calls to onRequestNextPage. | |
| @Composable | |
| fun ComposeExample() { | |
| val mangaListResult by viewModel.mangas.collectAsState() | |
| StateView( | |
| result = mangaListResult, | |
| onRetry = { onAction(LibraryAction.Reload) }, | |
| modifier = Modifier | |
| .padding(paddingValues) | |
| .fillMaxSize(), | |
| ) { mangaList -> | |
| MangaList( | |
| mangaList = mangaList, | |
| onRequestNextPage = { onAction(LibraryAction.RequestNextPage) }, | |
| ) | |
| } | |
| } | |
| @Composable | |
| fun MangaList( | |
| mangaList: PagedList<MangaDto>, | |
| onRequestNextPage: () -> Unit, | |
| ) { | |
| var maxAccessed by remember { mutableStateOf(0) } | |
| LazyColumn { | |
| itemsIndexed(mangaList.list) { index, manga -> | |
| if (index > maxAccessed) { | |
| maxAccessed = index | |
| if ( | |
| mangaList.appendState?.isSuccess == true && | |
| maxAccessed < mangaList.list.size + 30 | |
| ) { | |
| onRequestNextPage() | |
| } | |
| } | |
| MangaCard(manga = manga) | |
| } | |
| fun itemFullWidth(content: @Composable () -> Unit) { | |
| item(span = { GridItemSpan(maxCurrentLineSpan) }) { Box {} } | |
| item(span = { GridItemSpan(maxCurrentLineSpan) }) { content() } | |
| } | |
| mangaList.appendState | |
| ?.onFailure { itemFullWidth { ErrorItem(it) { onRequestNextPage() } } } | |
| ?: itemFullWidth { LoadingItem() } | |
| } | |
| } |
What is Connectivity in RemoteList.kt file? I am getting error on that.
Please, create a sample project for this, I'm having confusions with these gists, some properties are not found, maybe you put it thinking that I am smart enough, but it is not) Please, make one sample project on your github.
What is Connectivity in RemoteList.kt file? I am getting error on that.
Connectivity is my helper class that watches the network connection change. It has nothing to do with paging.
I used this code in https://github.com/FishHawk/lisu-android, although it's not a simple project.
What is Connectivity in RemoteList.kt file? I am getting error on that.
Connectivityis my helper class that watches the network connection change. It has nothing to do with paging.I used this code in
https://github.com/FishHawk/lisu-android, although it's not a simple project.
Thank you very much, really good sample project.
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i suggest to put the following code into LaunchEffect or other effect handlers:
it is on line 30 in file 4