Develop Reference

RecyclerView is not updated when an update occurs in Room

I have a RecyclerView where an item can be edited via a DialogFragment, so when an item is clicked a Dialog is shown, then I can change some properties of that item, the issue is that RecyclerView is not updated with the updated properties and I have to force a notifyItemChanged when the Dialog is closed.
When an item in RecyclerView is clicked I set a MutableLiveData in my ViewModel so then it can be manipulated in the Dialog.
My ViewModel looks like this:
#HiltViewModel
class DocumentProductsViewModel #Inject constructor(private val repository: DocumentProductsRepository) :
ViewModel() {
val barcode = MutableLiveData<String>()
private val _selectedProduct = MutableLiveData<DocumentProduct>()
val selectedProduct: LiveData<DocumentProduct> = _selectedProduct
private val _selectedDocumentId = MutableLiveData<Long>()
val selectedDocumentId: LiveData<Long> = _selectedDocumentId
val products: LiveData<List<DocumentProduct>> = _selectedDocumentId.switchMap { documentId ->
repository.getDocumentProducts(documentId).asLiveData()
}
fun insert(documentProduct: DocumentProduct) = viewModelScope.launch {
repository.insert(documentProduct)
}
fun setProductQuantity(quantity: Float) {
_selectedProduct.value = _selectedProduct.value.also {
it?.timestamp = System.currentTimeMillis()
it?.quantity = quantity
}
update()
}
fun start(documentId: Long?) = viewModelScope.launch{
if (documentId == null) {
_selectedDocumentId.value = repository.getHeaderByType("Etichette")?.id
}
documentId?.let { documentId ->
_selectedDocumentId.value = documentId
}
}
fun select(product: DocumentProduct) {
_selectedProduct.value = product
}
fun delete() = viewModelScope.launch {
_selectedProduct.value?.let { repository.delete(it) }
}
private fun update() = viewModelScope.launch {
_selectedProduct.value?.let { repository.update(it) }
}
}
And in my fragment I'm subscribed to products as this:
private fun initRecyclerView() {
binding.rvProducts.adapter = adapter
viewModel.products.observe(viewLifecycleOwner) { products ->
val productsCount = products.count()
binding.tvProductsCount.text =
resources.getQuantityString(R.plurals.articoli, productsCount, productsCount)
// TODO: create amount string and set it with resources
binding.tvProductsAmount.text = productsCount.toEuro()
adapter.submitList(products)
binding.rvProducts.smoothScrollToPosition(adapter.itemCount - 1)
}
initSwipe(adapter)
}
When setProductQuantity is called the RecyclerView remains unchanged until notify is called while delete works fine without the necessity of calling any notify on RecyclerView.
UPDATE:
The item position is actually changed in RecyclerView as it's sorted by it's last changed timestamp BUT not the quantity field.
Here is my Adapter:
class DocumentProductsListAdapter : ListAdapter<DocumentProduct, DocumentProductsListAdapter.ViewHolder>(ProductDiffCallback) {
override fun onCreateViewHolder(viewGroup: ViewGroup, viewType: Int): ViewHolder {
val view: View = LayoutInflater.from(viewGroup.context)
.inflate(R.layout.layout_item, viewGroup, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val product = getItem(position)
holder.bind(product)
}
class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
val barcode: TextView = itemView.findViewById(R.id.barcode)
val quantity: TextView = itemView.findViewById(R.id.quantity)
val description: TextView = itemView.findViewById(R.id.description)
val unitOfMeasure: TextView = itemView.findViewById(R.id.unitOfMeasure)
fun bind(product: DocumentProduct) {
barcode.text = product.barcode
quantity.text = product.quantity.formatForQta().replace(".", ",")
if (product.labelType != null && product.labelType != "") {
unitOfMeasure.text = product.labelType
} else {
unitOfMeasure.text = product.unitOfMeasure?.lowercase(Locale.ITALIAN)
}
description.text = product.description ?: "-"
}
}
}
object ProductDiffCallback : DiffUtil.ItemCallback<DocumentProduct>() {
override fun areItemsTheSame(oldItem: DocumentProduct, newItem: DocumentProduct): Boolean {
return oldItem.id == newItem.id
}
override fun areContentsTheSame(oldItem: DocumentProduct, newItem: DocumentProduct): Boolean {
return oldItem == newItem
}
}
data class DocumentProduct(
#PrimaryKey(autoGenerate = true)
var id: Long,
var barcode: String,
#Json(name = "desc")
var description: String?,
#ColumnInfo(defaultValue = "PZ")
#Json(name = "um")
var unitOfMeasure: String?,
#Json(name = "qta")
var quantity: Float,
#Json(name = "id_testata")
var documentId: Long,
#Json(name = "tipo_frontalino")
var labelType: String?,
var timestamp: Long?
) {
constructor(barcode: String, documentId: Long, labelType: String?) : this(
0,
barcode,
null,
"PZ",
1f,
documentId,
labelType,
null
)
override fun equals(other: Any?): Boolean {
return super.equals(other)
}
override fun hashCode(): Int {
return super.hashCode()
}
}

You have the implementations of areContentsTheSame() and areItemsTheSame() swapped.
areContentsTheSame() is asking if everything in the two items being compared is the same. Therefore, if the class has a proper equals()/hashcode() for all properties used by the ViewHolder, you can use oldItem == newItem. If you use a data class with all relevant properties in the primary constructor, then you don't need to manually override equals()/hashcode().
areItemsTheSame() is asking if the two items represent the same conceptual row item, with possible differences in their details. So it should be oldItem.id == newItem.id.
The problem with your data class is that you are overriding equals()/hashcode() without providing any implementation at all. This is effectively disabling the proper implementations that are provided by the data modifier by calling through to the super implementation in the Any class. You should not override them at all when you use data class.

How does Data binding bind data?

I'm trying to figure out how Data Binding works with RecyclerView.
I've got Sound objects that have names. I bind these objects to ViewHolders and somehow, these names are displayed on the items of my RecyclerView list.
Here is the code (not mine, I took it from a book)
Layout File:
<layout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">
<data>
<variable
name="viewModel"
type="ru.vsevolod.zimin.beatbox.SoundViewModel"/>
</data>
<Button
android:layout_height="120dp"
android:text="#{viewModel.title}"
android:layout_marginStart="5dp"
android:layout_marginEnd="5dp"
android:layout_width="match_parent"
tools:text="Sound Button"/>
</layout>
MainActivity:
class MainActivity : AppCompatActivity() {
private lateinit var beatBox: BeatBox
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
beatBox = BeatBox(assets)
beatBox.loadSounds()
val binding: ActivityMainBinding =
DataBindingUtil.setContentView(this, R.layout.activity_main)
binding.recyclerViewie.apply {
layoutManager = LinearLayoutManager(this#MainActivity)
adapter = SoundAdapter()
}
}
private inner class SoundHolder (val binding: ListItemSoundBinding):
RecyclerView.ViewHolder(binding.root) {
init {
binding.viewModel = SoundViewModel()
}
fun bind(sound: Sound) {
binding.viewModel?.sound = sound
}
}
private inner class SoundAdapter: RecyclerView.Adapter<SoundHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SoundHolder {
val binding = DataBindingUtil.inflate<ListItemSoundBinding> (layoutInflater,
R.layout.list_item_sound, parent, false)
return SoundHolder(binding)
}
override fun onBindViewHolder(holder: SoundHolder, position: Int) {
val sound = beatBox.sounds[position]
holder.bind(sound)
}
override fun getItemCount(): Int {
return beatBox.sounds.size
}
}
}
BeatBox (creates and contains the list of Sound objects that are going to be bound to the ViewHolders):
private const val SOUNDS_FOLDER = "sample_sounds"
class BeatBox(private val assets: AssetManager) {
val sounds: List<Sound>
init {
sounds = loadSounds()
}
fun loadSounds(): List<Sound> {
val soundNames: Array<String>
try {
soundNames = assets.list(SOUNDS_FOLDER)!!
}catch(e: Exception){
Log.e(TAG, "Couldn't list assets",e)
return emptyList()
}
val sounds = mutableListOf<Sound>()
soundNames.forEach {
val sound = Sound(it)
sounds.add(sound)
}
return sounds
}
}
Sound (class for Sound objects):
class Sound(val name: String)
SoundViewModel:
class SoundViewModel: BaseObservable() {
var sound: Sound? = null
set(sound) {
field = sound
notifyChange()
}
#get : Bindable
var title: String? = null
get() = sound?.name
}
What I fail to understand is how exactly the titles of the Sound objects are hooked up to the ViewHolders. I also noticed that when I remove the getter from SoundViewModel like that:
Before:
#get : Bindable
var title: String? = null
get() = sound?.name
After:
#get : Bindable
var title = sound?.name
...the titles are no longer bound and I end up with a nameless list.
Could you please explain how this happens?
Thank you in advance!

RecyclerView binding with LiveData displaying wrong values after item is removed

I'm using a RecyclerView with LiveData and databinding. The user can remove elements from the recyclerview, and sometimes, after an item is removed, the items in the list are reordered incorrectly and the wrong item is removed.
In printing the values in LogCat, the correct values/order are always printed, so it's somewhere in the display/binding that the items are getting (I believe) recycled improperly, but I haven't been able to resolve it.
Here's what I'm working with: Fragment, ViewModel, ItemPresenter, Adapter, list_item.xml
Below are what I believe to be the relevant parts of each file:
Fragment
viewModel
.personalFilesLiveData
.observe(viewLifecycleOwner, Observer {
personalFilesAdapter.bind(it)
if(personalFilesAdapter.itemCount == 0){
this.activity?.findViewById<ConstraintLayout>(R.id.no_results_container)?.visibility = View.VISIBLE
}
else{
this.activity?.findViewById<ConstraintLayout>(R.id.no_results_container)?.visibility = View.GONE
}
})
Presenter
class ItemPresenter(
private val openContentAction: (String) -> Unit,
private val removePersonalFileAction: (String) -> Unit) {
private lateinit var myPersonalFile: MyPersonalFileData
val name get() = myPersonalFile.name
val fileName get() = myPersonalFile.fileName
val month get() = myPersonalFile.monthDay
val year get() = myPersonalFile.year
fun bind(file: MyPersonalFileData) {
Log.d("MyFilesPersonalFileItemPresenter", "name: " + file.name)
this.myPersonalFile = file
}
fun contentClicked() {
openContentAction(myPersonalFile.contentId)
}
fun removeClicked() {
removePersonalFileAction(myPersonalFile.contentId)
}
}
Adapter
class Adapter(
private val openContentAction: (String) -> Unit,
private val removePersonalFileAction: (String) -> Unit
) : RecyclerView.Adapter<DataboundViewHolder<ViewMyPersonalFilesItemBinding>>() {
private var data = emptyList<MyPersonalFileData>()
fun bind(data: List<MyPersonalFileData>) {
val diff = RecyclerViewDiffHelper.simpleDiffUtil(this.data, data) {
first, second -> first.contentId == second.contentId
}
this.data = data
diff.dispatchUpdatesTo(this)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DataboundViewHolder<ViewMyPersonalFilesItemBinding> {
return DataboundViewHolder(
ViewMyPersonalFilesItemBinding.inflate(LayoutInflater.from(parent.context), parent, false).apply {
presenter = MyFilesPersonalFileItemPresenter(openContentAction, removePersonalFileAction)
}
)
}
override fun getItemCount() = data.count()
override fun onBindViewHolder(holder: DataboundViewHolder<ViewMyPersonalFilesItemBinding>, position: Int) {
AlternateBackgroundHelper.setBackground(holder.binding.root, position)
holder.binding.presenter?.bind(data[position])
}
}
class MyPersonalFileData(
val name: String,
val fileName: String,
val monthDay: String,
val year: String,
val contentId: String
) {
override fun toString(): String {
return "MyPersonalFileData(name='$name')"
}
}
list_item.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<variable
name="presenter"
type="com.storyslab.helper.myfiles.bookmarks.MyFilesBookmarkItemPresenter" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="80dp"
android:onClick="#{() -> presenter.contentClicked()}"
android:foreground="?selectableItemBackground"
tools:background="#313131">
<TextView
android:id="#+id/tv_content_name"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:textColor="#android:color/white"
android:textStyle="bold"
android:text="#{presenter.name}"
app:fontFamily="#font/oswald_regular"
app:layout_constraintVertical_chainStyle="packed"
app:layout_constraintEnd_toStartOf="#id/tv_date_top_line"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintBottom_toTopOf="#id/tv_file_name"
tools:text="Content Name" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
Any ideas?

I think the problem lies within this portion of your code in the adapter:
private var data = emptyList<MyPersonalFileData>()
fun bind(data: List<MyPersonalFileData>) {
val diff = RecyclerViewDiffHelper.simpleDiffUtil(this.data, data) {
first, second -> first.contentId == second.contentId
}
this.data = data // PROBLEM HERE!
diff.dispatchUpdatesTo(this)
}
You're replacing the main list of the adapter with the list that comes from your activity/fragment. In my opinion, we should never expose the same list reference to the adapter this way. Doing this may cause unexpected results like the one you're facing here.
Try like this and your problem should be resolved:
private val data = mutableListOf<MyPersonalFileData>()
fun bind(data: List<MyPersonalFileData>) {
val diff = RecyclerViewDiffHelper.simpleDiffUtil(this.data, data) {
first, second -> first.contentId == second.contentId
}
this.data.clear()
this.data.addAll(data)
diff.dispatchUpdatesTo(this)
}

Give it a try. Just replace the bind method and the data list with the following list.
private val differ = AsyncListDiffer(this, DIFF_CALLBACK)
fun bind(newList: List<Operator>) {
differ.submitList(newList)
}
companion object {
private val DIFF_CALLBACK = object : DiffUtil.ItemCallback<Operator>() {
override fun areItemsTheSame(oldItem: MyPersonalFileData, newItem: MyPersonalFileData): Boolean =
oldItem.contentId == newItem.contentId
override fun areContentsTheSame(oldItem: Operator, newItem: Operator): Boolean {
return oldItem == newItem
}
}
}

Room Data doesn't show in the RecyclerList

It's first time using Room Data while also using MVVM pattern. The aim is that I want my data to appeard on the RecyclerList but it's doesn't shut down nor shows me any error it's just appears empty.
Here is my Database class:
#Database(entities = [Plant::class, Plant_Category::class], version = 1)
abstract class PlantDatabase:RoomDatabase() {
abstract fun plantDao(): PlantOperations
abstract fun plantCategoryDao(): PlantCategoryOperations
companion object {
private var INSTANCE: PlantDatabase? = null
fun getDatabase(context: Context): PlantDatabase {
if (INSTANCE == null) {
INSTANCE = Room.databaseBuilder(
context.applicationContext,
PlantDatabase::class.java, DB_NAME // contains directory of sqlite database
)
.fallbackToDestructiveMigration()
.build()
}
return INSTANCE!!
}
}
}
My dao class:
#Dao
interface PlantOperations {
#Query("SELECT * FROM Plant")
fun getAll(): Flow<List<Plant>>
#Insert
fun insertPlant( plant: Plant)
#Delete
fun delete(plant:Plant)
#Update
fun updatePlant(plant:Plant)}
This is my repository class:
class PlantRepository(application:Application){
private var allPlants = MutableLiveData<List<Plant>>()
private val plantDAO = PlantDatabase.getDatabase(application).plantDao()
init {
CoroutineScope(Dispatchers.IO).launch {
val plantData = plantDAO.getAll()
plantData.collect{
allPlants.postValue(it)
}
}
}
fun getAllPlants(): MutableLiveData<List<Plant>> {
return allPlants
}
}
My Viewmodel class:
class PlantViewModel(
application: Application
): AndroidViewModel(application) {
private var repository = PlantRepository(application)
private var _allPlants = repository.getAllPlants()
val allPlants: MutableLiveData<List<Plant>>
get() = _allPlants
}
My Recycler in Fragment:
override fun onCreateView(inflater: LayoutInflater,
container: ViewGroup?, savedInstanceState: Bundle?): View? {
lateinit var photoAdapter: Photo_Adapter
lateinit var plantViewModel: PlantViewModel
val view: View = inflater.inflate(R.layout.fragment_edit__form, container, false)
val fab = view.findViewById(R.id.floatingActionButton) as FloatingActionButton
val recyclerView = view.findViewById(R.id.recyclerView) as RecyclerView
recyclerView.layoutManager = GridLayoutManager(context, 2)
photoAdapter = Photo_Adapter(context)
recyclerView.adapter = photoAdapter
plantViewModel = ViewModelProvider(this).get(PlantViewModel::class.java)
plantViewModel.allPlants.observe(viewLifecycleOwner, androidx.lifecycle.Observer {
photoAdapter.setDataList(it)
})
// photoAdapter.setDataList(dataList)
//Floating button that opens the Form in order to add plant
fab?.setOnClickListener {
val intent = Intent(view.context, Edit_Form::class.java)
startActivity(intent);
}
return view
}
This is my adapter class:
class Photo_Adapter(var context: Context?) : RecyclerView.Adapter<Photo_Adapter.ViewHolder>() {
var dataList = emptyList<Plant>()
internal fun setDataList(dataList: List<Plant>) {
this.dataList = dataList
notifyDataSetChanged()
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
// Get the data model based on position
var data = dataList[position]
holder.title.text = data.name
holder.desc.text = data.type.toString()
holder.image.setImageResource(data.image)
holder.relativeLayout.setOnClickListener { view -> //Toast.makeText(view.getContext(),"click on item: "+model.getTitle(),Toast.LENGTH_LONG).show();
val intent = Intent(view.context, PlantDetails::class.java)
intent.putExtra("plant_name", data.name)
intent.putExtra("plant_image",data.image)
intent.putExtra("plant_type", data.type.type)
intent.putExtra("plant_water", data.type.water_time)
intent.putExtra("plant_details", data.type.details)
view.context.startActivity(intent)
}
}
// Provide a direct reference to each of the views with data items
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
var image: ImageView
var title: TextView
var desc: TextView
var relativeLayout: CardView
init {
image = itemView.findViewById(R.id.image)
title = itemView.findViewById(R.id.title)
desc = itemView.findViewById(R.id.desc)
relativeLayout = itemView.findViewById<View>(R.id.relativeLayout) as CardView
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): Photo_Adapter.ViewHolder {
// Inflate the custom layout
var view = LayoutInflater.from(parent.context).inflate(R.layout.photo_layout, parent, false)
return ViewHolder(view)
}
// total count of items in the list
override fun getItemCount() = dataList.size
}
Perhaps I forgot to add something? In Anyway I will be grateful for your help.

You should not observe data on your repository, your activity/view should observe this data. Take a look at this:
First, add this dependency to your gradle:
implementation "androidx.lifecycle:lifecycle-livedata-ktx:2.3.1"
Then in your repository
class PlantRepository(application:Application){
private val plantDAO = PlantDatabase.getDatabase(application).plantDao()
fun getAllPlants(): Flow<List<Plant>> = plantDAO.getAll()
}
In your view model:
class PlantViewModel(
application: Application
): AndroidViewModel(application) {
private var repository = PlantRepository(application)
val allPlants = repository.getAllPlants()
.flowOn(Dispatchers.IO)
.asLiveData()
}
And your activity is fine, but check your adapter, make sure that you're notifing your adapter that your list has changed.
You can also work (collect) flows on your view, but this depends on you

Can't populate a recycler using a collection

I want each row of my RecyclerView to display all the details of one document of the collection.
I've used this exact same adapter code, albeit with a different class to serialize into. And it works well. But in this instance, it's simply not working.
But the code just doesn't get into populating the views.
My database is like:
reviews--Orange--vault--|
|-firstReview
|-secondReview
|-sjdeifhaih5aseoi
...
My query and adapter from the fragment:
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
viewModel = ViewModelProviders.of(this).get(ReviewViewModel::class.java)
val reviewQuery = FirebaseFirestore.getInstance().collection("reviews").document("Orange").collection("vault")
val reviewBurnOptions = FirestoreRecyclerOptions.Builder<Review>()
.setQuery(reviewQuery, object : SnapshotParser<Review> {
override fun parseSnapshot(snapshot: DocumentSnapshot): Review {
return snapshot.toObject(Review::class.java)!!.also {
it.id = snapshot.id
}
}
}).setLifecycleOwner(this)
reviewRecycler.adapter=ReviewBurnAdapter(reviewBurnOptions.build())}
class ReviewBurnAdapter(options: FirestoreRecyclerOptions<Review>) :
FirestoreRecyclerAdapter<Review, ReviewBurnAdapter.ViewHolder>(options) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {//I never reach this point
val view = LayoutInflater.from(parent.context).inflate(R.layout.row_review, parent, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int, item: Review) {
holder.apply {
holder.itemView.rowAuthor.text = item.author
}
}
inner class ViewHolder(override val containerView: View) :
RecyclerView.ViewHolder(containerView), LayoutContainer
}
Class to serialize into:
import com.google.firebase.firestore.Exclude
import com.google.firebase.firestore.PropertyName
import java.util.*
class Review(
#get:Exclude var id: String = "DEVIL",
#JvmField #PropertyName(AUTHOR) var author: String = "",
#JvmField #PropertyName(WRITEUP) var writeup: String = "",
//#JvmField #PropertyName(MOMENT) var moment:Date=Date(1997,12,1),
#JvmField #PropertyName(RATING) var rating: Int = 0
) {
companion object {
const val AUTHOR = "author"
const val WRITEUP = "writeup"
const val RATING = "rating"
//const val MOMENT="moment"
}
}
Also, there's no errors, it just never reaches the code that would generate and populate with viewHolders.

Alright, the fix was ultra simple, as #Prashant Jha pointed out, I hadn't specified a layout manager for my RecyclerView -_-
To be crystal clear, I added app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
to my xml, and everything worked.