CurrenciesAdapter.kt

class CurrenciesAdapter(private val context: Context, private var list: MutableList<CurrencyResponse>) : RecyclerView.Adapter<CurrenciesAdapter.MyViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val inflater = LayoutInflater.from(context)
        val view: View = inflater.inflate(R.layout.currency_layout,parent,false)
        return MyViewHolder(view)
    }

    override fun getItemCount(): Int {
        return list.size
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        val user = list.get(position)
        holder.name?.text = user.quotes.USDAOA.toString()
        holder.info1?.text = user?.quotes.USDALL.toString()
        holder.info2?.text = user?.quotes.USDAED.toString()
        val addressObj = user.quotes.USDAOA.toString()
        holder.address?.text = user.quotes.USDAFN.toString()
    }

    class MyViewHolder(var view: View) : RecyclerView.ViewHolder(view){

        var name: TextView? = null
        var info1: TextView? = null
        var info2: TextView? = null
        var address: TextView? = null

        init {
            name = view.findViewById(R.id.txt_user_name)
            info1 = view.findViewById(R.id.txt_user_info1)
            info2 = view.findViewById(R.id.txt_user_info2)
            address = view.findViewById(R.id.txt_user_address)
        }

    }

}

MainActivity.kt

class MainActivity : AppCompatActivity() {


    private var adapter: CurrenciesAdapter? = null


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


        recycler_main.layoutManager = LinearLayoutManager(this@MainActivity)
        adapter = CurrenciesAdapter(this)

        recycler_main.adapter = adapter

        if (isInternetAvailable()) {
            getUsersData()
        }
    }


    private fun getUsersData() {

        showProgressBar()

        var apiInterface: CurrenciesResponse = CurrencyClient().getApiClient()!!.create(
                CurrenciesResponse::class.java
        )

        apiInterface.getCurrencies().enqueue(object : Callback<List<CurrencyResponse>> {
            override fun onResponse(
                    call: Call<List<CurrencyResponse>>,
                    response: Response<List<CurrencyResponse>>)
        
             {
            hideProgressBar()
            val currencyResponse = response.body()
            adapter?.list = currencyResponse
        }

            override fun onFailure(call: Call<List<CurrencyResponse>>, t: Throwable) {
            hideProgressBar()
            Log.e("error", t.localizedMessage)
        }
        })
    }
}