android - AlarmManager fires alarms at wrong time

Question

I managed everything all right to create a notification service used to fire a notification as a result of an alarm. Unfortunately, setting the alarm using AlarmManager doesn't work right. It fires several minutes later (not exactly hours, which would indicate a timezone problem). The recurring period is 1 week, so I used the constant INTERVAL_DAY and multiplied it with 7. In order to make sure that one PendingIntent doesn't replace the other, I pass the dayOfWeek as second parameter to PendingIntent.getService(). I check the correctness of the time for the alarm to fire by logging it:

Log.d(TAG, "next alarm " + df.format(cal.getTime()));

Is there really no way to list all alarms set - at least those from my own app? I believe this is the only way to track down the error.

My code:

cal.setTimeInMillis(System.currentTimeMillis());
cal.add(Calendar.DATE, 1);
cal.set(Calendar.HOUR_OF_DAY, hour);
cal.set(Calendar.MINUTE, minute);
Log.d(TAG, "next alarm " + df.format(cal.getTime()));
Intent showNotificationIntent = new Intent(context, NotificationService.class);
dayOfWeek = cal.get(Calendar.DAY_OF_WEEK);
alarmIntent = PendingIntent.getService(context, dayOfWeek, showNotificationIntent, 0);
getAlarmManager(context).setInexactRepeating(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis(),
    INTERVAL_WEEK, alarmIntent);

I want to offer to have an alarm every day, but at various times, which can be set by the user. So I use up to 7 alarms, which should fire on a weekly basis.

Even after reading the numerous answers to similar questions (I don't intend to create a duplicate question), I haven't managed to find the problem.

Answer 1

For api levels below 19 you should use AlarmManager.setRepeating() and your alarms will trigger exactly at specified time. Thou on api levels 19 and above this will no longer work. There was change in android so that all repeating alarms are inexact. So if you would like to achieve exact repeating alarm you should schedule alarm with AlarmManager.setExact() and then when alarm triggers do it again for next week and so on every week.