Android set alarm manager when another is finished

Question

I tried to use the setRepeating of AlarmManager, and then I read that the method isn't working anymore in API 26+, so the another solution was to schedule each alarm when the previous is finish. How can I do that?

MainActivity.java

 public class MainActivity extends AppCompatActivity {
calendar = Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());

calendar.set(Calendar.HOUR_OF_DAY, Integer.parseInt(hour.getText().toString()));
calendar.set(Calendar.MINUTE, Integer.parseInt(minute.getText().toString()));
calendar.set(Calendar.SECOND, 00);


Intent intent = new Intent(getApplicationContext(), Notification_receiver.class);

pendingIntent = PendingIntent.getBroadcast(getApplicationContext(), 1, intent, PendingIntent.FLAG_UPDATE_CURRENT);

alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), pendingIntent);
}

Notification_reciever.java

public class Notification_receiver extends BroadcastReceiver {
NotificationManager notificationManager = (NotificationManager) context.getSystemService(context.NOTIFICATION_SERVICE);

        Intent repeating_intent = new Intent(context, MainActivity.class);

        repeating_intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

        PendingIntent pendingIntent = PendingIntent.getActivity(context, time, repeating_intent, PendingIntent.FLAG_UPDATE_CURRENT);

        NotificationCompat.Builder builder = new NotificationCompat.Builder(context)
                .setContentIntent(pendingIntent)
                .setChannelId(CHANNEL_ID)
                .setSmallIcon(R.drawable.ic_baseline_notifications_active_24)
                .setContentTitle("Notification Title")
                .setContentText("Notification Text")
                .setAutoCancel(true);


        notificationManager.notify(time, builder.build());
}

How can i create another alarm manager when the previous is finish?

Answer 1

You will need to schedule your next alarm, at the end of BroadcastReceiver

public class AlarmBroadcastReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        ...
        alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, nextAlarmTimeInMillis(), pendingIntent);

Please note that, due to different battery saving mechanism implemented by different OEMs, AlarmManager is not guarantee to work all the time. Please refer to https://issuetracker.google.com/issues/122098785

In short, AlarmManager is the current best available mechanism, for timed notification to work, even without Internet connection. But, it is not gurantee to work all the time.