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recyclerview not visible at run time

I implemented a simple recyclerview using databinding using kotlin language.
In xml, recyclerview seems to be the default,
but when I run it, it doesn't show up as default.
Other buttons and views included in the fragment appear normally when executed, but only the recyclerview is not visible. Which part is wrong?
class WorkFragment : Fragment() {
private var _binding: FragmentWorkBinding? = null
private val binding get() = _binding!!
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentWorkBinding.inflate(inflater, container, false)
val view = binding.root
return view
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val data = mutableListOf<WorkList>()
val adapter = WorkAdapter()
adapter.data = data
binding.recycler1.adapter = adapter
binding.recycler1.layoutManager = LinearLayoutManager(requireContext())
}
}
class WorkAdapter : RecyclerView.Adapter<WorkAdapter.ViewHolder>() {
var data = mutableListOf<WorkList>()
class ViewHolder(val binding: RecyclerviewWorkItemBinding) : RecyclerView.ViewHolder(binding.root) {
fun bind(workList: WorkList) {
binding.tvStarttime.text = workList.Starttime
binding.tvAdmin.text = workList.Admin
binding.tvPart.text = workList.Part
binding.tvStoptime.text = workList.Stoptime
binding.tvWorkers.text = workList.Workers.toString()
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): WorkAdapter.ViewHolder {
val binding = RecyclerviewWorkItemBinding.inflate(LayoutInflater.from(parent.context), parent, false)
return ViewHolder(binding)
}
override fun onBindViewHolder(holder: WorkAdapter.ViewHolder, position: Int) {
holder.bind(data[position])
}
override fun getItemCount(): Int {
return data.size
}
// fun replaceList(newList: MutableList<WorkList>) {
// data = newList.toMutableList()
// notifyDataSetChanged()
// }
}
Is there something wrong with my code?
For reference, I just used a fragment, not an activity.

its typically for the RecyclerView to behave like its hidden but actually its not. the reason is you are passing an empty list so the recycler will not be extended or show because there is no items in the list.

How to provide an implementation of the click listener interface for the recycler adapter?

Suppose we have a recycler view in a fragment, and we need to add a click handler to the adapter. Which one of the following approaches are better? Please tell me the pros and cons each one:
Approach One: implementing OnItemClickListener in the fragment:
In this approach we implement the OnItemClickListener in the fragment class MyFragment : Fragment() , MyAdapter.OnItemClickListener and pass it to the adapter using this keyword:
class MyFragment : Fragment() , MyAdapter.OnItemClickListener {
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
myRecyclerView.adapter = MyAdapter(it , this) // here we pass the fragment
return view
}
override fun onCLick(item: MyItem) {
Log.d("test","item name = " + item.Name)
}
}
class MyAdapter(val data: List<MyItem> , val onItemClickListener: OnItemClickListener) :
RecyclerView.Adapter<MyFragment.MyViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.support_simple_spinner_dropdown_item, parent, false)
return MyViewHolder(view)
}
override fun getItemCount() = data.size
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
holder.itemView.setOnClickListener{
onItemClickListener.onCLick(data[position])
}
with(holder) {
textView1?.let {
it.text = data[position].Name
}
}
}
interface OnItemClickListener{
fun onCLick(item: MyItem)
}
}
Approach Two: implementing OnItemClickListener using a anonymous object:
In this approach we use object: syntax to create an anonymous object, like inline interface implementation in java:
class MyFragment : Fragment(){
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
myRecyclerView.adapter = MyAdapter(it ,object : MyAdapter.OnItemClickListener{
override fun onCLick(item: MyItem) {
Log.d("test","name = " + item.Name)
}
})
return view
}
class MyAdapter(val data: List<MyItem> , val onItemClickListener: OnItemClickListener) :
RecyclerView.Adapter<MyViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.support_simple_spinner_dropdown_item, parent, false)
return MyViewHolder(view)
}
override fun getItemCount() = data.size
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
holder.itemView.setOnClickListener{
onItemClickListener.onCLick(data[position])
}
with(holder) {
textView1?.let {
it.text = data[position].Name
}
}
}
interface OnItemClickListener{
fun onCLick(item: MyItem)
}
}
Which one is more modern?
Which one gives a better performance? (If there is any difference)
Why in most tutorials and video lessons they use the first approach, while the second one needs fewer lines of codes?

Simple answer: it doesn't matter. Approach 2 simply allocates one extra object on the heap which is not a big deal. I would prefer 2 over 1 because 1 exposes that MyFragment implements MyAdapter.OnItemClickListener: that should remain an implementation detail, not a part of your fragment's contract.
However, there is something in your code that can affect performance. Your setOnClickListener() call allocates new listener whenever onBindViewHolder() is called, which is pretty often if you scroll fast enough. It adds to the work of your garbage collector.
You can always get ViewHolder's position in adapter with getBindingAdapterPosition() (or its deprecated counterpart getAdapterPosition() if you're using an older version of RecyclerView). As you can see from the docs, in marginal cases it may not be consistent with the position you use and is a more correct approach to handling user actions.
With that said, it is sufficient to set your listener only once, in onCreateViewHolder():
override fun onCreateViewHolder(
parent: ViewGroup,
viewType: Int
): MyViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.support_simple_spinner_dropdown_item, parent, false)
val holder = MyViewHolder(view)
holder.itemView.setOnClickListener {
holder
.bindingAdapterPosition
.takeUnless { it == RecyclerView.NO_POSITION }
?.let { position ->
onItemClickListener.onClick(data[position])
}
}
return holder
}

Here you can use Callback, it is the recommended choice of Google's Android team. You implement that as:
class MyFragment : Fragment(){
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
myRecyclerView.adapter = MyAdapter(it) { item ->
// You can use your item here.
}
return view
}
class MyAdapter(val data: List<MyItem> ,
private val callback: (MyItem) -> Unit) :
RecyclerView.Adapter<MyViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.support_simple_spinner_dropdown_item, parent, false)
return MyViewHolder(view)
}
override fun getItemCount() = data.size
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
holder.itemView.setOnClickListener{
callback.invoke(data[position])
}
with(holder) {
textView1?.let {
it.text = data[position].Name
}
}
}
}

How do I filter cards in a RecyclerView through a SearchView (Kotlin)?

I am currently working on a simple journal app where the user can make new entries, which get stored into a room database and displayed through a RecyclerView using cards. I am currently trying to implement a way to filter card entries based on the text within them using a SearchView. However, everything that I've found online seems to be entirely in Java, just filtering a list, etc, so I'm not sure how I would go about doing this. Any help would be massively appreciated!
Here is my code (without imports):
Fragment that displays entries through RecyclerView:
class HomeFragment : BaseFragment() {
private lateinit var homeViewModel: HomeViewModel
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
homeViewModel =
ViewModelProvider(this).get(HomeViewModel::class.java)
val root = inflater.inflate(R.layout.fragment_home, container, false)
return root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
recycler_view.setHasFixedSize(true)
recycler_view.layoutManager = StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL)
launch {
context?.let {
var journal = JournalDatabase.getDatabase(it).JournalDao().allJournal()
recycler_view.adapter = JournalAdapter(journal)
}
}
newEntryButton.setOnClickListener {
Navigation.findNavController(view).navigate(R.id.action_nav_home_to_nav_new_entry)
}
}
}
My adapter:
class JournalAdapter(val arrList: List<Journal>) :
RecyclerView.Adapter<JournalAdapter.JournalViewHolder>() {
class JournalViewHolder(view: View) : RecyclerView.ViewHolder(view) {
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): JournalViewHolder {
return JournalViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.recyclerview_entry, parent, false))
}
override fun onBindViewHolder(holder: JournalViewHolder, position: Int) {
holder.itemView.rvTitle.text = arrList[position].title
holder.itemView.rvText.text = arrList[position].journalText
holder.itemView.rvDateTime.text = arrList[position].dateTime
}
override fun getItemCount(): Int {
return arrList.size
}
}

How to Read Data from RecyclerView and send in BottomSheet

I am using recyclerView to show list of apps installed in device
image - Link
and for more details I use bottomSheet on LongPress i.e. in ViewHolder Class, but How to send data of selected tab to bottomSheet with more details(such as package name, API level etc.)...for reference see images
I want - Link
I get from below coding - Link
MainActivity.kt
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
recyclerView.adapter = Adapter // I set adapter here with function getApps()
recyclerView.layoutManager = LinearLayoutManager(this)
private fun getApps(): List<DataClass> {
// here I get apps icon,name,size and return list<DataClass>
return list
}
Adapter.kt
class Adapter(private val listOfApps: List<AppData>) :
RecyclerView.Adapter<Adapter.ViewHolder>() {
class ViewHolder(appView: View) : RecyclerView.ViewHolder(appView), View.OnClickListener,
View.OnLongClickListener {
init {
appView.setOnClickListener(this)
appView.setOnLongClickListener(this)
}
val icon: ImageView = appView.App_icon
val name: TextView = appView.App_name
val size: TextView = appView.App_size
override fun onClick(v: View?) {
Toast.makeText(v?.context, "OnClick", Toast.LENGTH_SHORT).show()
}
override fun onLongClick(v: View?): Boolean {
// I want here on Long press BottomSheet appears with details
val bottomSheetDialog = BottomSheetDialog()
// Show bottomSheet on LongPress
bottomSheetDialog.show(
(v?.context as FragmentActivity).supportFragmentManager, bottomSheetDialog.tag
)
return true
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context).inflate(
R.layout.list_apps, parent, false
)
return ViewHolder(view)
}
override fun getItemCount() = listOfApps.size
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val currentItem = listOfApps[position]
holder.icon.setImageDrawable(currentItem.icon)
holder.name.text = currentItem.name
holder.size.text = currentItem.size
}
}
BottomSheetDialog.kt
class BottomSheetDialog: BottomSheetDialogFragment() {
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.bottom_sheet, container, false)
}
override fun getTheme(): Int = R.style.RoundBottomSheetDialog
}
DataClass
data class AppData(
val icon: Drawable,
val name: String,
val size: String,
)

With your current code the easiest solution would be:
Modify your BottomSheetDialog to include AppData in the constructor
class BottomSheetDialog(val appData: AppData): BottomSheetDialogFragment() {
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.bottom_sheet, container, false)
}
override fun getTheme(): Int = R.style.RoundBottomSheetDialog
}
Add onBind method inside your ViewHolder class:
fun onBind(appData: AppData) {
icon.setImageDrawable(currentItem.icon)
name.text = currentItem.name
size.text = currentItem.size
}
Modify your onBindViewHolder method inside the Adapter to call that onBind method:
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.onBind(listOfApps[position])
}
Inside your ViewHolder add lateinit var currentItem: AppData that will be set inside onBind and we can use it in onLongClick:
class ViewHolder(appView: View) : RecyclerView.ViewHolder(appView), View.OnClickListener,
View.OnLongClickListener {
.
.
.
override fun onLongClick(v: View?): Boolean {
// I want here on Long press BottomSheet appears with details
**val bottomSheetDialog = BottomSheetDialog(currentItem)**
// Show bottomSheet on LongPress
bottomSheetDialog.show(
(v?.context as FragmentActivity).supportFragmentManager, bottomSheetDialog.tag
)
return true
}
**private lateinit var currentItem: AppData**
fun onBind(appData: AppData) {
**currentItem = appData**
icon.setImageDrawable(currentItem.icon)
name.text = currentItem.name
size.text = currentItem.size
}

attach your currentItem list item to ViewHolder inside onBindViewHolder and inside onLongClick pass this data to freshly created BottomSheetDialog, which is extending Fragment (so you may use Bundle - setArgument method). then inside onCreateView set your data to Views

Create an interface
interface OnListItemClicked {
fun onClicked(data : AppData)
}
Implement that interface in BottomSheetDialog
class BottomSheetDialog: BottomSheetDialogFragment(), OnListItemClicked {
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.bottom_sheet, container, false)
}
override fun onClicked(data: AppData) {
//show Details here
}
override fun getTheme(): Int = R.style.RoundBottomSheetDialog
}
Pass extra callback to the adapter from main activity.
Adapter(private val listOfApps: List<AppData>, val onClick: (AppData) -> Unit)
Invoke the click listener from adapter with listOfAppData[position]
On MainActivity pass a function into the Adapter initialisation.
fun passDataToBottomSheet(data: AppData) {
val listener = OnListItemClicked()
listener.onClicked(data)
}
Adapter(list, ::passDataToBottomSheet)
That's it. It should work now.

System services not available to Activities before onCreate(), with Android RecyclerView inside a fragment Kotlin

I'm having trouble with Android RecyclerView in Kotlin inside a fragment who is in Home activity.
Here's my code:
myFragmentLayout:
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rvChapterList"
android:layout_width="match_parent"
android:layout_height="match_parent" />
myFragmentCode:
val chaptersList: ArrayList<String> = ArrayList()
private lateinit var layoutManager: RecyclerView.LayoutManager
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.courses_layout, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
chaptersList.add("Android")
chaptersList.add("Kotlin")
chaptersList.add("RecyclerView")
layoutManager = LinearLayoutManager(context)
rvChapterList.layoutManager = layoutManager
rvChapterList.adapter = ChapterAdapter(Home(), chaptersList)
}
and myChapterAdapter:
class ChapterAdapter(private val context: Home, private val chaptersList: ArrayList<String>) : RecyclerView.Adapter<ChapterAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
return ViewHolder(LayoutInflater.from(context).inflate(R.layout.list_item, parent, false))
}
override fun getItemCount(): Int {
return chaptersList.size
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.chapterName?.text = chaptersList.get(position)
holder.itemView.setOnClickListener {
Toast.makeText(context, chaptersList.get(position), Toast.LENGTH_LONG).show()
}
}
class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
val chapterName = view.tvChapterName
}
}
It got this code from this tutorial, it's working inside an activity but not iside a fragment.

rvChapterList.adapter = ChapterAdapter(Home(), chaptersList)
Never create an Activity or other type of Context yourself. You always obtain them from the framework.
Replace that with:
rvChapterList.adapter = ChapterAdapter(requireActivity(), chaptersList)
and change the context property in ChapterAdapter to be a Context or Activity, not Home.