Paging with Jetpack Compose cause infinite retrofit calls - android

I am trying to implement paging for the TMDB API using paging3 and paging-compose.
Here the source of truth is database and api calls are handled by Remote-mediator.
Repository:
class Repository #Inject constructor(
val database: Database,
private val apiService: ApiService
){
#ExperimentalPagingApi
fun movies(): Flow<PagingData<Movie>> = Pager(
config = PagingConfig(pageSize = 20),
remoteMediator = MovieRemoteMediator(database,apiService),
){
database.movieDao().pagedTopRated()
}.flow
}
RemoteMediator:
#ExperimentalPagingApi
class MovieRemoteMediator(
private val database: Database,
private val networkService: ApiService
) : RemoteMediator<Int, Movie>() {
override suspend fun load(loadType: LoadType, state: PagingState<Int, Movie>): MediatorResult {
val page:Int = when(loadType){
LoadType.REFRESH -> {
val remoteKeys = getRemoteKeyClosestToCurrentPosition(state)
remoteKeys?.nextKey?.minus(1) ?: 1
}
LoadType.PREPEND -> {
val remoteKeys = getRemoteKeyForFirstItem(state)
val prevKey = remoteKeys?.prevKey
?: return MediatorResult.Success(endOfPaginationReached = remoteKeys != null)
prevKey
}
LoadType.APPEND -> {
val remoteKeys = getRemoteKeyForLastItem(state)
val nextKey = remoteKeys?.nextKey
?: return MediatorResult.Success(endOfPaginationReached = remoteKeys != null)
nextKey
}
}
return try {
val response
: MovieResponse = networkService.getTopRatedMovies(page)
val toInsert: MutableList<Movie> = mutableListOf();
for (i in response.results)
toInsert.add(i.mapToMovie());
val endOfPaginationReached = response.page + 1 > response.totalPages
database.withTransaction {
if (loadType == LoadType.REFRESH) {
database.movieKeyDao().clearRemoteKeys()
database.movieDao().clearMovies()
}
val prevKey = if (page == 1) null else page - 1
val nextKey = if (endOfPaginationReached) null else page + 1
val keys = response.results.map {
MovieKey(movieId = it.id, prevKey = prevKey, nextKey = nextKey)
}
database.movieDao().insertMovies(toInsert)
database.movieKeyDao().insertAll(keys)
}
MediatorResult.Success(
endOfPaginationReached = endOfPaginationReached
)
} catch (e: IOException) {
MediatorResult.Error(e)
} catch (e: HttpException) {
MediatorResult.Error(e)
}
}
private suspend fun getRemoteKeyForLastItem(state: PagingState<Int, Movie>): MovieKey? {
// Get the last page that was retrieved, that contained items.
// From that last page, get the last item
return state.pages.lastOrNull() { it.data.isNotEmpty() }?.data?.lastOrNull()
?.let { repo ->
// Get the remote keys of the last item retrieved
database.movieKeyDao().remoteKeysMovieId(repo.id)
}
}
private suspend fun getRemoteKeyForFirstItem(state: PagingState<Int, Movie>): MovieKey? {
// Get the first page that was retrieved, that contained items.
// From that first page, get the first item
return state.pages.firstOrNull { it.data.isNotEmpty() }?.data?.firstOrNull()
?.let { repo ->
// Get the remote keys of the first items retrieved
database.movieKeyDao().remoteKeysMovieId(repo.id)
}
}
private suspend fun getRemoteKeyClosestToCurrentPosition(
state: PagingState<Int, Movie>
): MovieKey? {
// The paging library is trying to load data after the anchor position
// Get the item closest to the anchor position
return state.anchorPosition?.let { position ->
state.closestItemToPosition(position)?.id?.let { repoId ->
database.movieKeyDao().remoteKeysMovieId(repoId)
}
}
}
ViewModel:
#HiltViewModel
class MovieViewModel #Inject constructor(
private val movieRepository: Repository
) : ViewModel() {
#ExperimentalPagingApi
fun getMovies() = movieRepository.movies().cachedIn(viewModelScope)
}
Ui Screen:
#ExperimentalCoilApi
#ExperimentalPagingApi
#Composable
fun MainScreen(){
val viewModel: MovieViewModel = viewModel()
val movieList = viewModel.getMovies().collectAsLazyPagingItems()
LazyColumn{
items(movieList){ movie ->
if (movie != null) {
Card(movie)
}
}
}
}
#ExperimentalCoilApi
#ExperimentalPagingApi
#Composable
fun Main(){
MainScreen()
}
MainActivty.kt
#AndroidEntryPoint
class MainActivity : ComponentActivity() {
#ExperimentalCoilApi
#ExperimentalPagingApi
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
JetpackComposePagingTheme {
// A surface container using the 'background' color from the theme
Surface(color = MaterialTheme.colors.background) {
Main()
}
}
}
}
}
I am following the paging3 Codelab for writing the remoteMediator.
On opening the app, it only loads the first 2 pages and then loops infinitely making infinite retrofit calls


You doesn't do exactly as The Codelab you're referencing suggests: they are creating paging Flow inside init and only update it when the query string changes.
On the other hand, you're calling viewModel.getMovies() on each recomposition which causes your problem. Check out how you should work with side effects in Compose in documentation.
In this particular case, as you don't have any parameters, you can simply create it once in the view model like this:
#HiltViewModel
class MovieViewModel #Inject constructor(
private val movieRepository: Repository
) : ViewModel() {
val moviesPagingFlow = movieRepository.movies().cachedIn(viewModelScope)
}


No idea why but in my case isolating the LazyPagingItems from LazyColumn worked.
Try the following:
#Composable
fun MainScreen(){
val viewModel: MovieViewModel = viewModel()
val movieList = viewModel.getMovies().collectAsLazyPagingItems()
MainScreen(movies = movieList)
}
#Composable
fun MainScreen(movies: LazyPagingItems<Movie>){
LazyColumn{
items(movies){ movie ->
if (movie != null) {
Card(movie)
}
}
}
}

Related

Issue with Paging3 and Rxjava in MVP

In my project I want to use paging 3 .
before adding paging into my project , I could get the data from server and show into my RecyclerView
but after adding paging I faced with this issue :
in my Paging Source class :
class RepoPagingSource #Inject constructor(
private val repository: ApiRepository,
val context: Context) : PagingSource<Int, RepositoryResponse>() {
private lateinit var sharedPref: SharedPref
private lateinit var data : MutableList<RepositoryResponse>
private lateinit var responseCode : String
override suspend fun load(params: LoadParams<Int>): LoadResult<Int, RepositoryResponse> {
sharedPref = SharedPref(context)
val responseData = mutableListOf<RepositoryResponse>()
return try {
val currentPage = params.key ?: 1
val response = repository
.getRepositories("bearer ${sharedPref.accessToken}", currentPage)
.applyIoScheduler()
.subscribe { response ->
responseCode=response.code().toString()
data = response.body()!!
Log.d("RepoPagingSource",responseCode)
Log.d("RepoPagingSource",data.size.toString())
Log.d("RepoPagingSource",data.toString())
}
responseData.addAll(data)
LoadResult.Page(
data = responseData,
prevKey = if (currentPage == 1) null else -1,
nextKey = currentPage.plus(1)
)
} catch (e: Exception) {
LoadResult.Error(e)
}
}
override fun getRefreshKey(state: PagingState<Int, RepositoryResponse>): Int? {
return null
}
}
these log is showed correct data :
Log.d("RepoPagingSource",responseCode)
Log.d("RepoPagingSource",data.size.toString())
Log.d("RepoPagingSource",data.toString())
result of these logs :
RepoPagingSource: 200
RepoPagingSource: 2
RepoPagingSource: [RepositoryResponse(id=5246349....
but my recyclerview is empty and i checked the code in debug mode
here :
responseData.addAll(data)
data is null!
thanks in advance for your help

I have done it like :
class RepoPagingSource #Inject constructor(
private val repository: ApiRepository,
val context: Context ) : RxPagingSource<Int, RepositoryResponse>() {
private lateinit var sharedPref: SharedPref
override fun loadSingle(params: LoadParams<Int>): Single<LoadResult<Int, RepositoryResponse>> {
sharedPref = SharedPref(context)
var nextPageNumber = params.key
if (nextPageNumber == null) {
nextPageNumber = 1
}
return repository.getRepositories("bearer ${sharedPref.accessToken}", nextPageNumber)
.subscribeOn(Schedulers.io())
.map { response: Response<MutableList<RepositoryResponse>> -> response.body()?.let { toLoadResult(it, nextPageNumber) } }
.onErrorReturn { LoadResult.Error(it) }
}
private fun toLoadResult(
response: MutableList<RepositoryResponse>,
position:Int
): LoadResult<Int, RepositoryResponse> {
return LoadResult.Page(
response,
null,
position + 1,
COUNT_UNDEFINED,
COUNT_UNDEFINED
)
}
override fun getRefreshKey(state: PagingState<Int, RepositoryResponse>): Int? {
return null
}}
in its work for me ,also i have changed my ver of library Rx into rxjava2

pagination not working when reaches to end of page in paging 3 android?

VideoStatusDataSource.kt
class VideoStatusDataSource(
private val categoryKey: String,
private val videosStatusApi: VideoStatusApiService
) : PagingSource<Int, VideoStatus>() {
companion object {
private const val VIDEO_STARTING_PAGE_INDEX = 0
}
override suspend fun load(params: LoadParams<Int>): LoadResult<Int, VideoStatus> {
return try {
val pageIndex = params.key ?: VIDEO_STARTING_PAGE_INDEX
logger(params.key)
logger(pageIndex)
val response =
videosStatusApi.getVideoStatusByPageNumberAndCategoryName(pageIndex, categoryKey)
val jsonCategoryResponse = response.getAsJsonArray(DATA_KEY)
val videoStatusList: List<VideoStatus> = Gson().fromJson(jsonCategoryResponse)
LoadResult.Page(
data = videoStatusList.orEmpty(),
prevKey = if (pageIndex == VIDEO_STARTING_PAGE_INDEX) null else pageIndex - 1,
nextKey = if (videoStatusList.isEmpty()) null else pageIndex.plus(1)
)
} catch (exception: IOException) {
LoadResult.Error(exception)
} catch (exception: HttpException) {
LoadResult.Error(exception)
} catch (exception: Exception) {
LoadResult.Error(exception)
}
}
override fun getRefreshKey(state: PagingState<Int, VideoStatus>): Int? {
return state.anchorPosition?.let { anchorPosition ->
val anchorPage = state.closestPageToPosition(anchorPosition)
anchorPage?.prevKey?.plus(1) ?: anchorPage?.nextKey?.minus(1)
}
}
}
video-API service is providing 10 results on each page but with this data source class it loads all data at once
I want only the first 10 items to load initially and then use scroll first 10 items it needs to load the next 10 items
here is my paging data repository
MainRepopsitory.kt
fun getVideoStatusPagingData(categoryKey: String): Pager<Int, VideoStatus> =
Pager(
config = PagingConfig(
pageSize = 10
),
pagingSourceFactory = { VideoStatusDataSource(categoryKey, videosStatusApi) }
)
ViewModel
#HiltViewModel
class PagingViewModel #Inject constructor(
private val mainRepository: MainRepository,
#IoDispatcher private val ioDispatcher: CoroutineDispatcher
) : ViewModel() {
fun getCurrentCategoryVideoStatus(categoryKey: String): Flow<PagingData<VideoStatus>> =
mainRepository
.getVideoStatusPagingData(categoryKey)
.flow.cachedIn(viewModelScope)
.flowOn(ioDispatcher)
}

This is how I'm using load function in my paging sources you can get help from this I have five to six paging sources in my app and all have same implementations like this
override suspend fun load(params: LoadParams<Int>): LoadResult<Int, Message> {
return try {
val nextPage = params.key ?: 0
chatWithSellerRequest.offset = nextPage.times(PAGE_SIZE_LIMIT)
val response = apiService.getSellerChatResponse(chatWithSellerRequest)
_chatWithSellerResultResponse.value = response.chatWithSellerResult
LoadResult.Page(
data = response.chatWithSellerResult?.messages!!,
prevKey = null,
nextKey = if (response.chatWithSellerResult.messages.isEmpty()) null else nextPage + 1
)
} catch (e: Exception) {
LoadResult.Error(e)
}

Android Paging 3 - experiencing flickers, glitches or jumps in position when scrolling & loading new pages

Hello Guys im using Android Jetpack Paging library 3, I'm creating a news app that implements network + database scenario, and im following the codelab by google https://codelabs.developers.google.com/codelabs/android-paging , im doing it almost like in the codelab i almost matched all the operations shown in the examples https://github.com/android/architecture-components-samples/tree/main/PagingWithNetworkSample.
It works almost as it should...but my backend response is page keyed, i mean response comes with the list of news and the next page url, remote mediator fetches the data, populates the database, repository is set, viewmodel is set...
The problem is :
when recyclerview loads the data , following happens:recyclerview flickers, items jump, are removed , added again and so on.
I dont know why recyclerview or its itemanimator behaves like that , that looks so ugly and glitchy.
More than that, when i scroll to the end of the list new items are fetched and that glitchy and jumping effect is happening again.
I would be very grateful if you could help me, im sitting on it for three days , thank you very much in advance.Here are my code snippets:
#Entity(tableName = "blogs")
data class Blog(
#PrimaryKey(autoGenerate = true)
val databaseid:Int,
#field:SerializedName("id")
val id: Int,
#field:SerializedName("title")
val title: String,
#field:SerializedName("image")
val image: String,
#field:SerializedName("date")
val date: String,
#field:SerializedName("share_link")
val shareLink: String,
#field:SerializedName("status")
val status: Int,
#field:SerializedName("url")
val url: String
) {
var categoryId: Int? = null
var tagId: Int? = null
}
Here's the DAO
#Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun insertAll(blogs: List<Blog>)
#Query("DELETE FROM blogs")
suspend fun deleteAllBlogs()
#Query("SELECT * FROM blogs WHERE categoryId= :categoryId ORDER BY id DESC")
fun getBlogsSourceUniversal(categoryId:Int?): PagingSource<Int, Blog>
#Query("SELECT * FROM blogs WHERE categoryId= :categoryId AND tagId= :tagId ORDER BY id DESC")
fun getBlogsSourceUniversalWithTags(categoryId:Int?,tagId:Int?): PagingSource<Int, Blog>
NewsDatabaseKt
abstract class NewsDatabaseKt : RoomDatabase() {
abstract fun articleDAOKt(): ArticleDAOKt
abstract fun remoteKeyDao(): RemoteKeyDao
companion object {
#Volatile
private var INSTANCE: NewsDatabaseKt? = null
fun getDatabase(context: Context): NewsDatabaseKt =
INSTANCE ?: synchronized(this) {
INSTANCE ?: buildDatabase(context).also { INSTANCE = it }
}
private fun buildDatabase(context: Context) =
Room.databaseBuilder(context.applicationContext,
NewsDatabaseKt::class.java,
"news_database_kt")
.build()
}
RemoteMediator
#ExperimentalPagingApi
class BlogsRemoteMediator(private val categoryId: Int,
private val service: NewsAPIInterfaceKt,
private val newsDatabase: NewsDatabaseKt,
private val tagId : Int? = null ,
private val initialPage:Int = 1
) : RemoteMediator<Int, Blog>() {
override suspend fun initialize(): InitializeAction {
return InitializeAction.LAUNCH_INITIAL_REFRESH
}
override suspend fun load(loadType: LoadType, state: PagingState<Int, Blog>): MediatorResult {
try {
val page = when (loadType) {
REFRESH ->{
initialPage
}
PREPEND -> {
return MediatorResult.Success(endOfPaginationReached = true)}
APPEND -> {
val remoteKey = newsDatabase.withTransaction {
newsDatabase.remoteKeyDao().remoteKeyByLatest(categoryId.toString())
}
if(remoteKey.nextPageKey == null){
return MediatorResult.Success(endOfPaginationReached = true)
}
remoteKey.nextPageKey.toInt()
}
}
val apiResponse =
if(tagId == null) {
service.getCategoryResponsePage(RU, categoryId, page.toString())
}else{
service.getCategoryTagResponsePage(RU,categoryId,tagId,page.toString())
}
val blogs = apiResponse.blogs
val endOfPaginationReached = blogs.size < state.config.pageSize
newsDatabase.withTransaction {
// clear all tables in the database
if (loadType == LoadType.REFRESH) {
newsDatabase.remoteKeyDao().deleteByLatest(categoryId.toString())
if(tagId == null) {
newsDatabase.articleDAOKt().clearBlogsByCatId(categoryId)
}else {
newsDatabase.articleDAOKt().clearBlogsByCatId(categoryId,tagId)
}
}
blogs.map {blog ->
blog.categoryId = categoryId
if(tagId != null) {
blog.tagId = tagId
}
}
newsDatabase.remoteKeyDao().insert(LatestRemoteKey(categoryId.toString(),
apiResponse.nextPageParam))
newsDatabase.articleDAOKt().insertAll(blogs)
}
return MediatorResult.Success(
endOfPaginationReached = endOfPaginationReached
)
} catch (exception: IOException) {
return MediatorResult.Error(exception)
} catch (exception: HttpException) {
return MediatorResult.Error(exception)
}
}
PagingRepository
class PagingRepository(
private val service: NewsAPIInterfaceKt,
private val databaseKt: NewsDatabaseKt
){
#ExperimentalPagingApi
fun getBlogsResultStreamUniversal(int: Int, tagId : Int? = null) : Flow<PagingData<Blog>>{
val pagingSourceFactory = {
if(tagId == null) {
databaseKt.articleDAOKt().getBlogsSourceUniversal(int)
}else databaseKt.articleDAOKt().getBlogsSourceUniversalWithTags(int,tagId)
}
return Pager(
config = PagingConfig(
pageSize = 1
)
,remoteMediator =
BlogsRemoteMediator(int, service, databaseKt,tagId)
,pagingSourceFactory = pagingSourceFactory
).flow
}
}
BlogsViewmodel
class BlogsViewModel(private val repository: PagingRepository):ViewModel(){
private var currentResultUiModel: Flow<PagingData<UiModel.BlogModel>>? = null
private var categoryId:Int?=null
#ExperimentalPagingApi
fun getBlogsUniversalWithUiModel(int: Int, tagId : Int? = null):
Flow<PagingData<UiModel.BlogModel>> {
val lastResult = currentResultUiModel
if(lastResult != null && int == categoryId){
return lastResult
}
val newResult: Flow<PagingData<UiModel.BlogModel>> =
repository.getBlogsResultStreamUniversal(int, tagId)
.map { pagingData -> pagingData.map { UiModel.BlogModel(it)}}
.cachedIn(viewModelScope)
currentResultUiModel = newResult
categoryId = int
return newResult
}
sealed class UiModel{
data class BlogModel(val blog: Blog) : UiModel()
}
PoliticsFragmentKotlin
#ExperimentalPagingApi
class PoliticsFragmentKotlin : Fragment() {
private lateinit var recyclerView: RecyclerView
private lateinit var pagedBlogsAdapter:BlogsAdapter
lateinit var viewModelKt: BlogsViewModel
lateinit var viewModel:NewsViewModel
private var searchJob: Job? = null
#ExperimentalPagingApi
private fun loadData(categoryId:Int, tagId : Int? = null) {
searchJob?.cancel()
searchJob = lifecycleScope.launch {
viewModelKt.getBlogsUniversalWithUiModel(categoryId, tagId).collectLatest {
pagedBlogsAdapter.submitData(it)
}
}
}
#ExperimentalPagingApi
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment_blogs, container, false)
viewModelKt = ViewModelProvider(requireActivity(),Injection.provideViewModelFactory(requireContext())).get(BlogsViewModel::class.java)
viewModel = ViewModelProvider(requireActivity()).get(NewsViewModel::class.java)
pagedBlogsAdapter = BlogsAdapter(context,viewModel)
val decoration = DividerItemDecoration(context, DividerItemDecoration.VERTICAL)
recyclerView = view.findViewById(R.id.politics_recyclerView)
recyclerView.addItemDecoration(decoration)
initAdapter()
loadData(categoryId)
initLoad()
return view
}
private fun initLoad() {
lifecycleScope.launchWhenCreated {
Log.d("meylis", "lqunched loadstate scope")
pagedBlogsAdapter.loadStateFlow
// Only emit when REFRESH LoadState for RemoteMediator changes.
.distinctUntilChangedBy { it.refresh }
// Only react to cases where Remote REFRESH completes i.e., NotLoading.
.filter { it.refresh is LoadState.NotLoading }
.collect { recyclerView.scrollToPosition(0) }
}
}
private fun initAdapter() {
recyclerView.adapter = pagedBlogsAdapter.withLoadStateHeaderAndFooter(
header = BlogsLoadStateAdapter { pagedBlogsAdapter.retry() },
footer = BlogsLoadStateAdapter { pagedBlogsAdapter.retry() }
)
lifecycleScope.launchWhenCreated {
pagedBlogsAdapter.loadStateFlow.collectLatest {
swipeRefreshLayout.isRefreshing = it.refresh is LoadState.Loading
}
}
pagedBlogsAdapter.addLoadStateListener { loadState ->
// Only show the list if refresh succeeds.
recyclerView.isVisible = loadState.source.refresh is LoadState.NotLoading
// Show loading spinner during initial load or refresh.
progressBar.isVisible = loadState.source.refresh is LoadState.Loading
// Show the retry state if initial load or refresh fails.
retryButton.isVisible = loadState.source.refresh is LoadState.Error
// Toast on any error, regardless of whether it came from RemoteMediator or PagingSource
val errorState = loadState.source.append as? LoadState.Error
?: loadState.source.prepend as? LoadState.Error
?: loadState.append as? LoadState.Error
?: loadState.prepend as? LoadState.Error
errorState?.let {
Toast.makeText(context, "\uD83D\uDE28 Wooops ${it.error}", Toast.LENGTH_LONG
).show()
}
}
}
companion object {
#JvmStatic
fun newInstance(categoryId: Int, tags : ArrayList<Tag>): PoliticsFragmentKotlin {
val args = Bundle()
args.putInt(URL, categoryId)
args.putSerializable(TAGS,tags)
val fragmentKotlin = PoliticsFragmentKotlin()
fragmentKotlin.arguments = args
Log.d("meylis", "created instance")
return fragmentKotlin
}
}
BlogsAdapter
class BlogsAdapter(var context: Context?, var newsViewModel:NewsViewModel) :
PagingDataAdapter<BlogsViewModel.UiModel.BlogModel, RecyclerView.ViewHolder>
(REPO_COMPARATOR) {
private val VIEW = 10
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return when (viewType) {
VIEW -> MyViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.card_layout, parent, false))
}
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
val uiModel = getItem(position)
if(uiModel == null){
if(uiModel is BlogsViewModel.UiModel.BlogModel){(holder as MyViewHolder).bind(null)}
}
if(uiModel is BlogsViewModel.UiModel.BlogModel){(holder as
MyViewHolder).bind(uiModel.blog)}
}
override fun getItemViewType(position: Int): Int {
return VIEW
}
companion object {
private val REPO_COMPARATOR = object : DiffUtil.ItemCallback<BlogsViewModel.UiModel.BlogModel>() {
override fun areItemsTheSame(oldItem: BlogsViewModel.UiModel.BlogModel, newItem: BlogsViewModel.UiModel.BlogModel): Boolean =
oldItem.blog.title == newItem.blog.title
override fun areContentsTheSame(oldItem: BlogsViewModel.UiModel.BlogModel, newItem: BlogsViewModel.UiModel.BlogModel): Boolean =
oldItem == newItem
}
}
MyViewHolder
class MyViewHolder(var container: View) : RecyclerView.ViewHolder(container) {
var cv: CardView
#JvmField
var mArticle: TextView
var date: TextView? = null
#JvmField
var time: TextView
#JvmField
var articleImg: ImageView
#JvmField
var shareView: View
var button: MaterialButton? = null
#JvmField
var checkBox: CheckBox
var progressBar: ProgressBar
private var blog:Blog? = null
init {
cv = container.findViewById<View>(R.id.cardvmain) as CardView
mArticle = container.findViewById<View>(R.id.article) as TextView
articleImg = container.findViewById<View>(R.id.imgvmain) as ImageView
//button = (MaterialButton) itemView.findViewById(R.id.sharemain);
checkBox = container.findViewById<View>(R.id.checkboxmain) as CheckBox
time = container.findViewById(R.id.card_time)
shareView = container.findViewById(R.id.shareView)
progressBar = container.findViewById(R.id.blog_progress)
}
fun bind(blog: Blog?){
if(blog == null){
mArticle.text = "loading"
time.text = "loading"
articleImg.visibility = View.GONE
}else {
this.blog = blog
mArticle.text = blog.title
time.text = blog.date
if (blog.image.startsWith("http")) {
articleImg.visibility = View.VISIBLE
val options: RequestOptions = RequestOptions()
.centerCrop()
.priority(Priority.HIGH)
GlideImageLoader(articleImg,
progressBar).load(blog.image, options)
} else {
articleImg.visibility = View.GONE
}
}
}
}
NewsApiInterface
interface NewsAPIInterfaceKt {
#GET("sort?")
suspend fun getCategoryResponsePage(#Header("Language") language: String, #Query("category")
categoryId: Int, #Query("page") pageNumber: String): BlogsResponse
#GET("sort?")
suspend fun getCategoryTagResponsePage(#Header("Language") language: String,
#Query("category") categoryId: Int,#Query("tag") tagId:Int, #Query("page") pageNumber: String)
:BlogsResponse
companion object {
fun create(): NewsAPIInterfaceKt {
val logger = HttpLoggingInterceptor()
logger.level = HttpLoggingInterceptor.Level.BASIC
val okHttpClient = UnsafeOkHttpClient.getUnsafeOkHttpClient()
return Retrofit.Builder()
.baseUrl(BASE_URL)
.client(okHttpClient)
.addConverterFactory(GsonConverterFactory.create())
.build()
.create(NewsAPIInterfaceKt::class.java)
}
}
}
I have tried setting initialLoadSize = 1
But the problem still persists
EDIT: Thanks for your answer #dlam , yes, it does , my network API returns the list of results ordered by id. BTW, items do this jump when the application is run offline as well.
Videos when refreshing and loading online
online loading and paging
online loading and paging(2)
Videos when refreshing and loading offline
offline loading and refreshing
Thanks again, here is my gist link https://gist.github.com/Aydogdyshka/7ca3eb654adb91477a42128de2f06ea9
EDIT
Thanks a lot to #dlam, when I set pageSize=10, jumping has disappeared...Then i remembered why i set pageSize=1 in the first place... when i refresh , 3 x pageSize of items are loaded, even if i overrided initialLoadSize = 10 , it still loads 3 x pageSize calling append 2x times after refresh , what could i be doing wrong, what's the correct way to only load first page when i refresh ?

Just following up here from comments:
Setting pageSize = 10 fixes the issue.
The issue was with pageSize being too small, resulting in PagingSource refreshes loading pages that did not cover the viewport. Since source refresh replaces the list and goes through DiffUtil, you need to provide an initialLoadSize that is large enough so that there is some overlap (otherwise scroll position will be lost).
BTW - Paging loads additional data automatically based on PagingConfig.prefetchDistance. If RecyclerView binds items close enough to the edge of the list, it will automatically trigger APPEND / PREPEND loads. This is why the default of initialLoadSize is 3 * pageSize, but if you're still experiencing additional loads, I would suggest either adjusting prefetchDistance, or increasing initialLoadSize further.

config = PagingConfig(
pageSize = PAGE_SIZE,
enablePlaceholders = true,
prefetchDistance = 3* PAGE_SIZE,
initialLoadSize = 2*PAGE_SIZE,
)
make sure enablePlaceholders is set to true and set the page size to around 10 to 20

recyclerview flickers becouse from dao you get items not the same order it was responded from network.
I will suggest you my solution.
we will get items from database order by primary key, databaseid, descending.
first of all delete autogenerated = true.
we will set databaseid manualy, in same order we got items from network.
next lets edit remoteMediator load function.
when (loadType) {
LoadType.PREPEND -> {
blogs.map {
val databaseid = getFirstBlogDatabaseId(state)?.databaseid?:0
movies.forEachIndexed{
index, blog ->
blog.databaseid = roomId - (movies.size -index.toLong())
}
}
}
LoadType.APPEND -> {
val roomId = getLastBlogDatabaseId(state)?.databaseid ?:0
blogs.forEachIndexed{
index, blog ->
blog.databaseid = roomId + index.toLong() + 1
}
}
LoadType.REFRESH -> {
blogs.forEachIndexed{
index, blog ->
blog.databaseid = index.toLong()
}
}
}
private fun getFirstBlogDatabaseId(state: PagingState<Int, Blog>): Blog? {
return state.pages.firstOrNull { it.data.isNotEmpty() }?.data?.firstOrNull()
}
private fun getLastBlogDatabaseId(state: PagingState<Int, Blog>): Blog? {
return state.lastItemOrNull()
}

Non-infinite paging

I'm using the newest Paging 3 library and trying to implement non-infinite paging by using PagingSource class which executes requests to my API.
What do I want to do?
When the user scrolls to the end of RecyclerView list instead of automatically getting the next chunk of data a next-button should be shown. By clicking on it PagingSource.load method should be invoked as if it would be in case of infinite scrolling.
This is how my PagingSource class looks like:
class LiveTickerPagingSource(
private val service: LiveTickerService
) : PagingSource<Int, LiveTickerEntry>() {
override suspend fun load(params: LoadParams<Int>): LoadResult<Int, LiveTickerEntry> {
val position = params.key ?: STARTING_PAGE_INDEX
return try {
val response = service.getEntries()//params.loadSize
val entries = response.items
LoadResult.Page(
data = entries,
prevKey = null,
nextKey = null
)
} catch (exception: IOException) {
LoadResult.Error(exception)
} catch (exception: HttpException) {
LoadResult.Error(exception)
}
}
}
ViewModel:
class LiveTickerModuleViewModel(private val repository: LiveTickerModuleRepository) : ViewModel() {
private var liveTickerResult: Flow<PagingData<LiveTickerEntry>>? = null
fun getEntries(): Flow<PagingData<LiveTickerEntry>> {
val newResult: Flow<PagingData<LiveTickerEntry>> = repository.getLiveTickerEntriesStream()
.cachedIn(viewModelScope)
liveTickerResult = newResult
return newResult
}
}
Repository:
class LiveTickerModuleRepository(private val service: LiveTickerModuleService) {
fun getLiveTickerEntriesStream(): Flow<PagingData<LiveTickerEntry>> {
return Pager(
config = PagingConfig(pageSize = NETWORK_PAGE_SIZE, initialLoadSize = NETWORK_PAGE_SIZE, enablePlaceholders = false),
pagingSourceFactory = { LiveTickerModulePagingSource(service) }
).flow
}
companion object {
private const val NETWORK_PAGE_SIZE = 3
}
}
And lastly Fragment:
class LiveTickerModuleFragment : Fragment() {
private lateinit var binding: FragmentLiveTickerModuleBinding
private lateinit var viewModel: LiveTickerModuleViewModel
private var liveTickerJob: Job? = null
private val adapter by lazy { LiveTickerModuleAdapter() }
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
viewModel = ViewModelProvider(this, Injection.provideViewModelFactory())
.get(LiveTickerModuleViewModel::class.java)
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
binding = FragmentLiveTickerModuleBinding.inflate(layoutInflater)
initAdapter()
getLiveTickerEntries()
return binding.root
}
private fun getLiveTickerEntries() {
liveTickerJob?.cancel()
liveTickerJob = lifecycleScope.launch {
viewModel.getEntries().collectLatest {
adapter.submitData(it)
}
}
}
private fun initAdapter() {
binding.list.adapter = adapter
adapter.addLoadStateListener { loadState ->
val sourceAppend = loadState.source.append
val sourcePrepend = loadState.source.prepend
val errorState = sourceAppend as? LoadState.Error
?: sourcePrepend as? LoadState.Error
val endOfPaginationReached = errorState?.endOfPaginationReached
}
}
}
I was using this codelab as my reference, which is based on infinite scrolling. I'm thankful for any kind of explanation. It doesn't necessarily have to be code.

This is supported, but you may find Paging adds more complexity than necessary if you don't need incremental loading.
For a static list you can simply use:
PagingDataAdapter.submitData(PagingData.from(myList)
Otherwise, if you're loading from a resource, you can implement a PagingSource which returns a LoadResult.Page with nextKey and prevKey set to null. You'll need to construct a Pager, then observe the PagingData stream to submit to PagingDataAdapter with adapter.submitData(PagingData)

Api call is not stopped calling again and again without any scrolling in Google Paging Library 3

I want to implement pagination to show a chunk of list of my desire item view in my app. That's why I choose to use Google newly released paging library i.e Paging library 3. I use Rxjava, Livedata, and ViewModel in my app.
After implementing the paging library, I am facing a weird problem. When I call the method for fetching list, it's calling again and again and not stopped calling the call. In fact, it automatically increases the page number although I did not scroll the list.
Here is the code I tried
JobListRestApi.kt
interface JobListRestApi {
#GET("job/list")
fun getJobResponse(
#Query("page") pageNumber: Int
): Single<Response<JobResponse>>
}
JobListDataSource.kt
class JobListDataSource #Inject constructor(
private val jobListRestApi: JobListRestApi
): RxPagingSource<Int, Job>() {
override fun loadSingle(params: LoadParams<Int>): Single<LoadResult<Int, Job>> {
val position = params.key ?: 1
return jobListRestApi.getJobResponse(position).toSingle()
.subscribeOn(Schedulers.io())
.map { jobResponse -> jobResponse.jobData.jobs }
.map { jobs -> toLoadResult(jobs, position) }
.onErrorReturn { LoadResult.Error(it) }
}
private fun toLoadResult(data: ArrayList<Job>, position: Int): LoadResult<Int, Job> {
val prevKey = if (position == 1) null else position-1
val nextKey = if (position == data.size) null else position+1
return LoadResult.Page(data, prevKey, nextKey)
}
}
JobListRepositoryImpl.kt
class JobListRepositoryImpl #Inject constructor(
private val jobListDataSource: JobListDataSource
): JobListRepository {
override fun getJobs(): Flowable<PagingData<Job>> {
return Pager(PagingConfig(pageSize = 20)) {
jobListDataSource
}.flowable
}
}
JobListViewModel.kt
class JobListViewModel #Inject constructor(
private val jobListRepository: JobListRepository
): BaseViewModel() {
val jobs: MutableLiveData<PagingData<Job>> = MutableLiveData()
fun getJobs() {
if (jobs.value == null) {
compositeDisposable += jobListRepository.getJobs()
.subscribe({
jobs.value = it
}, {
handleException(it)
})
}
}
}
JobListFragment.kt
class JobListFragment : BaseFragment<JobListViewModel>() {
private val jobAdapter: JobAdapter by lazy {
JobAdapter { }
}
override fun getLayoutResource() = R.layout.fragment_job_list
override fun initWidget() {
job_recycler_view.adapter = jobAdapter
}
override fun onResume() {
super.onResume()
viewModel.getJobs()
}
override fun observeLiveData() {
observe(viewModel.jobs) {
jobAdapter.submitData(lifecycle, it)
}
}
}
And the output log is
https://base-url/job/list?page=1
https://base-url/job/list?page=2
https://base-url/job/list?page=3
https://base-url/job/list?page=4
https://base-url/job/list?page=5
https://base-url/job/list?page=6
https://base-url/job/list?page=7
how can I stop calling serial api unless I go to the last item of the chunk in RecyclerView and scroll the list

You tell Paging there is no more to load by returning null for prevKey and nextKey inLoadResult.Page
Since its infinitely appending, it looks like you never set nextKey to null. Perhaps you meant to check data.isEmpty() instead of key == data.size?

Eventually, I got the error. In fact, the problem was in my Http response Data. The updated DataSource is given bellow
JobListDataSource.kt
class JobListDataSource #Inject constructor(
private val jobListRestApi: JobListRestApi
): RxPagingSource<Int, Job>() {
override fun loadSingle(params: LoadParams<Int>): Single<LoadResult<Int, Job>> {
val position = params.key ?: 1
return jobListRestApi.getJobResponse(position).toSingle()
.subscribeOn(Schedulers.io())
.map { jobResponse -> jobResponse.jobData }
.map { jobData -> toLoadResult(jobData, position) }
.onErrorReturn { LoadResult.Error(it) }
}
private fun toLoadResult(data: JobData, position: Int): LoadResult<Int, Job> {
val prevKey = if (position == 1) null else position-1
val nextKey = if (data.hasMore) position+1 else null
return LoadResult.Page(data.jobs, prevKey, nextKey)
}
}

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