TestAsyncAlertDialog.kt

package jp.radiko.testasyncalertdialog

import android.os.Bundle
import android.widget.Button
import android.widget.Toast
import androidx.appcompat.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.Job
import kotlinx.coroutines.launch
import kotlin.coroutines.CoroutineContext
import kotlin.coroutines.resume
import kotlin.coroutines.suspendCoroutine

class MainActivity : AppCompatActivity(), CoroutineScope {

    enum class AlertResult {
        Ok,
        Cancel,
    }

    private suspend fun myAlert(): AlertResult = suspendCoroutine { cont ->
        AlertDialog.Builder(this@MainActivity)
            .setMessage("this is a test.")
            .setPositiveButton("Ok") { _, _ -> cont.resume(AlertResult.Ok) }
            .setNegativeButton("Cancel") { _, _ -> cont.resume(AlertResult.Cancel) }
            .setOnCancelListener { cont.resume(AlertResult.Cancel) }
            .show()
    }

    private lateinit var job: Job

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


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

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        job = Job()
        setContentView(R.layout.activity_main)
        findViewById<Button>(R.id.btnHello).setOnClickListener {
            launch {
                val result = myAlert()
                Toast.makeText(this@MainActivity, result.toString(), Toast.LENGTH_SHORT)
                    .show()
                // OKボタン
                // キャンセルボタン
                // 戻るボタンでキャンセル
                // アクティビティを閉じてjobをキャンセル (再現手順は？)
            }
        }
    }
}