Jobs in Android

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Easy Job Scheduling with
Android-Job
In the modern app development era, running some
background tasks outside the scope of an
applications life-cycle have become one of the
key requirements. These tasks may be as simple as
just reminding the user of something or as
complex as syncing local data with server and
fetching latest data periodically to provide
better user experience. Implementing these
features in Android is really challenging and you
have to be very careful with your app performance
along with other aspects such as battery life.
Android provides several APIs for scheduling
background work (beyond the app life-cycle).
1. JobScheduler
JobScheduler was introduced in Lollipop and its
the most efficient way to perform background
work, especially networking. It performs
background work based on conditions, not on time.
These conditions may be whether the device
is connected to a network, charging or idle.
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JobScheduler comes with a very fluent API and its
very easy to implement. You can use JobScheduler
by registering jobs specifying their requirements
for network and timing. Then the system schedules
the jobs to run at appropriate times. It
also defers the execution as necessary to comply
with Doze mode and App Standby restrictions. Also
the jobs are batched together by the system to
save battery life. Another handy feature is that
the scheduled jobs are persisted through
system reboots.
JobScheduler is the way to go with API if your
app targets Lollipop (API level 21) and above.
Source developer.android.com
2. GCM Network Manager
GCM Network Manager comes with a similar API
like JobScheduler and it targets API level 9 and
above. It uses JobScheduler behind the scene for
API level 21 and higher. It
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has all the battery saving scheduling features
from JobScheduler.
The main disadvantage with GCM Network Manager is
its a part of Googles Play Services SDK and can
be used only on devices with Google Play
preinstalled. Another got you is that
all scheduled Services will be wiped out when the
application or Google Play Service updates.
3. Alarm Manager
Though JobScheduler and GCM Network Manager are
good at performing tasks based on conditions such
as network connectivity, device charging etc.
while keeping battery life in mind, they are not
meant for performing tasks immediately or at a
specific time. An Alarm Clock or Reminder App
which needs precision in timing should not use
any of these options. Instead use AlarmManager
when your app needs to post a notification or set
off an alarm at a very specific time.
The AlarmManager is typically used to fire off a
Pending Intent that will start a Service in the
future. It has the ability to wake up the device
if the alarm is urgent. We can use
AlarmManager for periodic tasks based on an
elapsed time interval. The main got you with
AlarmManager is that the API behaviour
differs between platform versions. Theres a lot
of boilerplate required to implement
AlarmManager. Also the device state is ignored.
Never use AlarmManager to perform networking
tasks.
As you can see, scheduling background work in
Android is quite a headache with 3 different APIs
all performing the same thing. To overcome this
problem, the nice folks at Evernote have open
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sourced a unified library to schedule jobs in
Android.
Meet Android-Job
?   Android
-
Job abstracts away which implementation you
want to use to perform background work.
?   Depending on the requirements, this library
decides which API to use to run your job.
?   It provides a superset of all
the features from JobScheduler, GCM Network
Manager and AlarmManager.
?   All features from Android Nougat
are backward compatible.
?   Less
boilerplate.
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Setting up Android-Job
Include android-job dependency in your
app modules build.gradle file and sync project.
Using Android-Job
Implementing Android-Job is super easy.
The API includes below classes/interfaces.
1. Job Your jobs need to extend this class
and override onRunJob method. The heavy lifting
is done here. You must return a Result from this
method so that the system knows whether to
attempt to run your job at a later time.
2. Job Request You can schedule a Job by
creating a JobRequest using its builder
constructor and passing your Job tag.
3. Job Creator Job Creator acts like a factory
to provide a Job based on a job tag. Your
concrete Job Creator class must implement the Job
Creator interface and override the create method.
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4. Job Manager The Job Manager class serves as
the entry point. Before using this class you must
initialize this as singleton. Job Manager takes a
Context. After creating the instance, you have to
add your Job Creator to Job Manager.
Here we will develop a simple app to show
notification to the user periodically.
Lets create our ShowNotificationJob class in the
first step.
In the onRunJob method we are simply showing a
notification and we are returning Result. SUCCESS
every time the job runs.
Also we have a static schedule Periodic method
which builds the Job Request through its Builder
and schedules the job by calling schedule (). We
are passing ShowNotificationJob. TAG in the
Builder constructor which tells our Job
Creator return a ShowNotificationJob instance.
JobRequest.Builder has many methods. Here we are
calling set Periodic to tell the system that this
is a periodic job which runs every 15 minutes.
Also we have passed 5 minutes as the 2nd
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parameter which is actually the flex time. This
helps the system to batch our job with any other
jobs with similar time interval.
setUpdateCurrent(true) will update the current
job instead of creating a new job.
set Persisted(true) tells the system to persist
the job through system reboots.
Next lets create our DemoJobCreator class
which implements JobCreatorinterface.
As you can see, in the create method we have a
switch construct which maps a tag with a specific
job.
In the next step we will create our MainApp class
which extends Application class. In the MainApp
class we will create the Job Manager instance by
passing our application context and add our
DemoJobCreator to the Job Manager.
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In the final step we will call the schedule
Periodic method of our ShowNotificationJob class
in the on Create method of Main Activity to
schedule our job when our application starts.
Thats it.
You can implement your Job using this library
very easily. You can create a much advanced job
by creating Job Request as per your requirements.
You can see all the methods available
for creating an advanced job in their GitHub
repo.
While debugging, you may set the interval time to
1 minute or less to test the app quickly. But in
Android N the minimum interval of periodic jobs
is 15 minutes. So you will get this error while
running the job.
Interval Ms is out of range
To overcome this error you can configure the
JobManager with setAllowSmallerIntervalsForMarshma
llow(true) method for debugging purpose. But
remember, in production you must
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set the minimum interval time to 15 times
otherwise your app may behave differently in
different platform versions.
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