Develop Reference

lateinit property recview has not been initialized

I have fragment which showing weather for 10 days with getting geolocation city and show exactly weather for this city for 10 days.
I have problem initialization with RecyclerView and Viewmodel.
Also I use Hilt to provide dependencies.
My goal is showing weather by location (already have permission) for 10 days.
import androidx.lifecycle.LiveData
import dagger.hilt.android.lifecycle.HiltViewModel
import db.entities.WeatherData
#HiltViewModel
interface ForecastViewmodel {
val dataforecast:LiveData<List<WeatherData>>
val city : LiveData<String>
val isRefreshing:LiveData<Boolean>
fun onRefresh()
}
#HiltViewModel
class ForecastViewmodelImpl(private val repository: ForecastRepository,
private val day: Day
) : ForecastViewmodel,
ViewModel(){
override val dataforecast = MutableLiveData<List<WeatherData>>()
override val city = MutableLiveData(day.city)
override val isRefreshing = MutableLiveData(true)
init {
loadForecast()
}
private fun loadForecast() {
isRefreshing.value = true
viewModelScope.launch {
try {
val data = repository.getForecast(day.days)
Timber.d("size is ${data}")
}catch (e:Exception){
Timber.e(e)
}
isRefreshing.value = false
}
}
override fun onRefresh() = loadForecast()
private fun Forecastday.toWeatherData() = WeatherData(
date = date,
temp = "${temp.roundToInt()}℃"
)
}
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.example.testtaskweatherappkevychsol.R
import db.entities.WeatherData
class WeatherRecView:RecyclerView.Adapter<WeatherRecView.WeatherHolder>() {
var listweather = emptyList<WeatherData>()
class WeatherHolder(view:View):RecyclerView.ViewHolder(view)
override fun onCreateViewHolder(
parent: ViewGroup,
viewType: Int
): WeatherHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.daily_weather_layout,
parent,false)
return WeatherHolder(view)
}
override fun onBindViewHolder(
holder: WeatherHolder,
position: Int
) {
holder.itemView.findViewById<TextView>(R.id.Dateitem).text = listweather[position].date
holder.itemView.findViewById<TextView>(R.id.tempitem).text = listweather[position]
.temp.toString()
}
override fun getItemCount(): Int {
return listweather.size
}
fun addlistintoUI(list: List<WeatherData>){
listweather = list
}
}
data class WeatherData(
val temp:String,
val date:String
)
import RecyclerView.WeatherRecView
import Viewmodel.ForecastViewmodel
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.recyclerview.widget.DividerItemDecoration
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.testtaskweatherappkevychsol.R
import com.example.testtaskweatherappkevychsol.databinding.FragmentWeatherBinding
import dagger.hilt.android.AndroidEntryPoint
#AndroidEntryPoint
class WeatherAtTheLifeMomentFragment : Fragment(R.layout.fragment_weather){
lateinit var recview:WeatherRecView
private var binding : FragmentWeatherBinding? = null
lateinit var viewmodel:ForecastViewmodel
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val binding = FragmentWeatherBinding.inflate(inflater,container,false)
this.binding = binding
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
with(binding){
this!!.refreshbt.setOnClickListener { viewmodel.isRefreshing }
containerlistweather.adapter = recview
containerlistweather.addItemDecoration(DividerItemDecoration(containerlistweather.context,
(containerlistweather
.layoutManager as LinearLayoutManager).orientation))
with(viewmodel){
dataforecast.observe(viewLifecycleOwner) { recview.listweather = it }
City.text = city.toString()
}
}
}
override fun onDestroyView() {
super.onDestroyView()
binding = null
}
}

lateinit property recview has not been initialized
you are getting this issue as you are trying to access lateinit property recview without initialising it
in WeatherAtTheLifeMomentFragment
From
containerlistweather.adapter = recview
To
recview = WeatherRecView() // initialise recview variable by creating instance of your adapter
containerlistweather.layoutManager = LinearLayoutManager(context) // not sure you have set layout manager in your xml so just adding it in your code as it is necessary to use
containerlistweather.adapter = recview
Also you have create method addlistintoUI in WeatherRecView class so use it and make below mentioned changes to load your data
in WeatherAtTheLifeMomentFragment class
From
dataforecast.observe(viewLifecycleOwner) { recview.listweather = it }
To
dataforecast.observe(viewLifecycleOwner) { recview.addlistintoUI(it) }
in WeatherRecView class
From
fun addlistintoUI(list: List<WeatherData>){
listweather = list
}
To
fun addlistintoUI(list: List<WeatherData>){
listweather.addAll(list)
notifyDataSetChanged()
}
```

Android Kotlin - Navigate between fragments using textView in recyclerView

I would like to navigate between fragments using a textView inside a recyclerview.
Currently I am successfully navigating between fragments using the item, but I would like to go further and navigate using the individual textViews within an item.
The recyclerview is inflated from a local room database.
Below is my adapter
package com.benb.inventory
import android.view.LayoutInflater
import android.view.ViewGroup
import android.widget.Toast
import androidx.recyclerview.widget.DiffUtil
import androidx.recyclerview.widget.ListAdapter
import androidx.recyclerview.widget.RecyclerView
import com.benb.inventory.data.Item
import com.benb.inventory.data.getFormattedPrice
import com.benb.inventory.databinding.ItemListItemBinding
class ItemListAdapter(private val onItemClicked: (Item) -> Unit) :
ListAdapter<Item, ItemListAdapter.ItemViewHolder>(DiffCallback) {
class ItemViewHolder(internal var binding: ItemListItemBinding) :
RecyclerView.ViewHolder(binding.root) {
fun bind(item: Item) {
binding.apply {
itemName.text = item.itemName
itemPrice.text = item.getFormattedPrice()
itemShop.text = item.shop.toString()
itemShop.setOnClickListener{
val shopName = itemShop.text.toString()
Toast.makeText(root.context, "Clicked: ${item.shop}", Toast.LENGTH_SHORT ).show()
}
}
}
}
companion object {
private val DiffCallback = object : DiffUtil.ItemCallback<Item>() {
override fun areItemsTheSame(oldItem: Item, newItem: Item): Boolean {
return oldItem == newItem
}
override fun areContentsTheSame(oldItem: Item, newItem: Item): Boolean {
return oldItem.itemName == newItem.itemName
}
}
}
override fun onCreateViewHolder(
parent: ViewGroup,
viewType: Int
): ItemListAdapter.ItemViewHolder {
return ItemViewHolder(ItemListItemBinding.inflate(LayoutInflater.from(parent.context)))
}
override fun onBindViewHolder(holder: ItemListAdapter.ItemViewHolder, position: Int) {
val current = getItem(position)
holder.itemView.setOnClickListener {
onItemClicked(current)
}
holder.binding.itemShop.setOnClickListener {
onItemClicked(current)
val shopName = current.shop
fun showShopList(shopName: String) {
val shopName = holder.binding.itemShop.text.toString()
val action = ItemListFragmentDirections.actionItemListFragmentToShopItemFragment(shopName)
}
}
holder.bind(current)
}
}
This is the fragment that contains the list
package com.benb.inventory
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.fragment.app.activityViewModels
import androidx.navigation.fragment.findNavController
import androidx.recyclerview.widget.LinearLayoutManager
import com.benb.inventory.databinding.ItemListFragmentBinding
import kotlinx.coroutines.InternalCoroutinesApi
#InternalCoroutinesApi
class ItemListFragment : Fragment() {
#InternalCoroutinesApi
private val viewModel: InventoryViewModel by activityViewModels {
InventoryViewModelFactory(
(activity?.application as InventoryApplication).database.itemDao()
)
}
private var _binding: ItemListFragmentBinding? = null
private val binding get() = _binding!!
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = ItemListFragmentBinding.inflate(inflater, container, false)
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val adapter = ItemListAdapter {
val action = ItemListFragmentDirections.actionItemListFragmentToItemDetailFragment(it.id)
this.findNavController().navigate(action)
}
binding.recyclerView.adapter = adapter
viewModel.allItems.observe(this.viewLifecycleOwner) {items ->
items.let {
adapter.submitList(it)
}
}
binding.itemShop.setOnClickListener{
val shop = binding.itemShop.text.toString()
val action = ItemListFragmentDirections.actionItemListFragmentToShopItemFragment(shop)
viewModel.retrieveShopItems(shop)
this.findNavController().navigate(action)
}
binding.recyclerView.layoutManager = LinearLayoutManager(this.context)
binding.floatingActionButton.setOnClickListener {
val action = ItemListFragmentDirections.actionItemListFragmentToAddItemFragment(
getString(R.string.add_fragment_title)
)
this.findNavController().navigate(action)
}
}
}
For clarity this is what the inflated recyclerview looks like, it can contain many items, I have only added one.
At the moment if I click anywhere on the item it takes you to a screen with more detail about the fragment.
[A screenshot of the recycler view][1]
I would like to be able to navigate to a specific fragment depending on the textView clicked.
For example one fragment that only contains other products from the same shop.
As you may notice, I have been able to add an onClickListener in the ViewHolder class, it creates a Toast.
I have not had success in using the same onClickListener to navigate.
Thank you very much.
P.S. Any other advice is welcome, particularly if anyone knows what the #internalcoroutinesAPI thing is about please tell me!
[1]: https://i.stack.imgur.com/k6Td3.png

Error in fragment with recyclerView (context) [duplicate]

This question already has answers here:
Using context in a fragment
(31 answers)
Closed 1 year ago.
I'm using Kotlin with SDK version 29.
I searched on several sites but I did not find anything on this subject.
I would like to use a recyclerview in my fragment using an adapter, but there is an error that i cannot resolve about my adapter.
Here is the error :
Type mismatch: inferred type is Flux but Context was expected
It is from the next line in the fragment :
adapter = PostsAdapter(this, posts)
Do you know how to set a context ?
There is my code :
The adapter :
Import :
import android.content.Context
import android.text.format.DateUtils
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.bumptech.glide.Glide
import com.example.givenaskv1.R
import kotlinx.android.synthetic.main.item_post.view.*
Code:
class PostsAdapter (val context: Context, val posts : List<Post>) :
RecyclerView.Adapter<PostsAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(context).inflate(R.layout.item_post, parent, false)
return ViewHolder(view)
}
override fun getItemCount() = posts.size
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.bind(posts[position])
}
inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
fun bind(post: Post) {
itemView.tvUsername.text = post.user?.firstName
itemView.tvDescription.text = post.description
Glide.with(context).load(post.imageUrl).into(itemView.ivPost)
itemView.tvRelativeTime.text = DateUtils.getRelativeTimeSpanString(post.creationTimeMs)
}
}
}
The fragment :
Import :
import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.givenaskv1.R
import com.example.givenaskv1.models.Post
import com.example.givenaskv1.models.PostsAdapter
import com.google.firebase.firestore.FirebaseFirestore
import com.google.firebase.firestore.Query
import kotlinx.android.synthetic.main.fragment_flux.*
Code :
private const val TAG = "Flux"
class Flux : Fragment() {
private lateinit var firestoreDb : FirebaseFirestore
private lateinit var posts : MutableList<Post>
private lateinit var adapter: PostsAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
posts = mutableListOf()
adapter = PostsAdapter(this, posts) <----- HERE IS THE ERROR
rvPosts.adapter = adapter
rvPosts.layoutManager = LinearLayoutManager(this.context)
firestoreDb = FirebaseFirestore.getInstance()
val postsReference = firestoreDb.collection("post")
// .limit() indique le nombre de post MAXIMIM a afficher en même temps, pour éviter le lagg
.limit(20)
// .orderBy() filtre selon le critère choisi (ici par ordre chonologique)
.orderBy("creation_time_ms", Query.Direction.DESCENDING)
postsReference.addSnapshotListener{ snapshot, exception ->
if (exception != null || snapshot == null) {
Log.e(TAG, "Exception when querying posts", exception)
return#addSnapshotListener
}
val postList = snapshot.toObjects(Post::class.java)
posts.clear()
posts.addAll(postList)
adapter.notifyDataSetChanged()
for (post in postList) {
Log.i(TAG, "Post ${post}")
}
}
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_flux, container, false)
}
}
fragment.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=".Flux.Flux">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rvPosts"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
when i try to replace
adapter = PostsAdapter(this, posts)
with
adapter = PostsAdapter(requireContext(), posts)
There is the following error :
java.lang.IllegalStateException: rvPosts must not be null
Thank you so much !

This is due that you get the RecyclerView instance in the fragment onCreate callback before the fragment view get created; As onCreate() callback is triggered before onCreateView() callback
Note: the fragment view is get created and returned by onCreateView().
To solve this transfer the code from onCreate() into onCreateView()
private const val TAG = "Flux"
class Flux : Fragment() {
private lateinit var firestoreDb : FirebaseFirestore
private lateinit var posts : MutableList<Post>
private lateinit var adapter: PostsAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
val view = inflater.inflate(R.layout.fragment_flux, container, false)
posts = mutableListOf()
adapter = PostsAdapter(requireContext(), posts)
val rvPosts = view.findViewById<RecyclerView>(R.id.rvPosts)
rvPosts.adapter = adapter
rvPosts.layoutManager = LinearLayoutManager(this.context)
firestoreDb = FirebaseFirestore.getInstance()
val postsReference = firestoreDb.collection("post")
// .limit() indique le nombre de post MAXIMIM a afficher en même temps, pour éviter le lagg
.limit(20)
// .orderBy() filtre selon le critère choisi (ici par ordre chonologique)
.orderBy("creation_time_ms", Query.Direction.DESCENDING)
postsReference.addSnapshotListener{ snapshot, exception ->
if (exception != null || snapshot == null) {
Log.e(TAG, "Exception when querying posts", exception)
return#addSnapshotListener
}
val postList = snapshot.toObjects(Post::class.java)
posts.clear()
posts.addAll(postList)
adapter.notifyDataSetChanged()
for (post in postList) {
Log.i(TAG, "Post ${post}")
}
return view
}
}

How to add RecyclerView in a Fragment?

Currently, I am trying to implement RecyclerView inside of Fragment but I cannot find a way to display it.
Here is my MainActivity:
package com.example
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import androidx.fragment.app.Fragment
import com.example.projectdrivemark.R
import com.example.projectdrivemark.databinding.ActivityMainBinding
import com.example.recyclerView.MockDatabase.Companion.createMockData
import com.example.recyclerView.PostAdapter
import com.example.recyclerView.RecyclerViewFragment
import com.example.tempConverter.TempConverterFragment
import com.example.uploaderView.UploaderFragment
class MainActivity : AppCompatActivity(), PostAdapter.OnPostClickListener {
private lateinit var binding: ActivityMainBinding
val dummyList = createMockData()
val adapter = PostAdapter(dummyList, this)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
title = "First Kotlin App"
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val recyclerView = RecyclerViewFragment()
val tempConverterView = TempConverterFragment()
// recyclerView.layoutManager = LinearLayoutManager(this)
val uploaderView = UploaderFragment(this)
setFragmentView(recyclerView)
binding.bottomNavBar.setOnNavigationItemSelectedListener {
when(it.itemId){
R.id.listView -> setFragmentView(recyclerView)
R.id.tempConverterView -> setFragmentView(tempConverterView)
R.id.videoUploaderView -> setFragmentView(uploaderView)
}
true
}
}
private fun setFragmentView(fragment: Fragment){
supportFragmentManager.beginTransaction().apply {
replace(R.id.main_fragment_view, fragment)
//Will return to previous page when tap "Back Button" on the phone
addToBackStack(null)
commit()
}
}
override fun onEditPost(position: Int){
val clickedPost = dummyList[position]
clickedPost.title = "Updated title"
clickedPost.body = "Updated body"
adapter.notifyItemChanged(position)
}
override fun onDeletePost(position: Int) {
dummyList.removeAt(position)
adapter.notifyItemRemoved(position)
}
fun celsiusFunction(view: View) {
val tempConverter = TempConverterFragment()
tempConverter.celsiusFunction(view)
}
fun farenheitFunction(view: View){
val fahrenheitConverter = TempConverterFragment()
fahrenheitConverter.farenheitFunction(view)
}
}
Here is my RecyclerFragment:
package com.example.recyclerView
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.example.MainActivity
import com.example.projectdrivemark.R
class RecyclerViewFragment: Fragment() {
var adapter: RecyclerView.Adapter<PostAdapter.PostViewHolder>? = null
var layoutManager: RecyclerView.LayoutManager? = null
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
super.onCreate(savedInstanceState)
val binding = inflater.inflate(R.layout.fragment_list, container, false)
return binding
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
view.apply{
layoutManager = LinearLayoutManager(activity)
adapter = PostAdapter(dummyData = ArrayList<Post>(), MainActivity())
}
}
}
Here is my PostAdapter code:
package com.example.recyclerView
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ImageView
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.example.MainActivity
import com.example.projectdrivemark.R
class PostAdapter(val dummyData: ArrayList<Post>, val myListener: MainActivity) : RecyclerView.Adapter<PostAdapter.PostViewHolder>() {
inner class PostViewHolder(postView: View) : RecyclerView.ViewHolder(postView), View.OnClickListener{
val iconImage: ImageView = postView.findViewById(R.id.icon_image_view)
val title: TextView = postView.findViewById(R.id.title)
val body: TextView = postView.findViewById(R.id.body)
val deleteIcon: ImageView = postView.findViewById(R.id.delete_post_image)
val editIcon: ImageView = postView.findViewById(R.id.edit_post_image)
init {
deleteIcon.setOnClickListener(this)
editIcon.setOnClickListener(this)
}
override fun onClick(v: View?){
val position = adapterPosition
if(v?.id == editIcon.id){
myListener.onEditPost(position)
}else{
myListener.onDeletePost(position)
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PostViewHolder {
val postView = LayoutInflater.from(parent.context).inflate(R.layout.post, parent, false)
return PostViewHolder(postView)
}
override fun onBindViewHolder(holder: PostViewHolder, position: Int) {
val currentPost = dummyData[position]
holder.iconImage.setImageResource(currentPost.image)
holder.title.text = currentPost.title
holder.body.text = currentPost.body
}
override fun getItemCount(): Int {
return dummyData.size
}
interface OnPostClickListener{
fun onEditPost(position: Int)
fun onDeletePost(position: Int)
}
}
If anyone saw something I miss, please do tell me because I am stuck at how to display the RecyclerView. Any help would be appreciate.
Edit:
Here is my MockDatabase:
package com.example.recyclerView
import com.example.projectdrivemark.R
class MockDatabase {
companion object{
fun createMockData(): ArrayList<Post>{
val list = ArrayList<Post>()
for(i in 0 until 20){
val imageToSelect = when (i % 3){
0 -> R.drawable.ic_baseline_account_balance
1 -> R.drawable.ic_baseline_account_circle
2 ->R.drawable.ic_baseline_ac_unit
else -> R.drawable.ic_baseline_access_alarms
}
list.add(
Post(
imageToSelect,
title = "Title post of $i",
body = "Title post of $i"
)
)
}
return list
}
}
}
Here is my Layout_list xml file:
<?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">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recycleViewMain"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dp"
tools:listitem="#layout/recycler_view_item" />
</androidx.constraintlayout.widget.ConstraintLayout>

You need to cast view to RecyclerView to access RecyclerView properties inside apply, also you cannot create instances of Activity by yourself,
MainActivity() is wrong and won't work, instead use requireActivity() which will provide context of Activity to which Fragment is attached to
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
view.findViewbyId<RecyclerView>(R.id.recycleViewMain).apply{
layoutManager = LinearLayoutManager(requireActivity())
adapter = PostAdapter(dummyData = ArrayList<Post>(), requireActivity() as OnPostClickListener)
}
}
Also, as #Necronet mentioned, add some mock data to see if it is actually rendering.
UPDATE
Instead of passing MainActivity to Adapter, pass OnPostClickListener
adapter = PostAdapter(dummyData = ArrayList<Post>(), requireActivity() as OnPostClickListener)
Adapter
class PostAdapter(val dummyData: ArrayList<Post>, val myListener: OnPostClickListener) : RecyclerView.Adapter<PostAdapter.PostViewHolder>(){
// you can use myListener to call methods
}

It's simple you are passing empty dummyData try using createMockData() instead. Also as a rule of thumb in Android, never ever instatiate an Activity yourself, if you need the reference from within a fragment you can use getActivity() method. So this:
adapter = PostAdapter(dummyData = ArrayList<Post>(), MainActivity())
Should be:
adapter = PostAdapter(dummyData = createMockData(), getActivity() as MainActivity)

Unable to bind LiveData List to Spinner entries

I have a Fragment MyFragment currently which has a Spinner my_spinner. For testing my app, I originally populated the contents of my_spinner manually by observing the property myLiveDataList in the AndroidViewModel MyViewModel as below:
my_fragment.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ui.fragments.MyFragment">
<Spinner
android:id="#+id/my_spinner"
android:layout_width="match_parent"
android:layout_height="100dp" />
</FrameLayout>
MyFragment.kt
import androidx.lifecycle.ViewModelProviders
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ArrayAdapter
import androidx.lifecycle.Observer
import com.example.app.R
import com.example.app.data.room.entities.MyEntity
import com.example.app.ui.viewmodels.MyViewModel
import kotlinx.android.synthetic.main.my_fragment.*
class MyFragment : Fragment() {
companion object {
fun newInstance() = MyFragment()
}
private lateinit var viewModel: MyViewModel
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.my_fragment, container, false)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
viewModel = ViewModelProviders.of(this).get(MyViewModel::class.java)
val myAdapter = ArrayAdapter<MyEntity>(this.context!!, android.R.layout.simple_spinner_item)
// This is where I populate my_spinner
viewModel.myLiveDataList.observe(this, Observer<List<MyEntity>> { data ->
data?.forEach {
myAdapter.add(it)
}
})
my_spinner.adapter = myAdapter
}
}
MyViewModel.kt
import android.app.Application
import androidx.lifecycle.AndroidViewModel
import androidx.lifecycle.LiveData
import androidx.lifecycle.toLiveData
import com.example.app.data.repositories.MyRepository
import com.example.app.data.room.entities.MyEntity
class MyViewModel(application: Application) : AndroidViewModel(application) {
private val myRepository = MyRepository(application)
val myLiveDataList: LiveData<List<MyEntity>>
get() = myRepository.getAllData().toLiveData()
}
This fills my_spinner successfully when I navigate to MyFragment:
Since it populates as expected, I went ahead to make the following changes to my_fragment.xml:
<?xml version="1.0" encoding="utf-8"?>
<layout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<variable name="viewmodel"
type="com.example.app.ui.viewmodels.MyViewModel" />
</data>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ui.fragments.MyFragment">
<Spinner
android:id="#+id/my_spinner"
android:layout_width="match_parent"
android:layout_height="100dp"
app:entries="#{viewmodel.myLiveDataList}"/>
</FrameLayout>
</layout>
I've added in a Binding Adapter file BindingAdapterUtil (following code was copied from this article):
import android.R
import android.view.View
import android.widget.AdapterView
import android.widget.ArrayAdapter
import android.widget.Spinner
import androidx.databinding.BindingAdapter
import androidx.databinding.InverseBindingAdapter
import androidx.databinding.InverseBindingListener
import com.example.app.ui.adapter.SpinnerExtensions.getSpinnerValue
import com.example.app.ui.adapter.SpinnerExtensions.setSpinnerEntries
import com.example.app.ui.adapter.SpinnerExtensions.setSpinnerInverseBindingListener
import com.example.app.ui.adapter.SpinnerExtensions.setSpinnerItemSelectedListener
import com.example.app.ui.adapter.SpinnerExtensions.setSpinnerValue
#BindingAdapter("entries")
fun Spinner.setEntries(entries: List<Any>?) {
setSpinnerEntries(entries)
}
#BindingAdapter("onItemSelected")
fun Spinner.setItemSelectedListener(itemSelectedListener: SpinnerExtensions.ItemSelectedListener?) {
setSpinnerItemSelectedListener(itemSelectedListener)
}
#BindingAdapter("newValue")
fun Spinner.setNewValue(newValue: Any?) {
setSpinnerValue(newValue)
}
#BindingAdapter("selectedValue")
fun Spinner.setSelectedValue(selectedValue: Any?) {
setSpinnerValue(selectedValue)
}
#BindingAdapter("selectedValueAttrChanged")
fun Spinner.setInverseBindingListener(inverseBindingListener: InverseBindingListener?) {
setSpinnerInverseBindingListener(inverseBindingListener)
}
#InverseBindingAdapter(attribute = "selectedValue", event = "selectedValueAttrChanged")
fun Spinner.getSelectedValue(): Any? {
return getSpinnerValue()
}
object SpinnerExtensions {
fun Spinner.setSpinnerEntries(entries: List<Any>?) {
if (entries != null) {
val arrayAdapter = ArrayAdapter(context, R.layout.simple_spinner_item, entries)
arrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item)
adapter = arrayAdapter
}
}
fun Spinner.setSpinnerItemSelectedListener(listener: ItemSelectedListener?) {
if (listener == null) {
onItemSelectedListener = null
} else {
onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
override fun onItemSelected(parent: AdapterView<*>, view: View, position: Int, id: Long) {
if (tag != position) {
listener.onItemSelected(parent.getItemAtPosition(position))
}
}
override fun onNothingSelected(parent: AdapterView<*>) {}
}
}
}
fun Spinner.setSpinnerInverseBindingListener(listener: InverseBindingListener?) {
if (listener == null) {
onItemSelectedListener = null
} else {
onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
override fun onItemSelected(parent: AdapterView<*>, view: View, position: Int, id: Long) {
if (tag != position) {
listener.onChange()
}
}
override fun onNothingSelected(parent: AdapterView<*>) {}
}
}
}
fun Spinner.setSpinnerValue(value: Any?) {
if (adapter != null ) {
val position = (adapter as ArrayAdapter<Any>).getPosition(value)
setSelection(position, false)
tag = position
}
}
fun Spinner.getSpinnerValue(): Any? {
return selectedItem
}
interface ItemSelectedListener {
fun onItemSelected(item: Any)
}
}
And I've modified the onActivityCreated in MyFragment like so:
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
viewModel = ViewModelProviders.of(this).get(MyViewModel::class.java)
DataBindingUtil.setContentView<MyFragmentBinding>(
this.activity!!, R.layout.my_fragment
).apply {
this.setLifecycleOwner(this#MyFragment)
this.viewmodel = viewModel
}
}
The result of this is that my_spinner is no longer populating with the contents of MyViewModel.myLiveDataList. To try to ascertain if the property was at fault, I created a new property in MyViewModel like so:
val myList: List<String>?
get() = listOf("First", "Second", "Third")
And I have bound this property to my_spinner just like MyViewModel.myLiveDataList above with success this time.
The function in MyRepository.getAllData() (which myLiveDataList returns) returns a Flowable<List<MyEntity>> (RxJava), which calls a Room DAO to get the data. My assumption here is that myLiveDataList doesn't have anything to serve when it tries to bind the values for the first time, and never tries again.
Am I missing something when trying to bind a LiveData datasource to a Spinner?

After reading this answer, I've modified my_fragment.xml to the following:
...
<data>
<import type="java.util.List" />
<import type="com.example.app.data.room.entities.MyEntity" />
<import type="androidx.lifecycle.LiveData" />
<variable name="viewmodel"
type="com.example.app.ui.viewmodels.MyViewModel" />
<variable name="myTestList"
type="LiveData<List<MyEntity>>" />
</data>
...
<Spinner
android:id="#+id/my_spinner"
android:layout_width="match_parent"
android:layout_height="100dp"
app:entries="#{myTestList}"/>
...
I've also removed the contents of MyFragment.onActivityCreated and modified MyFragment.onCreateView as followed:
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
viewModel = ViewModelProviders.of(this).get(MyViewModel::class.java)
val binding = MyFragmentBinding.inflate(inflater, container, false)
binding.setLifecycleOwner(this)
binding.viewmodel = viewModel
binding.myTestList = viewModel.myLiveDataList
return binding.root
}
Not a perfect solution, and I still don't know why my original bout at this problem didn't yield the desired results, but it will do. If there is a better way of binding a Spinner to LiveData in this fashion, please let me know.