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

RecyclerView swipe functionality breaks after orientation change

I created a RecyclerView that refreshes its list based on a database call. Each row has an options menu that is revealed when the user swipes. My original issue was that after an orientation change, the swipe gestures no longer revealed the menu. I hit all my expected breakpoints with onCreateViewHolder() and the onSwipe(). However, the row remained as the HIDE_MENU view type after swiping.
So I tried to introduce LiveData to persist the state of the list after orientation changes. The RecyclerView was still created and populated with items but now the swipe gesture crashes the application with an error:
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
Do I need to use LiveData to fix the original issue of preserving my swipe functionality after orientation changes? If not, please can someone explain why the item view types are no longer updated after orientation changes.
If I do need to use a ViewModel, what am I doing that is causing the list adapter not to receive the updated list?
HistoryFragment
class HistoryFragment : Fragment() {
private val historyViewModel by activityViewModels<HistoryViewModel>()
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val root = inflater.inflate(R.layout.fragment_history, container, false)
historyViewModel.getHistoryList().observe(viewLifecycleOwner, {
refreshRecyclerView(it)
})
return root
}
private fun updateHistoryList() {
val dbHandler = MySQLLiteDBHandler(requireContext(), null)
val historyList = dbHandler.getHistoryList() as MutableList<HistoryObject>
historyViewModel.setHistoryList(historyList)
}
private fun refreshRecyclerView(historyList: MutableList<HistoryObject>) {
val historyListAdapter = HistoryListAdapter(historyList)
val callback = HistorySwipeHelper(historyListAdapter)
val helper = ItemTouchHelper(callback)
history_list.adapter = historyListAdapter
helper.attachToRecyclerView(history_list)
}
private fun setupSort() {
val sortSpinner: Spinner = history_list_controls_sort
sortSpinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
override fun onNothingSelected(parent: AdapterView<*>?) {}
override fun onItemSelected(
parent: AdapterView<*>?,
view: View?,
position: Int,
id: Long
) {
updateHistoryList()
}
}
}
override fun onViewCreated(
view: View,
savedInstanceState: Bundle?
) {
setupSort()
}
}
HistoryListAdapter
const val SHOW_MENU = 1
const val HIDE_MENU = 2
class HistoryListAdapter(private var historyData: MutableList<HistoryObject>) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return if (viewType == SHOW_MENU) {
val inflatedView = LayoutInflater.from(parent.context).inflate(R.layout.history_list_view_row_items_menu, parent, false)
MenuViewHolder(inflatedView)
} else {
val inflatedView = LayoutInflater.from(parent.context).inflate(R.layout.history_list_view_row_items_description, parent, false)
HistoryItemViewHolder(inflatedView)
}
}
override fun getItemViewType(position: Int): Int {
return if (historyData[position].showMenu) {
SHOW_MENU
} else {
HIDE_MENU
}
}
override fun getItemCount(): Int {
return historyData.count()
}
fun showMenu(position: Int) {
historyData.forEachIndexed { idx, it ->
if (it.showMenu) {
it.showMenu = false
notifyItemChanged(idx)
}
}
historyData[position].showMenu = true
notifyItemChanged(position)
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
val item: HistoryObject = historyData[position]
if (holder is HistoryItemViewHolder) {
holder.bindItem(item)
...
}
if (holder is MenuViewHolder) {
holder.bindItem(item)
...
}
}
class HistoryItemViewHolder(v: View, private val clickHandler: (item: HistoryObject) -> Unit) : RecyclerView.ViewHolder(v) {
private var view: View = v
private var item: HistoryObject? = null
fun bindItem(item: HistoryObject) {
this.item = item
...
}
}
class MenuViewHolder(v: View, private val deleteHandler: (item: HistoryObject) -> Unit) : RecyclerView.ViewHolder(v) {
private var view: View = v
private var item: HistoryObject? = null
fun bindItem(item: HistoryObject) {
this.item = item
...
}
}
}
HistorySwipeHelper
class HistorySwipeHelper(private val adapter: HistoryListAdapter) : ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT) {
override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean { return false }
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
adapter.showMenu(viewHolder.adapterPosition)
}
override fun getSwipeThreshold(viewHolder: RecyclerView.ViewHolder): Float {
return 0.1f
}
}
HistoryViewModel
class HistoryViewModel(private var historyListHandle: SavedStateHandle) : ViewModel() {
fun getHistoryList(): LiveData<MutableList<HistoryObject>> {
return historyListHandle.getLiveData(HISTORY_LIST_KEY)
}
fun setHistoryList(newHistoryList: MutableList<HistoryObject>) {
historyListHandle.set(HISTORY_LIST_KEY, newHistoryList)
}
companion object {
const val HISTORY_LIST_KEY = "MY_HISTORY_LIST"
}
}
Activity
class MainActivity : AppCompatActivity() {
private val historyViewModel: HistoryViewModel by lazy {
ViewModelProvider(this).get(HistoryViewModel::class.java)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
historyViewModel.setHistoryList(mutableListOf())
}
}
Thanks in advance. If this question is too broad I can try again and decompose it.

You shouldn't create new adapter every time you get an update of your history list. Keep using the same adapter, just update the items and call notifyDataSetChanged() to update the state (of course you can use different methods to notify about the insertion/deletion/etc, but make it work with notifyDataSetChanged() first).
I'm pretty sure this will fix the issue.

Implementing ListAdapter for a RecyclerView Fragment

I've done this successfully with a normal ViewAdapter but I can't seem to get it working with a ListAdapter.
Here is my Fragment that does most of the work:
class CrimeListFragment: Fragment() {
//Required interface for hosting activities
interface Callbacks {
fun onCrimeSelected(crimeId: UUID)
}
private var callbacks: Callbacks? = null
private lateinit var crimeRecyclerView: RecyclerView
private val crimeListViewModel: CrimeListViewModel by lazy {
ViewModelProviders.of(this).get(CrimeListViewModel::class.java)
}
override fun onAttach(context: Context) {
super.onAttach(context)
callbacks = context as Callbacks?
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val view = inflater.inflate(R.layout.fragment_crime_list, container, false)
crimeRecyclerView =
view.findViewById(R.id.crime_recycler_view) as RecyclerView
crimeRecyclerView.layoutManager = LinearLayoutManager(context)
crimeRecyclerView.adapter = CrimeListAdapter(emptyList())
return view
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
crimeListViewModel.crimeListLiveData.observe(
viewLifecycleOwner,
Observer { crimes ->
crimes?.let {
Log.i(TAG, "Got crimes ${crimes.size}")
updateUI(crimes)
}
}
)
}
override fun onDetach() {
super.onDetach()
callbacks = null
}
private fun updateUI(crimes: List<Crime>) {
crimeRecyclerView.adapter = CrimeListAdapter(crimes)
}
companion object {
fun newInstance(): CrimeListFragment {
return CrimeListFragment()
}
}
private inner class CrimeHolder(view: View)
: RecyclerView.ViewHolder(view), View.OnClickListener {
private lateinit var crime: Crime
private val titleTextView = itemView.findViewById<TextView>(R.id.crime_title)
private val dateTextView = itemView.findViewById<TextView>(R.id.crime_date)
private val solvedImageView = itemView.findViewById<ImageView>(R.id.crime_solved)
init {
itemView.setOnClickListener(this)
}
fun bind(crime: Crime) {
this.crime = crime
titleTextView.text = crime.title
dateTextView.text = crime.date.toString()
solvedImageView.visibility = if(crime.isSolved) {
View.VISIBLE
} else {
View.GONE
}
}
override fun onClick(v: View) {
callbacks?.onCrimeSelected(crime.id)
}
}
private inner class CrimeListAdapter(var crimes: List<Crime>)
: ListAdapter<Crime, CrimeHolder>(DiffCallback()) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CrimeHolder {
val view =
layoutInflater.inflate(R.layout.list_item_crime, parent, false)
return CrimeHolder(view)
}
override fun onBindViewHolder(holder: CrimeHolder, position: Int) {
holder.bind(crimes[position])
}
}
private inner class DiffCallback: DiffUtil.ItemCallback<Crime>() {
override fun areItemsTheSame(oldItem: Crime, newItem: Crime): Boolean {
return oldItem.id == newItem.id
}
override fun areContentsTheSame(oldItem: Crime, newItem: Crime): Boolean {
return oldItem == newItem
}
}
}
And here is the fragment's viewmodel:
class CrimeListViewModel: ViewModel() {
private val crimeRepository = CrimeRepository.get()
val crimeListLiveData = crimeRepository.getCrimes() //returns LiveData<List<Crime>>
}
Android documentation has this regarding ListAdapter:
While using a LiveData is an easy way to provide data to the adapter, it isn't required - you can use submitList(List) when new lists are available.
I'm supposed to submit a new list instead of creating a new ListAdapter object each time I update the UI. But crimeRecyclerView.adapter has no .submitList() function. So how do I pass on the new list?
LiveData is still new to me so I'm not quite clear on this. I already observe a LiveData stored in my viewmodel. So what do I observe this time? Or do I just add code to my existing Observer?
Finally when I run the code in this state, phone shows an empty RecyclerView. Only UpdateUI() gets called, none of CrimeListAdapter's functions get called. I'm not sure if this is a real problem or just the consequence of the above.

1.I'm supposed to submit a new list instead of creating a new ListAdapter object each time I update the UI. But
crimeRecyclerView.adapter has no .submitList() function. So how do I
pass on the new list?
crimeRecyclerView.adapter return RecyclerView.Adapter type
submitList() is a method of ListAdapter, a sub-class of RecyclerView.Adapter
You need to cast from super to sub class before calling that method, like this.
(crimeRecyclerView.adapter as CrimeListAdapter).submitList(crimes)
2.LiveData is still new to me so I'm not quite clear on this. I already observe a LiveData stored in my viewmodel. So what do I
observe this time? Or do I just add code to my existing Observer?
Your code for this part is good, no need to do more.
3.Finally when I run the code in this state, phone shows an empty RecyclerView. Only UpdateUI() gets called, none of CrimeListAdapter's
functions get called. I'm not sure if this is a real problem or just
the consequence of the above.
The best part of using ListAdapter is you do not need to provide a list of data (crimes in your case) to constructor.
Back to your code, you need to change 3 things.
// crimeRecyclerView.adapter = CrimeListAdapter(emptyList())
crimeRecyclerView.adapter = CrimeListAdapter()
and
// crimeRecyclerView.adapter = CrimeListAdapter(crimes)
(crimeRecyclerView.adapter as CrimeListAdapter).submitList(crimes)
and
//private inner class CrimeListAdapter(var crimes: List<Crime>) :
// ListAdapter<Crime, CrimeHolder>(DiffCallback()) {
//
// override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CrimeHolder {
// val view = layoutInflater.inflate(R.layout.list_item_crime, parent, false)
// return CrimeHolder(view)
// }
//
// override fun onBindViewHolder(holder: CrimeHolder, position: Int) {
// holder.bind(crimes[position])
// }
//}
private inner class CrimeListAdapter : ListAdapter<Crime, CrimeHolder>(DiffCallback()) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CrimeHolder {
val view = layoutInflater.inflate(R.layout.list_item_crime, parent, false)
return CrimeHolder(view)
}
override fun onBindViewHolder(holder: CrimeHolder, position: Int) {
holder.bind(getItem(position))
}
}

RecyclerView Get view at particular position and retrieve data from it android kotlin

i have recyclerview item which has 4 edittexts. Also i have add new item button which add new item and new edittexts(they need to be populated from the use) i`m trying to retrieve all data from the fields when user click save button. Here is my code:
class SectionsRecyclerAdapter(private val educationList: MutableList<Any>) :
RecyclerView.Adapter<SectionsRecyclerAdapter.ViewHolder>() {
class ViewHolder(val item: View) : RecyclerView.ViewHolder(item)
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.item_new_section, parent, false)
return ViewHolder(view)
}
override fun getItemCount() = educationList.size
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
if (holder != null) {
holder.item.deleteBtn.visibility = if (position != 0) View.VISIBLE else View.GONE
holder.item.deleteBtn.setOnClickListener {
educationList.removeAt(position)
notifyItemRemoved(position)
notifyItemRangeRemoved(position, educationList.size)
}
}
}
fun addItem() {
educationList.add(EducationModel())
notifyItemInserted(educationList.size)
}
}
Education Fragment :
class EducationFragment : Fragment(), ValidationInterface {
private var educationList: MutableList<Any> = mutableListOf()
private lateinit var sectionAdapter : SectionsRecyclerAdapter
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment_education, container, false)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
educationList.add(EducationModel())
sectionAdapter = SectionsRecyclerAdapter(educationList)
educationRv.apply {
layoutManager = LinearLayoutManager(activity)
adapter = ScaleInAnimationAdapter(sectionAdapter)
itemAnimator = LandingAnimator()
}
addSectionBtn.setOnClickListener {
sectionAdapter.addItem()
educationRv.smoothScrollToPosition(educationList.size)
}
}
companion object {
val instance = EducationFragment()
}
override fun validateAndSave(): Boolean {
//Here i want to get data from every child and then parse it to my model EducationModel
val model = educationRv.getChildAt(0)
list.add(model)
CreateResumeActivity.modelInstance.educationList.addAll(list)
return true
}
Of course if there are better solution i will be glad, but for now i`m stuck with this... My main goal is when user click save i need to retrieve value from the edittext ( University, StartDate, EndDate, Summary) and put it in EducationModels

Inside a recycler view each view holder can recycle his views. For that reason you have to keep all edittext values in a public list inside your adapter and access it from component which hold that adapter. Here is an proof of concept:
class MyAdapter: RecyclerView.Adapter(private val educationList: MutableList<Any>) {
val holderList = educationList.map { EditTextValues(...) };
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
//fill edit text just in case that it is recycled
holder.editText.text = holderList[position].editTextValue
holder.editText.onTextChangeLister { holderList[position] = EditTextValues(holder.editText.text) }
}
}
class MyAndroidComponent : Fragment {
val adapter: MyAdapter = ...
fun onCreate() {
saveButton.setOnClickListener {
// you can access your edit texts values here
adapter.holderList
}
}
}

(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?) {
...
}