The RecyclerView doesn't retrieve any data from Firebase and doesn't show any data - kotlin

Question

I just started working with Android Studio, and I've been trying to figure out what's wrong with this code for a few days now. When I run the program it shows nothing, and also there is no errors from Android Studio. I read the posts on the subject, but unfortunately I found nothing appropriate.
This is my activity class.
package ie.wit.donationx.activities
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.recyclerview.widget.LinearLayoutManager
import com.google.firebase.database.*
import ie.wit.donationx.adapters.EventsAdapter
import ie.wit.donationx.databinding.ActivityEventsFeedBinding
import ie.wit.donationx.models.EventData
class EventsFeed : AppCompatActivity() {
lateinit var mDataBase: DatabaseReference
private lateinit var eventList:ArrayList<EventData>
private lateinit var mAdapter: EventsAdapter
private lateinit var binding: ActivityEventsFeedBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
//setContentView(R.layout.activity_events_feed)
binding = ActivityEventsFeedBinding.inflate(layoutInflater)
val view = binding.root
setContentView(view)
eventList = ArrayList()
mAdapter = EventsAdapter(this,eventList)
var linearLayoutManager = LinearLayoutManager(this)
binding.recyclerEvents.layoutManager = linearLayoutManager
binding.recyclerEvents.setHasFixedSize(true)
binding.recyclerEvents.adapter = mAdapter
getEventsData()
}
private fun getEventsData() {
mDataBase = FirebaseDatabase.getInstance().getReference("Events")
mDataBase.addValueEventListener(object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
if (snapshot.exists()) {
for (eventSnapshot in snapshot.children) {
val event = eventSnapshot.getValue(EventData::class.java)
eventList.add(event!!)
}
binding.recyclerEvents.adapter = mAdapter
}
}
override fun onCancelled(error: DatabaseError) {
TODO("Not yet implemented")
}
})
}
}
This is my Adapter
package ie.wit.donationx.adapters
import android.content.Context
import android.view.LayoutInflater
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.recyclerview.widget.RecyclerView
import ie.wit.donationx.R
import ie.wit.donationx.databinding.ItemListBinding
import ie.wit.donationx.models.EventData
class EventsAdapter(
var c: Context, var eventList: ArrayList<EventData>)
: RecyclerView.Adapter<EventsAdapter.EventViewHolder>() {
inner class EventViewHolder(var v: ItemListBinding): RecyclerView.ViewHolder(v.root){}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): EventViewHolder {
val infilter = LayoutInflater.from(parent.context)
val v = DataBindingUtil.inflate<ItemListBinding>(
infilter,R.layout.item_list,parent,
false
)
return EventViewHolder(v)
}
override fun onBindViewHolder(holder: EventViewHolder, position: Int) {
val newList = eventList[position]
holder.v.isEvent = eventList[position]
holder.adapterPosition
}
override fun getItemCount(): Int {
return eventList.size
}
}
XML recyclerView
<?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=".activities.EventsFeed">
<com.google.android.material.imageview.ShapeableImageView
android:id="#+id/main_shapeable"
android:layout_width="match_parent"
android:layout_height="40dp"
android:layout_marginStart="10dp"
android:layout_marginTop="5dp"
android:layout_marginEnd="10dp"
android:background="#color/white"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<EditText
android:id="#+id/main_search"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginEnd="20dp"
android:ems="10"
android:hint="search"
android:inputType="textPersonName"
android:textSize="14sp"
app:layout_constraintBottom_toBottomOf="#+id/main_shapeable"
app:layout_constraintEnd_toEndOf="#+id/main_shapeable"
app:layout_constraintStart_toStartOf="#+id/main_shapeable"
app:layout_constraintTop_toTopOf="#+id/main_shapeable" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerEvents"
tools:listitem="#layout/item_list"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginTop="5dp"
android:layout_marginBottom="10dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/main_shapeable"/>
</androidx.constraintlayout.widget.ConstraintLayout>
XML file for items in recyclerView
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<variable
name="isEvent"
type="ie.wit.donationx.models.EventData" />
</data>
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:cardCornerRadius="5dp"
>
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<LinearLayout
android:orientation="horizontal"
android:layout_margin="10dp"
android:padding="8dp"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<ImageView
android:id="#+id/eventImg"
android:imageUrl="#{isEvent.image}"
android:scaleType="centerCrop"
android:layout_width="140dp"
android:layout_height="140dp"/>
<LinearLayout
android:orientation="vertical"
android:gravity="center"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/eventTitle"
android:textColor="#color/black"
android:textSize="20sp"
android:gravity="center"
android:textStyle="bold|normal"
android:layout_gravity="center"
android:text="#{isEvent.evenTitle}"
android:layout_margin="10dp"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
<TextView
android:id="#+id/eventInfo"
android:textColor="#android:color/darker_gray"
android:textSize="15sp"
android:gravity="center"
android:textStyle="bold|normal"
android:layout_gravity="center"
android:text="#{isEvent.info}"
android:layout_margin="10dp"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
</LinearLayout>
</LinearLayout>
<View
android:background="#android:color/darker_gray"
android:layout_width="match_parent"
android:layout_height="1dp"/>
</LinearLayout>
</androidx.cardview.widget.CardView>
</layout>
Data file
package ie.wit.donationx.models
class EventData {
var evenTitle: String? = null
var info: String? = null
var image: String? = null
constructor(){}
constructor(
evenTitle:String?,
info:String?,
image:String?
){
this.evenTitle = evenTitle
this.info = info
this.image = image
}
}
Firebase DB structure

Answer 1

When adding new list to the RecyclerView Adapter you need to call NotifyDataSetChanged()
Also, i advise to remove the list from the constructor of the adapter, and make a public function inside the adapter class that will update the private list created in the class.
private var items: MutableList<EventData> = mutableListOf()
fun setItems(newItemsList : List<EventData>){
eventList.clear()
eventList.addAll(newItemsList)
notifyDataSetChanged()
}
If you only update part of the list, you can create a separate function for that and use the more efficient notifyItemRangeInserted(), notifyItemInserted() or notifyItemChanged() \ notifyItemRangeChanged

Answer 2

You don't need to setAdaper again after getting EventsData
Just replace this line in getEventsData() :
binding.recyclerEvents.adapter = mAdapter
With :
if (eventList.size > 0) {
mAdapter.notifyDataSetChanged()
}
Edit:
You should not to add
android:imageUrl="#{isEvent.image}" in the ImageView,
you can use library to download the images from URL Like:
Picasso.
or
Fresco.
For Example using Picasso in your adapter:
override fun onBindViewHolder(holder: EventViewHolder, position: Int) {
val newList = eventList[position]
holder.v.isEvent = eventList[position]
holder.adapterPosition
// here to download image for URL
Picasso.get().load(eventList[position].image)
.into(holder.v.eventImg)
}
Don't forget to add dependencies
implementation 'com.squareup.picasso:picasso:2.8'