Develop Reference

Type mismatch. Required: Fragment Found: DashboardFragment.Companion

I got this error while using the replace function to change the frame of the main Activity with the fragment that I created it shows type mismatch required fragment found DashboardFragmentComapnion
package com.shivanshu.bookhub
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.MenuItem
import android.widget.FrameLayout
import android.widget.Toast
import android.widget.Toolbar
import androidx.appcompat.app.ActionBarDrawerToggle
import androidx.coordinatorlayout.widget.CoordinatorLayout
import androidx.core.view.GravityCompat
import androidx.drawerlayout.widget.DrawerLayout
import com.google.android.material.navigation.NavigationView
class MainActivity : AppCompatActivity() {
lateinit var drawerLayout: DrawerLayout
lateinit var coordinatorLayout: CoordinatorLayout
lateinit var toolbar: androidx.appcompat.widget.Toolbar
lateinit var frameLayout: FrameLayout
lateinit var navigationView: NavigationView
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
drawerLayout = findViewById(R.id.drawerLayout)
coordinatorLayout = findViewById(R.id.coordinatorLayout)
toolbar = findViewById(R.id.toolbar)
frameLayout = findViewById(R.id.frameLayout)
navigationView = findViewById(R.id.navigationView)
setUpToolbar()
val actionBarDrawerToggle = ActionBarDrawerToggle(
this#MainActivity,
drawerLayout,
R.string.open_drawer,
R.string.close_drawer
)
drawerLayout.addDrawerListener(actionBarDrawerToggle)
actionBarDrawerToggle.syncState()
navigationView.setNavigationItemSelectedListener {
when(it.itemId){
R.id.dashboard -> {
supportFragmentManager.beginTransaction().
replace(R.id.frameLayout, DashboardFragment).commit()
}
R.id.profile ->{
Toast.makeText(this#MainActivity,"Profile Clicked",Toast.LENGTH_LONG)
}
R.id.about_app -> {
Toast.makeText(this#MainActivity,"About Section Clicked",Toast.LENGTH_LONG)
}
R.id.favourites -> {
Toast.makeText(this#MainActivity,"Favourites Clicked",Toast.LENGTH_LONG)
}
}
return#setNavigationItemSelectedListener true
}
}
fun setUpToolbar() {
setSupportActionBar(toolbar)
supportActionBar?.title = "Toolbar Title"
supportActionBar?.setHomeButtonEnabled(true)
supportActionBar?.setDisplayHomeAsUpEnabled(true)
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
val id = item.itemId
if(id == android.R.id.home){
drawerLayout.openDrawer(GravityCompat.START )
}
return super.onOptionsItemSelected(item)
}
}
The fragment file:
package com.shivanshu.bookhub
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"
/**
* A simple [Fragment] subclass.
* Use the [DashboardFragment.newInstance] factory method to
* create an instance of this fragment.
*/
class DashboardFragment : Fragment() {
// TODO: Rename and change types of parameters
private var param1: String? = null
private var param2: String? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
param1 = it.getString(ARG_PARAM1)
param2 = it.getString(ARG_PARAM2)
}
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_dashboard2, container, false)
}
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment DashboardFragment.
*/
// TODO: Rename and change types and number of parameters
#JvmStatic fun newInstance(param1: String, param2: String) =
DashboardFragment().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
}
}
}
I implement the NavigationDrawer having various menu items when I click on the dashboard menu item it will open the dashboard fragment I created

You should pass an instance of DashboardFragment to replace function.
val dashboardFragmentInctance = DashboardFragment.newInstance("param","param")
supportFragmentManager.beginTransaction().
replace(R.id.frameLayout, dashboardFragmentInctance).commit()

How to pass from recyclerview fragment to another recyclerview fragment

Can someone help me on how to transfer data from one recyclerview fragment to another recyclerview fragment?
This is my newly created CartRecyclerAdapter.kt for my cart recyclerview from a fragment. The main idea of SubmitItem() is to accept the selected item in the Itemrecyclerview.
package com.example.karawapplication
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import android.widget.ImageView
import android.widget.TextView
import android.widget.Toast
import androidx.recyclerview.widget.RecyclerView
import com.bumptech.glide.Glide
import com.bumptech.glide.request.RequestOptions
import com.example.karawapplication.models.ItemPost
import kotlinx.android.synthetic.main.layout_item_cart_list.view.*
import kotlinx.android.synthetic.main.layout_item_list_item.view.*
class CartRecyclerAdapter : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
private var Items : List<ItemPost> = emptyList()
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return ItemRecyclerAdapter.ItemViewHolder(
LayoutInflater.from(parent.context)
.inflate(R.layout.layout_item_cart_list, parent, false)
)
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
when(holder)
{
is ItemRecyclerAdapter.ItemViewHolder ->
{
holder.bind(Items.get(position))
}
}
}
override fun getItemCount(): Int {
return Items.size
}
fun SubmitItem(Item : ItemPost)
{
Items.toMutableList().add(Item)
}
class ItemViewHolder constructor(
Itemview : View
): RecyclerView.ViewHolder(Itemview)
{
val ItemImage : ImageView = Itemview.Item_image_cart
val ItemTitle : TextView = Itemview.Item_title_cart
val ItemCategory: TextView = Itemview.Item_category_cart
val ItemPrice : TextView = Itemview.Item_price_cart
fun bind (itempost : ItemPost)
{
ItemTitle.setText(itempost.Itemtitle)
ItemCategory.setText(itempost.ItemCategory)
ItemPrice.setText(itempost.ItemPrice)
val requestOptions = RequestOptions()
.placeholder(R.drawable.ic_baseline_brush_24)
.error(R.drawable.ic_baseline_brush_24)
Glide.with(itemView.getContext())
.applyDefaultRequestOptions(requestOptions)
.load(itempost.image)
.into(ItemImage)
}
}
}
This is where I use the SubmitItem() in my ItemRecyclerAdapter.kt which contains items of my shop app and displayed from another fragment. CartAdapter is the adapter of the cart that I recently created in order to access the function SubmitItem().
ItemButton.setOnClickListener()
{
Toast.makeText(itemView.context, "${itempost.image}, ${itempost.Itemtitle}, ${itempost.ItemPrice}", Toast.LENGTH_SHORT).show()
CartAdapter.SubmitItem(ItemPost(itempost.image,itempost.Itemtitle,itempost.ItemCategory,itempost.ItemPrice))
}
This is my code for my fragments
ShopFragment.kt contains the recyclerview of my items.
package com.example.karawapplication.fragments
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Toast
import androidx.recyclerview.widget.LinearLayoutManager
import com.android.volley.Request
import com.android.volley.VolleyError
import com.android.volley.toolbox.JsonArrayRequest
import com.android.volley.toolbox.Volley
import com.example.karawapplication.ItemRecyclerAdapter
import com.example.karawapplication.R
import com.example.karawapplication.models.ItemPost
import kotlinx.android.synthetic.main.fragment_shop.*
import org.json.JSONException
import org.json.JSONObject
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"
/**
* A simple [Fragment] subclass.
* Use the [Shop.newInstance] factory method to
* create an instance of this fragment.
*/
class Shop : Fragment(){
// TODO: Rename and change types of parameters
private lateinit var ItemAdapter : ItemRecyclerAdapter
private var param1: String? = null
private var param2: String? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
param1 = it.getString(ARG_PARAM1)
param2 = it.getString(ARG_PARAM2)
}
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_shop, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
initRecyclerView()
addDataSet()
}
// CUSTOM FUNCTIONS
private fun addDataSet()
{
createDataset {
list -> ItemAdapter.SubmitList(list)
}
}
private fun initRecyclerView()
{
ShopRecycleView.layoutManager = LinearLayoutManager(activity)
ItemAdapter = ItemRecyclerAdapter()
ShopRecycleView.adapter = ItemAdapter
//Toast.makeText(context, "Recycler Trigger", Toast.LENGTH_SHORT).show()
}
// https://tutorials.eu/json-parsing-and-how-to-use-gson-in-android/
// Generates the data for the recycleview
fun createDataset(onSuccess: (List<ItemPost>) -> Unit){
val url = "http://api.karawcraftventure.com/item"
// LIST DATA VARIABLE FOR RECYCLEVIEW
val list = ArrayList<ItemPost>()
// VOLLEY API REQUEST
val Queue = Volley.newRequestQueue(activity)
val jsonObject = JsonArrayRequest(
Request.Method.GET,url,null,
{response ->
try
{
for (i in 0 until response.length())
{
val item : JSONObject = response.getJSONObject(i)
val API_Image : String = item.getString("product_url_image")
val API_ItemName : String = item.getString("product_name")
val API_Price : String = item.getString("product_price")
val API_Category : String = item.getString("product_category")
// Toast Notif if data is extracted or not
//Toast.makeText(context, "$API_ItemName - $API_Price - $API_Category", Toast.LENGTH_SHORT).show()
list.add(ItemPost(API_Image, API_ItemName, API_Category, API_Price))
}
onSuccess(list)
}
catch (e: JSONException)
{
e.printStackTrace()
}
},
{ error: VolleyError? -> Toast.makeText(context, error?.message.toString(), Toast.LENGTH_SHORT).show()
}
)
Queue.add(jsonObject)
}
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment Shop.
*/
// TODO: Rename and change types and number of parameters
#JvmStatic
fun newInstance(param1: String, param2: String) =
Shop().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
}
}
}
Cart.kt fragment on the other hand, contains my shopping cart.
package com.example.karawapplication.fragments
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.karawapplication.CartRecyclerAdapter
import com.example.karawapplication.ItemRecyclerAdapter
import com.example.karawapplication.R
import kotlinx.android.synthetic.main.fragment_cart.*
import kotlinx.android.synthetic.main.fragment_shop.*
import kotlinx.android.synthetic.main.fragment_shop.ShopRecycleView
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"
/**
* A simple [Fragment] subclass.
* Use the [Cart.newInstance] factory method to
* create an instance of this fragment.
*/
class Cart : Fragment() {
// TODO: Rename and change types of parameters
private lateinit var ItemAdapter : CartRecyclerAdapter
private var param1: String? = null
private var param2: String? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
param1 = it.getString(ARG_PARAM1)
param2 = it.getString(ARG_PARAM2)
}
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
initRecyclerView()
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_cart, container, false)
}
private fun initRecyclerView()
{
Cart_RecyclerView.layoutManager = LinearLayoutManager(activity)
ItemAdapter = CartRecyclerAdapter()
Cart_RecyclerView.adapter = ItemAdapter
//Toast.makeText(context, "Recycler Trigger", Toast.LENGTH_SHORT).show()
}
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment Cart.
*/
// TODO: Rename and change types and number of parameters
#JvmStatic
fun newInstance(param1: String, param2: String) =
Cart().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
}
}
}
The code has no errors, but it does not show any output in my cart recyclerview fragment.

(I'm going to follow the "starts with a lowercase letter" convention for variables and functions here, because I'm tired and it's less confusing)
Your submitItem function just creates a new copy of items (items.toMutableList()) and adds to that. Then it's immediately discarded when you exit the function.
All your adapter code that handles your data (getItemCount, onBindViewHolder) references items, so you need to update that instead, and let the adapter know it's changed:
fun submitItem(item: ItemPost) {
// plus creates a copy, but adds the new item without making the result mutable
items = items.plus(item)
// we also need to tell the adapter that the data has changed, so it can
// update - there are more efficient calls (you'll probably get a lint
// warning telling you to use one) but this is the simplest
notifyDataSetChanged()
}
This is just making your adapter update correctly - I'm assuming you've got your communication between the two fragments set up properly (communicating through the parent activity, passing one fragment's adapter into the other, using a view model). Have a read of this if you need to: Communicating with fragments

java.lang.NullPointerException: findViewById<RecyclerVie…(R.id.recyclerView) must not be null

I'm trying to set up recycler view to work with the fragment I created, and in MainActivity after "val recyclerV = findViewById(R.id.plantsRecyclerView)" I'm getting " java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.MainActivity}: java.lang.NullPointerException: findViewById<RecyclerVie…(R.id.plantsRecyclerView) must not be null" even though the recycler with that Id exists, any ideas how can I fix that?
Thanks in advance!
(code:
Main Activity:
private var numPlants = 4
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
//there is some parts that I'm not posting because they are not relevant (at least I think so <it's mainly code that creates notifications>)
val recyclerV = findViewById<RecyclerView>(R.id.plantsRecyclerView)
recyclerV.layoutManager = LinearLayoutManager(this)
recyclerV.adapter = MyRecyclerViewAdapter(this, numPlants)
}
}
MyRecyclerViewAdapter:
package com.example.myapplication
import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
class MyRecyclerViewAdapter(private val context: Context, private val numPlants: Int) :
RecyclerView.Adapter<MyRecyclerViewAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(context).inflate(R.layout.card_layout, parent, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.bind(position)
}
override fun getItemCount() = numPlants
inner class ViewHolder(itemView: View): RecyclerView.ViewHolder(itemView) {
fun bind(position: Int){
// not implemented yet
}
}
}
fragment main (the fragment that recycler view inside of it):
<?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"
android:background="#color/darker_green"
tools:context=".MainActivity">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/plantsRecyclerView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginEnd="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
MainFragment (I haven't changed anything here after creation, and I suppose that is the problem):
package com.example.myapplication
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"
/**
* A simple [Fragment] subclass.
* Use the [MainFragment.newInstance] factory method to
* create an instance of this fragment.
*/
class MainFragment : Fragment() {
// TODO: Rename and change types of parameters
private var param1: String? = null
private var param2: String? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
param1 = it.getString(ARG_PARAM1)
param2 = it.getString(ARG_PARAM2)
}
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_main, container, false)
}
companion object {
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment MainFragment.
*/
// TODO: Rename and change types and number of parameters
#JvmStatic
fun newInstance(param1: String, param2: String) =
MainFragment().apply {
arguments = Bundle().apply {
putString(ARG_PARAM1, param1)
putString(ARG_PARAM2, param2)
}
}
}
}

Because your RecyclerView is in MainFragment. Not in MainActivity. Make your RecyclerView in MainFragment.

No Adapter Attached: Skipping layout with Kotlin Framents

I am trying to display items on a recyclerview but it says
"No adapter attached; skipping layout"
.
I can't figure out the error. I tried with Activities instead of Fragements and it works super well. I am not yet so familiar with Framents. Kindly help.
RecyclerAdapter
package com.manzugerald.shukuruyesu.adapter
import android.content.Context
import android.content.Intent
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.core.view.isVisible
import androidx.recyclerview.widget.RecyclerView
import com.manzugerald.shukuruyesu.HymnDetailActivity
import com.manzugerald.shukuruyesu.R
import com.manzugerald.shukuruyesu.model.Hymns
class HymnsItemAdapter(
val context: Context,
val dataset: List<Hymns>
) : RecyclerView.Adapter<HymnsItemAdapter.ItemViewHolder>() {
//provide a reference to the views for each data item (in this case there is only one item)
//Complex data items may need more than one view per item, and
//you provide access to all the views for a data item in a view holder
//Each data item is just an Affirmation object
inner class ItemViewHolder(private val view: View) : RecyclerView.ViewHolder(view) {
//val hymn_imageView: ImageView =view.findViewById(R.id.item_image)
val hymn_title: TextView = view.findViewById(R.id.textView_hymn_title)
val hymn_language: TextView = view.findViewById(R.id.textView_hymn_language)
val hymn_number: TextView = view.findViewById(R.id.textView_hymn_number)
var hymn_detail: TextView = view.findViewById(R.id.textView_hymn_text)
//This has been unused. I will try to see how best to use it in the future
var hymnPosition = 0
/**
* //So as the contents of the views displayed are clickable, append the setOnClickListener to the view holder rather than individual views
* An explicit intent is used for exchanging information between two or more fragements or activities (screen)
* The information to be carried to the next screen is passed as a key-value pair
* The key is retrieved in the receiving activity or fragment
* Then the data the key carries is gotten and assigned to the views so as to be viewed
*/
init {
view.setOnClickListener {
val intent = Intent(context,HymnDetailActivity::class.java)
val message = hymn_number.text.toString()
val message_two = hymn_language.text.toString()
val message_three = hymn_title.text.toString()
val message_four = hymn_detail.text.toString()
intent.putExtra("key_one", message)
intent.putExtra("key_two",message_two)
intent.putExtra("key_three",message_three)
intent.putExtra("key_four",message_four)
context.startActivity(intent)
}
}
}
/**
* Create new views (invoked by the layout manager)
*/
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ItemViewHolder {
val adapterLayout = LayoutInflater.from(parent.context).inflate(R.layout.list_item_hymn_list, parent, false)
return ItemViewHolder(adapterLayout)
}
/**
* Replace the contents of a view (invoked by the layout manager)
*/
/**
* Binds or attaches data to the views.
* Does this by interacting with the itemViewHolder
*/
override fun onBindViewHolder(holder: ItemViewHolder, position: Int) {
val item = dataset[position]
//holder.hymn_imageView.setImageResource(item.imageResourceId)
holder.hymn_title.text = context.resources.getString(item.titleStringResourceId)
holder.hymn_language.text = context.resources.getString(item.languageStringResourceId)
holder.hymn_number.text = "Song Number: " + context.resources.getString(item.numberStringResourceId)
holder.hymn_detail.text = context.resources.getString(item.detailStringResourceId)
holder.hymnPosition = position
holder.hymn_detail.isVisible=false
}
/**
* Return the size of the dataset (invoked by the layout manager)
*/
//Takes not of the size of the data, number of rows so that binding can be done with ease
override fun getItemCount(): Int = dataset.size
}
The data source:
package com.manzugerald.shukuruyesu.data
import com.manzugerald.shukuruyesu.R
import com.manzugerald.shukuruyesu.model.Hymns
class HymnsDataSource {
//Gets the data from the string resources
fun loadHymns():List<Hymns>{
return listOf<Hymns>(
Hymns(R.string.affirmation1,R.string.affirmationNum1,R.string.affirmationLang1,R.string.affirmationDetail1),
Hymns(R.string.affirmation2,R.string.affirmationNum2,R.string.affirmationLang2,R.string.affirmationDetail2),
Hymns(R.string.affirmation3,R.string.affirmationNum3,R.string.affirmationLang3,R.string.affirmationDetail3),
Hymns(R.string.affirmation4,R.string.affirmationNum4,R.string.affirmationLang4,R.string.affirmationDetail4),
Hymns(R.string.affirmation5,R.string.affirmationNum5,R.string.affirmationLang5,R.string.affirmationDetail5),
Hymns(R.string.affirmation6,R.string.affirmationNum6,R.string.affirmationLang6,R.string.affirmationDetail6),
Hymns(R.string.affirmation7,R.string.affirmationNum7,R.string.affirmationLang7,R.string.affirmationDetail7),
Hymns(R.string.affirmation8,R.string.affirmationNum8,R.string.affirmationLang8,R.string.affirmationDetail8),
Hymns(R.string.affirmation9,R.string.affirmationNum9,R.string.affirmationLang9,R.string.affirmationDetail9),
Hymns(R.string.affirmation10,R.string.affirmationNum10,R.string.affirmationLang10,R.string.affirmationDetail10)
)
}
}
The Data class:
package com.manzugerald.shukuruyesu.model
import androidx.annotation.DrawableRes
import androidx.annotation.StringRes
data class Hymns(
#StringRes var titleStringResourceId: Int,
#StringRes var numberStringResourceId: Int,
#StringRes var languageStringResourceId: Int,
#StringRes var detailStringResourceId: Int
// #DrawableRes val imageResourceId: Int
)
The Fragment to display the recyclerview:
package com.manzugerald.shukuruyesu
import android.content.Context
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.manzugerald.shukuruyesu.data.HymnsDataSource
import com.manzugerald.shukuruyesu.databinding.FragmentHymnListBinding
import com.manzugerald.shukuruyesu.adapter.HymnsItemAdapter
import com.manzugerald.shukuruyesu.model.Hymns
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"
/**
* A simple [Fragment] subclass.
* Use the [HymnListFragment.newInstance] factory method to
* create an instance of this fragment.
*/
class HymnListFragment : Fragment() {
// TODO: Rename and change types of parameters
//enable and refrence binding
private var _binding: FragmentHymnListBinding? = null
private val binding get() = _binding!!
//property for the recycler view
private lateinit var recyclerView: RecyclerView
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setHasOptionsMenu(true)
}
//To inflate the layout, call teh onCreatView Method
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentHymnListBinding.inflate(inflater,container,false)
val view = binding.root
return view
}
//Bind the views in onViewCreated
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
val myDataSource = HymnsDataSource().loadHymns()
recyclerView = binding.recyclerView
recyclerView.apply {
layoutManager=LinearLayoutManager(requireContext())
adapter= HymnsItemAdapter(dataset = myDataSource, context = requireContext())
adapter= HymnsItemAdapter(context,myDataSource)
}
}
override fun onDestroyView() {
super.onDestroyView()
_binding=null
}
}
HymnListFragment Layout 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"
tools:context=".HymnListFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recycler_View"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:listitem="#layout/list_item_hymn_list"/>
</androidx.constraintlayout.widget.ConstraintLayout>

I got the solution to the question...
Neither the Adapter nor the Fragments had a problem.
The problem was in my MainActivity.kt file, which I didn't upload here...
The error came about when I tried changing from activities to Fragments....
Initially, I forgot to take off or comment the inflation of the layouts (Layouts are inflated in the respective Fragments, not the main activity).
For illustration purposes, I will comment the said error in the code.
My bad!
Main Activity class:
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
//val binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(R.layout.activity_main)
}
}

How to replace FrameLayout in Activity with a fragment?

I am a newbie to Android and was just trying to implement the fragments by referring the online tutorial.
I am getting an error on the first line of Fragment.kt. I followed all steps perfectly as shown and even tried to search for error on google but nothing seems to be working for me.The error I am getting is as follows.
12-23 19:15:53.369 11656-11656/com.example.mandar.testapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.mandar.testapp, PID: 11656
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mandar.testapp/com.example.mandar.testapp.MainActivity}: java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter savedInstanceState
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2687)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2753)
at android.app.ActivityThread.access$1100(ActivityThread.java:186)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1609)
at android.os.Handler.dispatchMessage(Handler.java:111)
at android.os.Looper.loop(Looper.java:238)
at android.app.ActivityThread.main(ActivityThread.java:6016)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:937)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:798)
Caused by: java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter savedInstanceState
at com.example.mandar.testapp.BlankFragment.onCreateView(BlankFragment.kt:0)
at android.app.Fragment.performCreateView(Fragment.java:2236)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:986)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1161)
at android.app.BackStackRecord.run(BackStackRecord.java:800)
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1575)
at android.app.FragmentController.execPendingActions(FragmentController.java:325)
at android.app.Activity.performStart(Activity.java:6481)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2650)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2753) 
at android.app.ActivityThread.access$1100(ActivityThread.java:186) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1609) 
at android.os.Handler.dispatchMessage(Handler.java:111) 
at android.os.Looper.loop(Looper.java:238) 
at android.app.ActivityThread.main(ActivityThread.java:6016) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:937) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:798) 
MainActivity.kt
package com.example.mandar.testapp
import android.app.Activity
import android.app.Fragment
import android.os.Bundle
class MainActivity : Activity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
var manager = fragmentManager
var fragment : Fragment? = manager.findFragmentById(R.id.lll)
if(fragment == null){
fragment = BlankFragment()
manager.beginTransaction().replace(R.id.lll,fragment).commit()
}
}
}
activity_main.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"
tools:context="com.example.mandar.testapp.MainActivity">
<FrameLayout
android:id="#+id/lll"
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
</LinearLayout>
BlankFragment.kt
package com.example.mandar.testapp
import android.os.Bundle
import android.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
/**
* A simple [Fragment] subclass.
* Use the [BlankFragment.newInstance] factory method to
* create an instance of this fragment.
*/
class BlankFragment : Fragment() {
// TODO: Rename and change types of parameters
private var mParam1: String? = null
private var mParam2: String? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
if (arguments != null) {
mParam1 = arguments.getString(ARG_PARAM1)
mParam2 = arguments.getString(ARG_PARAM2)
}
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_blank, container, false)
}
companion object {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private val ARG_PARAM1 = "param1"
private val ARG_PARAM2 = "param2"
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment BlankFragment.
*/
// TODO: Rename and change types and number of parameters
fun newInstance(param1: String, param2: String): BlankFragment {
val fragment = BlankFragment()
val args = Bundle()
args.putString(ARG_PARAM1, param1)
args.putString(ARG_PARAM2, param2)
fragment.arguments = args
return fragment
}
}
}// Required empty public constructor
and fragment_blank.xml
<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="com.example.mandar.testapp.BlankFragment">
<!-- TODO: Update blank fragment layout -->
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="#string/hello_blank_fragment" />
</FrameLayout>
Any Suggestion why this simple code is not working?
Here I am replacing FrameLayout lll with fragment.

The error says: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter savedInstanceState. Then savedInstanceState can be null and so you have to add ? after Bundle in your fragment.
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_blank, container, false)
}

Please use AppCompatActivity instead of Activity and import import android.support.v4.app.Fragment instead of import android.app.Fragment
for BlankFragment fragment and replace fragmentManager with supportFragmentManager it works perfectly.
Here is your modified code
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
var manager = supportFragmentManager
var fragment : Fragment? = manager.findFragmentById(R.id.lll)
if(fragment == null){
fragment = BlankFragment()
manager.beginTransaction().replace(R.id.lll,fragment).commit()
}
}
}
and fragment
import android.os.Bundle
import android.support.annotation.Nullable
import android.support.v4.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
class BlankFragment : Fragment() {
// TODO: Rename and change types of parameters
private var mParam1: String? = null
private var mParam2: String? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
if (arguments != null) {
mParam1 = arguments.getString(ARG_PARAM1)
mParam2 = arguments.getString(ARG_PARAM2)
}
}
override fun onCreateView(inflater: LayoutInflater?, #Nullable container: ViewGroup?, #Nullable savedInstanceState: Bundle?): View? {
// Inflate the layout for this fragment
return inflater?.inflate(R.layout.fragment_blank, container, false)
}
companion object {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private val ARG_PARAM1 = "param1"
private val ARG_PARAM2 = "param2"
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment BlankFragment.
*/
// TODO: Rename and change types and number of parameters
fun newInstance(param1: String, param2: String): BlankFragment {
val fragment = BlankFragment()
val args = Bundle()
args.putString(ARG_PARAM1, param1)
args.putString(ARG_PARAM2, param2)
fragment.arguments = args
return fragment
}
}
}