retrieving data from firebase kotlin

package com.example.espl.myapplication22

import android.os.Bundle
import android.support.design.widget.Snackbar
import android.support.design.widget.NavigationView
import android.support.v4.view.GravityCompat
import android.support.v4.view.ViewPager
import android.support.v7.app.ActionBarDrawerToggle
import android.support.v7.app.AppCompatActivity
import android.view.Menu
import android.view.MenuItem
import com.google.firebase.database.*
import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.android.synthetic.main.app_bar_main.*


class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelectedListener {

    lateinit var mDatabaseReference : DatabaseReference

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setSupportActionBar(toolbar)

        mDatabaseReference = FirebaseDatabase.getInstance().getReference();

        databasereference.child("desc").addValueEventListener(object : ValueEventListener{
            override fun onDataChange(snapshot: DataSnapshot) {
            println("TestBed: ${snapshot.value}")
        }

                override fun onCancelled(error: DatabaseError) {}
    })


    }

 
}