firebase realtime. basic access.

main.kt

package es.codekai.firebase_curso

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Toast
import com.google.firebase.database.DataSnapshot
import com.google.firebase.database.DatabaseError
import com.google.firebase.database.ValueEventListener
import com.google.firebase.database.ktx.database
import com.google.firebase.ktx.Firebase
import es.codekai.firebase_curso.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {
    private lateinit var mBinding: ActivityMainBinding
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        mBinding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(mBinding.root)

        Firebase.database.setPersistenceEnabled(true)
        val db = Firebase.database.reference
        val dataRef = db.child("holaFirebase").child("datax")

        val myContext = this
        val listener = object : ValueEventListener {
            override fun onDataChange(snapshot: DataSnapshot) {
                mBinding.tvTexto.text = snapshot.getValue(String::class.java)
            }

            override fun onCancelled(error: DatabaseError) {
                Toast.makeText(myContext, "Error ${error.message}", Toast.LENGTH_LONG ).show()
            }
        }

        

        dataRef.addValueEventListener(listener)

        mBinding.btnActualizar.setOnClickListener {

            dataRef.setValue(mBinding.etValor.text.toString())

        }

        mBinding.btnActualizar.setOnLongClickListener {
            dataRef.removeValue()
            true
        }

    }
}