realtimeDatabaseDataEventListener.kt

// Create Database Object
val database = FirebaseDatabase.getInstance("<database path>")
val databaseRef = database.reference
// Read from the database
databaseRef.addValueEventListener(object : ValueEventListener {
  override fun onDataChange(dataSnapshot: DataSnapshot) {
    // This method is called once with the initial value and again
    // whenever data at this location is updated.
    val value = dataSnapshot.value
    Log.d(TAG, "Value is: $value")
  }
  
  override fun onCancelled(error: DatabaseError) {
    // Failed to read value
    Log.w(TAG, "Failed to read value.", error.toException())
  }
})