Develop Reference

RecyclerViewAdapter in Android Kotlin

I have an array that save different sensors data (in non-activity class) and I want the RecyclerView to be updated based on data of that array. Is it possible to automatically change the presented data?
I used setOnClickListener but nothing updated. The RecyclerView just display the default data. Also, I used text view however the data is updated with each click not continuously.
Thanks for your help.
In fragment:
override fun onClick(v: View?) {
when (v?.id) {
R.id.buttonStart-> {
start(v)
}
R.id.buttonStop-> {
stop(v)
}
}
}
fun start (_v: View) {
listListSensors.adapter = SensorsRecyclerViewAdapter(model.listSensors(), mListener!!)
}
In the other class:
fun listSensors(): Sensors {
return currentSensor
}
In recycle view:
class SensorsRecyclerViewAdapter (items: Sensors, listener: ListSensorsFragment.OnListFragmentInteractionListener)
: RecyclerView.Adapter<SensorsRecyclerViewAdapter.SensorsViewHolder>() {
private var mValues: Sensors = items
private var mListener: ListSensorsFragment.OnListFragmentInteractionListener = listener
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SensorsViewHolder {
val itemView = LayoutInflater.from(parent.context).inflate(R.layout.recyclerviewlistsensors_item, parent, false)
return SensorsViewHolder(itemView)
}
override fun onBindViewHolder(holder: SensorsViewHolder, position: Int) {
holder.mItem = mValues
holder.listSensorsLightView.text = mValues.getLight()
holder.listSensorsTemperatureView.text = mValues.getTemperature()
holder.listSensorsGyroscopeView.text = mValues.getGyroscope()
holder.listSensorsAccelerometerView.text = mValues.getAccelerometer()
holder.listSensorsGravityView.text = mValues.getGravity()
holder.mView.setOnClickListener { mListener.onListFragmentInteraction(holder.mItem) }
}

in your Adapter
var itemClickListener: ((position: Int, name: String) -> Unit)? = null
fun setData(data:List<AnyList>){
this.list.clear()
this.list.addAll(data)
notifyDataSetChanged()
}
//bindviewholder
itemClickListner.invoke(1,"anyvalue")
// in fragment
adapter.itemClickListener = {
position, name ->
Toast.makeText(requireContext(),"position is $position name is $name ",Toast.LENGTH_SHORT).show()
}
// call setData() any place in fragment

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.

android checkbox recyclerview using kotlin

i wanna ask something about my code.
so, I wanna retrieve the data that i have selected in the checkbox recyclerview, and then put it into variabel arraylist. and then when i click button next, i can use variabel arraylist in main code and then i can move to next page. can you help me to add that code on my coding?
anyway i use kotlin, so i need code kotlin
here my main coding
private fun getData() {
mDatabaseReference.addValueEventListener(object : ValueEventListener {
override fun onCancelled(databaseError: DatabaseError) {
Toast.makeText(this#ChooseCategoryActivity, ""+databaseError.message, Toast.LENGTH_SHORT).show()
}
override fun onDataChange(dataSnapshot: DataSnapshot) {
dataCategory.clear()
for(getdataSnapshot in dataSnapshot.getChildren()) {
Log.i("dataKey", getdataSnapshot.key.toString())
val kategori = getdataSnapshot.getValue(Kategori::class.java)
dataCategory.add(kategori!!)
}
rv_user_kategori.adapter = UserCategoryAdapter(dataCategory) {
}
}
})
here my adapter recyclerview
class UserCategoryAdapter(private var data: List<Kategori>, private var listener: (Kategori) -> Unit) : RecyclerView.Adapter<UserCategoryAdapter.ViewHolder>() {
lateinit var ContextAdapter : Context
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val layoutInflater = LayoutInflater.from(parent.context)
ContextAdapter = parent.context
val inflatedView = layoutInflater.inflate(R.layout.layout_row_kategori, parent, false)
return ViewHolder(inflatedView)
}
override fun getItemCount(): Int = data.size
override fun onBindViewHolder(holder: UserCategoryAdapter.ViewHolder, position: Int) {
holder.bindItem(data[position], listener,ContextAdapter, position)
}
class ViewHolder(v: View) : RecyclerView.ViewHolder(v) {
private val namaKategori:TextView = v.findViewById(R.id.txt_row_kategori)
var checkbox:CheckBox = v.findViewById(R.id.txt_row_kategori)
fun bindItem(data: Kategori, listener: (Kategori) -> Unit, context : Context, position : Int) {
namaKategori.text = data.nama
itemView.setOnClickListener {
listener(data)
}
}
}
}
please help me to find that solution.

Your listener currently return only the Kategori. Make it return also the position of the item on the list and/r the status of the checkbox. You can get the state of the checkbox with Checkbox.isChecked.

To use a listener you need to add invoke, so the flow should be :
Your adapter declaration
class UserCategoryAdapter(private var data: List<Kategori>, private var listener: (Kategori) -> Unit) : RecyclerView.Adapter<UserCategoryAdapter.ViewHolder>()
Then in your bind you send the listener via constructor as well
holder.bindItem(data[position], listener,ContextAdapter, position)
Once you are in the ViewHolder and you want to detect the state change listener you need to call it like
itemView.setOnClickListener { listener.invoke(data) }

How to get position of the item in RecyclerView

I'm new in Android dev.
In my code i don't using onClick method, but i using setOnClickListener and Callback. The main problem that is in this way i don't know how to get the position of the item in RecyclerView.
Here is my Adapter:
class TestAdapter(val test : ArrayList<Test>, private val testAdapterCallback: (Test, Int)->Unit) : RecyclerView.Adapter<TestAdapter.ViewHolder>(){
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val v = LayoutInflater.from(parent.context).inflate(R.layout.test_view_item, parent, false)
return ViewHolder(v)
}
override fun getItemCount(): Int {
return test.size
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val num : Test = test[position]
holder.textView.text = num.id.toString()
holder.cardView.setTag(position)
holder.cardView.setOnClickListener(){
testAdapterCallback(num)
}
}
inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView){
val cardView = itemView.findViewById<CardView>(R.id.testCardView)
val textView = itemView.findViewById<TextView>(R.id.testTextView)
}
}
I have added second parametr into callback but i don't know how i must change my adapter's inicializations in this peace of code:
val adapter = TestAdapter(list) { item ->
testAdapterItemClick(item)
}
In activity i'm using this method :
private fun testAdapterItemClick(item: Test) {}
Please, help me to check the position of the choosen element. I need it later.
Thanks in advance)
P.S. Sorry for my English

Add the position as parameter in the callback.
So, instead of: private val testAdapterCallback: (Test)->Unit
Use: private val testAdapterCallback: (Test, Int)->Unit.
This way you can pass the position in the callback.
holder.cardView.setOnClickListener(){
testAdapterCallback(num, position)
}
In your activity:
val adapter = TestAdapter(list) { item, position ->
testAdapterItemClick(item)
}

Create interface for your OnClickListener
interface OnClickListener{
fun clickItem(test: Test, index: Int)
}
Pass listener to your adapter like below.
class TestAdapter(
var test : ArrayList<Test>?,
val clickListener: OnClickListener,
var mActivity: Activity
) :
RecyclerView.Adapter<TestAdapter.MyViewHolder>() {
}
Now in your onBindViewHolder add click listener.
var mtest= test !!.get(i)
holder.cardView.setOnClickListener {
clickListener.clickItem(mtest, i)
}
Implement Listener to your activity and initialize it.
this.mOnClickListener = this
Pass listener to your adapter where you passing the arraylist.
mTestAdapter = TestAdapter(arrayList, mOnClickListener ,mActivity)
You'll get the position in your activity override method.
override fun editItem(mTest: Test, index: Int) {
if (mTest!= null) {
}
}

(Kotlin) Position of RecyclerView returns -1 when trying to click on an item

I'm new to Android development (and Kotlin).
I'm trying to implement a RecyclerView (which works fine) and when I click on a specific row it opens a new activity (Intent).
However, whenever I've press/click on one of the rows, I'm only able to get the value "-1" returned.
I've tried a number of different approaches (you should see the number of tabs in my browser).
This seems like it should be a fairly straightforward occurrence for something as common as a RecyclerView, but for whatever reason I'm unable to get it working.
Here is my RecyclerView Adapter file:
class PNHLePlayerAdapter (val players : ArrayList<PNHLePlayer>, val context: Context) : RecyclerView.Adapter<ViewHolder>() {
var onItemClick: ((Int)->Unit) = {}
// Gets the number of items in the list
override fun getItemCount(): Int {
return players.size
}
// Inflates the item views
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val itemView = LayoutInflater.from(context).inflate(
R.layout.pnhle_list_item,
parent,
false
)
val viewHolder = ViewHolder(itemView)
itemView.setOnClickListener {
onItemClick(viewHolder.adapterPosition)
}
return ViewHolder(itemView)
}
// Binds each item in the ArrayList to a view
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.tvPlayerName?.text = players[position].Name
holder.tvPlayerRank?.text = position.toString()
holder.tvPNHLe?.text = players[position].PNHLe.toString()
holder.tvTeam?.text = players[position].Team
holder.ivLeague?.setImageResource(leagueImageID)
}
}
class ViewHolder (view: View) : RecyclerView.ViewHolder(view) {
val linLayout = view.hor1LinearLayout
val ivTeam = view.teamImageView
val tvPlayerName = view.playerNameTextView
val tvPlayerRank = view.rankNumTextView
val tvPNHLe = view.pnhleTextView
val tvTeam = view.teamTextView
val ivLeague = view.leagueImageView
}
As you can see, there is a class property "onItemClick" which uses a lambda as the click callback.
I setOnClickListener in the onCreateViewHolder method after the view is inflated.
Next, in my Activity I add the list to my Adapter and set the call back.
However, every time I 'Toast' the position it is displayed as '-1'.
val adapter = PNHLePlayerAdapter(list, this)
adapter.onItemClick = { position ->
Toast.makeText(this, position.toString(),Toast.LENGTH_SHORT).show()
var intent = Intent(this, PlayerCardActivity::class.java)
//startActivity(intent)
}
rv_player_list.adapter = adapter
Perhaps I'm not thinking about this properly, but shouldn't the position represent the row number of the item out of the RecyclerView???
Ideally, I need to use the position so that I can obtain the correct item from the 'list' (ArrayList) so that I can pass information to my next Activity using the Intent

I found the issue.
Change this line in onCreateViewHolder:
return ViewHolder(itemView)
to this one:
return viewHolder

I would reorganize the adapter like this:
class PNHLePlayerAdapter : androidx.recyclerview.widget.RecyclerView.Adapter<Adapter.ViewHolder>() {
interface AdapterListener {
fun onItemSelected(position: Int?)
}
var players: List<Player> = listOf()
set(value) {
field = value
this.notifyDataSetChanged()
}
var listener: AdapterListener? = null
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.item_car_selector, parent, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.bind(position)
}
override fun getItemCount(): Int {
return brands.size
}
inner class ViewHolder(view: View): androidx.recyclerview.widget.RecyclerView.ViewHolder(view) {
private var position: Int? = null
private val baseView: LinearLayout? = view.findViewById(R.id.baseView) as LinearLayout?
...
init {
baseView?.setOnClickListener {
listener?.onManufacturerSelected(position)
}
}
fun bind(position: Int) {
this.position = position
...
}
}
}
And from your activity/fragment set the listener as adapter.listener = this, and implement the onItemSelected(position: Int?)
override fun onItemSelected(position: Int?) {
...
}