Develop Reference

ListAdapter submitlist not update after deleting the data instead its giving me duplicate data

when i try to delete first row i get first row back and with duplicate second row
enter image description here
after delete any row from the list gives me duplicate data like this
enter image description here
This is my Adapter class. On my deleteItem function position is passed from fragment class and
it is supposed to delete an item from the given position and update the list but its rendering the duplicate data.
class MyListAdapter :ListAdapter<Article,MyListAdapter.MyViewHolder>(MyDiffUtil()) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.recycler_item,parent,false)
return MyViewHolder(view)
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
val item = getItem(position)
holder.onBind(item)
// to click each item of list
holder.itemView.setOnClickListener {
onItemClickListener?.let {it(item) }
}
}
class MyViewHolder(itemView :View) : RecyclerView.ViewHolder(itemView)
{
fun onBind(article: Article) = with(itemView)
{
Glide.with(this)
.load(article.urlToImage)
.error(R.drawable.notfound)
.into(imageView)
webSource.text = article.source?.name
newsDate.text = article.publishedAt
newsTitle.text = article.title
newsDescription.text = article.description
}
}
// lamda function for handling web view
private var onItemClickListener : ((Article) -> Unit)? = null
fun setOnItemClickListener(listener : (Article) ->Unit)
{
onItemClickListener = listener
}
// implementing diffutil class
class MyDiffUtil : DiffUtil.ItemCallback<Article>()
{
override fun areItemsTheSame(oldItem: Article, newItem: Article): Boolean {
return oldItem.url == newItem.url
}
override fun areContentsTheSame(oldItem: Article, newItem: Article): Boolean {
return oldItem == newItem
}
}
fun deleteItem(pos : Int)
{
var myl = ArrayList<Article>()
val currentList= currentList.toMutableList()
currentList.removeAt(pos)
myl.addAll(currentList)
submitList(myl)
}
}
`
I tried to delete the saved news from the ListAdapter and update the recycler view with animation of DiffUtill class but its not updating the recycler view and
giving duplicate data . How can i delete data with diffutil animation as its normal way. Thanks in advance.
this is my fragment
package com.example.news.Fragments
class SavedNews : Fragment() {
lateinit var mymainViewModel: MainViewModel
lateinit var databaseObject: MyDataBase
lateinit var myAdapter: MyListAdapter
lateinit var convertedArticleList : ArrayList<Article>
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
myAdapter = MyListAdapter()
convertedArticleList = ArrayList()
return inflater.inflate(R.layout.fragment_saved_news, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
savedNewsRecyclerView.layoutManager = LinearLayoutManager(activity,LinearLayoutManager.VERTICAL,
false)
savedNewsRecyclerView.adapter = myAdapter
ItemTouchHelper(object :ItemTouchHelper.SimpleCallback(0,ItemTouchHelper.RIGHT){
override fun onMove(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder,
target: RecyclerView.ViewHolder
): Boolean {
// this method is called
// when the item is moved.
return true
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
// this method is called when we swipe our item to right direction.
// on below line we are getting the item at a particular position.
val deletedCourse: Article =
convertedArticleList.get(viewHolder.adapterPosition)
myAdapter.deleteItem(viewHolder.adapterPosition)
mymainViewModel.deleteSavedNews(deletedCourse.id!!)
// myAdapter.notifyItemRemoved(viewHolder.adapterPosition)
// myAdapter.submitList(myCurrentList)
// Snackbar.make(savedNewsRecyclerView,"Deleted" + deletedCourse.title,
// Snackbar.LENGTH_LONG).setAction(
// "Undo",
// View.OnClickListener {
//
// convertedArticleList.add(position,deletedCourse)
// myAdapter.notifyItemInserted(position)
// }
// ).show()
}
}).attachToRecyclerView(savedNewsRecyclerView)
}
override fun onResume() {
super.onResume()
Log.d("LIFE","ON Resume")
val myInterfaceObject = ApiInterface.MyObject.getInstance()
databaseObject = MyDataBase.MyObjectDB.getDBInstance(activity as MainActivity)
val myRepository = Repository(myInterfaceObject, databaseObject)
mymainViewModel = ViewModelProvider(
this,
MainViewModelFactory(myRepository)
).get(MainViewModel::class.java)
//listAdapter things
// show saved news in savednews fragment
lifecycleScope.launch(Dispatchers.Main) {
//abstract data from saved room database and converting likedartcile datacass object to
// Artticle data class article
mymainViewModel.abstractSavedNews().observe(viewLifecycleOwner, Observer {
it.forEach { eachLikedArticle ->
val obj = toArticle(eachLikedArticle)
convertedArticleList.add(obj)
}
myAdapter.submitList(convertedArticleList)
})
//clicking the item of save news
myAdapter.setOnItemClickListener {
val bundle = Bundle().apply {
putSerializable("article", it)
}
convertedArticleList.clear()
findNavController().navigate(R.id.action_savedNews_to_article, bundle)
}
}
}
private fun toArticle(rawObject: LikedArticle) = Article(
rawObject.author, rawObject.content,
rawObject.description, rawObject.publishedAt, rawObject.source, rawObject.title,
rawObject.url, rawObject.urlToImage, rawObject.id
)
}

There is not enough information to actually replicate how you're trying to use this in your Fragment/Activity but without changing your code too much, this works (note I used view binding):
class MyListAdapter :
ListAdapter<Article, MyViewHolder>(MyDiffUtil()) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) = MyViewHolder(
RecyclerItemBinding.inflate(
LayoutInflater.from(parent.context),
parent,
false
)
)
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
val item = getItem(position)
holder.onBind(item)
}
fun deleteItem(pos: Int) {
var myl = ArrayList<Article>()
val currentList = currentList.toMutableList()
currentList.removeAt(pos)
myl.addAll(currentList)
submitList(myl)
}
}
class MyViewHolder(private val binding: RecyclerItemBinding) : RecyclerView.ViewHolder(binding.root) {
fun onBind(article: Article) = with(binding) {
textView.text = article.url
}
}
class MyDiffUtil : DiffUtil.ItemCallback<Article>() {
override fun areItemsTheSame(oldItem: Article, newItem: Article): Boolean {
return oldItem.url == newItem.url
}
override fun areContentsTheSame(oldItem: Article, newItem: Article): Boolean {
return oldItem == newItem
}
}
Overall this should work.
You can also refactor deleteItem to something more meaningful:
fun deleteItem(pos: Int) {
val oldList = currentList.toMutableList()
oldList.removeAt(pos)
val updatedList = oldList
submitList(updatedList)
}

RecyclerView only displays first item

So, I am creating a cocktail app, based on the https://www.thecocktaildb.com/ api. Thus far, I have only created a screen to display options based on the ingredient I put in the search bar (search bar is not done yet). Yet when I run the app, only the first entry is displayed
By putting Log.e("TAG", "$position") inside of my onBindViewHolder, of the adapter, I saw that the position variable never increases from 0
class CocktailsAdapter: RecyclerView.Adapter<CocktailsAdapter.CocktailsViewHolder>() {
inner class CocktailsViewHolder(val binding: ItemCocktailPreviewBinding) :
RecyclerView.ViewHolder(binding.root)
private val differCallback = object : DiffUtil.ItemCallback<CocktailsByBaseDto>() {
override fun areItemsTheSame( oldItem: CocktailsByBaseDto, newItem: CocktailsByBaseDto): Boolean {
return oldItem.drinks[0].idDrink == newItem.drinks[0].idDrink
}
override fun areContentsTheSame(oldItem: CocktailsByBaseDto, newItem: CocktailsByBaseDto): Boolean {
return oldItem.drinks[0] == newItem.drinks[0]
}
}
val differ = AsyncListDiffer(this, differCallback)
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CocktailsViewHolder {
return CocktailsViewHolder(
ItemCocktailPreviewBinding.inflate(
LayoutInflater.from(parent.context),
parent,
false
)
)
}
override fun onBindViewHolder(holder: CocktailsViewHolder, position: Int) {
val binding = holder.binding
val cocktail = differ.currentList[position]
holder.itemView.apply {
Glide.with(this).load(cocktail.drinks[position].strDrinkThumb).into(binding.imgCocktailsMainRecyclerViewImage)
binding.tvCocktailsMainRecyclerViewTitle.text = cocktail.drinks[position].strDrink
Log.e("TAG", "$position")
setOnClickListener {
onItemClickListener?.let { it(cocktail) }
}
}
}
override fun getItemCount(): Int {
return differ.currentList.size
}
private var onItemClickListener: ((CocktailsByBaseDto) -> Unit)? = null
fun setOnItemClickListener(listener: (CocktailsByBaseDto) -> Unit) {
onItemClickListener = listener
}
I have tried both position and 0 (which makes more sense) inside val cocktail = differ.currentList[position], but neither gave me a different result

Fixed it by changing the class I had passed to DiffUtil.ItemCallback

Strange behaviour happen in onBindViewHolder android kotlin

Hey I am working in android kotlin. I am working in reyclerview. I want to do single selection in my items. I tried some code which is working fine.
OptionsViewAdapter.kt
class OptionsViewAdapter : ListAdapter<ProductVariant, OptionsViewHolder>(PRODUCT_COMPARATOR) {
private var selectedItemPosition: Int = 0
companion object {
private val PRODUCT_COMPARATOR = object : DiffUtil.ItemCallback<ProductVariant>() {
override fun areItemsTheSame(
oldItem: ProductVariant,
newItem: ProductVariant
): Boolean {
return oldItem == newItem
}
override fun areContentsTheSame(
oldItem: ProductVariant,
newItem: ProductVariant
): Boolean {
return oldItem == newItem
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): OptionsViewHolder {
return OptionsViewHolder.bindView(parent)
}
override fun onBindViewHolder(holder: OptionsViewHolder, position: Int) {
holder.binding.root.setOnClickListener {
selectedItemPosition = holder.bindingAdapterPosition
notifyAdapter()
}
val drawableColor = if (selectedItemPosition == position)
R.drawable.options_item_selected_background
else
R.drawable.options_item_default_background
holder.binding.root.background =
ContextCompat.getDrawable(holder.binding.root.context, drawableColor)
holder.bindItem(getItem(position), position)
}
fun notifyAdapter() {
notifyDataSetChanged()
}
}
OptionsViewHolder.kt
class OptionsViewHolder(
val binding: OptionsItemLayoutBinding,
) : RecyclerView.ViewHolder(binding.root) {
companion object {
fun bindView(parent: ViewGroup): OptionsViewHolder {
return OptionsViewHolder(
OptionsItemLayoutBinding.inflate(
LayoutInflater.from(parent.context),
parent,
false
)
)
}
}
fun bindItem(item: ProductVariant?, position: Int) {
}
}
Video for single click is working fine.
When I move onBindViewHolder code inside bindItem it not working. Can someone guide me why this is happening.
vs
OptionsViewAdapter.kt
class OptionsViewAdapter : ListAdapter<ProductVariant, OptionsViewHolder>(PRODUCT_COMPARATOR) {
companion object {
private val PRODUCT_COMPARATOR = object : DiffUtil.ItemCallback<ProductVariant>() {
override fun areItemsTheSame(
oldItem: ProductVariant,
newItem: ProductVariant
): Boolean {
return oldItem == newItem
}
override fun areContentsTheSame(
oldItem: ProductVariant,
newItem: ProductVariant
): Boolean {
return oldItem == newItem
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): OptionsViewHolder {
return OptionsViewHolder.bindView(parent)
}
override fun onBindViewHolder(holder: OptionsViewHolder, position: Int) {
holder.bindItem(getItem(position), position ,::notifyAdapter)
}
fun notifyAdapter() {
notifyDataSetChanged()
}
}
OptionsViewHolder.kt
class OptionsViewHolder(
val binding: OptionsItemLayoutBinding,
) : RecyclerView.ViewHolder(binding.root) {
private var selectedItemPosition: Int = 0
companion object {
fun bindView(parent: ViewGroup): OptionsViewHolder {
return OptionsViewHolder(
OptionsItemLayoutBinding.inflate(
LayoutInflater.from(parent.context),
parent,
false
)
)
}
}
fun bindItem(
item: ProductVariant?,
position: Int,
onAdapterChange: () -> Unit
) {
binding.root.setOnClickListener {
selectedItemPosition = position
onAdapterChange()
}
val drawableColor = if (selectedItemPosition == position)
R.drawable.options_item_selected_background
else
R.drawable.options_item_default_background
binding.root.background =
ContextCompat.getDrawable(binding.root.context, drawableColor)
}
}
The video for single click is not working.

You moved the selectedItemPosition into the ViewHolder class, so you have a separate copy of this property for every instance of the ViewHolder class so you are no longer affecting other items in the list when any one list item is clicked.
This would be much easier to implement by making the view holder class an inner class of the Adapter so it can directly modify the adapter’s selectedItemPosition property. And I would give the property a custom setter so you can automatically notify the adapter of the change instead of having to work with a separate function call. You can also make it notify the adapter specifically of which two row items changed instead of the whole data set (more efficient and by doing it in the property setter you have access to the old and new row positions in one place easily—field and value).
private var selectedItemPosition: Int = 0
set(value) {
val oldPos = field
field = value
notifyItemChanged(oldPos)
notifyItemChanged(value)
}

Even though you are passing the method reference notifyAdapter() in bindItem() function you are not calling it in the OnClickListener that is why it is not working.

RecyclerView swipe functionality breaks after orientation change

I created a RecyclerView that refreshes its list based on a database call. Each row has an options menu that is revealed when the user swipes. My original issue was that after an orientation change, the swipe gestures no longer revealed the menu. I hit all my expected breakpoints with onCreateViewHolder() and the onSwipe(). However, the row remained as the HIDE_MENU view type after swiping.
So I tried to introduce LiveData to persist the state of the list after orientation changes. The RecyclerView was still created and populated with items but now the swipe gesture crashes the application with an error:
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
Do I need to use LiveData to fix the original issue of preserving my swipe functionality after orientation changes? If not, please can someone explain why the item view types are no longer updated after orientation changes.
If I do need to use a ViewModel, what am I doing that is causing the list adapter not to receive the updated list?
HistoryFragment
class HistoryFragment : Fragment() {
private val historyViewModel by activityViewModels<HistoryViewModel>()
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val root = inflater.inflate(R.layout.fragment_history, container, false)
historyViewModel.getHistoryList().observe(viewLifecycleOwner, {
refreshRecyclerView(it)
})
return root
}
private fun updateHistoryList() {
val dbHandler = MySQLLiteDBHandler(requireContext(), null)
val historyList = dbHandler.getHistoryList() as MutableList<HistoryObject>
historyViewModel.setHistoryList(historyList)
}
private fun refreshRecyclerView(historyList: MutableList<HistoryObject>) {
val historyListAdapter = HistoryListAdapter(historyList)
val callback = HistorySwipeHelper(historyListAdapter)
val helper = ItemTouchHelper(callback)
history_list.adapter = historyListAdapter
helper.attachToRecyclerView(history_list)
}
private fun setupSort() {
val sortSpinner: Spinner = history_list_controls_sort
sortSpinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
override fun onNothingSelected(parent: AdapterView<*>?) {}
override fun onItemSelected(
parent: AdapterView<*>?,
view: View?,
position: Int,
id: Long
) {
updateHistoryList()
}
}
}
override fun onViewCreated(
view: View,
savedInstanceState: Bundle?
) {
setupSort()
}
}
HistoryListAdapter
const val SHOW_MENU = 1
const val HIDE_MENU = 2
class HistoryListAdapter(private var historyData: MutableList<HistoryObject>) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return if (viewType == SHOW_MENU) {
val inflatedView = LayoutInflater.from(parent.context).inflate(R.layout.history_list_view_row_items_menu, parent, false)
MenuViewHolder(inflatedView)
} else {
val inflatedView = LayoutInflater.from(parent.context).inflate(R.layout.history_list_view_row_items_description, parent, false)
HistoryItemViewHolder(inflatedView)
}
}
override fun getItemViewType(position: Int): Int {
return if (historyData[position].showMenu) {
SHOW_MENU
} else {
HIDE_MENU
}
}
override fun getItemCount(): Int {
return historyData.count()
}
fun showMenu(position: Int) {
historyData.forEachIndexed { idx, it ->
if (it.showMenu) {
it.showMenu = false
notifyItemChanged(idx)
}
}
historyData[position].showMenu = true
notifyItemChanged(position)
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
val item: HistoryObject = historyData[position]
if (holder is HistoryItemViewHolder) {
holder.bindItem(item)
...
}
if (holder is MenuViewHolder) {
holder.bindItem(item)
...
}
}
class HistoryItemViewHolder(v: View, private val clickHandler: (item: HistoryObject) -> Unit) : RecyclerView.ViewHolder(v) {
private var view: View = v
private var item: HistoryObject? = null
fun bindItem(item: HistoryObject) {
this.item = item
...
}
}
class MenuViewHolder(v: View, private val deleteHandler: (item: HistoryObject) -> Unit) : RecyclerView.ViewHolder(v) {
private var view: View = v
private var item: HistoryObject? = null
fun bindItem(item: HistoryObject) {
this.item = item
...
}
}
}
HistorySwipeHelper
class HistorySwipeHelper(private val adapter: HistoryListAdapter) : ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT) {
override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean { return false }
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
adapter.showMenu(viewHolder.adapterPosition)
}
override fun getSwipeThreshold(viewHolder: RecyclerView.ViewHolder): Float {
return 0.1f
}
}
HistoryViewModel
class HistoryViewModel(private var historyListHandle: SavedStateHandle) : ViewModel() {
fun getHistoryList(): LiveData<MutableList<HistoryObject>> {
return historyListHandle.getLiveData(HISTORY_LIST_KEY)
}
fun setHistoryList(newHistoryList: MutableList<HistoryObject>) {
historyListHandle.set(HISTORY_LIST_KEY, newHistoryList)
}
companion object {
const val HISTORY_LIST_KEY = "MY_HISTORY_LIST"
}
}
Activity
class MainActivity : AppCompatActivity() {
private val historyViewModel: HistoryViewModel by lazy {
ViewModelProvider(this).get(HistoryViewModel::class.java)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
historyViewModel.setHistoryList(mutableListOf())
}
}
Thanks in advance. If this question is too broad I can try again and decompose it.

You shouldn't create new adapter every time you get an update of your history list. Keep using the same adapter, just update the items and call notifyDataSetChanged() to update the state (of course you can use different methods to notify about the insertion/deletion/etc, but make it work with notifyDataSetChanged() first).
I'm pretty sure this will fix the issue.

RecyclerView only displaying data after restarting Activity

So i have this strange behaviour where my RecyclerView only Displays data when i start the App and then restart the activity via Android Studio. Or make a change in XML, then undo it and restart.
The then displayed data is correct and also updates when i add things, but it is not visible after starting the app.
Can anyone help me out? I am really clueless why that would be.
Fragment:
#AndroidEntryPoint
class HistoryFragment : Fragment(R.layout.fragment_history) {
private val viewModel: PurchaseViewmodel by viewModels()
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val binding = FragmentHistoryBinding.bind(view)
val exampleAdapter = ExampleAdapter()
binding.apply{
recyclerView.apply{
layoutManager = LinearLayoutManager(requireContext())
adapter = exampleAdapter
setHasFixedSize(true)
}
ItemTouchHelper(object : ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT) {
override fun onMove(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder,
target: RecyclerView.ViewHolder
): Boolean {
return false /// We dont need any interaction with Drag&Drop we only want swipe left&right
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
val receipt = exampleAdapter.currentList[viewHolder.adapterPosition]
viewModel.onSwipe(receipt)
}
}).attachToRecyclerView(recyclerView)
}
setFragmentResultListener("add_receipt_request"){_,bundle ->
val result = bundle.getInt("add_receipt_request")
viewModel.onAddResult(result)
}
viewModel.receipts.observe(viewLifecycleOwner){ /// New Items get passed to the List
exampleAdapter.submitList(it)
}
viewLifecycleOwner.lifecycleScope.launchWhenStarted { //as soon as we close our app the events will be suspended, but not deleted and will remain after restart
viewModel.addTaskEvent.collect { event->
when(event){
is PurchaseViewmodel.TasksEvent.ShowUndoDelete -> {
Snackbar.make(requireView(),"Tasks deleted", Snackbar.LENGTH_LONG)
.setAction("UNDO"){
viewModel.unDoDeleteClick(event.receipts)
}.show()
}
}
}
}
}
}
Adapter:
class ExampleAdapter : ListAdapter<Receipts,ExampleAdapter.ExampleViewHolder>(DiffCallback()) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ExampleViewHolder {
val binding = ReceiptsBinding.inflate(LayoutInflater.from(parent.context),parent,false)
return ExampleViewHolder(binding)
}
override fun onBindViewHolder(holder: ExampleViewHolder, position: Int) {
val currentItem = getItem(position)
holder.bind(currentItem)
}
override fun getItemCount(): Int {
return super.getItemCount()
}
class ExampleViewHolder(private val binding: ReceiptsBinding) : RecyclerView.ViewHolder(binding.root){ //Examples One Row in our list
fun bind (receipts: Receipts) {
binding.apply {
storeHistory.text = receipts.store
amountHistory.text = receipts.total
dateHistory.text = receipts.date
}
}
}
class DiffCallback : DiffUtil.ItemCallback<Receipts>() {
override fun areItemsTheSame(oldItem: Receipts, newItem: Receipts) =
oldItem.id == newItem.id
override fun areContentsTheSame(oldItem: Receipts, newItem: Receipts) =
oldItem == newItem
}
}

You should compare corresponding fields of old/new Receipts in areContentsTheSame() instead of comparing the entire old/new objects
override fun areContentsTheSame(oldItem: Receipts, newItem: Receipts) =
oldItem.store == newItem.store
&& oldItem.total == newItem.total
&& oldItem.date == newItem.date