Android AlarmManager 小时警报运行错误间隔

Question

Im trying to set and run an alarm that run every hour, and is set by a few variables so as it will not run instantly, if the time is greater then the 58th minute The idea is to set it @ X hour and 58 minute, so it will run every hour, at the given minute(58).

Calendar calCurrent = Calendar.getInstance();

int time = 58 ;
Calendar calx = Calendar.getInstance();

calx.set(Calendar.MINUTE, time);
calx.set(Calendar.SECOND, 5);
if (calCurrent.get(Calendar.MINUTE) > time) {
            calx.add(Calendar.HOUR, +1);
}
System.out.println("Alarm is set to - " + calx.get(Calendar.HOUR)+":"+
        calx.get(Calendar.MINUTE));
alarmSwap = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
alarmSwap.setRepeating(AlarmManager.RTC_WAKEUP,
calx.getTimeInMillis(), 60 * 60 * 1000, pintent);

The code works and runs correctly for the 1st instance, then the alarm will for some reason run @ 0 minute the following hour.

Timeline looks like

1:23 - Repeating Alarm Set for 1:58 (1 hour intervals)

1:58 - alarm is triggered

3:00 - alarm is triggered

I have no idea why this alarm is being triggered @ :00 for the last alarm. It is not being called from anywhere else.

Any help is greatly appreciated.

All alarms are resetting after the hour clocks over the hour-

  Calendar calnew = Calendar.getInstance(); calnew.add(Calendar.SECOND, +5); 
  alarm =      (AlarmManager) getSystemService(Context.ALARM_SERVICE);     
  alarm.setRepeating(AlarmManager.RTC_WAKEUP, calnew.getTimeInMillis(),900000 , pintent);

Timeline-

1:20 triggered

1:35 triggered

1:50 triggered

2:00 triggered

2:15 triggered

2:30 triggered

Answer 1

From android documentation.

Note: as of API 19, all repeating alarms are inexact. If your application needs precise delivery times then it must use one-time exact alarms, rescheduling each time as described above. Legacy applications whose targetSdkVersion is earlier than API 19 will continue to have all of their alarms, including repeating alarms, treated as exact.

repeating alarms are not exact after API 19. This improves androids performance as android groups alarms which are at close interval and wakes system once and finishes all alarms(from other applications also). If you really want exact alarms the you will have to set normal one time alarm, and then set alarm again in first alarm's call.

Answer 2

Try this code to repeat alarm every hour

    alarmSwap.setInexactRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP,
    calx.getTimeInMillis(),
    AlarmManager.INTERVAL_HOUR, pintent);

Hope this will help.You can ask if you have any further queries.

Answer 3

This worked for me to trigger alarm after every 1hour

alarmmgr = (AlarmManager) getSystemService(ALARM_SERVICE);
long interval = 60 * 60 * 1000; // 1 hour
xassert alarmmgr != null;
alarmmgr.setInexactRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), interval, pendingIntent);