Develop Reference

Incorrect data in recycleview

I am using RecycleView in android studio. When data is coming from Firebase it is correct at first. Later, when I add 1 sms to the list of type List(), I get wrong data as a result.
For example:
If List is {1,2,3,4,5},
Add 6 to the list on the screen
The elements of List {1,2,3,4,5,6} should appear in this order.
In this case,
After the chase
List {1,2,3,4,5,1,2,3,4,5,6} is like this. After 1 update it works fine.
class ChatAdapter(var list:MutableList<Sms>,var context: Context):RecyclerView.Adapter<RecyclerView.ViewHolder>(){
companion object {
private const val ITEM_RECEIVE = 1
private const val ITEM_SENT = 2
}
private val shared by lazy {
SharedPref(context)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return if (viewType == 1) {
val view = LayoutInflater.from(context).inflate(R.layout.item_he_sms, parent, false)
ReceiveVewHolder(view)
}else{
val view = LayoutInflater.from(context).inflate(R.layout.item_my_sms, parent, false)
SentViewHolder(view)
}
}
override fun getItemViewType(position: Int): Int {
val currentMessage = list[position]
return if (currentMessage.emailAddress==shared.getEmail()){
ITEM_SENT
}else{
ITEM_RECEIVE
}
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
if (shared.getEmail()==list[position].emailAddress){
holder as SentViewHolder
holder.textView.text = list[position].smsText
}else{
holder as ReceiveVewHolder
holder.textView.text = list[position].smsText
if (list[position].gender=="Male"){
holder.imagePerson.setImageResource(R.drawable.male_avatar)
}else{
holder.imagePerson.setImageResource(R.drawable.female_avatar)
}
}
}
override fun getItemCount(): Int =list.size
inner class SentViewHolder(view: View) : RecyclerView.ViewHolder(view) {
val textView: TextView = view.findViewById(R.id.my_message)
}
inner class ReceiveVewHolder(view: View) : RecyclerView.ViewHolder(view) {
val textView: TextView = view.findViewById(R.id.he_message)
val imagePerson:CircleImageView=view.findViewById(R.id.imagePerson)
}
}

Create this methode inside your Adapter :
fun updateList(list: List<Sms>){
this.list.clear()
this.list.addAll(list)
notifyDataSetChanged()
}
then call it from inside your observer method, it should resolve your problem.

Xato Firebase'dan getAllSms da, sendSms() usuli ishlayotganda, {1,2,3,4,5,1,2,3,4,5,6} ro'yxat sifatida qaytariladi. result.invoke ni bajarishdan oldin onDataChange-da list.clear ni bajarishingiz kerak.
override fun getAllSms(result: (UiState<ArrayList<Sms>>) -> Unit) {
CoroutineScope(Dispatchers.IO).launch {
val list = ArrayList<Sms>()
myRef.getReference("global")
.addValueEventListener(object :ValueEventListener{
override fun onDataChange(snapshot: DataSnapshot) {
list.clear()
snapshot.children.forEach {
val sms:Sms=it.getValue(Sms::class.java)!!
list.add(sms)
}
list.forEach {
Log.d("LLIISSTT", it.smsText)
}
result.invoke(UiState.Success(list))
}
override fun onCancelled(error: DatabaseError) {
result.invoke(UiState.Failure(error.message))
}
})
}
}

How to combine two Adapter from call response in Android Java?

Is there a way to combine two adapters that are inside a Callback from Model?
Like, I get data from two sources and I want to display both of them in the same recyclerView
I tried to load the method first then put both adapters on concatAdapter but I got a null from this concatAdapter and then my app crashed
here is my method in Java
private void fetchDataKabupaten(){
progressBar.setVisibility(View.VISIBLE);
token = getIntent().getStringExtra("token");
Call<KabupatenModel> kabupatenModelCall = RetrofitClient.getLoginInterface().getKabupatenData("Bearer "+token);
kabupatenModelCall.enqueue(new Callback<KabupatenModel>() {
#Override
public void onResponse(Call<KabupatenModel> call, Response<KabupatenModel> response) {
kabupatenList = response.body().getKabupaten();
adKabupaten = new KabupatenAdapter(MainActivity.this, kabupatenList);
progressBar.setVisibility(View.GONE);
}
}
private void fetchDataKecamatan(){
progressBar.setVisibility(View.VISIBLE);
token = getIntent().getStringExtra("token");
Call<KecamatanModel> kecamatanModelCall = RetrofitClient.getLoginInterface().getKecamatanData("Bearer " + token);
kecamatanModelCall.enqueue(new Callback<KecamatanModel>() {
#Override
public void onResponse(Call<KecamatanModel> call, Response<KecamatanModel> response) {
kecamatanList = response.body().getKecamatan();
adKecamatan = new KecamatanAdapter(MainActivity.this, kecamatanList);
progressBar.setVisibility(View.GONE);
}
}
I have tried to call both in MainActivity then setAdapter with concatAdapter like this:
fetchDataKabupaten();
fetchDataKecamatan();
concatAdapter = new ConcatAdapter(adKecamatan, adKabupaten);
rV.setAdapter(concatAdapter);
why is it null?
but, when I only set one Adapter inside the response method it works.

you can only use one adapter in recyclerview, but adapter can have multiple view.
for example I have adapter for chat, with right and left view
Adapter Chat Detail
class AdapterChatDetail(val datas: ArrayList<ChatMessage>) :
RecyclerView.Adapter<RecyclerView.ViewHolder>() {
private lateinit var ctx: Context
companion object {
const val LEFT = 0
const val RIGHT = 1
}
inner class ViewHolderLeft(val binding: AdapterMyChatLeftBinding) :
RecyclerView.ViewHolder(binding.root) {
fun bind(data: ChatMessage) {
}
}
inner class ViewHolderRight(val binding: AdapterMyChatRightBinding) :
RecyclerView.ViewHolder(binding.root) {
fun bind(data: ChatMessage) {
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
ctx = parent.context
return when (viewType) {
LEFT -> ViewHolderLeft(
AdapterMyChatLeftBinding.inflate(
LayoutInflater.from(ctx),
parent,
false
)
)
RIGHT -> ViewHolderRight(
AdapterMyChatRightBinding.inflate(
LayoutInflater.from(ctx),
parent,
false
)
)
else -> ViewHolderLeft(
AdapterMyChatLeftBinding.inflate(
LayoutInflater.from(ctx),
parent,
false
)
)
}
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
when (getItemViewType(position)) {
LEFT -> (holder as ViewHolderLeft).bind(datas[position])
RIGHT -> (holder as ViewHolderRight).bind(datas[position])
}
}
override fun getItemCount() = datas.size
override fun getItemViewType(position: Int): Int {
val data = datas[position]
return if (data.position == "right") RIGHT else LEFT
}
}

RecyclerView Adapter methods not getting called kotlin

In the Adapter method. i am able to print list elements in updateUsers(newUsers: List)
that means I am getting dataset in the Adapter, but none of the Adapter methods are getting called.
I have set the layout manager too.
I have breakpoints for All adapter methods onCreateViewHolder, onBindViewHolder. but control is not entering code block.
class MainActivity : AppCompatActivity() {
lateinit var viewModel: ListViewModel
private val usersAdapter = UserListAdapter(arrayListOf(),this)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
viewModel = ViewModelProviders.of(this).get(ListViewModel::class.java)
viewModel.refresh()
usersList.apply {
layoutManager = LinearLayoutManager(this.context)
adapter = usersAdapter
}
usersList.adapter = usersAdapter
observeViewModel()
}
fun observeViewModel() {
viewModel.users.observe(this, Observer {
it?.let {
it.forEach {
Log.d("Each Item", it.toString());
}
loading_view.visibility = View.VISIBLE
usersAdapter.updateUsers(it)
}
})
viewModel.userLoadError.observe(this, Observer {
it?.let {
list_error.visibility = if (it) View.VISIBLE else View.GONE
}
})
viewModel.loading.observe(this, Observer {
it?.let {
loading_view.visibility = if (it) View.VISIBLE else View.GONE
if (it) {
list_error.visibility = View.GONE
usersList.visibility = View.GONE
}
}
})
}
}
class UserListAdapter(private var users: ArrayList<User>, private val context : Context) : RecyclerView.Adapter<UserListAdapter.UserViewHolder>() {
fun updateUsers(newUsers: List<User>) {
newUsers.forEach() {
Log.d("updateUsers", it.firstName)
}
users.clear()
users.addAll(newUsers)
notifyDataSetChanged()
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) : UserViewHolder{
val layoutInflator = LayoutInflater.from(parent.context)
val view = layoutInflator.inflate(R.layout.item_layout,parent,false)
return UserViewHolder(view)
}
override fun getItemCount():Int {
return users.size
}
override fun onBindViewHolder(holder: UserViewHolder, position: Int) {
holder.bind(users[position])
}
class UserViewHolder(view: View) : RecyclerView.ViewHolder(view) {
private val imageView = view.imageView
private val userName = view.name
private val userEmail = view.email
fun bind(country: User) {
userName.text = country.firstName + " " + country.lastName
userEmail.text = country.email
imageView.loadImage(country.avatar)
}
}
}

I am not exactly sure why your code is not working, here I have implemented using your code and it's working.
MainActivity
class MainActivity : AppCompatActivity() {
private lateinit var viewModel: ListViewModel
private val usersAdapter = UserListAdapter(arrayListOf(), this)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
viewModel = ViewModelProviders.of(this).get(ListViewModel::class.java)
viewModel.refresh()
usersList.apply {
layoutManager = LinearLayoutManager(this.context,
RecyclerView.VERTICAL, false)
adapter = usersAdapter
}
// usersList.adapter = usersAdapter // Don't need, you already set the
// adapter above.
observeViewModel()
}
private fun observeViewModel() {
viewModel.users.observe(this, Observer {
it?.let {
it.forEach {
Log.d("Each Item", it.toString());
}
//loading_view.visibility = View.VISIBLE
usersAdapter.updateUsers(it)
}
})
// commented for simplicity
//viewModel.userLoadError.observe(this, Observer {
// it?.let {
//list_error.visibility = if (it) View.VISIBLE else View.GONE
// }
//})
// viewModel.loading.observe(this, Observer {
// it?.let {
// loading_view.visibility = if (it) View.VISIBLE else View.GONE
// if (it) {
// list_error.visibility = View.GONE
// usersList.visibility = View.GONE
// }
//
// }
// })
}
}
UserListAdapter
class UserListAdapter(private var users: ArrayList<User>, private val context : Context) : RecyclerView.Adapter<UserListAdapter.UserViewHolder>() {
fun updateUsers(newUsers: List<User>) {
newUsers.forEach() {
Log.d("updateUsers", it.firstName)
}
users.clear()
users.addAll(newUsers)
notifyDataSetChanged()
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) : UserViewHolder {
val inflater = LayoutInflater.from(parent.context)
val view = inflater.inflate(R.layout.item_layout,parent,false)
return UserViewHolder(view)
}
override fun getItemCount():Int {
return users.size
}
override fun onBindViewHolder(holder: UserViewHolder, position: Int) {
holder.bind(users[position])
}
class UserViewHolder(view: View) : RecyclerView.ViewHolder(view) {
private val imageView = view.imageView
private val userName = view.name
private val userEmail = view.email
fun bind(country: User) {
userName.text = country.firstName + " " + country.lastName
userEmail.text = country.email
//imageView.loadImage(country.avatar)
}
}
}
ListViewModel
class ListViewModel: ViewModel() {
val users : MutableLiveData<List<User>> = MutableLiveData()
fun refresh() {
val userList = mutableListOf<User>()
userList.add(User(
"User1 First Name",
"User1 last Name",
"example#gmail.com"
))
userList.add(User(
"User2 First Name",
"User2 First Name",
"example#gmail.com"
))
userList.add(User(
"User3 First Name",
"User3 First Name",
"example#gmail.com"
))
userList.add(User(
"User4 First Name",
"User4 First Name",
"example#gmail.com"
))
userList.add(User(
"User5 First Name",
"User5 First Name",
"example#gmail.com"
))
userList.add(User(
"User6 First Name",
"User6 First Name",
"example#gmail.com"
))
users.value = userList
}
}
Hope this helps.

Trying to set an Listener which is abstracted [duplicate]

This question already has answers here:
Can we instantiate an abstract class?
(16 answers)
Closed 3 years ago.
I'm working right now on an little app to test arround with motion and touch events. I am facing the problem that my Listener class has to be abstracted but I cannot create an object from that listener which I would need to put it on the "setOnTouchListener" method of an imageView.
Listener class:
abstract class GestureListener(directionDisplayer: TextView) : View.OnTouchListener,` GestureDetector.OnGestureListener {
private var directionDisplayer: TextView = directionDisplayer
override fun onTouch(v: View?, event: MotionEvent?): Boolean {
val gestureDetector = GestureDetector(this)
gestureDetector.onTouchEvent(event)
return true
}
override fun onFling(
downEvent: MotionEvent?,
moveEvent: MotionEvent?,
velocityX: Float,
velocityY: Float
): Boolean {
var result = false
if (downEvent != null && moveEvent != null) {
var diffY: Float = moveEvent.y - downEvent.y
var diffX: Float = moveEvent.x - downEvent.x
val SWIPE_MIN = 100
val SWIPE_Velocity = 100 //TODO WIDTH
if (Math.abs(diffX) > Math.abs(diffY)) {
//RIGHT OR LEFT
if (Math.abs(diffX) > SWIPE_MIN && Math.abs(velocityX) > SWIPE_Velocity) {
if (diffX > 0) {
swipeRight()
} else {
swipeLeft()
}
result = true
}
} else {
//UP OR DOWN
if(Math.abs(diffY) > SWIPE_MIN && Math.abs(velocityY) > SWIPE_Velocity) {
if(diffY > 0) {
swipeUp()
} else {
swipeDown()
}
result = true
}
}
}
return result
}
private fun swipeDown() {
directionDisplayer.text = "Direction: DOWN"
}
private fun swipeUp() {
directionDisplayer.text = "Direction: UP"
}
private fun swipeLeft() {
directionDisplayer.text = "Direction: LEFT"
}
private fun swipeRight() {
directionDisplayer.text = "Direction: RIGHT"
}
MainActivity (only the important):
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
requestWindowFeature(Window.FEATURE_NO_TITLE)
window.setFlags(
WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN
)
setContentView(R.layout.activity_main)
val canvasImage: ImageView = findViewById(R.id.canvas)
canvasImage.setOnTouchListener(GestureListener(findViewById(R.id.showDirection)))
Does anybody have an idea how to fix this?

GestureListener is an abstract class. So, you have to implement the members of iew.OnTouchListener and GestureDetector.OnGestureListener not yet implemented either in the abstract class itself or in your code like this-
canvasImage.setOnTouchListener(object : GestureListener(textView) {
override fun onShowPress(e: MotionEvent?) {
TODO("not implemented")
}
override fun onSingleTapUp(e: MotionEvent?): Boolean {
TODO("not implemented")
}
override fun onDown(e: MotionEvent?): Boolean {
TODO("not implemented")
}
override fun onScroll(
e1: MotionEvent?,
e2: MotionEvent?,
distanceX: Float,
distanceY: Float
): Boolean {
TODO("not implemented")
}
override fun onLongPress(e: MotionEvent?) {
TODO("not implemented")
}
})

How to sync TabLayout with Recyclerview?

I have a TabLayout with Recyclerview so that when tabs are clicked then the Recyclerview is scrolled to a particular position.
I want the reverse procedure as well such that when the Recyclerview is scrolled to a particular position then the particular tab is highlighted.
For example: If there are 4 tabs in the TabLayout and when Recyclerview is scrolled to 5th position (item visible and below TabLayout) then 3rd tab should be highlighted.
Here when 'How it works' appears below TabLayout then tabs 'How it works' should be highlighted.

Try this
follow this steps
Add a ScrollListener to your RecyclerView
than find first visible item of your RecyclerView
set the select the tab in TabLayout as per position of your RecyclerView
SAMPLE CODE
myRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int itemPosition=linearLayoutManager.findFirstCompletelyVisibleItemPosition();
if(itemPosition==0){ // item position of uses
TabLayout.Tab tab = myTabLayout.getTabAt(Index);
tab.select();
}else if(itemPosition==1){// item position of side effects
TabLayout.Tab tab = myTabLayout.getTabAt(Index);
tab.select();
}else if(itemPosition==2){// item position of how it works
TabLayout.Tab tab = myTabLayout.getTabAt(Index);
tab.select();
}else if(itemPosition==3){// item position of precaution
TabLayout.Tab tab = myTabLayout.getTabAt(Index);
tab.select();
}
}
});
EDIT
public class MyActivity extends AppCompatActivity {
RecyclerView myRecyclerView;
TabLayout myTabLayout;
LinearLayoutManager linearLayoutManager;
ArrayList<String> arrayList = new ArrayList<>();
DataAdapter adapter;
private boolean isUserScrolling = false;
private boolean isListGoingUp = true;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
myTabLayout = findViewById(R.id.myTabLayout);
myRecyclerView = findViewById(R.id.myRecyclerView);
linearLayoutManager = new LinearLayoutManager(this);
myRecyclerView.setLayoutManager(linearLayoutManager);
myRecyclerView.setHasFixedSize(true);
for (int i = 0; i < 120; i++) {
arrayList.add("Item " + i);
}
adapter= new DataAdapter(this,arrayList);
myRecyclerView.setAdapter(adapter);
myTabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
isUserScrolling = false ;
int position = tab.getPosition();
if(position==0){
myRecyclerView.smoothScrollToPosition(0);
}else if(position==1){
myRecyclerView.smoothScrollToPosition(30);
}else if(position==2){
myRecyclerView.smoothScrollToPosition(60);
}else if(position==3){
myRecyclerView.smoothScrollToPosition(90);
}
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
myRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
#Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
if (newState == RecyclerView.SCROLL_STATE_DRAGGING) {
isUserScrolling = true;
if (isListGoingUp) {
//my recycler view is actually inverted so I have to write this condition instead
if (linearLayoutManager.findLastCompletelyVisibleItemPosition() + 1 == arrayList.size()) {
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
if (isListGoingUp) {
if (linearLayoutManager.findLastCompletelyVisibleItemPosition() + 1 == arrayList.size()) {
Toast.makeText(MyActivity.this, "exeute something", Toast.LENGTH_SHORT).show();
}
}
}
}, 50);
//waiting for 50ms because when scrolling down from top, the variable isListGoingUp is still true until the onScrolled method is executed
}
}
}
}
#Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int itemPosition = linearLayoutManager.findFirstVisibleItemPosition();
if(isUserScrolling){
if (itemPosition == 0) { // item position of uses
TabLayout.Tab tab = myTabLayout.getTabAt(0);
tab.select();
} else if (itemPosition == 30) {// item position of side effects
TabLayout.Tab tab = myTabLayout.getTabAt(1);
tab.select();
} else if (itemPosition == 60) {// item position of how it works
TabLayout.Tab tab = myTabLayout.getTabAt(2);
tab.select();
} else if (itemPosition == 90) {// item position of precaution
TabLayout.Tab tab = myTabLayout.getTabAt(3);
tab.select();
}
}
}
});
}
}

private fun syncTabWithRecyclerView() {
// Move recylerview to the position selected by user
menutablayout.addOnTabSelectedListener(object : TabLayout.OnTabSelectedListener {
override fun onTabSelected(tab: TabLayout.Tab) {
if (!isUserScrolling) {
val position = tab.position
linearLayoutManager.scrollToPositionWithOffset(position, 0)
}
}
override fun onTabUnselected(tab: TabLayout.Tab) {
}
override fun onTabReselected(tab: TabLayout.Tab) {
}
})
// Detect recyclerview position and select tab respectively.
menuRecyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
if (newState == RecyclerView.SCROLL_STATE_DRAGGING) {
isUserScrolling = true
} else if (newState == RecyclerView.SCROLL_STATE_IDLE)
isUserScrolling = false
}
}
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
if (isUserScrolling) {
var itemPosition = 0
if (dy > 0) {
// scrolling up
itemPosition = linearLayoutManager.findLastVisibleItemPosition()
} else {
// scrolling down
itemPosition = linearLayoutManager.findFirstVisibleItemPosition()
}
val tab = menutablayout.getTabAt(itemPosition)
tab?.select()
}
}
})
}

I figured you don't even need those flags and it was enough to override RecyclerView's onScrolled and select tab and scroll to position when tab is selected and that Tab wasn't already selected:
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
val llm = recyclerView.layoutManager as LinearLayoutManager
// depending on sections'heights one may want to add more logic
// on how to determine which section to scroll to
val firstCompletePos = llm.findFirstCompletelyVisibleItemPosition()
if (firstCompletePos != tabLayout.selectedTabPosition)
tabLayout.getTabAt(firstCompletePos)?.select()
}
Then I have a TextView which is set as customView to tabLayout:
tabLayout.addTab(newTab().also { tab ->
tab.customView = AppCompatTextView(context).apply {
// set layout params match_parent, so the entire section is clickable
// set style, gravity, text etc.
setOnClickListener {
tabLayout.selectTab(tab)
recyclerView.apply {
val scrollTo = tabLayout.selectedTabPosition
smoothScrollToPosition(scrollTo)
}
}
}
})
With this setup you have:
Tab selected when user both scrolls and flings
RecyclerView is scrolled when user clicks on the tab.

I use information from another answers but here is some omissions in code, that makes it not complete and bad working. My solution 100% work without lags. Photo of complete screen you may see in the end.
This is the code inside Fragment:
private val layoutManager get() = recyclerView?.layoutManager as? LinearLayoutManager
/**
* [SmoothScroller] need for smooth scrolling inside [tabListener] of [recyclerView]
* to top border of [RecyclerView.ViewHolder].
*/
private val smoothScroller: SmoothScroller by lazy {
object : LinearSmoothScroller(context) {
override fun getVerticalSnapPreference(): Int = SNAP_TO_START
}
}
/**
* Variable for prevent calling of [RecyclerView.OnScrollListener.onScrolled]
* inside [scrollListener], when user click on [TabLayout.Tab] and
* [tabListener] was called.
*
* Fake calls happens because of [tabListener] have smooth scrolling to position,
* and when [scrollListener] catch scrolling and call [TabLayout.Tab.select].
*/
private var isTabClicked = false
/**
* Variable for prevent calling of [TabLayout.OnTabSelectedListener.onTabSelected]
* inside [tabListener], when user scroll list and function
* [RecyclerView.OnScrollListener.onScrolled] was called inside [scrollListener].
*
* Fake calls happens because [scrollListener] contains call of [TabLayout.Tab.select],
* which in turn calling click handling inside [tabListener].
*/
private var isScrollSelect = false
private val scrollListener = object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
/**
* Reset [isTabClicked] key when user start scroll list.
*/
if (newState == RecyclerView.SCROLL_STATE_DRAGGING) {
isTabClicked = false
}
}
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
/**
* Prevent scroll handling after tab click (see inside [tabListener]).
*/
if (isTabClicked) return
val commonIndex = commonIndex ?: return
val karaokeIndex = karaokeIndex ?: return
val socialIndex = socialIndex ?: return
val reviewIndex = reviewIndex ?: return
val addIndex = addIndex ?: return
when (layoutManager?.findFirstVisibleItemPosition() ?: return) {
in commonIndex until karaokeIndex -> selectTab(TabIndex.COMMON)
in karaokeIndex until socialIndex -> selectTab(TabIndex.KARAOKE)
in socialIndex until reviewIndex -> {
/**
* In case if [reviewIndex] can't reach top of the list,
* to become first visible item. Need check [addIndex]
* (last element of list) completely visible or not.
*/
if (layoutManager?.findLastCompletelyVisibleItemPosition() != addIndex) {
selectTab(TabIndex.CONTACTS)
} else {
selectTab(TabIndex.REVIEWS)
}
}
in reviewIndex until addIndex -> selectTab(TabIndex.REVIEWS)
}
}
/**
* It's very important to skip cases when [TabLayout.Tab] is checked like current,
* otherwise [tabLayout] will terribly lagging on [recyclerView] scroll.
*/
private fun selectTab(#TabIndex index: Int) {
val tab = tabLayout?.getTabAt(index) ?: return
if (!tab.isSelected) {
recyclerView?.post {
isScrollSelect = true
tab.select()
}
}
}
}
private val tabListener = object : TabLayout.OnTabSelectedListener {
override fun onTabSelected(tab: TabLayout.Tab?) = scrollToPosition(tab)
override fun onTabUnselected(tab: TabLayout.Tab?) = Unit
/*
* If user click on tab again.
*/
override fun onTabReselected(tab: TabLayout.Tab?) = scrollToPosition(tab)
private fun scrollToPosition(tab: TabLayout.Tab?) {
/**
* Prevent scroll to position calling from [scrollListener].
*/
if (isScrollSelect) {
isScrollSelect = false
return
}
val position = when (tab?.position) {
TabIndex.COMMON -> commonIndex
TabIndex.KARAOKE -> karaokeIndex
TabIndex.CONTACTS -> socialIndex
TabIndex.REVIEWS -> reviewIndex
else -> null
}
if (position != null) {
isTabClicked = true
smoothScroller.targetPosition = position
layoutManager?.startSmoothScroll(smoothScroller)
}
}
}
private val commonIndex get() = adapter.list.validIndexOfFirst { it is ClubScreenItem.Info }
private val karaokeIndex get() = adapter.list.validIndexOfFirst { it is ClubScreenItem.Karaoke }
private val socialIndex get() = adapter.list.validIndexOfFirst { it is ClubScreenItem.Social }
private val reviewIndex get() = adapter.list.validIndexOfFirst { it is ClubScreenItem.ReviewHeader }
private val addIndex get() = adapter.list.validIndexOfFirst { it is ClubScreenItem.AddReview }
Extension:
private const val ND_INDEX = -1
fun <T> List<T>.validIndexOfFirst(predicate: (T) -> Boolean): Int? {
return indexOfFirst(predicate).takeIf { it != ND_INDEX }
}
TabIndex class for getting tab by position:
#IntDef(TabIndex.COMMON, TabIndex.KARAOKE, TabIndex.CONTACTS, TabIndex.REVIEWS)
private annotation class TabIndex {
companion object {
const val COMMON = 0
const val KARAOKE = 1
const val CONTACTS = 2
const val REVIEWS = 3
}
}
And it's how looks my ClubScreenItem:
sealed class ClubScreenItem {
class Info(val data: ClubItem): ClubScreenItem()
...
class Karaoke(...): ClubScreenItem()
class Social(...): ClubScreenItem()
...
class ReviewHeader(...): ClubScreenItem()
...
object AddReview : ClubScreenItem()
}
This is how looks screen:

Try this,
Simple Step :
Detect RecyclerView scroll state
Use findFirstVisibleItemPosition() to return the adapter position of the first visible view
Change the tab based on RecyclerView item position
Done
private fun syncTabWithRecyclerView() {
var isUserScrolling = false
val layoutManager = binding.recyclerViewGroup.layoutManager as LinearLayoutManager
val tabListener = object : TabLayout.OnTabSelectedListener {
override fun onTabSelected(tab: TabLayout.Tab?) {
val tabPosition = tab?.position
if (tabPosition != null) {
viewModel.setTabPosition(tabPosition)
// prevent RecyclerView to snap to its item start position while user scrolling,
// idk how to explain this XD
if (!isUserScrolling){
layoutManager.scrollToPositionWithOffset(tabPosition, 0)
}
}
}
override fun onTabUnselected(tab: TabLayout.Tab?) {}
override fun onTabReselected(tab: TabLayout.Tab?) {}
}
binding.tabLayout.addOnTabSelectedListener(tabListener)
// Detect recyclerview scroll state
val onScrollListener = object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
if (newState == RecyclerView.SCROLL_STATE_DRAGGING) {
isUserScrolling = true
} else if (newState == RecyclerView.SCROLL_STATE_IDLE) {
isUserScrolling = false
}
}
// this just represent my tab name using enum class ,
// and ordinal is just the index of its position in enum
val hardcase3D = CaseType.HARDCASE_3D.ordinal
val softcaseBlackmatte = CaseType.SOFTCASE_BLACKMATTE.ordinal
val softcaseTransparent = CaseType.SOFTCASE_TRANSPARENT.ordinal
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
if (isUserScrolling) {
when (layoutManager.findFirstVisibleItemPosition()) {
in hardcase3D until softcaseBlackmatte -> {
viewModel.setTabPosition(hardcase3D)
}
in softcaseBlackmatte until softcaseTransparent -> {
viewModel.setTabPosition(softcaseBlackmatte)
}
softcaseTransparent -> {
viewModel.setTabPosition(softcaseTransparent)
}
}
}
}
}
binding.recyclerViewGroup.addOnScrollListener(onScrollListener)
}
viewModel , you can simply use liveData if you want
private var _tabPosition = MutableStateFlow(CaseType.HARDCASE_3D)
val tabPostition : StateFlow<CaseType>
get() = _tabPosition
fun setTabPosition(position: Int){
_tabPosition.value = CaseType.values()[position]
}
Observer
lifecycleScope.launch(Dispatchers.Default) {
viewModel.tabPostition.collect { caseType ->
val positionIndex = CaseType.values().indexOf(caseType)
handleSelectedTab(positionIndex)
}
}
and handleSelectedTab
private fun handleSelectedTab(index: Int) {
val tab = binding.tabLayout.getTabAt(index)
tab?.select()
}
enum
enum class CaseType(val caseTypeName:String) {
HARDCASE_3D("Hardcase 3D"),
SOFTCASE_BLACKMATTE("Softcase Blackmatte"),
SOFTCASE_TRANSPARENT("Softcase Transparent")
}