Develop Reference

android spinner in recyclerview

RecyclerView is using a spinner.
For example, if you have three items,
The second item is made of TEMP through a spinner. (The default is test.)
EX)
test
temp
test
When the delete button of the first position is pressed,
I want the contents I want to be displayed as below.
test
test
But in reality,
test
temp
I deleted the temp, but why does the temp keep being exposed?
What should I do?
RecycleItemadapter.kt
#SuppressLint("MissingPermission") class RecycleItemAdapter(val calculateWeight: (MutableList<RecycleDropDownData>, Int) -> Unit,
private val itemList: MutableList<RecycleDropDownData>) : RecyclerView.Adapter<RecycleItemAdapter.DevicesAdapterViewHolder>() {
private var recycleItemList = mutableListOf<RecycleDropDownData>()
#SuppressLint("NewApi")
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DevicesAdapterViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.item_recycler, parent, false)
return DevicesAdapterViewHolder(view)
}
#SuppressLint("RecyclerView", "NotifyDataSetChanged")
override fun onBindViewHolder(holder: DevicesAdapterViewHolder, pos: Int) {
holder.recycleItem.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
override fun onItemSelected(parent: AdapterView<*>?, view: View?, position: Int, id: Long) {
val weight = recycleItemList[pos].weight
recycleItemList[pos] = itemList[position]
recycleItemList[pos].weight = weight
}
override fun onNothingSelected(parent: AdapterView<*>?) {
}
}
holder.recycleWeight.text = recycleItemList[pos].weight
// TODO
holder.recycleDelete.setOnClickListener {
recycleItemList.removeAt(pos)
notifyDataSetChanged()
}
}
fun setData(recyclerList: MutableList<RecycleDropDownData>) {
this.recycleItemList = recyclerList
}
fun getData(): MutableList<RecycleDropDownData> {
return recycleItemList
}
override fun getItemCount(): Int {
return recycleItemList.size
}
inner class DevicesAdapterViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
val recycleWeight: TextView
private val recycleCalculate: Button
val recycleDelete: Button
val recycleItem: Spinner
init {
recycleItem = itemView.findViewById(R.id.recycle_item_spinner)
recycleItem.adapter = ArrayAdapter(itemView.context, R.layout.item_drop_down, itemList)
recycleWeight = itemView.findViewById(R.id.recycler_item_weight)
recycleCalculate = itemView.findViewById(R.id.recycler_item_weight_calculate)
recycleDelete = itemView.findViewById(R.id.recycler_item_delete)
}
}
}
item_recycler
<Spinner
android:id="#+id/recycle_item_spinner"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:listitem="#layout/item_drop_down" />
<TextView
android:id="#+id/recycler_item_weight"
android:layout_width="100dp"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toRightOf="#id/recycle_item_spinner"
app:layout_constraintTop_toTopOf="parent" />
<androidx.appcompat.widget.AppCompatButton
android:id="#+id/recycler_item_weight_calculate"
style="#style/station_detail_item_passenger_button"
android:background="#color/color_mint_code_75f8ff"
android:text="무게"
app:layout_constraintLeft_toRightOf="#id/recycler_item_weight"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<androidx.appcompat.widget.AppCompatButton
android:id="#+id/recycler_item_delete"
style="#style/station_detail_item_passenger_button"
android:text="삭제"
app:layout_constraintLeft_toRightOf="#id/recycler_item_weight"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="#id/recycler_item_weight_calculate" />

onCreateViewHolder() of child recycler view not being called in Android [Kotlin]

I have a nested recycler view structure. The data for the recycler view is coming from Room Database and it follows MVVM architecture with repositories and viewmodels.
I am able to inflate the parent recycler view and get the list on screen but the child recycler view is not being inflated. I can see the value being passed through the adapter by using logs. But that is not being used on onBindViewHolder() and neither onCreateViewHolder() is called
Any help would be appreciated.
My CODE:
Fragment :
class ControlPanelFragment : Fragment() {
private var _binding: FragmentControlPanelBinding? = null
private val binding: FragmentControlPanelBinding get() = _binding!!
private lateinit var controlPanelViewModel: ControlPanelViewModel
//floor adapter
private lateinit var adapter: FloorsAdapter
//rooms adapter
private lateinit var roomAdapter: RoomsAdapter
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentControlPanelBinding.inflate(layoutInflater)
controlPanelViewModel = ViewModelProvider(this)[ControlPanelViewModel::class.java]
adapter = FloorsAdapter()
roomAdapter = RoomsAdapter()
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding.rvFloors.adapter = adapter
binding.rvFloors.layoutManager = LinearLayoutManager(requireContext())
ListItemControlPanelFloorsBinding.inflate(layoutInflater).apply {
rvRoomControlPanel.adapter = roomAdapter
rvRoomControlPanel.layoutManager = LinearLayoutManager(activity)
Timber.d("Inside list item")
}
controlPanelViewModel.getAllFloors.observe(viewLifecycleOwner, Observer {
Timber.d("List is $it")
//Remove duplicates from received list
val distinct = it.toSet().toList().sorted()
Timber.d("List after removing duplicates and sorting: $distinct")
adapter.floorList(distinct)
for (i in distinct) {
controlPanelViewModel.getAllRooms(i).observe(viewLifecycleOwner, Observer { rooms ->
Timber.d("Floor: $i, Rooms: $rooms")
val distinctRooms = rooms.toSet().toList()
roomAdapter.roomList(distinctRooms)
})
}
})
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}
Parent recycler view adapter
open class FloorsAdapter() : RecyclerView.Adapter<FloorsAdapter.FloorViewHolder>() {
private var floorList = emptyList<String>()
inner class FloorViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {}
override fun onCreateViewHolder(
parent: ViewGroup,
viewType: Int
): FloorViewHolder {
val layoutInflater = LayoutInflater.from(parent.context)
val binding = ListItemControlPanelFloorsBinding.inflate(layoutInflater, parent, false)
return FloorViewHolder(binding.root)
}
#SuppressLint("NotifyDataSetChanged")
override fun onBindViewHolder(holder: FloorsAdapter.FloorViewHolder, position: Int) {
val item = floorList[position]
Timber.d("Current floor is $item, Floor List is : $floorList")
ListItemControlPanelFloorsBinding.bind(holder.itemView).apply {
Timber.d("Current floor is $item, Floor List is : $floorList")
tvFloor.text = "Floor : $item"
}
}
#SuppressLint("NotifyDataSetChanged")
fun floorList(floors: List<String>) {
this.floorList = floors
notifyDataSetChanged()
}
override fun getItemCount(): Int {
return floorList.size
}
}
Child Recycler view adapter:
class RoomsAdapter() : RecyclerView.Adapter<RoomsAdapter.RoomsViewHolder>() {
private var roomList = emptyList<String>()
inner class RoomsViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView)
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RoomsViewHolder {
val inflater = LayoutInflater.from(parent.context)
val binding = ListItemControlPanelRoomsBinding.inflate(inflater, parent, false)
return RoomsViewHolder(binding.root)
}
override fun onBindViewHolder(holder: RoomsViewHolder, position: Int) {
Timber.d("Room List onBindViewHolder: $roomList")
val item = roomList[position]
ListItemControlPanelRoomsBinding.bind(holder.itemView).apply {
tvRoom.text = item
}
}
override fun getItemCount(): Int {
return roomList.size
}
#SuppressLint("NotifyDataSetChanged")
fun roomList(room: List<String>) {
this.roomList = room
Timber.d("Room List: $roomList")
notifyDataSetChanged()
}
}
Fragment 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:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".ui.controlPanel.ui.ControlPanelFragment">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:elevation="10dp">
<com.google.android.material.switchmaterial.SwitchMaterial
android:id="#+id/switchFactory"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="60dp"
android:checked="false"
android:text="Factory"
android:textOff="OFF"
android:textOn="ON"
android:textSize="16sp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Spinner
android:id="#+id/spnChooseFloor"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="200dp"
android:layout_marginEnd="16dp"
app:layout_constraintBottom_toBottomOf="#+id/switchFactory"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="#+id/switchFactory"
app:layout_constraintTop_toTopOf="#+id/switchFactory" />
</androidx.constraintlayout.widget.ConstraintLayout>
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginStart="16dp"
android:layout_marginTop="10dp"
android:layout_marginEnd="16dp"
android:layout_marginBottom="10dp"
android:elevation="8dp"
app:cardCornerRadius="8dp">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rvFloors"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:listitem="#layout/list_item_control_panel_floors" />
</androidx.cardview.widget.CardView>
</LinearLayout>
List Item for fragment recycler view(parent recycler view)
<?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="200dp"
android:orientation="vertical">
<TextView
android:id="#+id/tvFloor"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="4dp"
android:text="Floor 1"
android:textColor="#color/black"
android:textSize="20sp" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rvRoomControlPanel"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
tools:listitem="#layout/list_item_control_panel_rooms" />
</LinearLayout>
List item for child recycler view
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="40dp">
<TextView
android:id="#+id/tvRoom"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="8dp"
android:text="Conference Room"
android:textSize="20sp" />
</LinearLayout>
Edit 1:
My entity :
data class AddedDevicesInformation(
#ColumnInfo(name = "floor_name")
var floorName: String = "",
#ColumnInfo(name = "room_name")
var roomName: String = "",
#ColumnInfo(name = "machine_name")
var machineName: String = "",
#ColumnInfo(name = "device_name")
var deviceName: String = "",
#ColumnInfo(name = "factory_status")
var factoryStatus: Boolean? = false,
#PrimaryKey(autoGenerate = true)
var id: Int? = null,
) {
}
DAO query :
//returns all rooms associated with a floor
#Query("SELECT room_name from added_device_information where floor_name =:floor")
fun readAllRoomsOnAFloor(floor: String): LiveData<List<String>>
Repository:
class ControlPanelRepository(private val devicesInformationDao: DevicesInformationDao) {
fun getAllRooms(floor: String): LiveData<List<String>> = devicesInformationDao.readAllRoomsOnAFloor(floor)
ViewModel:
class ControlPanelViewModel(application: Application) : AndroidViewModel(application) {
//repository instance
val repository: ControlPanelRepository
//Variable for getting all floors
val getAllFloors: LiveData<List<String>>
init {
val database = PowerManagementDatabase.getDatabase(application)
val dao = database.getAddedDevicesInformationDao()
repository = ControlPanelRepository(dao)
getAllFloors = repository.getAllFloors
}
fun getAllRooms(floor: String): LiveData<List<String>> {
return repository.getAllRooms(floor)
}
}

The problem is that each "floor" (row in the floor RecyclerView) has its own unique "room" RecyclerView, but you never attach an adapter to those room RecyclerViews. Instead, you inflate an unused "floor" layout in the Fragment and attach a room adapter to it. That layout will never be displayed anywhere so its adapter is never used.
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding.rvFloors.adapter = adapter
binding.rvFloors.layoutManager = LinearLayoutManager(requireContext())
// The problem is this part.
// This view isn't shown anywhere, and the views inflated in FloorsAdapter
// never get a RoomAdapter attached
ListItemControlPanelFloorsBinding.inflate(layoutInflater).apply {
rvRoomControlPanel.adapter = roomAdapter
rvRoomControlPanel.layoutManager = LinearLayoutManager(activity)
Timber.d("Inside list item")
}
Each displayed floor layout is inflated in the floor adapter in onCreateViewHolder and the data for the floor then gets set in onBindViewHolder. This means you need to create a separate RoomsAdapter for each floor and attach it inside the floor adapter somewhere.
This makes accessing the room adapters more difficult with your current pattern, but if you make a Floor object that contains both its name and its list of rooms, then the floor object selected in onBindViewHolder can pass the list of rooms to its RoomAdapter. This means the FloorsAdapter would take a List<Floor> instead of List<String>. Then in the main fragment you only need to pass the list of Floor objects to the floor adapter and it will handle passing room lists on to the room adapters appropriately.
data class Floor(val name: String, val rooms: List<String>) {}
The floor adapter would look something like this:
// modify the ViewHolder to store the binding (so you don't have to
// re-bind the views so often) and store the room adapter for this
// floor. There should be one room adapter per floor.
inner class FloorViewHolder(val binding: ListItemControlPanelFloorsBinding,
val roomAdapter: RoomsAdapter)
: RecyclerView.ViewHolder(binding.root) {}
override fun onCreateViewHolder(
parent: ViewGroup,
viewType: Int
): FloorViewHolder {
val layoutInflater = LayoutInflater.from(parent.context)
val binding = ListItemControlPanelFloorsBinding.inflate(layoutInflater, parent, false)
// Create one adapter per floor here
val adapter = RoomsAdapter()
binding.rvRoomControlPanel.adapter = adapter
binding.rvRoomControlPanel.layoutManager = LinearLayoutManager(activity)
return FloorViewHolder(binding, adapter)
}
override fun onBindViewHolder(holder: FloorsAdapter.FloorViewHolder, position: Int) {
// for a given floor, set the rooms on that floor's room adapter
val currentFloor = floorList[position]
holder.roomAdapter.roomList(currentFloor.rooms)
holder.binding.tvFloor.text = "Floor : ${currentFloor.name}"
}
Here's an example of how that might look in the ViewModel, when it constructs the list of Floor objects, and the activity would observe the floorList LiveData. Each Floor contains all the data (including nested data) that it needs to display.
private val floorListLiveData = MutableLiveData<List<Floor>>()
val floorList: LiveData<List<Floor>>
get() = floorListLiveData
fun load() {
viewModelScope.launch {
val floors = mutableListOf<Floor>()
val floorList = dao.readFloors()
for(floorName in floorList) {
val rooms = dao.readRoomsInFloor(floorName)
floors.add(Floor(floorName, rooms))
}
floorListLiveData.postValue(floors)
}
}

I'm trying to print a list on the screen using the recyclerview, but the code in the adapter part is not working

MainActivity is as follows.
Nothing comes out on the screen, but I don't know which part is wrong.
How can I add the value of TV_item_name?
And in the log, it's from the DetailViewAdapter of the inner class.
Log.d (logTag,onCreateViewHolder11iscaled") value is also not output, so what is the problem?
package com.example.test_recyclerview
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.cardview.widget.CardView
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.example.test_recyclerview.databinding.ActivityMainBinding
class MainActivity : AppCompatActivity() {
private lateinit var binding : ActivityMainBinding
var logTag : String? = "로그 MainActivity"
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
val view = binding.root
setContentView(view)
Log.d(logTag,"111 onCreate is called")
binding.mRecyclerView.layoutManager = LinearLayoutManager(this)
val adapter = DetailViewAdapter()
Log.d(logTag,"222 onCreate is called")
binding.mRecyclerView.adapter = adapter
}
override fun onDestroy() {
super.onDestroy()
binding.mRecyclerView.adapter = null
}
inner class DetailViewAdapter : RecyclerView.Adapter<DetailViewAdapter.ViewHolder>() {
private var list = ArrayList<String>()
var logTag : String? = "로그 MainActivity"
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DetailViewAdapter.ViewHolder {
Log.d(logTag,"onCreateViewHolder11 is called")
list = getItemList()
val view = LayoutInflater.from(parent.context).inflate(R.layout.item_custom_row, parent, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
Log.d(logTag,"onBindViewHolder is called")
for (i in 1 until list.size) {
Log.d(logTag,"onBindViewHolder is called // list[$i] =" + list[i])
holder.tvItem.text = list[i]
}
}
override fun getItemCount(): Int {
return list.size
}
private fun getItemList(): ArrayList<String> {
for (i in 1..8) {
list.add(i, "Item $i")
}
return list
}
inner class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
val tvItem : TextView = view.findViewById(R.id.tv_item_name)
val cardViewItem : CardView = view.findViewById(R.id.card_view_item)
}
}
}
item_custom_row.xml
<?xml version="1.0" encoding="utf-8"?>
`enter code here`<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:layout_width="match_parent"
android:layout_height="wrap_content">
<androidx.cardview.widget.CardView
android:id="#+id/card_view_item"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="5dp"
android:padding="10dp"
app:cardCornerRadius="5dp"
app:cardElevation="3dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="horizontal"
tools:ignore="UseCompoundDrawables">
<ImageView
android:layout_width="50dp"
android:layout_height="50dp"
android:contentDescription="#string/app_name"
android:src="#mipmap/ic_launcher" />
<TextView
android:id="#+id/tv_item_name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:textColor="#android:color/black"
android:textSize="18sp"
android:textStyle="bold"
tools:text="Item" />
</LinearLayout>
</androidx.cardview.widget.CardView>
</LinearLayout>
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">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/m_RecyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

The issue is you're assigning list in onCreateViewHolder but it won't be called since your list.size is returning 0.
Rightly pointed out in this answer
Create list outside adapter & pass it from constructor
Change implementation in onBindViewHolder
Following is the complete example for your use case:
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
var logTag: String? = "로그 MainActivity"
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
val view = binding.root
setContentView(view)
Log.d(logTag, "111 onCreate is called")
binding.mRecyclerView.layoutManager = LinearLayoutManager(this)
val adapter = DetailViewAdapter(getItemList())
Log.d(logTag, "222 onCreate is called")
binding.mRecyclerView.adapter = adapter
}
private fun getItemList(): ArrayList<String> {
val list = ArrayList<String>()
for (i in 1..8) {
list.add("Item $i")
}
return list
}
override fun onDestroy() {
super.onDestroy()
binding.mRecyclerView.adapter = null
}
inner class DetailViewAdapter(private val list: ArrayList<String>) :
RecyclerView.Adapter<DetailViewAdapter.ViewHolder>() {
var logTag: String? = "로그 MainActivity"
override fun onCreateViewHolder(
parent: ViewGroup,
viewType: Int
): DetailViewAdapter.ViewHolder {
Log.d(logTag, "onCreateViewHolder11 is called")
val view =
LayoutInflater.from(parent.context).inflate(R.layout.item_custom_row, parent, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
Log.d(logTag, "onBindViewHolder is called")
holder.tvItem.text = list[position]
}
override fun getItemCount(): Int {
return list.size
}
inner class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
val tvItem: TextView = view.findViewById(R.id.tv_item_name)
val cardViewItem: CardView = view.findViewById(R.id.card_view_item)
}
}
}

From the code you posted I can see two problems with your code.
First one is that you are trying to populate the list of data from inside the view holder. What happens is the following:
The adapter is created
The adapter wants to know how many viewholders it should create to see how to populate the recycler view.
The adapter calls getItemCount and this method returns 0, since the list hasen't been populated.
Nothing else is called since nothing else has to be executed.
So, to fix this, the easiest way would be to make getItemCount return 8 and you are set. But, a better way to fix this is to instaintiate your list outside of your adapter, in your activity for example, and pass it as a constructor parameter when you initialize your adapter.
The second problem I'm seeing is on the method onBindViewHolder. You are iterating trough the list to set the text and this will cause that for all items you will only set the text as in the last item (item 8). You need to remember that onBindViewHolder is a method that is called when a view holder needs to refresh it contents because it is going to be used to display a different item of the list, that's why this method is passed the position as parameter, so you can do something like:
holder.tvItem.text = list[position]
** As a side note for the second issue, a more general approach I have seen and used to render the contents of the view holder, is to create a public method called "bind" which is passed the item that needs to be rendered and on the view holder you will have the logic on how to paint it. Something like:
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.bind(list[position])
}
/// Inside the view holder
fun bind(item: String) {
tvItem.text = item
}

ImageView doesn't load images in the RecyclerView after binding the Url

I am a newbie with android databinding, but the ImageView doesn't bind in the RecyclerView. I have read several blogs but no luck. What am I missing?
Below are some of the blog posts I have read:
link 1
link2
Below is how I have styled my xml 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">
<data>
<variable
name="movie"
type="com.movieapp.huxymovies.model.Result" />
</data>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:background="#color/bg"
android:orientation="vertical">
<android.support.v7.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:cardCornerRadius="4dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="0dp"
android:layout_marginTop="8dp"
android:background="#color/bg"
android:orientation="horizontal">
<ImageView
android:id="#+id/img"
android:layout_width="70dp"
android:layout_height="100dp"
android:layout_marginLeft="8dp"
app:movieImage="#{movie.MPosterPath}" />
</LinearLayout>
</LinearLayout>
</android.support.v7.widget.CardView>
</LinearLayout>
</layout>
Then this is the modal class which contains all the attributes:
#Entity(tableName = "Results")
class Result {
companion object {
#JvmStatic
#BindingAdapter("movieImage")
fun LoadImage(view: View, mPosterPath: String?) {
val imageView = view as ImageView
Glide.with(view.context)
.load(Utils.IMAGE_BASE_URL + mPosterPath)
.into(imageView)
}
#BindingAdapter("rating")
fun setRating(ratingBar: RatingBar, rating: Float) {
if (rating != null) {
ratingBar.rating = rating
}
}
}
constructor(mId: Long?, mOverview: String?, mPosterPath: String?, mTitle: String?, mVoteAverage: Double?) {
this.mId = mId
this.mOverview = mOverview
this.mPosterPath = mPosterPath
this.mTitle = mTitle
this.mVoteAverage = mVoteAverage
}
constructor()
#PrimaryKey
#SerializedName("id")
var mId: Long? = null
#SerializedName("overview")
var mOverview: String? = null
#SerializedName("poster_path")
var mPosterPath: String? = null
#SerializedName("title")
var mTitle: String? = null
#SerializedName("vote_average")
var mVoteAverage: Double? = null
}
Then finally, in my adapter class, I tried to bind the item layout.
class ResultAdapter(private val context: Context) : PagedListAdapter<Result, ResultAdapter.ResultViewHolder>(DIFF_CALLBACK) {
public lateinit var mBinding: ItemActivitymainBinding
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ResultViewHolder {
mBinding = DataBindingUtil.inflate(LayoutInflater.from(context), R.layout.item_activitymain, parent, false)
return ResultViewHolder(mBinding)
}
override fun onBindViewHolder(holder: ResultViewHolder, position: Int) {
val result = getItem(position)
if (result != null) {
holder.itemActivitymainBinding.titleTxt.text = result.mTitle
}
}
class ResultViewHolder(itemView: ItemActivitymainBinding) : RecyclerView.ViewHolder(itemView.root) {
var itemActivitymainBinding: ItemActivitymainBinding
var root: View
init {
root = itemView.root
itemActivitymainBinding = itemView
}
}
companion object {
const val MOVIE_ID = "MOVIE_ID"
const val MOVIE_NAME = "MOVIE_NAME"
const val MOVIE_OVERVIEW = "MOVIE_OVERVIEW"
private val DIFF_CALLBACK = object : DiffUtil.ItemCallback<Result>() {
override fun areItemsTheSame(oldItem: Result, newItem: Result): Boolean {
return oldItem.mId === newItem.mId
}
override fun areContentsTheSame(oldItem: Result, newItem: Result): Boolean {
return oldItem == newItem
}
}
}
}
Now I am still wondering why the image doesn't display because I have read some of the blog posts about this and I followed all their procedures.

First, you binding is missing its lifecycle owner (i.e., the activity or fragment in which you use the adapter). You should pass it to your adapter and then set it:
class ResultAdapter(private val lifecycleOwner: LifecycleOwner)
: PagedListAdapter<Result, ResultAdapter.ResultViewHolder>(DIFF_CALLBACK) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ResultViewHolder {
val inflater = LayoutInflater.from(parent.context)
val binding = DataBindingUtil.inflate<ItemActivitymainBinding>(inflater, R.layout.item_activitymain, parent, false)
// We set the lifecycle owner here
binding.setLifecycleOwner(lifecycleOwner)
return ResultViewHolder(binding)
}
...
}
// In your activity/fragment, pass the view as a parameter when creating the adapter
adapter = ResultAdapter(this)
(In the adapter, I have removed the property mBinding and the constructor parameter context, as neither of them were necessary.)
Second, you are defining the property movie in your layout, but you are not setting it with an actual value. To fix this, you have to update your implementation of onBindViewHolder():
override fun onBindViewHolder(holder: ResultViewHolder, position: Int) {
val movie = getItem(position)
// Here we set the layout variable "movie" with its corresponding value
holder.itemActivitymainBinding.movie = movie
}
(Please note that here I have removed the code you had written to change the title of your textview because you should change it through data-binding in the layout by doing this: android:text="#{movie.mTitle}".)
With these changes, your implementation should hopefully work!

kotlin recyclerview data not showing

Our question is how to show Parent and Child data from two SQLite DB tables?
We have two tables that are added to two ArrayLists childList and parentList.
Here are the Model Class's for each
class ModelParent {
var idD:Int = 0
var dept:String = ""
var fkD:Int = 0
var children: List<ModelChild> = mutableListOf()
//var children: ArrayList<ModelChild>? = null
//var children: List<ModelChild> by Delegates.notNull()
constructor (children: List<ModelParent>) : this()
companion object {
var globalVar = 1
}
}
class ModelChild {
var idI:Int = 0
var item:String = ""
var fkI:Int = 0
}
We have two Adapters for each table and will post that code
We are able to iterate through the two ArrayList with this code and display the data in the format we would like to show in the ViewActivity.
fun theGET(){
val db = DBHelper(this)
childList = db.queryITEM()
parentList = db.queryDEPT()
var PL = parentList.size
do {
var DEPT: String = parentList[z].dept
var PARENT_LIST_FK = parentList.get(z).fkD
println("========== Dept " + DEPT + " fkD " + PARENT_LIST_FK)
val FK = PARENT_LIST_FK
childList = db.queryALL(FK)
var CL = childList.size
for (a in 0..CL - 1) {
var CHILD_ITEM = childList[a].item
var CHILD_LIST_FK = childList[a].fkI
println("========== item " + CHILD_ITEM+" fkI "+CHILD_LIST_FK)
}
z++
}
while (z <= PL-1)
}
We will post the View Activity
class ViewActivity : AppCompatActivity() {
lateinit var recyclerView: RecyclerView
private var parentList:List<ModelParent> = ArrayList()
private var childList:List<ModelChild> = ArrayList()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_view)
initRecycler()
}// end onCreate
private fun initRecycler() {
val db = DBHelper(this)
childList = db.queryITEM()
parentList = db.queryDEPT()
recyclerView = rv_parent
recyclerView.apply{
layoutManager = LinearLayoutManager(this#ViewActivity, LinearLayout.VERTICAL, false)
adapter = ViewAdapter(parentList)
adapter = ViewChildAdapter(children = childList)
}
}
}
ViewActivity has this XML file
<?xml version="1.0" encoding="utf-8"?>
<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"
tools:context=".ViewActivity">
<android.support.v7.widget.RecyclerView
android:id="#+id/rv_parent"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</android.support.constraint.ConstraintLayout>
The Two Adapters and coresponding XML files
class ViewAdapter(private val parents:List<ModelParent>):RecyclerView.Adapter<ViewAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.the_view,parent,false)
return ViewHolder(view)
}
override fun getItemCount(): Int {
return parents.size
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val parent = parents[position]
holder.textView.text = parent.dept
holder.recyclerView.apply {
layoutManager = LinearLayoutManager(holder.recyclerView.context, LinearLayout.VERTICAL, false) as RecyclerView.LayoutManager?
adapter = ViewChildAdapter(parent.children!!)
}
}
inner class ViewHolder(itemView : View) : RecyclerView.ViewHolder(itemView){
val recyclerView : RecyclerView = itemView.rv_child
val textView: TextView = itemView.textView
}
}
class ViewChildAdapter(private val children:List<ModelChild>):RecyclerView.Adapter<ViewChildAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.child_recycler,parent,false)
return ViewHolder(view)
}
override fun getItemCount(): Int {
return children.size
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val child = children[position]
holder.textView.text = child.item
}
inner class ViewHolder(itemView : View) : RecyclerView.ViewHolder(itemView){
val textView : TextView = itemView.child_textView
}
}
Inflated XML files
<android.support.v7.widget.CardView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/card_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_margin="2dp"
card_view:cardBackgroundColor="#fff"
card_view:cardCornerRadius="5dp"
card_view:cardElevation="4dp"
card_view:cardUseCompatPadding="true">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:id="#+id/textView"
style="#style/Base.TextAppearance.AppCompat.Subhead"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignStart="#+id/rv_child"
android:layout_alignParentTop="true"
android:padding="20dp"
android:background="#color/color_super_lightGray"
android:text="Dept Header"
android:textColor="#color/color_Purple"
android:textSize="24sp"
android:textStyle="bold" />
<android.support.v7.widget.RecyclerView
android:id="#+id/rv_child"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_alignParentBottom="true"
android:layout_marginTop="70dp"
android:layout_marginBottom="0dp"
android:orientation="horizontal"
android:paddingLeft="4dp"
android:paddingTop="8dp"
tools:layout_editor_absoluteX="74dp" />
</RelativeLayout>
</android.support.v7.widget.CardView>
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<TextView
android:id="#+id/child_textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginStart="32dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="8dp"
android:background="#color/color_Transparent"
android:padding="10dp"
android:text="TextView"
android:textColor="#color/color_Black"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0" />
When the ViewActivity is loaded ONLY the childList is displayed.
We have tried various changes and can not display the parent List though using theGET fun the parentList data is displayed so we know it is in the list.
We can run the fun theGET and crate a new ArrayList that seems futile.
Our concern is that the parentList is displayed and then removed when the childList is displayed.
We do not know how to prove this.
So our question is how to show Parent and Child data in a organized fashion in the View Activity?
We are adding New CODE based on #Cruces answer
Some issues with this code are beyond out understanding
1. We have no way to run the fun join to create the newList
2. Parent and Child ViewHolder can be called only with receiver of containing Class
3. Too many inner Class's and do we need an Outer Nested annotation?
4. or if both parent and child implement an interface a List< IItem > )
We do not know how to write an interface and connect it to the JoinAdapter
While the answer poses new question we feel it better to ask with in this context = Context HUMOR
Here is the FIX for the JoinAdapter
class JoinAdapter(internal var context: Context, val parents: List<ModelParent>) : RecyclerView.Adapter<JoinAdapter.MyViewHolder>() {
val items = mutableListOf<Any>()
init {
parents //parents should be passed as a constructor argument
.forEach {
items.add(it)
items.addAll(it.children)
}
}
override fun getItemCount(): Int = items.size;
fun getItem(position: Int): Any = items[position]
override fun getItemViewType(position: Int): Int = if (getItem(position) is ModelParent) 0 else 1
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
var view: View? = null
if (viewType == 0) {
view = LayoutInflater.from(parent.context).inflate(R.layout.the_view, parent, false)
return ParentViewHolder(view!!)
} else {
view = LayoutInflater.from(parent.context).inflate(R.layout.child_recycler, parent, false)
return ChildViewHolder(view!!)
}
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) = holder.bindData(position, getItem(position))
inner abstract class MyViewHolder(view: View) : RecyclerView.ViewHolder(view) {
abstract fun bindData(position: Int, item: Any)
}
inner class ParentViewHolder(view: View) : MyViewHolder(view) {
override fun bindData(position: Int, item: Any) {
val parent = item as? ModelParent ?: return
parent.dept
parent.fkD
parent.children
//bind the data here
}
init {
val textView: TextView = view.textView
var editCLICK: RelativeLayout = view.findViewById(R.id.editCLICK) as RelativeLayout
//do the view setup here
}
}
inner class ChildViewHolder(view: View) : MyViewHolder(view) {
init {
val textView : TextView = itemView.child_textView
//do the view setup here
}
override fun bindData(position: Int, item: Any) {
val child = item as? ModelChild ?: return
child.item
child.idI
//bind the data here
}
}
I am going to post the View Activity call to Join Adapter
Code does not FAIL it just shows nothing?
RecyclerAdapter1 = JoinAdapter(parents = ArrayList(),context = applicationContext)
(recyclerView as RecyclerView).adapter = RecyclerAdapter1
Here is the ViewJoinActivity it will load the Parent Data NO Child Data
class ViewJoinActivity : AppCompatActivity() {
lateinit var recyclerView: RecyclerView
private var RecyclerAdapter: JoinAdapter? = null
private var linearLayoutManager: LinearLayoutManager? = null
private val db = DBHelper(this)
private var parentList:List<ModelParent> = ArrayList()
private var childList:List<ModelChild> = ArrayList()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_view_join)
initRecycler()
}// end onCreate
override fun onResume() {
super.onResume()
initDB()
}
private fun initDB() {
parentList = db.queryDEPT()
//childList = db.queryCHILD(1)
childList = db.queryITEM()
// queryCHILD only selects records with a fkI equal to idD
// SEE THE ModelChild and ModelParent
if(parentList.isEmpty()){
title = "No Records in DB"
}else{
title = "Parent List"
}
RecyclerAdapter = JoinAdapter(parents = parentList, context = applicationContext)
(recyclerView as RecyclerView).adapter = RecyclerAdapter
}
private fun initRecycler() {
val db = DBHelper(this)
childList = db.queryITEM()
parentList = db.queryDEPT()
//recyclerView = rv_parent
/*var PL = parentList.size
newList.clear()
do {
var DEPT: String = parentList[z].dept
var ND:String = DEPT
var PARENT_LIST_FK = parentList.get(z).fkD
var PL_ST = ND+" "+PARENT_LIST_FK
newList.add(PL_ST)
println("========== Dept " + DEPT + " fkD " + PARENT_LIST_FK)
val FK = PARENT_LIST_FK
childList = db.queryCHILD(FK)
var CL = childList.size
for (a in 0..CL - 1) {
var CHILD_ITEM = childList[a].item
var NI:String = childList[a].item
var CHILD_LIST_FK = childList[a].fkI
var IL_ST = NI+" "+CHILD_LIST_FK
newList.add(IL_ST)
println("========== item " + CHILD_ITEM+" fkI "+CHILD_LIST_FK)
}
z++
g++
}
while (z <= PL-1)
var ui = newList.size
g=0
for(g in 0..ui-1){
var N2 = newList[g]
if(N2.toString().contains("1")){
println("********************** We Found "+N2)
}
println("############### BOTH = "+N2)
}*/
recyclerView = this.findViewById(R.id.rv_parent)
RecyclerAdapter = JoinAdapter(parents = parentList, context = applicationContext)
linearLayoutManager = LinearLayoutManager(applicationContext)
(recyclerView as RecyclerView).layoutManager = linearLayoutManager!!
//recyclerView.apply {
//layoutManager = LinearLayoutManager(this#ViewJoinActivity, LinearLayout.VERTICAL, false)
//adapter = JoinAdapter(children = childList)
//}
}
}
Calling the Join Adapter from a Activity is the issue? ?
This Activity has a XML associated file with a RecyclerView rv_parent

The way I would do it is flatten the list edit: like this in the constructor
val items : MutableList<Any> = mutableListOf<Any>()
init() {
parents //parents should be passed as a constructor argument
.asSequence() //this is only needed if you want to also order them
.sortedBy { it.idD } //again only if you want to sort them
.forEach {
items.add(it)
items.addAll(it.children)
}
}
I would create a List < Any > (or if both parent and child implement an interface a List< IItem > ) that would contain all the data as you wish to see it, so for example it could look like this:
val items : List<Any> = listOf(parent1, child11,child12,child13,parent2,child12,child13,child14.....etc)
then I would implement a single adapter with multiple view types like this:
override fun getItemCount(): Int {
return items.size
}
fun getItem(position: Int) : Any { //or the interface
return items[position]
}
override getItemViewType (position: Int) : Int {
if (getItem(position) is ModelParent)
return 0
return 1
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
var view : View? = null
if (viewType == 0) {
view = LayoutInflater.from(parent.context).inflate(R.layout.parent_layout,parent,false)
return ParentViewHolder(view);
} else {
view = LayoutInflater.from(parent.context).inflate(R.layout.child_layout,parent,false)
return ChildViewHolder(view);
}
}
and then I would use two view holders to represent how the data is shown for the specific item
inner class ParentViewHolder(itemView : View) : RecyclerView.ViewHolder(itemView){ ...}
inner class ChildViewHolder(itemView : View) : RecyclerView.ViewHolder(itemView){ ...}
after that I could perform different bindings by getting the type of the view ,something like this:
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
if (getItemType(position) == 0) {
(holder as ParentViewHolder).bindData(....)
} else {
(holder as ChildViewHolder).bindData(....)
}
}
edit: Here is the complete adapter I built, it is based on two layout files:
list_item_child:
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/card_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_margin="2dp"
card_view:cardBackgroundColor="#fff"
card_view:cardCornerRadius="5dp"
card_view:cardElevation="4dp"
card_view:cardUseCompatPadding="true">
<TextView
android:id="#+id/child_item"
style="#style/Base.TextAppearance.AppCompat.Display3"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:padding="20dp"
android:textSize="24sp"
android:textStyle="bold"
tools:text="Dept Header" />
</android.support.v7.widget.CardView>
list_item_parent:
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/card_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_margin="2dp"
card_view:cardBackgroundColor="#fff"
card_view:cardCornerRadius="5dp"
card_view:cardElevation="4dp"
card_view:cardUseCompatPadding="true">
<TextView
android:id="#+id/parent_department"
style="#style/Base.TextAppearance.AppCompat.Headline"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:padding="20dp"
tools:text="Dept Header"
android:textSize="24sp"
android:textStyle="bold" />
</android.support.v7.widget.CardView>
and the adapter would look something like this:
import android.content.Context
import android.support.v7.widget.RecyclerView
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
data class ModelParent(val id: Int, val children: List<ModelChild>)
data class ModelChild(val id: Int)
class JoinAdapter(internal var context: Context, val parents: List<ModelParent>) : RecyclerView.Adapter<JoinAdapter.MyViewHolder>() {
val items = mutableListOf<Any>()
init {
parents //parents should be passed as a constructor argument
.forEach {
items.add(it)
items.addAll(it.children)
}
}
override fun getItemCount(): Int = items.size;
fun getItem(position: Int): Any = items[position]
override fun getItemViewType(position: Int): Int = if (getItem(position) is ModelParent) 0 else 1
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
var view: View? = null
if (viewType == 0) {
view = LayoutInflater.from(parent.context).inflate(R.layout.rv_list_item_parent, parent, false)
return ParentViewHolder(view!!)
} else {
view = LayoutInflater.from(parent.context).inflate(R.layout.rv_list_item_child, parent, false)
return ChildViewHolder(view!!)
}
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) = holder.bindData(position, getItem(position))
inner abstract class MyViewHolder(view: View) : RecyclerView.ViewHolder(view) {
abstract fun bindData(position: Int, item: Any)
}
inner class ParentViewHolder(view: View) : MyViewHolder(view) {
var parentDept: TextView = view.findViewById(R.id.parent_department) as TextView
override fun bindData(position: Int, item: Any) {
val parent = item as? ModelParent ?: return
parentDept.text = parent.dept
}
}
inner class ChildViewHolder(view: View) : MyViewHolder(view) {
var childItem: TextView = view.findViewById(R.id.child_item) as TextView
override fun bindData(position: Int, item: Any) {
val child = item as? ModelChild ?: return
childItem.text = child.item
}
}
}
this when used on a single recyclerview will display all children under their parent in a list

Here is a answer and some observations about the design of this app
The answer does NOT place both the parent and child data on the same Recycler View List But the answer may help to solve the issue With further exploration!
What we did was create the parent list and when the Parent Dept is clicked on the corresponding Child Items will be displayed. This may be a more functional design while shopping you only need to look at Produce items while in that section. This means less scrolling through a single master list of Parents and Children.
A word or two about the design we are guessing a grocery store might have 20 or more Departments (Parents) so how you plan to know which Items (Child data) is connected to the appropriate Dept (Parent) needs drastic redesign when building these two lists.
If you downloaded the code from GitHub you will have a better grasp about this design deficiency
Here is all the code with the XML files
Main Activity navigates to View Activity
fun onViewAll(view: View){
val intent = Intent(this,ViewActivity::class.java)
intent.putExtra("pickADAPTER",2)
startActivity(intent)
}
Here is the View Activity
class ViewActivity : AppCompatActivity() {
lateinit var recyclerView: RecyclerView
private var RecyclerAdapter1: ViewAdapter? = null
private var RecyclerAdapter2: ViewChildAdapter? = null
private var linearLayoutManager: LinearLayoutManager? = null
private val db = DBHelper(this)
private var parentList:List<ModelParent> = ArrayList()
private var childList:List<ModelChild> = ArrayList()
var idD = 0
var whichADAPTER = 0
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_view)
val bundle: Bundle = intent.extras
idD = bundle.getInt("BIGi", 0)
whichADAPTER = bundle.getInt("pickADAPTER",0)
initRecycler()
}// end onCreate
override fun onResume() {
super.onResume()
initDB()
}
private fun initDB() {
parentList = db.queryDEPT()
childList = db.queryCHILD(idD)
// queryCHILD only selects records with a fkI equal to idD
// SEE THE ModelChild and ModelParent
if(parentList.isEmpty()){
title = "No Records in DB"
}else{
title = "Parent List"
}
if(whichADAPTER == 2) {
RecyclerAdapter1 = ViewAdapter(parents = parentList, context = applicationContext)
(recyclerView as RecyclerView).adapter = RecyclerAdapter1
}else{
RecyclerAdapter2 = ViewChildAdapter(children = childList)
(recyclerView as RecyclerView).adapter = RecyclerAdapter2
}
}
private fun initRecycler() {
val db = DBHelper(this)
childList = db.queryITEM()
parentList = db.queryDEPT()
recyclerView = rv_parent
recyclerView = this.findViewById(R.id.rv_parent)
RecyclerAdapter1 = ViewAdapter(parents = parentList, context = applicationContext)
linearLayoutManager = LinearLayoutManager(applicationContext)
(recyclerView as RecyclerView).layoutManager = linearLayoutManager!!
}
Here the XML file for View Activity
<android.support.v7.widget.RecyclerView
android:id="#+id/rv_parent"
android:layout_width="match_parent"
android:layout_height="match_parent" />
Here is the View Adapter
class ViewAdapter(private val parents: List<ModelParent>, internal var context: Context):RecyclerView.Adapter<ViewAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.the_view,parent,false)
return ViewHolder(view)
}
override fun getItemCount(): Int {
return parents.size
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val parent = parents[position]
holder.textView.text = parent.dept
holder.editCLICK.setOnClickListener {
val i = Intent(context, ViewActivity::class.java)
i.putExtra("BIGi",parent.idD)
i.flags = Intent.FLAG_ACTIVITY_NEW_TASK
context.startActivity(i)
}
}
inner class ViewHolder(itemView : View) : RecyclerView.ViewHolder(itemView){
//val recyclerView : RecyclerView = itemView.rv_child
val textView: TextView = itemView.textView
var editCLICK: RelativeLayout = itemView.findViewById(R.id.editCLICK) as
RelativeLayout
And the inflated XML
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/card_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_margin="2dp"
card_view:cardBackgroundColor="#FF0000"
card_view:cardCornerRadius="5dp"
card_view:cardElevation="4dp"
card_view:cardUseCompatPadding="true">
<RelativeLayout
android:id="#+id/editCLICK"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:id="#+id/textView"
style="#style/Base.TextAppearance.AppCompat.Subhead"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignStart="#+id/rv_child"
android:layout_alignParentTop="true"
android:padding="10dp"
android:background="#color/color_lightGray"
android:text="Dept Header"
android:textColor="#color/color_Purple"
android:textSize="24sp"
android:textStyle="bold" />
<android.support.v7.widget.RecyclerView
android:id="#+id/rv_child"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_alignParentBottom="true"
android:layout_marginTop="50dp"
android:layout_marginBottom="0dp"
android:orientation="horizontal"
android:paddingLeft="4dp"
android:paddingTop="6dp"
tools:layout_editor_absoluteX="74dp" />
</RelativeLayout>
This is the search routine in DBHelper
fun queryCHILD(fkI: Int): List<ModelChild> {
val db = this.writableDatabase
val childList = ArrayList<ModelChild>()
val selectQuery = "SELECT * FROM $CHILD_TABLE WHERE $colCFK = ?"
val cursor = db.rawQuery(selectQuery, arrayOf(fkI.toString()))
if (cursor != null) {
if (cursor.moveToFirst()) {
do {
val contact = ModelChild()
contact.idI = Integer.parseInt(cursor.getString(cursor.getColumnIndex(colidI)))
contact.item = cursor.getString(cursor.getColumnIndex(colItem))
contact.fkI = Integer.parseInt(cursor.getString(cursor.getColumnIndex(colCFK)))
childList.add(contact)
} while (cursor.moveToNext())
}
}
cursor.close()
return childList
}
One thing to make note of we attached the OnClickListener to a Relative Layout
holder.editCLICK.setOnClickListener
Why we are not sure you can obtain parent.idD type information from a RecyclerView set as a listener?
We need to explore this but in our testing the code failed when we tried.

In the ViewActivity class, you have first set the recyclerView adapter to ViewAdapter and then to ViewChildAdapter thus, now, the adapter of recyclerView is ViewChildAdapter instead of ViewAdapter. Remove this line and the problem will be resolved.