public class AlarmReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
       // For our recurring task, we'll just display a message
        Toast.makeText(context, "I'm running", Toast.LENGTH_SHORT).show();
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest>
  <application>
    <receiver
        android:name=".AlarmReceiver"
        android:enabled="true"
        android:exported="true">
    </receiver>
  </application>
</manifest>

// Get AlarmManager instance
 alarmManager = getSystemService(Context.ALARM_SERVICE) as AlarmManager
// Intent part
 intent = Intent(this, AlarmReceiver::class.java)
intent.action = "FOO_ACTION"
intent.putExtra("KEY_FOO_STRING", "Medium AlarmManager Demo")
 pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0)
// Alarm time
 ALARM_DELAY_IN_SECOND = 10
 alarmTimeAtUTC = System.currentTimeMillis() + ALARM_DELAY_IN_SECOND * 1_000L
// Set with system Alarm Service
// Other possible functions: setExact() / setRepeating() / setWindow(), etc
alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, alarmTimeAtUTC, pendingIntent)

pendingIntentRequestCode = 0
 flag = 0
 pendingIntent = PendingIntent.getBroadcast(this, pendingIntentRequestCode, intent, flag)

alarmManager = getSystemService(Context.ALARM_SERVICE) as AlarmManagerv
 alarmTime = System.currentTimeMillis() + 4000
 tagStr = "TAG"
 handler = null // `null` means the callback will be run at the Main thread
alarmManager.setExact(AlarmManager.RTC_WAKEUP, alarmTime, tagStr, object : AlarmManager.OnAlarmListener {
  override fun onAlarm() {
    Toast.makeText(this, "AlarmManager.OnAlarmListener", Toast.LENGTH_LONG).show()
  }
}, null)

setAndAllowWhileIdle(...)
setExactAndAllowWhileIdle(...)

onAlarmListener = object : AlarmManager.OnAlarmListener {
  override fun onAlarm() {
     toast("Alarm goes off.")
  }
}
alarmManager.cancel(onAlarmListener)