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How to give context to fragment in Kotlin?

I am really noob into kotlin and I was trying to implement applandeo calendar library o my project in kotlin. Everything works well if you use activities but when changing into fragments I don't know how to give context because "this" is not working as a Context. In te function openDatePicker() the first parameter should be the context, but no idea about how to get it.
Also I don't know if its possible to pass from a fragment to an activity. My project is structured as a main activity with a bottom navigation bar where every elements redirects to the fragment. This code is inside one of those fragments. Any help or idea will be great ! :)
class CalendarFragment : Fragment(), OnDayClickListener, OnSelectDateListener{
private lateinit var binding: CalendarViewFragmentBinding
private val notes = mutableMapOf<EventDay, String>()
private lateinit var appContext: Context
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?,
): View? {
val context = this.context
// Inflate the layout for this fragment
val calendar_view = inflater.inflate(R.layout.calendar_view_fragment, container, false)
binding = CalendarViewFragmentBinding.inflate(layoutInflater)
binding.fabButton.setOnClickListener { openDatePicker() }
binding.calendarView.setOnDayClickListener(this)
return calendar_view
}
private fun openDatePicker() {
DatePickerBuilder(************, this)
.pickerType(CalendarView.ONE_DAY_PICKER)
.headerColor(R.color.md_theme_light_primary)
.todayLabelColor(R.color.md_theme_light_primary)
.selectionColor(R.color.md_theme_light_secondary)
.dialogButtonsColor(R.color.md_theme_light_secondary)
.build()
.show()
}
I tried functions such as requireContext(), requireActivity(), requireContext().applicationContext, this.context, but no one working as I expect.

Your Fragment is attached to its context when its onAttach() callback is invoked. This happens before it reaches the CREATED lifecycle state:
When your fragment reaches the CREATED state, it has been added to a FragmentManager and the onAttach() method has already been called.
What this means is that by the time onCreate is called (or any lifecycle callbacks after that, including onCreateView, onViewCreated, onStart etc.) your fragment will have a context, and you can access it using requireContext().
You could also use getContext(), which you can access as a property with context, but that returns null if the Fragment isn't associated with a context yet - meaning you have to null-check and handle that possibility. requireContext() will throw an exception if you don't have that context yet, but if you're making sure to only call it when the fragment is in the CREATED state (or later) then it will be safe, and you won't need to check the return value. This is the recommended way of doing things.
So as long as you're accessing the Context in a lifecycle callback like onCreateView, requireContext() will work - that's how you get the Fragment's context. Because you're calling openDatePicker from inside onCreateView, you can just use requireContext() in that function - it's safe at that point!
But you can't define it as a normal top-level variable like this:
class MyFragment : Fragment {
var appContext: Context = requireContext()
}
because that variable is assigned at construction time, which happens way before the fragment reaches the CREATED state. You don't have access to the context at construction time, so any top-level stuff that requires it will end up throwing an exception. This goes for Activities too! That's why you have to assign stuff later, like in onCreate (and this is where lateinit comes in useful, you can have a top-level variable without having to assign it before you're ready)
And no, you can't pass this as a Context when you're in a Fragment, because a Fragment isn't a Context. It works for an Activity because that is a Context - to be more accurate it's able to provide one, but that only works after it's in the CREATED state. That's why you can get in trouble using it in top-level declarations like this
class MyActivity : AppCompatActivity {
val thing = ThingThatRequiresContext(this)
}
because like we just talked about, at construction time the Activity doesn't have access to a context, and the thing that requires it (if it tries to access it immediately) will end up throwing an exception. You see that error a lot, where an Activity can't be started because something like this is happening during initialisation.

Just use it from Fragment. Here is the documentation
private fun openDatePicker() {
DatePickerBuilder(requireContext(), this)
.pickerType(CalendarView.ONE_DAY_PICKER)
.headerColor(R.color.md_theme_light_primary)
.todayLabelColor(R.color.md_theme_light_primary)
.selectionColor(R.color.md_theme_light_secondary)
.dialogButtonsColor(R.color.md_theme_light_secondary)
.build()
.show()
}

Hi fragment has the context. You just have to use context instead of this, and if you want a context that is never null, use requireContext()

Android requireActivity() on Adapter

I need a help.
requireActivity().supportFragmentManager.beginTransaction()
　　　　.replace(R.id.nav_host_fragment, testFragment)
　　　　.addToBackStack(testFragment.tag)
　　　　.commit()
TestFragment.kt
→worked
TestAdapter.kt
→didn't work
→requireActivity() seems to be unavailable.
What is the difference? And what should I do to display TestFragment in TestAdapter.kt?
There is a button for click in TestAdapter.kt. That's why I need to do this.

An Adapter is not a Fragment, so it doesn't have the same functions available that Fragment does. If you need an Activity reference inside an Adapter (which you shouldn't because that is poor design--poor encapsulation), you need to add a constructor parameter or property to your class that allows you to pass an Activity reference to your Adapter. For example:
class ExpandableListAdapter(val activity: Activity): ListAdapter { //...
and then when you create it in your Fragment, you could pass requireActivity() as a constructor parameter.
But like I said, this would be poor encapsulation. Maybe you just need a Context reference for when you're creating view holders? In that case, you can get it from the parent parameter:
override fun createViewHolder(parent: ViewGroup, viewType: Int) {
val context = parent.context
// use context to create view holder's layout
}

Use composable instead of marker in google maps?

I know it's possible to use a custom view instead of a basic map marker in Google Maps doing what's described in this answer. I was curious if it was possible to achieve a similar affect with Compose?
Since ComposeView is a final class, couldn't extend that directly so I was thinking of having a FrameLayout that could add it as a child. Although this seems to be causing a race condition since composables draw slightly differently from normal android Views.
class MapMarkerView : FrameLayout {
constructor(context: Context) : super(context) {
initView()
}
constructor(context: Context, attrs: AttributeSet?) : super(context, attrs) {
initView()
}
private fun initView() {
val composeView = ComposeView(context).apply {
layoutParams = LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT)
}
composeView.setContent {
// this runs asynchronously making the the bitmap generation not include composable at runtime?
Text(text = "2345", modifier = Modifier.background(Color.Green, RoundedCornerShape(4.dp)))
}
addView(composeView)
}
}
Most articles I have read have some callback function for generating a bitmap like this which wouldn't necessarily work in this use case where each view is generated dynamically and needed to be converted to a bitmap right away for the map.

The MapMarkerView you are attempting to create is an indirect child of ViewGroup. ComposeView is also an indirect child of ViewGroup which means you can directly substitute a ComposeView in places where you intend to use this class. The ComposeView class is not meant to be subclassed. The only thing you really need to be concerned with as a developer is its setContent method.
val composeView: View = ComposeView(context).apply{
setContent {
Text(text = "2345", modifier = Modifier.background(Color.Green, RoundedCornerShape(4.dp)))
}
}
Now you can replace the MapMarkerView with this composeView in your code or even use it at any location where a View or any of it's subclasses is required.

ConstraintLayout view binding migration from Kotlin synthetics

I have an existing view that extends from ConstraintLayout which looks something like this:
class LandingTemplate: ConstraintLayout {
init {
inflate(context, R.layout.landing_template, this)
// Currently this 'recyclerView' is a kotlin synthetic
recyclerView.run {
// this sets up the recycler view
}
}
I'm familiar with view binding with activities and fragments, but I can't find any documentation around the extends layout case.
My question is, what do I replace that initial inflate call with here?

I'm assuming you have a context available from your constructor and your XML layout's top level tag is <merge>. You can use your binding class's inflate to create and add the child layout.
And since this can all be set up in the constructor, you don't need lateinit var like in the Activity/Fragment examples, and can just use val instead.
class LandingTemplate(context: Context, attrs: AttributeSet): ConstraintLayout(context, attrs) {
private val binding = LandingTemplateBinding.inflate(LayoutInflater.from(context), this)
init {
binding.recyclerView.run {
// this sets up the recycler view
}
}
}

you can get layout inflater like below
val inflater = context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
val view = inflater.inflate(R.layout.landing_temple,this,true)
and you must have valid view construct too
LandingTemple(Context) // for creating view programmatically
LandingTemple(Context,AttrributeSet) // to inflate view from xml , and
//the constructor context is one that you use to call `getSystemService
for more information check

How to set OnClickListener on RecyclerView item in MVVM structure

I have an app structured in MVVM. I have different fragments within the same activity. Each fragment has its own ViewModel and all data are retrieved from a REST API.
In FragmentA, there is a RecyclerView that lists X class instances. I want to set OnClickListener on the RecyclerView and I want to pass related X object to FragmentB when an item clicked in the RecyclerView. How can I achieve this?

How I imagine it is the following.
The Fragment passes a listener object to the adapter, which in turn passes it to the ViewHolders
Here is a quick sketch of how it should look like
class Fragment {
val listener = object: CustomAdapter.CustomViewHolderListener() {
override fun onCustomItemClicked(x: Object) {}
}
fun onViewCreated() {
val adapter = CustomAdapter(listener)
}
}
---------------
class CustomAdapter(private val listener: CustomViewHolderListener) {
val listOfXObject = emptyList() // this is where you save your x objects
interface CustomViewHolderListener{
fun onCustomItemClicked(x : Object)
}
override fun onBindViewHolder(holder: CustomViewHolder, position: Int) {
holder.itemView.setOnClickListener {
listener.onCustomItemClicked(listOfXObject[position])
}
}
}
Here are some articles that might help you get the general gist of the things.
They don't answer your question directly though
Hope it is helpful
link 1 link 2

if you're using data binding you need to pass your view(which is Fragment in your case) into the layout via adapter class and you need to import your view in layout file to be able to call view's method
android:onClick="#{() -> view.onXXXClick(item)}"
pass your current model class which is item into this new method and then create onXXXClick method in your view and do whatever you wish.
if you will be doing view related operations such as navigation from one fragment to another or starting a service you should create above function in your view, if you're doing network or db related operations it should be in your ViewModel
you can check out my GitHub repository to understand better.