Does periodic notifications work when device is in sleep

Question

I am working with Android API especially Alarms, IntentService and notifications. I am using AlarmManager to schedule a periodic IntentService which might or might not fire notifications.

My questions is What happens when the device is in sleep mode?

1. Alarm will not fire and thus IntentService will not run at all. I am not sure if this will be the case.Will it make a difference if I make it a WakefulIntentService? I believe wake locks are needed to ensure the service keeps running after the BroadCastReciever returns. However, in this case there is no broadcast reciever.

2. Alarm and IntentService will run, but any notification will not have any impact since the device is sleeping. In this case, do I have to explicitly get a wakelock from PowerManager to fire notification ?

Answer 1

What happens when the device is in sleep mode?

That depends upon your type of alarm and the component your PendingIntent is to invoke.

If your alarm type ends in _WAKEUP, and you are using a broadcast PendingIntent, the device will wake up and remain awake through the call to onReceive() of the BroadcastReceiver. Once onReceive() returns, the device can fall asleep again. This is why WakefulIntentService and WakefulBroadcastRecevier were created -- to offer tested patterns for how to pass control to an IntentService and keep the device awake while the service completes its work.

If your alarm type ends in _WAKEUP and you are not using a broadcast PendingIntent, as the saying goes, your mileage may vary. You may not get control before the device falls back asleep. This is not a recommended pattern.

If your alarm types does not end in _WAKEUP, the device will not wake up due to your alarm.

With respect to the Notification, given the nature of the API, one hopes that it is the OS' responsibility to keep the device awake long enough for the ringtone or vibration pattern to play, as we do not know the precise instant when the Notification appears, nor do we know whether the ringtone will play (e.g., device is on silent mode).