[Android] 003. AlarmManager(バックグラウンド処理)

internal class AlarmBroadcastReceiver : BroadcastReceiver() {
    override fun onReceive(context: Context, intent: Intent) {
        var text = "alarm!"
        Toast.makeText(context, text, Toast.LENGTH_LONG).show()
        sendNotification(context, "AlarmManager", text)
    }

    private fun sendNotification(context: Context, title: String, text: String) {
        val channelId = "channel_id"
        val channel = NotificationChannel(
            channelId,
            "channel_name",
            NotificationManager.IMPORTANCE_DEFAULT).apply {
            description = "channel description"
            setShowBadge(true)
        }

        val manager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
        manager.createNotificationChannel(channel)

        val builder = NotificationCompat.Builder(context, channelId)
            .setSmallIcon(R.drawable.ic_launcher_background)
            .setContentTitle(title)
            .setContentText(text)
            .setPriority(NotificationCompat.PRIORITY_DEFAULT)

        var notificationId = 1
        with(NotificationManagerCompat.from(context)) {
            if (ActivityCompat.checkSelfPermission(
                    context,
                    Manifest.permission.POST_NOTIFICATIONS
            ) != PackageManager.PERMISSION_GRANTED) {
                return
            }
            notify(notificationId, builder.build())
        }
    }
}

<manifest>
    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
    <application>
        <receiver
            android:name=".AlarmBroadcastReceiver"
            android:process=":remote" />
    </application>
</manifest>

var context = LocalContext.current
var alarmMgr = context.getSystemService(Context.ALARM_SERVICE) as AlarmManager
var alarmIntent: PendingIntent = Intent(context, AlarmBroadcastReceiver::class.java).let { intent ->
    PendingIntent.getBroadcast(context, 0, intent, PendingIntent.FLAG_IMMUTABLE)
}

Button(onClick = {
    alarmMgr?.set(
        AlarmManager.ELAPSED_REALTIME_WAKEUP,
        SystemClock.elapsedRealtime() + 20 * 1000,
        alarmIntent
    )
}) {
    Text("Start")
}