یک سوال درباره interface ها در کاتلین

با سلام من کلاسی ساختم که وقتی پیامک اومد کار خاصی انجام بده الان میخوام پیامک اومد یک اینترفیسی صدا زده بشه و بتونم داخل MainActivity ازش استفاده کنم
الان میگه متغیر اینترفیس شما مقداردهی نشده NullPointerExeption میده
ممنون میشم بهم کمک کنید

 package project.services

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.telephony.SmsMessage
import project.room.model.SMSModel
import project.services.SmsReceiver.OnSmsReceived

class SmsReceiver : BroadcastReceiver() {

 interface OnSmsReceived {
 fun smsReceived(smsModel: SMSModel)
 }

 private var onSmsReceived: OnSmsReceived? = null
 override fun onReceive(context: Context?, intent: Intent?) {
 //onSmsReceived = OnSmsReceived ????????? 
 if (intent!!.action == "android.provider.Telephony.SMS_RECEIVED") {
 val bundle = intent.extras //---get the SMS message passed in---
 val msgs: Array<SmsMessage?>

 val msg_from: String

 if (bundle != null) {
 //---retrieve the SMS message received---
 val pdus = bundle.get("pdus") as Array<*>
 msgs = arrayOfNulls(pdus.size)
 var smsModel: SMSModel? = null
 val smsBuilder = StringBuilder()
 for (i in 0 until msgs.size) {
 msgs[i] = SmsMessage.createFromPdu(pdus[i] as ByteArray)
 //val msg = msgs[i]!!!!
 val msgBody = msgs[i]!!.messageBody
 smsModel = SMSModel()
 if (msgBody != null && msgBody.isNotEmpty()) {
 smsBuilder.append(msgBody)
 smsModel.displayMessageBody = msgs[i]!!.displayMessageBody
 smsModel.displayOriginatingAddress = msgs[i]!!.displayOriginatingAddress
 smsModel.emailBody = msgs[i]!!.emailBody
 smsModel.emailFrom = msgs[i]!!.emailFrom
 smsModel.indexOnIcc = msgs[i]!!.indexOnIcc
 smsModel.messageBody = smsBuilder.toString()
 //SmsMessage.MessageClass messageClass = msgs[i]!!.getMessageClass();
 //byte[] pdu = msgs[i]!!.getPdu();
 smsModel.protocolIdentifier = msgs[i]!!.protocolIdentifier
 smsModel.originatingAddress = msgs[i]!!.originatingAddress
 smsModel.pseudoSubject = msgs[i]!!.pseudoSubject
 smsModel.serviceCenterAddress = msgs[i]!!.serviceCenterAddress
 //byte[] userData = msgs[i]!!.getUserData();
 smsModel.status = msgs[i]!!.status
 smsModel.timestampMillis = msgs[i]!!.timestampMillis
 }
 }
 if (smsModel != null) {
 //SMSModel.insertData(smsModel)
 //DBHelper.insertSms(smsModel)
 onSmsReceived!!.smsReceived(smsModel)
 }
 }
 }
 }
}

کد های MainActivity:

class MainActivity : AppCompatActivity(), SmsReceiver.OnSmsReceived {

    override fun smsReceived(smsModel: SMSModel) {
        //SMSModel.insertData(smsList, smsModel)
        //DBHelper.insertSms(compositeDisposable, smsRepository, smsModel)
        Toast.makeText(this, "smsReceived called!", Toast.LENGTH_SHORT).show()
    }

    private var smsList: MutableList<SMSModel> = ArrayList()

    //Database
    private var compositeDisposable: CompositeDisposable? = null
    private var smsRepository: SmsRepository? = null

    private var lst: ArrayList<SMSModel> = ArrayList()
    private var hasSendSmsPermission: Boolean = false

    //adapter
    private lateinit var adapter: RecyclerViewAdapter

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