这是我的code设置报警每24小时。我怎么能重复这个只有20天呢？

  alarmManager.setRepeating（AlarmManager.RTC_WAKEUP，     calendar.getTimeInMillis（），     24 * 60 * 60 * 1000，     的PendingIntent）; 

解决方案

直到你取消它，将永远重复。所以，你可以做什么，这是火的东西在20天内，并管理该事件时，取消报警。

This is my code to set the alarm for every 24 hours. How can I repeat this for 20 days only?

alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, 
     calendar.getTimeInMillis(), 
     24*60*60*1000, 
     pendingIntent);

that will be repeating forever until you cancel it. So, what you can do, it's to fire something in 20 days,and when managing that event, cancel your alarm.