Android-Job: Xamarin Binding Library

A utility library for Android to run jobs delayed in the background. Depending on the Android version either the JobScheduler, GcmNetworkManager or AlarmManager is getting used. You can find out in this blog post or in these slides why you should prefer this library than each separate API. All features from Android Nougat are backward compatible.

Download

Install-Package Naxam.AndroidJob.Droid

Usage

The class JobManager serves as entry point. Your jobs need to extend the class Job. Create a JobRequest with the corresponding builder class and schedule this request with the JobManager.

Before you can use the JobManager you must initialize the singleton. You need to provide a Context and add a JobCreator implementation after that. The JobCreator maps a job tag to a specific job class. It's recommended to initialize the JobManager in the onCreate() method of your Application object, but there is an alternative, if you don't have access to the Application class.

public class App extends Application {

    @Override
    public void onCreate() {
        super.onCreate();
        JobManager.create(this).addJobCreator(new DemoJobCreator());
    }
}

public class DemoJobCreator implements JobCreator {

    @Override
    public Job create(String tag) {
        switch (tag) {
            case DemoSyncJob.TAG:
                return new DemoSyncJob();
            default:
                return null;
        }
    }
}

After that you can start scheduling jobs.

public class DemoSyncJob extends Job {

    public static final String TAG = "job_demo_tag";

    @Override
    @NonNull
    protected Result onRunJob(Params params) {
        // run your job here
        return Result.SUCCESS;
    }

    public static void scheduleJob() {
        new JobRequest.Builder(DemoSyncJob.TAG)
                .setExecutionWindow(30_000L, 40_000L)
                .build()
                .schedule();
    }
}

Advanced

The JobRequest.Builder class has many extra options, e.g. you can specify a required network connection, make the job periodic, pass some extras with a bundle, restore the job after a reboot or run the job at an exact time.

Each job has a unique ID. This ID helps to identify the job later to update requirements or to cancel the job.

private void scheduleAdvancedJob() {
    PersistableBundleCompat extras = new PersistableBundleCompat();
    extras.putString("key", "Hello world");

    int jobId = new JobRequest.Builder(DemoSyncJob.TAG)
            .setExecutionWindow(30_000L, 40_000L)
            .setBackoffCriteria(5_000L, JobRequest.BackoffPolicy.EXPONENTIAL)
            .setRequiresCharging(true)
            .setRequiresDeviceIdle(false)
            .setRequiredNetworkType(JobRequest.NetworkType.CONNECTED)
            .setExtras(extras)
            .setRequirementsEnforced(true)
            .setPersisted(true)
            .setUpdateCurrent(true)
            .build()
            .schedule();
}

private void schedulePeriodicJob() {
    int jobId = new JobRequest.Builder(DemoSyncJob.TAG)
            .setPeriodic(TimeUnit.MINUTES.toMillis(15), TimeUnit.MINUTES.toMillis(5))
            .setPersisted(true)
            .build()
            .schedule();
}

private void scheduleExactJob() {
    int jobId = new JobRequest.Builder(DemoSyncJob.TAG)
            .setExact(20_000L)
            .setPersisted(true)
            .build()
            .schedule();
}

private void cancelJob(int jobId) {
    JobManager.instance().cancel(jobId);
}

If a non periodic Job fails, then you can reschedule it with the defined back-off criteria.

public class RescheduleDemoJob extends Job {

    @Override
    @NonNull
    protected Result onRunJob(Params params) {
        // something strange happened, try again later
        return Result.RESCHEDULE;
    }

    @Override
    protected void onReschedule(int newJobId) {
        // the rescheduled job has a new ID
    }
}

Warning: With Android Marshmallow Google introduced the auto backup feature. All job information are stored in a shared preference file called evernote_jobs.xml and in a database called evernote_jobs.db. You should exclude these files so that they aren't backed up.

You can do this by defining a resource XML file (i.e., res/xml/backup_config.xml) with content:

<?xml version="1.0" encoding="utf-8"?>
<full-backup-content>
    <exclude domain="sharedpref" path="evernote_jobs.xml" />
    <exclude domain="database" path="evernote_jobs.db" />
</full-backup-content>

And then referring to it in your application tag in AndroidManifest.xml:

<application ...  android:fullBackupContent="@xml/backup_config">

Proguard

The library doesn't use reflection, but it relies on three Services and two BroadcastReceivers. In order to avoid any issues, you shouldn't obfuscate those four classes. The library bundles its own Proguard config and you don't need to do anything, but just in case you can add these rules in your configuration.

FAQ

See here.

Google Play Services

This library does not automatically bundle the Google Play Services, because the dependency is really heavy and not all apps want to include them. That's why you need to add the dependency manually, if you want that the library uses the GcmNetworkManager on Android 4.

dependencies {
    compile "com.google.android.gms:play-services-gcm:latest_version"
}

Crashes after removing the GCM dependency is a known limitation of the Google Play Services. Please take a look at this workaround to avoid those crashes.