例1

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.TextView
import kotlinx.coroutines.*

// 1到100间隔一秒跳动
class MainActivity : AppCompatActivity() {

    private val job: Job = SupervisorJob()

    private val scope = CoroutineScope(Dispatchers.Main + job)

    private lateinit var tv : TextView

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

        scope.launch {
            count()
        }
    }

    private suspend fun count() {
        for (i in 1..100) {
            withContext(Dispatchers.Main) {
                tv.text = "$i"
            }
            delay(1000)
        }
    }

    override fun onDestroy() {
        super.onDestroy()
        job.cancel()
    }

}

例2

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.TextView
import kotlinx.coroutines.*
import kotlin.coroutines.CoroutineContext

// 1到100间隔一秒跳动
class MainActivity : AppCompatActivity(), CoroutineScope {

    lateinit var job: Job

    override val coroutineContext: CoroutineContext
        get() = Dispatchers.Main + job

    private lateinit var tv :TextView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        tv = findViewById(R.id.tv)
        job = SupervisorJob()

        launch {
            count()
        }

    }

    private suspend fun count() {
        for (i in 1..100) {
            withContext(Dispatchers.Main) {
                tv.text = "$i"
            }
            delay(1000)
        }
    }

    override fun onDestroy() {
        super.onDestroy()
        job.cancel()
    }

}