DevTut

# Job Scheduling

# Basic usage

# Create a new JobService

This is done by extending the JobService class and implementing/overriding the required methods onStartJob() and onStopJob().

public class MyJobService extends JobService
{
    final String TAG = getClass().getSimpleName();
    
    @Override
    public boolean onStartJob(JobParameters jobParameters) {
        Log.i(TAG, "Job started");

        // ... your code here ...
        
        jobFinished(jobParameters, false);  // signal that we're done and don't want to reschedule the job
        return false;                       // finished: no more work to be done
    }

    @Override
    public boolean onStopJob(JobParameters jobParameters) {
        Log.w(TAG, "Job stopped");
        return false;
    }
}

# Add the new JobService to your AndroidManifest.xml

The following step is mandatory, otherwise you won't be able to run your job:

Declare your MyJobService class as a new <service> element between <application> </application> in your AndroidManifest.xml.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example">
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <service
            android:name=".MyJobService"
            android:permission="android.permission.BIND_JOB_SERVICE" />
    </application>
</manifest>

# Setup and run the job

After you implemented a new JobService and added it to your AndroidManifest.xml, you can continue with the final steps.

  • onButtonClick_startJob() prepares and runs a periodical job. Besides periodic jobs, JobInfo.Builder allows to specify many other settings and constraints. For example you can define that a plugged in charger or a network connection is required to run the job.
  • onButtonClick_stopJob() cancels all running jobs
public class MainActivity extends AppCompatActivity
{
    final String TAG = getClass().getSimpleName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void onButtonClick_startJob(View v) {
        // get the jobScheduler instance from current context
        JobScheduler jobScheduler = (JobScheduler) getSystemService(JOB_SCHEDULER_SERVICE);

        // MyJobService provides the implementation for the job
        ComponentName jobService = new ComponentName(getApplicationContext(), MyJobService.class);

        // define that the job will run periodically in intervals of 10 seconds
        JobInfo jobInfo = new JobInfo.Builder(1, jobService).setPeriodic(10 * 1000).build();

        // schedule/start the job
        int result = jobScheduler.schedule(jobInfo);
        if (result == JobScheduler.RESULT_SUCCESS)
            Log.d(TAG, "Successfully scheduled job: " + result);
        else
            Log.e(TAG, "RESULT_FAILURE: " + result);
    }

    public void onButtonClick_stopJob(View v) {
        JobScheduler jobScheduler = (JobScheduler) getSystemService(JOB_SCHEDULER_SERVICE);
        Log.d(TAG, "Stopping all jobs...");
        jobScheduler.cancelAll(); // cancel all potentially running jobs
    }
}

After calling onButtonClick_startJob(), the job will approximately run in intervals of 10 seconds, even when the app is in the paused state (user pressed home button and app is no longer visible).

Instead of cancelling all running jobs inside onButtonClick_stopJob(), you can also call jobScheduler.cancel() to cancel a specific job based on it's job ID.

# Remarks

Beware of running lots of code or doing heavy work inside your JobService, for example in onStartJob(). The code will run on the main/UI thread and therefore can lead to a blocked UI, no longer responding app or even a crash of your app!

Because of that, you must offload the work, for example by using a Thread or AsyncTask.

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