Android スレッド内でUIの表示を変更する

package com.a.thread

import android.os.Bundle
import android.os.Handler
import android.util.Log
import android.widget.Button
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
import java.util.concurrent.atomic.AtomicInteger

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

        val handler = Handler(mainLooper)

        val myRunnable = object : Runnable {
            var count: AtomicInteger = AtomicInteger(0)

            override fun run() {
                handler.postDelayed(this, 1000)

                count.incrementAndGet()

                Log.d("count", "" + count)

                val textView = findViewById<TextView>(R.id.text_view)
                textView.text = count.toString()
            }
        }

        val startBtn = findViewById<Button>(R.id.button_start)
        val interruptBtn = findViewById<Button>(R.id.button_interrupt)

        startBtn.setOnClickListener {
            handler.post(myRunnable)
        }

        interruptBtn.setOnClickListener {
            handler.removeCallbacks(myRunnable)
        }
    }
}