[kotlin, 앱 만들기] 타이머

시작 및 멈추기 버튼을 누르면 1초 단위로 움직입니다. 1000초가 max인 타이머. 

package com.example.myapplication

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.os.Parcel
import android.os.Parcelable
import android.widget.Button
import android.widget.TextView
import java.util.Timer
import kotlin.concurrent.timer

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

        var timerTask: Timer? = null
        var isRunning = false

        var sec: Int = 0
        val tv: TextView = findViewById(R.id.tv_hello)
        val btn: Button = findViewById(R.id.btn_kor)

        btn.setOnClickListener {
            isRunning = !isRunning
            if (isRunning == true) {
                timerTask = kotlin.concurrent.timer(period = 1000) {
                    sec++
                    runOnUiThread {
                        tv.text = sec.toString()
                    }
                }
            } else {
                timerTask?.cancel()
            }
        }
    }
}