如何在协程中更新Android UI？

import kotlinx.coroutines.*

class MainActivity : AppCompatActivity() {
    private val mainScope = CoroutineScope(Dispatchers.Main)

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

        mainScope.launch {
            // 在后台线程执行耗时操作
            val result = withContext(Dispatchers.IO) {
                // 执行耗时操作，例如网络请求或数据库查询
                performLongRunningTask()
            }

            // 切换回主线程更新UI
            updateUI(result)
        }
    }

    override fun onDestroy() {
        super.onDestroy()
        mainScope.cancel() // 取消协程
    }

    private suspend fun performLongRunningTask(): String {
        // 执行耗时操作
        delay(1000) // 模拟耗时操作
        return "结果"
    }

    private fun updateUI(result: String) {
        textView.text = result
    }
}