我想我找到了答案here：

public void setRepeating (int type, long triggerAtMillis, long intervalMillis, PendingIntent operation)

Added in API level 1

Schedule a repeating alarm. Note: for timing operations (ticks, timeouts, etc) it is easier and much more efficient to use Handler. If there is already an alarm scheduled for the same IntentSender, it will first be canceled.

Like set(int, long, PendingIntent), except you can also supply a rate at which the alarm will repeat. This alarm continues repeating until explicitly removed with cancel(PendingIntent). If the time occurs in the past, the alarm will be triggered immediately, with an alarm count depending on how far in the past the trigger time is relative to the repeat interval.

If an alarm is delayed (by system sleep, for example, for non _WAKEUP alarm types), a skipped repeat will be delivered as soon as possible. After that, future alarms will be delivered according to the original schedule; they do not drift over time. For example, if you have set a recurring alarm for the top of every hour but the phone was asleep from 7:45 until 8:45, an alarm will be sent as soon as the phone awakens, then the next alarm will be sent at 9:00.

If your application wants to allow the delivery times to drift in order to guarantee that at least a certain time interval always elapses between alarms, then the approach to take is to use one-time alarms, scheduling the next one yourself when handling each alarm delivery.

Parameters

type One of ELAPSED_REALTIME, ELAPSED_REALTIME_WAKEUP}, RTC or RTC_WAKEUP.

triggerAtMillis time in milliseconds that the alarm should first go off, using the appropriate clock (depending on the alarm type).

intervalMillis interval in milliseconds between subsequent repeats of the alarm.

operation Action to perform when the alarm goes off; typically comes from IntentSender.getBroadcast().

您使用该功能的方法是：

am.setRepeating(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis(), 1440*60000 ,sender);

试试这个：

//The only variable here is the desired hour of the alarm, which

// has to be obtained in milliseconds

long alarmSetAt = // The hour of the Alarm for the current date in milliseconds

long time = cal.getTimeInMillis() - alarmSetAt;

if(time > 0){

time = -time + cal.getTimeInMillis();

}

else{

time = time + cal.getTimeInMillis() + 1440*60000;

}

am.setRepeating(AlarmManager.RTC_WAKEUP, cal.getTimeInMillis(), 1440*60000 ,sender);