unresolved reference in Firestore UI and display it - firebase

Question

am using Firebase UI for displaying data in recyler view from Firestore.And i wanna that this query will display on my app but i can't add this reference. Can anyone please guide me on this?
i do my app witch a tutorial but its expired and i try to do and lern a lot of my self but with this i cant do enything
MainACtivity.kt
package com.example.nfc
import android.content.Intent
import android.os.Bundle
import android.view.*
import android.widget.Button
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.auth.ktx.auth
import com.google.firebase.firestore.ktx.firestore
import com.google.firebase.ktx.Firebase
import com.firebase.ui.firestore.FirestoreRecyclerAdapter
import com.firebase.ui.firestore.FirestoreRecyclerOptions
data class User(
val displayName: String = "",
val emojis: String = ""
)
class UserViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView)
class MainActivity : AppCompatActivity() {
private val db = Firebase.firestore
private lateinit var auth: FirebaseAuth
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
auth = Firebase.auth
// Query the users collection
val query = db.collection("users")
val options = FirestoreRecyclerOptions.Builder<User>().setQuery(query, User::class.java)
.setLifecycleOwner(this).build()
val adapter = object: FirestoreRecyclerAdapter<User, UserViewHolder>(options) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): UserViewHolder {
val view = LayoutInflater.from(this#MainActivity).inflate(android.R.layout.simple_list_item_2,parent,false)
return UserViewHolder(view)
}
override fun onBindViewHolder(holder: UserViewHolder, position: Int, model: User) {
val tvName: TextView=holder.itemView.findViewById(android.R.id.text1)
val tvEmojis: TextView=holder.itemView.findViewById(android.R.id.text2)
tvName.text = model.displayName
tvEmojis.text = model.emojis
}
}
uzytkownicy.adapter = adapter
uzytkownicy.layoutManager = LinearLayoutManager(this)
//end
val addButton = findViewById(R.id.addButton)as Button
addButton.setOnClickListener{
val intent = Intent(this, addtrasa::class.java)
startActivity(intent)
}
}
}
activity_main.xml
<?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/szarytlo"
tools:context=".MainActivity">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rvUsers"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
and thats my error
enter image description here

Answer 1

You do not assign an object to uzytkownicy anywhere in your MainActivity, so it is not clear to the compiler what type of object it is meant to be. From the context of the code, it looks like you mean for it to be a RecyclerView, and you probably want to use the one in activity_main.xml. If so, you would need to assign it as such:
val uzytkownicy: RecyclerView = findViewById(R.id.rvUsers)
Then you can go ahead and use that reference to set the adapter and layout manager as you're already attempting to do.