This is a Lollipop-specific question, since the API has changed. To find out how to do this on earlier versions, see related question:
I would like to know how to turn on / off the system Alarm icon in the status bar as shown in this image:
Timely Alarm Clock controls this icon on Lollipop as of release 1.3. Prior to that release, the code was using private APIs as detailed in the related question.
The new technique they use works on an unrooted Nexus 5 running v5.0.1.
Update
It looks like there is a lot more the this new API than just changing the icon. The lock screen now also displays the time I have set the alarm for.
AlarmManager has a new api to set this.
AlarmManager.setAlarmClock (AlarmManager.AlarmClockInfo info, PendingIntent operation)
If you do this, the alarm shows on notification bar and LockScreen .
来源：https://stackoverflow.com/questions/28367822/lollipop-api-for-controlling-the-alarm-icon-in-status-bar