CWAC Wakeful: Staying Awake At Work
The recommended pattern for Android's equivalent to cron
jobs and Windows scheduled tasks is to use
This works well when coupled with an
IntentService, as the
service will do its work on a background thread and shut down
when there is no more work to do.
There's one small problem:
IntentService does nothing to keep
the device awake. If the alarm was a
WAKEUP variant, the phone
will only stay awake on its own while the
handling the alarm is in its
onReceive() method. Otherwise,
the phone may fall back asleep.
WakefulIntentService attempts to combat this by combining
the ease of
IntentService with a partial
This is available as a JAR file from the downloads area of this GitHub repo. The project itself is set up as an Android library project, in case you wish to use the source code in that fashion.
WakefulIntentService v0.4.0 and newer requires Android 2.0+, so it
can take advantage of
onStartCommand() for better handling of
crashed services. Use earlier versions of
you wish to try to use it on older versions of Android, though this
is not supported.
Any component that wants to send work to a
WakefulIntentService subclass needs to call either:
MyService.class is the
intentOfWork is an
Intent that will be used to call
startService() on your
WakefulIntentService must override
doWakefulWork() instead of
will be processed within the bounds of a
the semantics of
doWakefulWork() are identical to
doWakefulWork() will be passed the
Intent supplied to
sendWakefulWork() (or an
Intent created by the
method, depending on which flavor of that method you use).
And that's it.
WakefulIntentService handles the rest.
NOTE: this only works with local services. You have no means
of accessing the static
WakeLock of a remote service.
NOTE #2: Your application must hold the
This is version v0.4.5 of this module, meaning it is being beaten to a pulp by reusers, prompting some revisions.
demo/ project directory and
com.commonsware.cwac.wakeful.demo package you will find
OnBootReceiver designed to be attached to the
OnBootReceiver schedules an alarm, which is sent
OnAlarmReceiver in turn asks
WakefulIntentService) to do some work in a background
thread. It uses
the library project itself to access the source code and
resources of the
Note that when you build the JAR via
ant jar, the sample
activity is not included, nor any resources -- only the
compiled classes for the actual library are put into the JAR.
The code in this project is licensed under the Apache Software License 2.0, per the terms of the included LICENSE file.
If you have questions regarding the use of this code, please post a question
on StackOverflow tagged with
android. Be sure to indicate
what CWAC module you are having issues with, and be sure to include source code
and stack traces if you are encountering crashes.
- v0.4.5: completed switch to
- v0.4.4: switched to
- v0.4.3: added better recovery from an
- v0.4.2: added
volatilekeyword to static
WakeLockfor better double-checked locking implementation
- v0.4.1: added
setIntentRedelivery()call, nuked extraneous permissions check
- v0.4.0: switched to
onStartCommand(), requiring Android 2.0+ (API level 5 or higher)
- v0.3.0: converted to Android library project, added test for