Background
Google has multiple solutions for job/task scheduling, such as JobScheduler
and GcmTaskService
. Each has its own advantages and disadvantages.
Recently, Google presented a new library called "Firebase JobDispatcher".
The problem
Sadly, there is very little to read about this new API. In fact, it's really hard to find anything about it.
Only thing I've found is their announcement video and a sample. But even their, there is not much to know about this API.
The questions
Looking at previous questions, investigations and comparisons I had with the other APIs (here, for example), I'd like to ask how the new API works and know what to take into consideration when using it:
Can a job have parameters that stay with it and can even be modified when needed? They say in the sample "An optional Bundle of user-supplied extras. The default is an empty Bundle." Is this it? Can it be modified by the job upon execution of it?
Can jobs be re-scheduled easily? It is said "A boolean indicating whether the Job should repeat" . How can it be chosen when to re-schedule? I've tried the sample, and chose "Recurring", but it doesn't seem to run again, only once.
Can it be protected vs library's jobs (because of unique ids)?
Does it needs extra care when updating the app (as previous APIs did)? Can jobs still be scheduled after an update of the app? Testing on the sample, it seems the jobs are completely gone after an update of the app. Can it be avoided?
Does it need
RECEIVE_BOOT_COMPLETED
in case I want the job to still be scheduled even when the device is restarted? The sample seems to have it.Is it possible to get a list of all scheduled jobs and their information (including parameters), and be able to cancel specific/all of them and even modify them ?
Will a job be removed upon clear-data operation of the app?
Is it possible to tell the job that it's best that it will run in a range of time (example : between 7:00 and 8:00 in the morning)? It is mentioned "ExecutionWindowTrigger-which specifies a time window in which the Job should be executed". Is that it? What happens when it misses this window?
The method
onStartJob
inJobService
class return a boolean and the description for it is "whether there is more work remaining." What does it mean? What does theneedsReschedule
parameter ofjobFinished
method mean? Are they related to each other?Are there any restrictions I should know about? For example minimal & maximal values for each of the functions?
Actually Firebase Android JobDispatcher is a layer of abstraction around job scheduling engines on Android. And for now they only have one driver implementation for GCM Network Manager. That means currently it behaves the same way as GCM Network Manager behaves. Hopefully in the future more Drivers will be implemented.
1. Can a job have parameters that stay with it and can even be modified when needed? They say in the sample "An optional Bundle of user-supplied extras. The default is an empty Bundle." . Is this it? Can it be modified by the job upon execution of it?
Job.Builder
has methodsetExtras
with arbitrary bundle which later may be accessed viajobParameters.getExtras()
. You cannot modify the bundle (jobParameters
contains only getters). You could reschedule your job with flagsetReplaceCurrent(true)
and specify a new bundle.2. Can jobs be re-scheduled easily ? It is said "A boolean indicating whether the Job should repeat" . How can it be chosen when to re-schedule? I've tried the sample, and chose "Recurring", but it doesn't seem to run again, only once.
setRecurring(true)
,setTrigger(Trigger.executionWindow(10, 20))
3. Can it be protected vs library's jobs (because of unique ids) ?
Job tags must be unique in your application. Other apps on the phone have their own 'endpoints' (package name/service name). To see all scheduled/finished jobs for
GooglePlayDriver
please useadb shell dumpsys activity service GcmService
4. Does it needs extra care when updating the app (as previous APIs did) ? Can jobs still be scheduled after an update of the app ? Testing on the sample, it seems the jobs are completely gone after an update of the app. Can it be avoided?
GooglePlayDriver
doesn't reschedule Jobs after Google Play Services or the app is updated. Here is an open issue for this. So for now this is your responsibility.5. Does it need RECEIVE_BOOT_COMPLETED in case I want the job to still be scheduled even when the device is restarted? The sample seems to have it.
setLifetime(Lifetime.FOREVER | UNTIL_NEXT_BOOT)
Of course if you're going to create your own driver you'll have to take care of the lifetime yourself.6. Is it possible to get a list of all scheduled jobs and their information(including parameters), and be able to cancel specific/all of them and even modify them ?
7. Will a job be removed upon clear-data operation of the app?
8. Is it possible to tell the job that it's best that it will run in a range of time (example : between 7:00 and 8:00 in the morning) ? It is mentioned "ExecutionWindowTrigger-which specifies a time window in which the Job should be executed" . Is that it? What happens when it misses this window?
executionWindow(0, 60*60)
. The job will run between 7:00 - 8:00.You cannot use recurring job because
Also, ExecutionWindowTrigger specifies approximate time. It's not guaranteed it would run at the given window. If it misses the window the job will run any time later.
9. The method "onStartJob" in "JobService" class return a boolean and the description for it is "whether there is more work remaining." . What does it mean? What does the "needsReschedule" parameter of "jobFinished" method mean? Are they related to each other?
onStartJob
returns false that means you completed your work. No Need to invokejobFinished
. TheRESULT_SUCCESS
is sent automatically.if
onStartJob
returns true that means you started a thread and waiting for results. As soos as you're done you must invokejobFinished
to inform google play services whether the job should be rescheduled or not. If yes the job will be rescheduled depending onRetryStrategy
.10. Are there any restrictions I should know about? For example minimal&maximal values for each of the functions?
onStartJob
should offload work to another thread of execution as soon as possible. They provide aSimpleJobService
as an example of what is expected from you.JobScheduler
. Also need to handle the situation when google play services are not available, we should probably implementDriver
based onAlarmManager
.