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How to display JSON data from Horizontal recycle view kotlin using MVP method

I hope is all well with you.
I have constructed my code and build according the MVP style as well pulling JSON data but when I run the the code the horizontal recycle view and the JSON data is not being displayed. I tried going through every line of code and watching other tutorials but still no results.
Here is below my main activity:
class ProductCategoryActivity : BaseMvpActivity<ProductCategoryActivityView, ProductCategoryActivityPresnter> (),
ProductCategoryActivityView, CategoryAdapter.onItemClickListener{
private lateinit var binding: FragmentProductCategoryBinding
val data :MutableList<CateogryResponse> = ArrayList()
val adapter= CategoryAdapter(data, this)
#Inject
lateinit var presenter: ProductCategoryActivityPresnter
#Inject
lateinit var progressDialog: ProgressDialog
override fun onCreateComponent() {
userComponent.plus(CategoryActivityModule(this)).inject(this)
}
override fun providePresenter(): ProductCategoryActivityPresnter {
return presenter
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = FragmentProductCategoryBinding.inflate(layoutInflater)
val view = binding.root
setContentView(view)
presenter.fetchcatogries()
showdata(ArrayList())
}
override fun showError(message: String) {
}
override fun showProgress() {
}
override fun hideProgress() {
}
override fun showdata(data: ArrayList<CateogryResponse>) {
val layoutManager = LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false)
recyclerViewPrimary.layoutManager = layoutManager
recyclerViewPrimary.setHasFixedSize(true)
recyclerViewPrimary.adapter = adapter
for(i in data)
data.add(CateogryResponse("product"))
}
override fun onItemClick(position: Int) {
Toast.makeText(this, "Item $position clicked", Toast.LENGTH_SHORT).show()
val clickedItem = data[position]
adapter.notifyItemChanged(position)
}
}
Here is my presenter:
#ActivityScope
class ProductCategoryActivityPresnter #Inject constructor(
private val stringProvider: StringProvider,
#AndroidScheduler private val observeOnScheduler: Scheduler,
#IOScheduler private val subscribeOnScheduler: Scheduler,
private val getCategoryUseCase: CategoryUseCase
) : BasePresenter<ProductCategoryActivityView>() {
lateinit var catogriesservice: CategoryRepositoryImpl
val catogriesLoadError = MutableLiveData<Boolean>()
val loading = MutableLiveData<Boolean>()
var catogries: ArrayList<CateogryResponse> = arrayListOf()
override fun onCreatePresenter(savedInstanceState: Bundle?) {
}
override fun onSaveInstanceState(outState: Bundle?) {
}
override fun onLoadData(arguments: Bundle?) {
fetchcatogries()
}
fun fetchcatogries() {
getCategoryUseCase.execute()
.observeOn(observeOnScheduler)
.subscribeOn(subscribeOnScheduler)
.subscribe(
SingleRequestSubscriber(
{
it
if (it != null && it.size > 0) {
catogries.removeAll(catogries)
catogries.addAll(it)
}
},
onFailure = { appException ->
view?.showError(
ErrorHandler.getErrorMessage(
appException,
stringProvider
)
)
},
onApiError = { apiException ->
view?.showError(
ErrorHandler.getErrorMessage(
apiException,
stringProvider
)
)
},
onAuthenticationError = { requestxception ->
view?.showError(
ErrorHandler.getErrorMessage(
requestxception,
stringProvider
)
)
},
onShowProgress = {
if (it) {
view?.showProgress()
} else {
view?.hideProgress()
}
},
onSubscribed = {
disposable.add(it)
})
)
}
}
Here is my view:
interface ProductCategoryActivityView {
fun showError(message: String)
fun showProgress()
fun hideProgress()
fun showdata ( data: ArrayList<CateogryResponse>)
}
Here is my adapter:
class CategoryAdapter(
private val data: List<CateogryResponse>,
private val listener: onItemClickListener
) : RecyclerView.Adapter<CategoryAdapter.ViewHolder>() {
private val items: MutableList<CardView>
init {
this.items = ArrayList()
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val v = LayoutInflater.from(parent.context)
.inflate(R.layout.fragment_category_adapter, parent, false)
return ViewHolder(v)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.tvTitle.text = data[position].product
items.add(holder.card)
}
override fun getItemCount(): Int {
return data.size
}
inner class ViewHolder(itemView: View
) : RecyclerView.ViewHolder(itemView),
View.OnClickListener {
val tvTitle: TextView = itemView.featured_title
val card: CardView = itemView.CardView
init {
itemView.setOnClickListener(this)
}
override fun onClick(v: View?) {
val position: Int = adapterPosition
if (position != RecyclerView.NO_POSITION) {
listener.onItemClick(position)
}
}
}
interface onItemClickListener {
fun onItemClick(position: Int)
}
}
Image:
Fragment Category Adapter:
android:id="#+id/CardView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="10dp"
app:cardCornerRadius="2dp"
app:cardElevation="8dp">
<!-- We Will Add here the card & ImageViews -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="15dp">
<ImageView
android:id="#+id/featured_image"
android:layout_width="match_parent"
android:layout_height="140dp"
android:scaleType="centerCrop" />
<TextView
android:id="#+id/featured_title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:lineHeight="23dp"
android:text="Chairs"
android:textColor="#color/colorAccent"
android:textSize="20sp" />
<TextView
android:id="#+id/featured_desc"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="asbkd asudhlasn saudnas jasdjasl hisajdl asjdlnas" />
</LinearLayout>
</androidx.cardview.widget.CardView>
Fragment Product Category:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#fafcfe"
tools:context="ui.category.ProductCategoryActivity">
<ImageView
android:id="#+id/imageView3"
android:layout_width="0dp"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
/>
<ImageView
android:id="#+id/imageView"
android:layout_width="wrap_content"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/constraintLayout"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="32dp"
android:layout_marginTop="48dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="#+id/imageView"
app:layout_constraintTop_toTopOf="parent">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerViewPrimary"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
<TextView
android:id="#+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="48dp"
android:layout_marginTop="20dp"
android:text="#string/topselling"
android:textSize="18sp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/constraintLayout" />
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/constraintLayout2"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginStart="32dp"
android:layout_marginLeft="32dp"
android:layout_marginTop="16dp"
app:layout_constraintBottom_toTopOf="#+id/imageView3"
app:layout_constraintEnd_toEndOf="#+id/constraintLayout"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/textView">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerViewSecondary"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
<ImageView
android:id="#+id/imageView4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="32dp"
app:layout_constraintBottom_toBottomOf="#+id/imageView3"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.498"
app:layout_constraintStart_toStartOf="parent"
/>
<TextView
android:id="#+id/textViewCategories"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="48dp"
android:layout_marginTop="20dp"
android:layout_marginBottom="15dp"
android:text="#string/catogries"
android:textSize="18sp"
app:layout_constraintBottom_toTopOf="#+id/constraintLayout"
app:layout_constraintStart_toStartOf="parent"
tools:layout_editor_absoluteX="39dp" />
</androidx.constraintlayout.widget.ConstraintLayout>
Not sure what went wrong.
If someone can point it out or show me what needs to be done to be able to display the data in horzintal recycle view, I would be really thanlful

You should update your recycler view adapter once your fetch call is executed, not before it ends.
Modify your fetchcatogries declaration so it accepts a callback method, which will be executed after the data are loaded.
This method will accept a list object as a parameter, which you will manage in your ProductCategoryActivity to populate the RecyclerView.
fun fetchcatogries(callback: (MutableList<CateogryResponse>) -> Unit) {
getCategoryUseCase.execute()
.observeOn(observeOnScheduler)
.subscribeOn(subscribeOnScheduler)
.subscribe(
SingleRequestSubscriber(
{ categories ->
callback(categories)
},
...
)
}
You can now edit your onCreate and showdata methods in ProductCategoryActivity like this:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = FragmentProductCategoryBinding.inflate(layoutInflater)
val view = binding.root
setContentView(view)
presenter.fetchcatogries { categories ->
showdata(categories as ArrayList<CateogryResponse>)
}
}
override fun showdata(data: ArrayList<CateogryResponse>) {
val layoutManager = LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false)
recyclerViewPrimary.layoutManager = layoutManager
recyclerViewPrimary.setHasFixedSize(true)
recyclerViewPrimary.adapter = CategoryAdapter(data.toList(), this)
}

How can I update the UI without skipping frames

So I am developing and android app in Kotlin with coroutines and no matter what change I make, I still keep getting the message:
I/Choreographer: Skipped 59 frames! The application may be doing too much work on its main thread.
How can I get rid of it. I mean like I am only displaying nine photos... Below is my code
Model:
data class Food (
val id: String,
val name: String,
val price: String,
#Json(name = "img_url") val imgSrcUrl: String,
val type: String,
val description: String,
val average_rating: String,
val number_of_raters: String,
val special_price: String
)
data class FoodCategory(
val id: String,
val title: String,
val foods: List<Food>
)
ViewModel:
enum class NetworkStatus {LOADING, DONE, FAILED}
enum class FontFamily (#FontRes val fontRes: Int) {
POPPINS_BOLD(R.font.poppins_bold),
POPPINS(R.font.poppins)
}
class FoodOverviewViewModel(private val foodRepository: FoodRepository): ViewModel() {
private lateinit var foodProducts: List<Food>
//This is the data that is gonna be exposed to the viewmodel
//It will be submitted to a ListAdapter
private val _foodCategory = MutableLiveData<List<FoodCategory>>()
val foodCategory: LiveData<List<FoodCategory>>
get() = _foodCategory
//Used to display a progress bar for network status
private val _status = MutableLiveData<NetworkStatus>()
val status: LiveData<NetworkStatus>
get() = _status
init {
getOverviewProducts()
}
private fun getOverviewProducts() {
viewModelScope.launch(Dispatchers.Default) {
_status.postValue(NetworkStatus.LOADING)
try {
getUpdatedFood()
Log.i("getOverviewProducts","I am running on tread: $coroutineContext")
_status.postValue(NetworkStatus.DONE)
}catch (e: Exception) {
_status.postValue(NetworkStatus.FAILED)
}
}
}
private suspend fun getUpdatedFood() {
//withContext(Dispatchers.Default) {
val limiter = 6 //Number of items I want to get from the server
val foodCategory = arrayListOf<FoodCategory>()
Log.i("getUpdatedFood","I am running on tread: $coroutineContext")
val getRecommended = foodRepository.getRecommendedFood(limiter.toString())
foodCategory += FoodCategory(id = 0.toString(), title = "Recommended for you", foods = getRecommended)
val getSpecials = foodRepository.getSpecials(limiter.toString())
foodCategory += FoodCategory(id = 1.toString(), title = "Specials", foods = getSpecials)
_foodCategory.postValue(foodCategory)
//}
}
}
Repository:
class FoodRepository {
suspend fun getRecommendedFood(limiter: String) = withContext(Dispatchers.IO) {
Log.i("Resp-getRecommended","I am running on tread: $coroutineContext")
return#withContext ProductApi.retrofitService.getRecommended(limiter)
}
suspend fun getSpecials(limiter: String) = withContext(Dispatchers.IO) {
Log.i("Resp-getSpecials","I am running on tread: $coroutineContext")
return#withContext ProductApi.retrofitService.getSpecials(limiter)
}
}
BindingAdapters:
//Load image using Glide (in Food item recycleview)
#BindingAdapter("imageUrl")
fun bindImage(imgView: ImageView , imgUrl: String?) {
imgUrl?.let {
val imgUri = imgUrl.toUri().buildUpon().scheme("http").build()
Glide.with(imgView.context)
.load(imgUri)
.apply(
RequestOptions()
.placeholder(R.drawable.loading_animation)
.error(R.drawable.ic_broken_image))
.into(imgView)
}
}
//set raters count (in Food item recycleview)
#BindingAdapter("ratersCount")
fun bindText(txtView: TextView, number_of_raters: String?) {
number_of_raters?.let {
val ratersCount = "(${number_of_raters})"
txtView.text = ratersCount
}
}
//update the progressbar visibilty (in outer-parent recycleview)
#BindingAdapter("updateStatus")
fun ProgressBar.updateStatus(status: NetworkStatus?) {
visibility = when (status) {
NetworkStatus.LOADING -> View.VISIBLE
NetworkStatus.DONE -> View.GONE
else -> View.GONE
}
}
//Hide or view an imageview based in the network Status. When network Error, an error image
//will show (in outer-parent recycleview)
#BindingAdapter("setNoInternet")
fun ImageView.setNoInternet(status: NetworkStatus?) {
when(status) {
NetworkStatus.LOADING -> {
visibility = View.GONE
}
NetworkStatus.DONE -> {
visibility = View.GONE
}
NetworkStatus.FAILED -> {
visibility = View.VISIBLE
setImageResource(R.drawable.ic_connection_error)
}
}
}
//Submit the list of FoodCatergory item to the outer-parent recycleview
#BindingAdapter("listData")
fun bindRecyclerView(recyclerView: RecyclerView, data: List<FoodCategory>?) {
(recyclerView.adapter as FoodCategoryAdapter).submitList(data)
}
//Submit list the the Food item recyclew view (child recycleView)
#BindingAdapter("setProducts")
fun RecyclerView.setProducts(foods: List<Food>?) {
if (foods != null) {
val foodAdapter = FoodItemAdapter()
foodAdapter.submitList(foods)
adapter = foodAdapter
}
}
I have a Recycleview of Food Item and a Recycleview Pool of FoodCategory. If I comment out
_foodCategory.postValue(foodCategory)
in ViewModel: getUpdatedFood() than I do not get the message. However, when I submit the list to the outer recycleview (The one the hold the viewpool), than I get this answer. Please help. I been stuck on it for a while tryna get rid of that message.
Thank you..
Updated
Below is the adapeters and its view holders
FoodItem layout
<layout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<import type="android.view.View"/>
<variable
name="foodItem"
type="com.example.e_commerceapp.models.Food"/>
<variable
name="font"
type="com.example.e_commerceapp.products.overview.FontFamily"/>
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/child_item_main_layout"
android:background="#drawable/search_background"
android:layout_marginTop="10dp"
android:layout_marginStart="10dp"
android:layout_marginBottom="10dp"
android:layout_width="150dp"
android:layout_height="250dp">
<ImageView
android:layout_width="120dp"
android:layout_marginStart="10dp"
android:layout_marginEnd="10dp"
android:id="#+id/burger_image"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
android:layout_height="160dp"
/>
<!-- app:imageUrl="#{foodItem.imgSrcUrl}"-->
<TextView
android:layout_width="match_parent"
android:layout_height="34dp"
android:layout_marginStart="5dp"
android:id="#+id/burger_title"
app:layout_constraintStart_toStartOf="parent"
android:layout_marginEnd="5dp"
android:singleLine="true"
android:textColor="#B4000000"
app:layout_constraintTop_toBottomOf="#id/burger_image"
android:text="#{foodItem.name}"
android:textSize="12sp"
android:fontFamily="#font/poppins"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="35dp"
app:layout_constraintTop_toBottomOf="#id/burger_title"
android:layout_marginEnd="5dp"
android:gravity="center"
android:id="#+id/burger_price"
android:layout_marginStart="5dp"
app:layout_constraintStart_toEndOf="#id/special_price"
android:textColor="#D0000000"/>
<!-- app:price="#{foodItem.price}"-->
<!-- app:specialPrice="#{foodItem.special_price}"-->
<!-- app:fontRes="#{foodItem.special ? font.POPPINS : font.POPPINS_BOLD}"-->
<TextView
android:layout_width="wrap_content"
android:layout_height="35dp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#id/burger_title"
android:layout_marginEnd="5dp"
android:gravity="center_vertical"
android:layout_marginStart="5dp"
android:id="#+id/special_price"
android:textColor="#D0000000"
android:visibility="gone"
android:textStyle="normal"
android:fontFamily="#font/poppins_bold"/>
<!-- app:setSpecialPrice="#{foodItem.special_price}"-->
<ImageView
android:layout_width="15dp"
android:layout_height="15dp"
app:layout_constraintTop_toBottomOf="#id/burger_price"
android:src="#drawable/ic_baseline_star_24"
android:visibility="#{foodItem.hasRating ? View.GONE : View.VISIBLE}"
android:id="#+id/rating_star"
app:layout_constraintStart_toStartOf="parent"
android:layout_marginStart="5dp"
android:layout_marginBottom="10dp"
app:layout_constraintBottom_toBottomOf="parent"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="15dp"
android:layout_marginStart="5dp"
android:gravity="center"
android:textSize="12sp"
android:visibility="#{foodItem.hasRating ? View.GONE : View.VISIBLE}"
android:id="#+id/rating_count"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintTop_toBottomOf="#id/burger_price"
android:text="#{foodItem.average_rating}"
android:layout_marginBottom="10dp"
app:layout_constraintStart_toEndOf="#id/rating_star"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="15dp"
android:id="#+id/number_of_raters"
android:textSize="12sp"
android:visibility="#{foodItem.hasRating ? View.GONE : View.VISIBLE}"
android:layout_marginStart="2dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toEndOf="#id/rating_count"
app:ratersCount="#{foodItem.number_of_raters}"
android:layout_marginBottom="10dp"
app:layout_constraintTop_toBottomOf="#id/burger_price"/>
<ImageView android:layout_width="20dp"
android:layout_height="20dp"
android:layout_marginEnd="10dp"
android:layout_marginTop="10dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
FoodItem Adapter
class FoodItemAdapter: ListAdapter<Food ,
FoodItemAdapter.ItemFoodViewHolder>(DiffCallback) {
override fun onCreateViewHolder(parent: ViewGroup , viewType: Int): ItemFoodViewHolder {
return ItemFoodViewHolder(
FoodItemBinding.inflate(LayoutInflater.from(parent.context),
parent, false))
}
override fun onBindViewHolder(holder: ItemFoodViewHolder , position: Int) {
val currentFood = getItem(position)
holder.bind(currentFood)
}
class ItemFoodViewHolder(private var binding: FoodItemBinding): RecyclerView.ViewHolder(binding.root) {
fun bind(food: Food) {
binding.foodItem = food
binding.executePendingBindings()
}
}
object DiffCallback: DiffUtil.ItemCallback<Food>() {
override fun areItemsTheSame(oldItem: Food , newItem: Food): Boolean {
return oldItem === newItem
}
override fun areContentsTheSame(oldItem: Food , newItem: Food): Boolean {
return oldItem.id == newItem.id
}
}
}
FoodCategory layout
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<data>
<variable
name="foodCategory"
type="com.example.e_commerceapp.models.FoodCategory"/>
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:background="#fff"
android:layout_marginTop="5dp"
android:layout_marginBottom="5dp"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:id="#+id/category_title"
android:layout_marginTop="16dp"
android:text="#{foodCategory.title}"
android:textColor="#2B2A2A"
android:fontFamily="#font/poppins_bold"
android:textSize="16sp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/nestedRecyclerView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="4dp"
app:setProducts="#{foodCategory.foods}"
android:orientation="horizontal"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/category_title"
tools:itemCount="4"
tools:listitem="#layout/food_item"/>
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
FoodCategory Adapter
class FoodCategoryAdapter: ListAdapter<FoodCategory,
FoodCategoryAdapter.CategoryFoodViewHolder>(Companion) {
private val viewPool = RecyclerView.RecycledViewPool()
override fun onCreateViewHolder(parent: ViewGroup , viewType: Int): CategoryFoodViewHolder {
return CategoryFoodViewHolder(FoodCategoryBinding.inflate(LayoutInflater.from(parent.context),
parent, false))
}
override fun onBindViewHolder(holder: CategoryFoodViewHolder , position: Int) {
val currentFoodCategory = getItem(position)
holder.bind(currentFoodCategory)
}
inner class CategoryFoodViewHolder(private var binding: FoodCategoryBinding): RecyclerView.ViewHolder(binding.root) {
fun bind(currentFoodCategory: FoodCategory?) {
binding.foodCategory = currentFoodCategory
binding.nestedRecyclerView.setRecycledViewPool(viewPool)
binding.executePendingBindings()
}
}
companion object: DiffUtil.ItemCallback<FoodCategory>() {
override fun areItemsTheSame(oldItem: FoodCategory , newItem: FoodCategory): Boolean {
return oldItem === newItem
}
override fun areContentsTheSame(oldItem: FoodCategory, newItem: FoodCategory): Boolean {
return oldItem.id == newItem.id
}
}
}
The parent recycleView
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
tools:context=".products.overview.FoodOverviewFragment">
<data>
<variable
name="foodOverview"
type="com.example.e_commerceapp.products.overview.FoodOverviewViewModel"/>
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:background="#color/grey"
android:layout_width="match_parent"
android:layout_height="match_parent">
<RelativeLayout
android:layout_width="match_parent"
android:id="#+id/relative_layout"
android:layout_height="105dp"
android:elevation="8dp"
android:layout_marginBottom="5dp"
android:background="#fff"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintEnd_toEndOf="parent">
<ImageView
android:layout_width="200dp"
android:layout_marginTop="10dp"
android:layout_height="35dp"
android:id="#+id/logo_and_name"
android:src="#drawable/compony_logo_and_name"
android:layout_alignParentStart="true"/>
<ImageView
android:layout_width="wrap_content"
android:layout_height="35dp"
android:layout_marginTop="10dp"
android:id="#+id/notifications"
android:src="#drawable/ic_baseline_notifications_24"
android:layout_alignParentEnd="true"
android:paddingEnd="20dp"
android:paddingStart="20dp"/>
<TextView
android:layout_width="match_parent"
android:id="#+id/search"
android:layout_marginTop="10dp"
android:layout_marginStart="20dp"
android:layout_marginEnd="20dp"
android:background="#drawable/search_background"
android:layout_below="#id/logo_and_name"
android:gravity="center_vertical"
android:layout_height="match_parent"
android:layout_marginBottom="10dp"
android:paddingEnd="10dp"
android:paddingStart="10dp"
android:text="#string/search_text"
tools:ignore="RtlSymmetry"
app:drawableEndCompat="#drawable/ic_baseline_search_24"/>
</RelativeLayout>
<ProgressBar
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:updateStatus="#{foodOverview.status}"
app:layout_constraintTop_toBottomOf="#id/relative_layout"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
android:id="#+id/progressbar"/>
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintTop_toBottomOf="#id/relative_layout"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
android:id="#+id/noInternetImage"/>
<androidx.recyclerview.widget.RecyclerView
android:layout_width="0dp"
android:id="#+id/foodCategory"
android:clipToPadding="false"
tools:itemCount="4"
tools:listitem="#layout/food_category"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
android:layout_height="0dp"
app:listData="#{foodOverview.foodCategory}"
app:layout_constraintTop_toBottomOf="#id/relative_layout"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintBottom_toBottomOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>

The skipping frames likely has nothing to do with the code you posted: it sounds like a misconfiguration of RecyclerViews / Adapters to me. You'll need to post that code for it be more clear though.
However, even though what you posted likely isn't the culprit you can still optimize the coroutines code you have:
class FoodOverviewViewModel(private val foodRepository: FoodRepository): ViewModel() {
private lateinit var foodProducts: List<Food>
private val _foodCategory = MutableLiveData<List<FoodCategory>>()
val foodCategory: LiveData<List<FoodCategory>>
get() = _foodCategory
private val _status = MutableLiveData<NetworkStatus>()
val status: LiveData<NetworkStatus>
get() = _status
init {
getOverviewProducts()
}
private fun getOverviewProducts() {
viewModelScope.launch { // <------- Don't apply a custom scope here
_status.value = NetworkStatus.LOADING // <--- Don't call "postValue" here
try {
val food = getUpdatedFood() // <------ This is already using a background dispatcher
_foodCategory.value = food // <------- Emit this value here
_status.value = NetworkStatus.DONE
} catch (e: Exception) {
_status.value = NetworkStatus.FAILED
}
}
}
private suspend fun getUpdatedFood(): List<FoodCategory> { // <---- Return a value here
val limiter = 6 //Number of items I want to get from the server
val foodCategory = arrayListOf<FoodCategory>()
Log.i("getUpdatedFood","I am running on tread: $coroutineContext")
val getRecommended = foodRepository.getRecommendedFood(limiter.toString())
foodCategory += FoodCategory(id = 0.toString(), title = "Recommended for you", foods = getRecommended)
val getSpecials = foodRepository.getSpecials(limiter.toString())
foodCategory += FoodCategory(id = 1.toString(), title = "Specials", foods = getSpecials)
return foodCategories
}
}
The key ideas here:
Use viewModelScope.launch { ... } rather than applying a scope. You want everything in there that is not a coroutine to run on the main thread. See, for example, https://developer.android.com/kotlin/coroutines/coroutines-best-practices#main-safe
Return a value from getUpdatedFood so you can just update the _foodCategory value on the main thread in the viewModelScope

How to update recycleView in android after deleting item in kotlin?

I have created a recycle view and inside that using card view for items. I have a delete button inside a card view whenever I click on that button my item is deleted from SQLite database. But to reflect it on UI, app need to restart. How can I notify adpater that item is deleted?
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:layout_width="57dp"
android:layout_height="64dp"
android:layout_marginEnd="40dp"
android:layout_marginBottom="40dp"
android:clickable="true"
android:onClick="addNewCredentials"
app:backgroundTint="#270867"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:srcCompat="#android:drawable/ic_menu_add" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginStart="1dp"
android:layout_marginTop="1dp"
android:layout_marginEnd="1dp"
android:layout_marginBottom="1dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0" >
</androidx.recyclerview.widget.RecyclerView>
</androidx.constraintlayout.widget.ConstraintLayout>
list_item_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="wrap_content">
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="5dp">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/urlView"
android:layout_width="300dp"
android:layout_height="30dp"
android:layout_marginTop="16dp"
android:layout_marginBottom="16dp"
android:text="url"
android:textAppearance="#style/TextAppearance.AppCompat.Large"
android:textSize="24sp"
android:textStyle="bold"
app:layout_constraintBottom_toTopOf="#+id/userNameView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.1"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="1.0" />
<TextView
android:id="#+id/userNameView"
android:layout_width="300dp"
android:layout_height="25dp"
android:layout_marginBottom="16dp"
android:text="userName"
app:layout_constraintBottom_toTopOf="#+id/passwordView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.1"
app:layout_constraintStart_toStartOf="parent" />
<TextView
android:id="#+id/passwordView"
android:layout_width="300dp"
android:layout_height="25dp"
android:layout_marginBottom="16dp"
android:text="password"
app:layout_constraintBottom_toTopOf="#+id/noteView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.1"
app:layout_constraintStart_toStartOf="parent" />
<TextView
android:id="#+id/noteView"
android:layout_width="300dp"
android:layout_height="30dp"
android:layout_marginBottom="16dp"
android:text="note"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.1"
app:layout_constraintStart_toStartOf="parent" />
<Button
android:id="#+id/delButton"
android:layout_width="78dp"
android:layout_height="40dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="36dp"
android:background="#E6360F"
android:text="#string/delete_credential_button"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.cardview.widget.CardView>
</LinearLayout>
MainActivity.kt
package com.example.passwordmanager
import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.Toast
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val recyclerView = findViewById<RecyclerView>(R.id.recyclerView)
recyclerView.layoutManager = LinearLayoutManager(this, RecyclerView.VERTICAL,false)
val db = DataBaseHandler(this)
val detailsData = db.readCredentials()
val adapter = CredentialAdapter(detailsData,this,{credentialsModel: CredentialsModel->deleteClick(credentialsModel)})
recyclerView.adapter = adapter
}
fun deleteClick(credential: CredentialsModel){
val db = DataBaseHandler(this)
if(db.deleteData(credential.id)){
//adapter.notifyItemRemoved(position)
Toast.makeText(applicationContext,"Deleted", Toast.LENGTH_SHORT).show()
}
}
fun addNewCredentials(view : View){
print("hello world")
val intent = Intent(this, AddDetailActivity::class.java)
intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
startActivity(intent)
}
}
CredentialAdapter.kt
package com.example.passwordmanager
import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import kotlinx.android.synthetic.main.list_item_layout.view.*
class CredentialAdapter(
private val items: List<CredentialsModel>,
ctx: Context, val clickListener: (CredentialsModel) -> Unit
): RecyclerView.Adapter<CredentialAdapter.ViewHolder>() {
var context = ctx
class ViewHolder(itemView: View):RecyclerView.ViewHolder(itemView){
fun bind(credential: CredentialsModel,clickListener: (CredentialsModel) -> Unit){
itemView.urlView.text = credential.url
itemView.userNameView.text = credential.userName
itemView.passwordView.text = credential.password
itemView.noteView.text = credential.note
itemView.delButton.setOnClickListener{clickListener(credential)}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
return ViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.list_item_layout,parent,false))
}
override fun getItemCount(): Int {
return items.size
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val credential:CredentialsModel = items[position]
holder.bind(credential,clickListener)
}
}

add remove setOnClickListener in your onBindViewHolder.
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.remove.setOnClickListener {
val db = DataBaseHandler(this)
if(db.deleteData(credential.id)){
notifyItemRemoved(holder.getAdapterPosition())
}
}
}

The best way to handle these kinds of situations is to use LiveData.
LiveData is basically an observable class which reads data only when there is a change.
What you can do is create a set function in your adapter like:
internal fun setData(data: List<Data>) {
this.data= dataList //this datalist is a list defined in your adapter
notifyDataSetChanged()
}
now in your main activity/fragment, create a LiveData List outside the onCreate function like this:
private lateinit var allData:LiveData<List<Data>>
Now inside your onCreate function, use can observe the livedata and set the data for recyclerview like this:
allData.observe(this, Observer { data->
data?.let { adapter.setData(it) }
})

You are deleting the item from database but not from the list inside recyclerview adapter.
class CredentialAdapter(
private val items: ArrayList<CredentialsModel>, // Change list to arraylist
ctx: Context, val clickListener: (CredentialsModel, Int) -> Unit
): RecyclerView.Adapter<CredentialAdapter.ViewHolder>() {
...
...
fun remove(position: Int) {
// Remove and notify the adapter to reload
items.removeAt(position)
notifyItemRemoved(position)
}
class ViewHolder(itemView: View):RecyclerView.ViewHolder(itemView) {
fun bind(credential: CredentialsModel,clickListener: (CredentialsModel, Int) -> Unit){
...
...
// Pass adapter item position so that we can update the list after delete
itemView.delButton.setOnClickListener{clickListener(credential, adapterPosition)
}
}
...
...
}
Inside MainActivity.kt
fun deleteClick(credential: CredentialsModel, position: Int) {
val db = DataBaseHandler(this)
if(db.deleteData(credential.id)){
adapter.remove(position)
Toast.makeText(applicationContext,"Deleted", Toast.LENGTH_SHORT).show()
}
}

use ListAdpater
class AdapterMain(var onClickListener: (Int) -> Unit) :
ListAdapter<Note, AdapterMain.NoteViewHolder>(DIFFCALBACK) {
companion object DIFFCALBACK : DiffUtil.ItemCallback<Note>() {
override fun areItemsTheSame(oldItem: Note, newItem: Note): Boolean {
return oldItem.id == newItem.id
}
override fun areContentsTheSame(oldItem: Note, newItem: Note): Boolean {
return oldItem.title == newItem.title &&
oldItem.description == newItem.description &&
oldItem.priority == newItem.priority
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): NoteViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.note_item, parent, false)
return NoteViewHolder(view)
}
override fun onBindViewHolder(holder: NoteViewHolder, position: Int) {
holder.txtTitle.text = getItem(position).title
holder.txtDesc.text = getItem(position).description
holder.txtPriority.text = getItem(position).priority.toString()
}
inner class NoteViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
var txtTitle: TextView = itemView.txt_title
var txtDesc: TextView = itemView.txt_desc
var txtPriority: TextView = itemView.txt_priority
init {
itemView.setOnClickListener { onClickListener(adapterPosition) }
}
}
fun getNoteAt(position: Int): Note {
return getItem(position)
}
}
you can see complete code of simple NoteApp with kotlin , recyclerView , MVVM and..

class coba : AppCompatActivity() {
private lateinit var recycleView :RecyclerView
private lateinit var datalis :ArrayList
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_coba)
recycleView = findViewById(R.id.rcycoba)
datalis = ArrayList()
val dtnama = arrayOf(
"Danial Sanganus",
"Bijonia Skolin",
"Alianes Pertoli",
"Sivanian Pertici",
"Olehsan alausi"
)
for (i in dtnama.indices){
datalis.add(
dataCoba(
dtnama[i]
)
)
populateData()
}
}
private fun populateData(){
val linearManager = LinearLayoutManager(this)
linearManager.reverseLayout=true
linearManager.stackFromEnd=true
recycleView.layoutManager=linearManager
val adp =adpCoba(this,datalis)
recycleView.adapter=adp
}
}

How to display data in RecyclerView using Retrofit2 API?

First of all, I'm new to Android/Java/Kotlin development. I'm using Retrofit2 to retrieve data from Udacity API. I can see the response in the Logcat, but when I try to display it in RecyclerView there is just a blank screen. I think the error is in the MainActivity, but I'm still clueless and need help.
My model classes
class Course(var title: String,
var subtitle: String,
var key: String,
var instructors: List<Instructor>,
var expected_learning: String,
var required_knowledge: String)
class Instructor(var name: String,
var bio: String)
My interface
interface ApiServiceInterface {
#GET("courses")
fun list() : Call<UdacityCatalog>
}
My adapter
class CourseAdapter(val listCourses: ArrayList<Course?>, val context: Context) : RecyclerView.Adapter<CourseAdapter.CourseViewHolder>() {
class CourseViewHolder(viewItem: View) : RecyclerView.ViewHolder(viewItem) {
val courseTitle = viewItem.findViewById<TextView?>(R.id.tv_title) as TextView
val courseSubtitle = viewItem.findViewById<TextView?>(R.id.tv_subtitle) as TextView
val courseKey = viewItem.findViewById<TextView?>(R.id.tv_course_key) as TextView
val instructorName = viewItem.findViewById<TextView?>(R.id.tv_instructor_name) as TextView
}
override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): CourseViewHolder {
val viewHolder = LayoutInflater.from(parent?.context).inflate(R.layout.activity_item_list, parent, false)
val itemViewHolder = CourseViewHolder(viewHolder)
return itemViewHolder
}
override fun onBindViewHolder(holder: CourseViewHolder?, position: Int) {
holder?.courseTitle?.text = listCourses[position].title
holder?.courseSubtitle?.text = listCourses[position].subtitle
holder?.courseKey?.text = listCourses[position].key
holder?.instructorName?.text = listCourses[position].instructors.toString()
}
override fun getItemCount(): Int = listCourses.size
}
My MainActivity -- I think the error is in here, but I haven't figured it out yet
class MainActivity : AppCompatActivity() {
internal val TAG = "Testing Retrofit2 API"
lateinit var mRecyclerView: RecyclerView
lateinit var mCourseAdapter: RecyclerView.Adapter<CourseAdapter.CourseViewHolder>
val listCourse = arrayListOf<Course?>()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main_recyclerview)
mRecyclerView = findViewById<RecyclerView?>(R.id.id_recycler_view) as RecyclerView
val mLayoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
mRecyclerView.layoutManager = mLayoutManager
mRecyclerView.setHasFixedSize(true)
mCourseAdapter = CourseAdapter(listCourse, applicationContext)
mRecyclerView.adapter = mCourseAdapter
mCourseAdapter.notifyDataSetChanged()
val call = RetrofitInitializer().createService().list()
call.enqueue(object : Callback<UdacityCatalog> {
override fun onResponse(call: Call<UdacityCatalog>, response: Response<UdacityCatalog>) {
response.body()
if (!response.isSuccessful) {
Log.i(TAG, "[ ERROR ] " + response.code())
} else {
if (listCourse.isEmpty()) {
Toast.makeText(applicationContext, "Empty list!", Toast.LENGTH_LONG).show()
} else {
Toast.makeText(applicationContext, "Full list!", Toast.LENGTH_LONG).show()
}
val catalog = response.body()
for (c in catalog!!.courses!!) {
Log.i(TAG, String.format("%s: %s", c.title, c.subtitle, c.key, c.required_knowledge, c.expected_learning))
for (i in c.instructors!!) {
Log.i(TAG, i.name)
}
Log.i(TAG, "\n****************************************************************************************************\n")
}
}
}
override fun onFailure(call: Call<UdacityCatalog>?, t: Throwable?) {
Log.d(TAG, "onFailure() : " + t?.message)
}
})
}
}
An initializer class for Retrofit instance
class RetrofitInitializer {
companion object Factory {
val BASE_URL = "https://www.udacity.com/public-api/v0/"
}
private val retrofit = Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build()
fun createService(): ApiServiceInterface = retrofit.create(ApiServiceInterface::class.java)
}
My RecyclerView xml file
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:paddingBottom="16dp"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:paddingTop="16dp"
tools:context="activities.MainActivity">
<android.support.v7.widget.RecyclerView
android:id="#+id/id_recycler_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
</android.support.v7.widget.RecyclerView>
</LinearLayout>
My CardView xml file
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="16dp"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="16dp"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:paddingTop="16dp">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:text="#string/udacity_catalog"
android:textAppearance="?android:textAppearanceLarge"
android:textColor="#9C27B0"
android:textStyle="bold" />
<TextView
android:id="#+id/tv_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:gravity="start"
android:hint="#string/hint_title"
android:textAppearance="?android:textAppearanceMedium"
android:textColor="#000000" />
<TextView
android:id="#+id/tv_subtitle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:gravity="start"
android:hint="#string/hint_subtitle"
android:textAppearance="?android:textAppearanceMedium"
android:textColor="#000000" />
<TextView
android:id="#+id/tv_course_key"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:gravity="start"
android:hint="#string/hint_key"
android:textAppearance="?android:textAppearanceMedium"
android:textColor="#000000" />
<TextView
android:id="#+id/tv_instructor_name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:gravity="start"
android:hint="#string/hint_name"
android:textAppearance="?android:textAppearanceMedium"
android:textColor="#000000" />
</LinearLayout>
</android.support.v7.widget.CardView>

You have an empty list of courses (listCourse) in your Activity. You pass that empty list to the adapter via it's constructor.
That list stays empty even after you fetched the courses. So the adapter / RecyclerView stays empty.
Try creating the adapter after you fetched the courses, with
mCourseAdapter = CourseAdapter(catalog!!.courses!!, applicationContext)
or have a courses property in your adapter lile
YourAdapter(...) {
var courses = listOf(Course)
}
and then in your Activity (after fetching the courses):
adapter.courses = catalog!!.courses!!
adapter.notifyDataSetChanged()

RecyclerView Items doesn't appear until i scroll it

I'm using Recyclerview inside a Fragment Following Google's sample of MVP Android architecture and I tried to make the View part passive as possible following this article , which makes the whole Recyclerview Adapter passive of the Data Models and the presenter handles it.
Here is my code of the Fragment:
class OrderHistoryFragment : Fragment(), OrderHistoryContract.View {
lateinit var mPresenter: OrderHistoryContract.Presenter
lateinit var rvOrderHistory: RecyclerView
lateinit var orderHistoryAdapter : OrderHistoryAdapter
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
val root = inflater!!.inflate(R.layout.order_history_fragment, container, false)
rvOrderHistory = root.findViewById<RecyclerView>(R.id.rvOrderHistory)
rvOrderHistory.layoutManager = LinearLayoutManager(context, LinearLayout.VERTICAL, false)
orderHistoryAdapter = OrderHistoryAdapter(mPresenter, object : HistoryItemListener {
override fun onReorder(orderHistory: OrderHistory) {
}
override fun onOpenOrder(orderHistory: OrderHistory) {
val orderIntent = Intent(activity, OrderDetailActivity::class.java)
orderIntent.putExtra("orderId", orderHistory.id)
startActivity(orderIntent)
}
})
rvOrderHistory.adapter = orderHistoryAdapter
return root
}
override fun onResume() {
super.onResume()
mPresenter.start()
}
override fun setPresenter(presenter: OrderHistoryContract.Presenter) {
mPresenter = checkNotNull<OrderHistoryContract.Presenter>(presenter)
}
override fun showLoadingIndicator(load: Boolean?) {
}
override fun updateOrdersAdapter() {
orderHistoryAdapter.notifyDataSetChanged()
}
override fun showSnackBar(Message: String) {
val parentLayout = activity.findViewById<View>(android.R.id.content)
val snackBar = Snackbar
.make(parentLayout, Message, Snackbar.LENGTH_INDEFINITE)
snackBar.setAction("Dismiss") { snackBar.dismiss() }
snackBar.setActionTextColor(Color.RED)
snackBar.show()
}
interface HistoryItemListener {
fun onReorder(orderHistory: OrderHistory)
fun onOpenOrder(orderHistory: OrderHistory)
}
companion object {
fun newInstance(): OrderHistoryFragment {
return OrderHistoryFragment()
}
}
fun OrderHistoryFragment() {
}
}
And this is my RecyclerView Adapters code
class OrderHistoryAdapter(internal var orderHistoryPresenter: OrderHistoryContract.Presenter, private val listener: OrderHistoryFragment.HistoryItemListener) : RecyclerView.Adapter<OrderHistoryAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.order_history_item, parent, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
orderHistoryPresenter.onBindOrdersRow(position, holder)
holder.bReOrder!!.setOnClickListener { v -> listener.onReorder(orderHistoryPresenter.getOrderHistoryItem(position)) }
holder.cvOrderItem!!.setOnClickListener { v -> listener.onOpenOrder(orderHistoryPresenter.getOrderHistoryItem(position)) }
}
override fun getItemId(position: Int): Long {
return position.toLong()
}
override fun getItemCount(): Int {
return orderHistoryPresenter.getOrdersCount()
}
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView), OrderHistoryContract.orderRowView {
internal var ivOrderVendor: ImageView? = null
internal var tvOrderId: TextView? = null
internal var tvOrderItems: TextView? = null
internal var tvOrderDate: TextView? = null
internal var tvOrderPrice: TextView? = null
internal var bReOrder: Button? = null
internal var cvOrderItem: CardView? = null
init {
ivOrderVendor = itemView.findViewById<ImageView>(R.id.ivOrderVendor)
tvOrderId = itemView.findViewById<TextView>(R.id.tvOrderId)
tvOrderItems = itemView.findViewById<TextView>(R.id.tvOrderItems)
tvOrderDate = itemView.findViewById<TextView>(R.id.tvOrderDate)
tvOrderPrice = itemView.findViewById<TextView>(R.id.tvOrderPrice)
bReOrder = itemView.findViewById<Button>(R.id.bReOrder)
cvOrderItem = itemView.findViewById<CardView>(R.id.cvOrderItem)
}
override fun setOrderImage(url: String) {
Glide.with(itemView.context).load(url).into(ivOrderVendor!!)
}
override fun setOrderDate(orderDate: String) {
tvOrderDate!!.text = orderDate
}
override fun setOrderId(orderId: String) {
tvOrderId!!.text = orderId
}
override fun setOrderItems(orderItems: ArrayList<String>) {
val stringBuilder = StringBuilder()
for (item in orderItems) {
stringBuilder.append(item)
}
tvOrderItems!!.text = stringBuilder.toString()
}
override fun setOrderPrice(orderPrice: String) {
tvOrderPrice!!.text = R.string.price.toString() + " " + orderPrice + " " + R.string.egp
}
}
}
And Here is code of the presenter which handles the Adapter data and it's binding to the ViewHolder
class OrderHistoryPresenter internal constructor(mDataRepository: DataRepository, mOrdeHistoryView: OrderHistoryContract.View) : OrderHistoryContract.Presenter {
private val mDataRepository: DataRepository
//refrence of the View to trigger the functions after proccessing the task
private val mOrdeHistoryView: OrderHistoryContract.View
private var orderHistoryItems = ArrayList<OrderHistory>()
init {
this.mDataRepository = checkNotNull(mDataRepository, "tasksRepository cannot be null")
this.mOrdeHistoryView = checkNotNull<OrderHistoryContract.View>(mOrdeHistoryView, "tasksView cannot be null!")
mOrdeHistoryView.setPresenter(this)
}
override fun start() {
mOrdeHistoryView.showLoadingIndicator(true)
mDataRepository.getCurrentUser(object : LocalDataSource.userRequestCallback {
override fun onUserRequestSuccess(botitUser: BotitUser) {
val urlParams = HashMap<String, String>()
urlParams.put(Endpoints.USER_ID_KEY, botitUser.userId!!)
val url = Endpoints.getUrl(Endpoints.urls.ORDER_HISTORY, urlParams)
mDataRepository.buildEndPointRequest(url, " ", Endpoints.requestsType.GET, object : EndpointDataSource.RequestCallback {
override fun onRequestSuccess(Body: String) {
try {
mOrdeHistoryView.showLoadingIndicator(false)
orderHistoryItems = JSONParser.parseData(JSONParser.parsers.ORDER_HISTORY, JSONObject(Body)) as ArrayList<OrderHistory>
mOrdeHistoryView.updateOrdersAdapter()
} catch (e: JSONException) {
e.printStackTrace()
}
}
override fun onRequestError(Body: String) {
mOrdeHistoryView.showLoadingIndicator(false)
mOrdeHistoryView.showSnackBar("Cannot load data")
}
})
}
override fun onUserRequestError(Body: String) {
}
})
}
override fun refreshData() {
}
override fun getOrdersCount(): Int {
return orderHistoryItems.size
}
override fun onBindOrdersRow(position: Int, orderViewHolder: OrderHistoryContract.orderRowView) {
if (orderHistoryItems.isNotEmpty()) {
val orderHistory = orderHistoryItems[position]
// orderViewHolder.setOrderDate(orderHistory.orderDate!!)
orderViewHolder.setOrderId(orderHistory.orderId!!)
orderViewHolder.setOrderImage(orderHistory.orderImage!!)
orderViewHolder.setOrderItems(orderHistory.orderItems)
orderViewHolder.setOrderPrice(orderHistory.orderPrice!!)
}
}
override fun getOrderHistoryItem(position: Int): OrderHistory {
return orderHistoryItems[position]
}
override fun actionReOrder(ordreId: String) {
}
}
Here is the Fragment XML
<android.support.v7.widget.RecyclerView android:layout_width="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/rvOrderHistory"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
</android.support.v7.widget.RecyclerView>
and Here is the RecyclerView Item XML order_history_item.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/cvOrderItem"
android:layout_margin="4dp"
android:orientation="vertical">
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="8dp">
<ImageView
android:id="#+id/ivOrderVendor"
android:layout_width="60dp"
android:layout_height="60dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#drawable/mac" />
<TextView
android:id="#+id/tvOrderId"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="Order #2123"
android:textAppearance="#style/TextAppearance.AppCompat.Body2"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toRightOf="#+id/ivOrderVendor"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/tvOrderItems"
android:layout_width="242dp"
android:layout_height="35dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:text="MacDonald’s: Big Mac Beef, Big Tasty Beef. El Ezaby: Signal 2, Pantene Shampoo"
android:textAppearance="#style/TextAppearance.AppCompat.Small"
android:layout_marginRight="8dp"
app:layout_constraintRight_toRightOf="parent"
android:layout_marginTop="8dp"
app:layout_constraintTop_toBottomOf="#+id/tvOrderId"
app:layout_constraintLeft_toRightOf="#+id/ivOrderVendor"
android:layout_marginLeft="8dp"
app:layout_constraintHorizontal_bias="0.0" />
<TextView
android:id="#+id/tvOrderDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:layout_marginTop="8dp"
android:text="03:22 PM 23/2/2017"
app:layout_constraintBottom_toTopOf="#+id/tvOrderItems"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0"
android:layout_marginLeft="8dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintHorizontal_bias="1.0" />
<TextView
android:id="#+id/tvOrderPrice"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="16dp"
android:text="Price: 225.50 LE"
android:textAppearance="#style/TextAppearance.AppCompat.Body2"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="#+id/tvOrderItems" />
<Button
android:id="#+id/bReOrder"
android:layout_width="wrap_content"
android:layout_height="35dp"
android:layout_margin="4dp"
android:background="#drawable/chip_accent"
android:foreground="?attr/selectableItemBackground"
android:orientation="vertical"
android:padding="8dp"
android:text="Order Again"
android:textAllCaps="false"
android:textColor="#color/colorAccent"
android:textSize="15sp"
app:layout_constraintHorizontal_bias="0.937"
app:layout_constraintLeft_toRightOf="#+id/tvOrderPrice"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="#+id/tvOrderItems"
tools:layout_editor_absoluteY="74dp" />
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.CardView>
The issue is that when I start the Activity showing the Fragment, the RecyclerView doesn't show the Item. It only appears if I scrolled the empty RecyclerView or by leaving the App on the foreground and go back to it again.
At the initialization the data of the Adapter is empty but onResume() I make a request which updates the data at the Presenter, Then I notifyDataChange() on the Adapter but nothing updates.
When I debugged I found that onBindViewHolder() isn't called after notifyDataChange() on the Adapter so i don't know why the notifyDataChange() doesn't notify the Adapter that the data is changed.
Anyone has an idea or any solution that might fix this issue?

You need to use runOnUiThread.
if(activity != null) {
activity!!.runOnUiThread {
root.Recycleview.adapter = Adapter(Array)
Adapter(Array).notifyDataSetChanged()
}
}

have a look at this answer
As stupid as it might sound, calling this line of code after setting data for recyclerView, helped me for this issue:
recyclerView.smoothScrollToPosition(0)
PS: technologies that I was using that may have something to do with this were: RJava, Retrofit2, NavigationUI, Fragments, LiveData, and Databinding.
EDIT:
I followed #SudoPlz comment and answer on another question and it also worked too, you have to extend RecyclerView and override requestLayout:
private boolean mRequestedLayout = false;
#SuppressLint("WrongCall")
#Override
public void requestLayout() {
super.requestLayout();
// We need to intercept this method because if we don't our children will never update
// Check https://stackoverflow.com/questions/49371866/recyclerview-wont-update-child-until-i-scroll
if (!mRequestedLayout) {
mRequestedLayout = true;
this.post(() -> {
mRequestedLayout = false;
layout(getLeft(), getTop(), getRight(), getBottom());
onLayout(false, getLeft(), getTop(), getRight(), getBottom());
});
}
}
while still, I would have preferred this to fixed after 4, 5 years, however, this was a good workaround, and you won't forget about them in your view.

I noticed in your item xml your constraintLayout height is match_parent right?
I recommend you to use it as wrap_content