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Please tell me how to transfer the ID (position) of the view element on recyclerview to another class

Please tell me how to transfer the ID (position) of the view element on recyclerview to another class?
class CardAdapter : RecyclerView.Adapter<CardAdapter.CardViewHolder>(), View.OnClickListener {
private var cardList = ArrayList<Card>()
private lateinit var card: Card
class CardViewHolder(
val binding: FragmentCardBinding
) : RecyclerView.ViewHolder(binding.root)
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CardViewHolder {
val inflater = LayoutInflater.from(parent.context)
val binding = FragmentCardBinding.inflate(inflater, parent, false)
return CardViewHolder(binding)
}
#SuppressLint("SetTextI18n")
override fun onBindViewHolder(holder: CardViewHolder, position: Int) {
card = cardList[position]
..
}
override fun getItemCount(): Int = cardList.size
override fun onClick(v: View) {
when (v.id) {
R.id.root_card_template -> {
val intent = Intent(v.context, ProductActivity::class.java)
// need put id into ProductActivty
intent.putExtra("item", card.id)
v.context.startActivity(intent)
}
}
}
At the moment, it only passes the ID of the last generated element. For some reason there is almost no information on the Internet on this score

Just create an interface and implement that in the calling activity. While creating an instance of your adapter inside the activity, pass that interface along and on the click event of the view in the adapter class, call the interface's method with the data that you want to pass back to the activity.
interface OnItemClickListener{
fun onClick(pos: Int)
}
class YourActivity: AppCompatActivity(), OnItemClickListener {
override fun onStart() {
super.onStart()
//Create an instance of your adapter and pass the interface.
// Here #this context is being passed as Activity is implementing the interface.
val cardListAdapter = CardListAdapter(this)
}
override fun onClick(pos: Int) {
//Add your logic
}
}
// Then in your adapter class
class YourAdapter(private val itemClickListener: OnItemClickListener) :
RecyclerView.Adapter<CardListAdapter.CardViewHolder>() {
//Your code
override fun onBindViewHolder(holder: CardListAdapter.CardViewHolder, position: Int) {
yourView.setOnClickListener {
itemClickListener.onClick(position)
}
}
}

first you need to creat an interface
interface OnItemListener {
fun onItemSelect(position: Int)
}
then in your class that calls the recyclerview adapter, pass it to your recyclerView Adapter like this
var cardAdapter = CardAdapter(object :
OnItemListener {
override fun onItemSelect(position: Int) {
// you can handle your data here
// your position that you passed comes here
}
})
var layoutManager = GridLayoutManager(context, 2)
yourRecyclerViewId.adapter = cardAdapter
yourRecyclerViewId.layoutManager = layoutManager
finally in your adapter do like this
class CardAdapter(
private val onItemListener: OnItemListener
)
: RecyclerView.Adapter<CardAdapter.CardViewHolder>(), View.OnClickListener {
private var cardList = ArrayList<Card>()
private lateinit var card: Card
and in your on click event in the adapter call it as below:
onItemListener.onItemSelect(yourPosition)

How to use viewmodel in recyclerview adapter

I am creating Recyclerview using MVVM and data binding. Now I need to perform some network operation in Recycler view adapter. So how can we create ViewModel and Live data for adapter. How can adapter observe live data.
I have create ViewModel using activity context and but not working proper
class CartAdapter(cartList: ArrayList<ProductData>, context: BaseActivity) :
RecyclerView.Adapter<CartAdapter.MyViewHolder>() {
private val itemList = cartList
private val activity = context
private var viewModel: CartAdapterViewModel =
ViewModelProvider(context).get(CartAdapterViewModel::class.java)
init {
initObserver()
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
val view =
LayoutInflater.from(parent.context).inflate(R.layout.cart_item_layout, parent, false)
return MyViewHolder(view)
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
val item = itemList[position]
holder.setData(item)
}
override fun getItemCount(): Int {
return itemList.size
}
class MyViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
var binding: CartItemLayoutBinding? = DataBindingUtil.bind(itemView)
fun setData(model: ProductData) {
binding?.item = model
}
}
private fun initObserver() {
viewModel.statusResponse.observe(activity, {
activity.hideLoader()
})
viewModel.serverError.observe(activity, {
activity.hideLoader()
})
}
}

You should not create a separate ViewModel for adapter.
The Classic way:
The adapter should expose an interface whose implementation would later handle e.g. clicks on an item in the RecyclerView.
class CartAdapter(
cartList: ArrayList<ProductData>,
private val itemClickListener: ItemClickListener // This is the interface implementation
// that will be provided for an item click in this example
) : RecyclerView.Adapter<CartAdapter.MyViewHolder>() {
interface ItemClickListener {
fun onItemClick(position: Int)
}
override fun onBindViewHolder(holder: ScanResultViewHolder, position: Int) {
holder.binding.root.setOnClickListener {
itemClickListener.onItemClick(position)
}
}
// this function would be useful for retrieving an item from the recyclerview
fun getItemAt(position: Int): ProductData = itemList[position]
...
}
Later on when instantiating the CartAdapter in Your Activity or Fragment You would have to provide that interface implementation:
private val cartAdapter: CartAdapter = CartAdapter(
cartList,
object : CartAdapter.ItemClickListener {
override fun onItemClick(position: Int) {
// this function will handle the item click on a provided position
doSomethingWithARecyclerViewItemFrom(position)
}
}
)
private fun doSomethingWithARecyclerViewItemFrom(position: Int) {
// get the adapter item from the position
val item = cartAdapter.getItemAt(position)
// later on You can use that item to make something usefull with Your ViewModel of an activity/fragment
...
}
This way the Adapter doesn't have to have any ViewModels - the corresponding actions on RecyclerView items can be handled by the Activity view model.
In my example this action is an item click but for a more specific action, You would have to update Your question with those details.
The more compact way:
You can implement the same functionality as above using even more compact and neat way by using function types:
class CartAdapter(
cartList: ArrayList<ProductData>,
private val itemClickListener: (productData: ProductData) -> Unit // notice here
) : RecyclerView.Adapter<CartAdapter.MyViewHolder>() {
override fun onBindViewHolder(holder: ScanResultViewHolder, position: Int) {
holder.binding.root.setOnClickListener {
itemClickListener(position) // slight change here also
}
}
}

My suggestion is using constructor to pass viewModel instance.
Without concerns of unhandled instance scope problem anyway.
Have a happy day.

visit ViewModel in Recycler´s Adapter

i am stuck in the problem that, i want to visit my ViewModel in a RecyclerView´s Adapter, but i have the Exception:
"Your activity is not yet attached to the Application instance. You can't request ViewModel before onCreate call"
class FoodInSortAdapter( val activity:MainActivity,private val list:List<String>):RecyclerView.Adapter<FoodInSortAdapter.Holder>() {
val viewModel :FoodViewModel by lazy {
println("servus")
ViewModelProvider(activity).get(FoodViewModel::class.java)}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): Holder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.sortitem, parent, false)
return Holder(view)
}
override fun onBindViewHolder(holder: Holder, position: Int) {
holder.sortName.text = list[position]
holder.itemView.setOnClickListener {
val m=list[position]
viewModel.setQuery(m)
}
}
anyone know what ´s wrong?
thanks

First things first, you should not initialize viewModel outside of activity or fragment.
I assume you do not create adapter in onCreate but during initialization phase. There are two solution for your concern.
Initialize vm in activity, and set it in adapter by newly added method setupViewModel, called in onCreate. That's the better one.
class FooActivity : Activity{
private val viewModel: FoodViewModel by lazy {
println("servus")
ViewModelProvider(activity).get(FoodViewModel::class.java)
}
private val adapter = FoodInSortAdapter(emptyList())
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
adapter.setupViewModel(viewModel)
}
}
class FoodInSortAdapter(private val list:List<String>):RecyclerView.Adapter<FoodInSortAdapter.Holder>() {
private lateinit var viewModel: FoodViewModel
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): Holder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.sortitem, parent, false)
return Holder(view)
}
override fun onBindViewHolder(holder: Holder, position: Int) {
holder.sortName.text = list[position]
holder.itemView.setOnClickListener {
val m=list[position]
viewModel.setQuery(m)
}
}
fun setupViewModel(vm: FoodViewModel){
viewModel = vm
}
}
Create adapter in onCreate method, that should also work for you.
Cheers

android - Creating and using ViewBinder inside a RecyclerView adapter

In my app, there is an Activity which has a RecyclerView inside, which loads the list of options needed for that screen.
In the code below, i tried to implement a binder, which is needed because of the recent Android changes.
However, when i open the activity starts, the application crashes, throwing this error, linking the line with binding = ItemSettingsBinding.bind(binding.root):
kotlin.UninitializedPropertyAccessException: lateinit property binding has not been initialized
What am i doing wrong? What's the correct way to implement a binder inside an adapter?
AdapterSettings.kt
class AdapterSettings(
var settingsList: List<DataItemSettings>,
var listener: OnItemClickListener
) : RecyclerView.Adapter<AdapterSettings.SettingsViewHolder>() {
private lateinit var binding: ItemSettingsBinding
inner class SettingsViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView), View.OnClickListener {
init {
itemView.setOnClickListener(this)
}
override fun onClick(p0: View?) {
val position : Int = adapterPosition
if (position != RecyclerView.NO_POSITION) {
listener.OnItemClick(position)
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SettingsViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.item_settings, parent, false)
return SettingsViewHolder(view)
}
override fun getItemCount(): Int {
return settingsList.size
}
override fun onBindViewHolder(holder: SettingsViewHolder, position: Int) {
binding = ItemSettingsBinding.bind(binding.root)
holder.itemView.apply {
binding.rvTitle.text = settingsList[position].stringTitle
binding.rvDescription.text = settingsList[position].stringDescription
binding.rvIcon.setImageResource(settingsList[position].itemIcon)
}
}
interface OnItemClickListener {
fun OnItemClick(position: Int)
}
}

I believe you're missing your inflate in onCreateViewHolder:
// Pseudo-Code
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SettingsViewHolder {
val binding = ItemSettingsBinding
.inflate(LayoutInflater.from(parent.context), parent, false)
return SettingsViewHolder(binding)
}
Then you can make use of it.

Create the binding in onCreateViewHolder and pass the binding into the ViewHolder instead of the inflated View. Thus you create a binding for each created view and only need to do the apply stuff in the onBindViewHolder
Example:
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SettingsViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.item_settings, parent, false)
val binding = ItemSettingsBinding.bind(view)
return SettingsViewHolder(binding)
}
override fun onBindViewHolder(holder: SettingsViewHolder, position: Int) {
holder.binding.apply {
rvTitle.text = settingsList[position].stringTitle
rvDescription.text = settingsList[position].stringDescription
rvIcon.setImageResource(settingsList[position].itemIcon)
}
}
Adapt your ViewHolder accordingly

There is indeed another way to ViewBind in an adapter.
First, we need to setup the ViewHolder in a different way:
inner class SettingsViewHolder(private val binding: ItemSettingsBinding):
RecyclerView.ViewHolder(binding.root), View.OnClickListener {
With this, we created a binding value inside the brackets, so we are able to call the items of the actual view or layout trough binding.root
Inside the viewholder, we need to create a function used to bind our items. We can either bind like this:
fun bind(item: Item) {
binding.item = item
binding.executePendingBindings()
}
Or like this:
fun bind(item: DataItemSettings) {
binding.rvTitle.text = settingsList[position].stringTitle
binding.rvDescription.text = settingsList[position].stringDescription
binding.rvIcon.setImageResource(settingsList[position].itemIcon)
}
NOTICE: 'getter for position: Int' is deprecated. Deprecated in Java.
And, final step, we need to write this, inside bindViewHolder:
override fun onBindViewHolder(holder: SettingsViewHolder, position: Int) {
holder.bind(settingsList[position])
}

Recyclerview illegal state exception with data binding and viewModel

I am fetching a list of categories from an api and setting them into recyclerview . Adapter code is written in viewModel class and is called by the fragment that is calling the api. Below are the methods for setting adapters.
fun getAdapter(
listener: OtherVideoCategoriesRecyclerAdapter.OtherVideoCategoriesRecyclerAdapterListener,context: Context
): OtherVideoCategoriesRecyclerAdapter {
if (categoriesRecyclerAdapter == null)
categoriesRecyclerAdapter = OtherVideoCategoriesRecyclerAdapter(listener,context)
return categoriesRecyclerAdapter as OtherVideoCategoriesRecyclerAdapter
}
fun setItems(categories: ArrayList<OtherCategoriesItem>) {
categoriesList = categories
categoriesRecyclerAdapter!!.setItems(categoriesList!!)
}
And this is how I call these methods from my fragment class.
otherVideoViewModel.setItems(it.first.data!!.otherCategories as ArrayList<OtherCategoriesItem>)
Set Adapter method
private fun setAdapter() {
otherVideosCategoriesBinding.recyclerView.layoutManager = LinearLayoutManager(activity)
otherVideosCategoriesBinding.recyclerView.itemAnimator = DefaultItemAnimator()
adapter = otherVideoViewModel.getAdapter(adapterListener,activity!!)
otherVideosCategoriesBinding.recyclerView.adapter = adapter
}
And this is the adapter class.
class OtherVideoCategoriesRecyclerAdapter(private val listener: OtherVideoCategoriesRecyclerAdapterListener,val context: Context): RecyclerView.Adapter<OtherVideoCategoriesRecyclerAdapter.ViewHolder>() {
var categories = ArrayList<OtherCategoriesItem>()
interface OtherVideoCategoriesRecyclerAdapterListener {
fun onItemClicked(position: Int)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): OtherVideoCategoriesRecyclerAdapter.ViewHolder {
val inflater=LayoutInflater.from(context)
val binding = ItemOtherVideoCategoryBinding.inflate(inflater, parent, false)
return OtherVideoCategoriesRecyclerAdapter.ViewHolder(binding)
}
override fun getItemCount(): Int {
return categories.size
}
override fun onBindViewHolder(holder: OtherVideoCategoriesRecyclerAdapter.ViewHolder, position: Int) {
val item = categories[position]
holder.bindViews(item)
}
class ViewHolder(private val binding: ItemOtherVideoCategoryBinding): RecyclerView.ViewHolder(binding.root) {
fun bindViews(model: OtherCategoriesItem){
binding.model=model
binding.executePendingBindings()
}
}
fun setItems(categoriesList: ArrayList<OtherCategoriesItem>) {
categories = categoriesList
notifyDataSetChanged()
}
}
When I run this code, it crashes with following exception.
java.lang.IllegalStateException: ViewHolder views must not be attached when created. Ensure that you are not passing 'true' to the attachToRoot parameter of LayoutInflater.inflate(..., boolean attachToRoot)
I have tried all the related answers to this error but none of them worked for my case as many of those answers doesn't included data binding.

Hey just changing your onCreateViewHolder a bit. Try this:
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): OtherVideoCategoriesRecyclerAdapter.ViewHolder {
val inflater=LayoutInflater.from(context)
val binding:ItemOtherVideoCategoryBinding = DataBindingUtil.inflate(inflater,R.layout.your_layout_name, parent, false)
return OtherVideoCategoriesRecyclerAdapter.ViewHolder(binding)
}