Fragment using MVVM, cardview inside recyclerview

BuyFragment.kt

package com.example.drake.kunuk.ui.buy

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProviders
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.drake.kunuk.R
import com.example.drake.kunuk.data.model.Buy
import kotlinx.android.synthetic.main.buy_fragment.*
import java.util.*

class BuyFragment : Fragment() {
    companion object {
        fun newInstance() = BuyFragment()
    }

    private lateinit var viewModel: BuySharedViewModel
    private val buyList = ArrayList<Buy>()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        viewModel = ViewModelProviders.of(this).get(BuySharedViewModel::class.java)

        viewModel.getBuys().observe(this, Observer<List<Buy>> { buys ->
            buyList.addAll(buys)
            (rvBuy.adapter as BuyAdapter).notifyDataSetChanged()

        })
    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.buy_fragment, container, false)
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        rvBuy.layoutManager = LinearLayoutManager(context)
        rvBuy.adapter = BuyAdapter(activity!!.applicationContext,
            R.layout.buy_card, buyList)

    }
}