How can i keep the job service running when the app is closed from recent task list by user

问题

I am using Job Scheduler API in my app to schedule a job for me after specific time interval. It runs fine when the app is running. But whenever the user closes the app or clears it from the recent task list the app stops and the scheduled job never executes afterwards until you open the app and it is rescheduled again from the time it is opened.

Now i want someone to help me to keep the jobs on executing even if the app is closed or cleared from the recent task list.

If there is any alternative solution please tell me.

i am looking for the solution from the past 3 days. Tried everything said by developers on StackOverFlow and other sites and none of them worked for me.

This is where is schedule the job!

ComponentName componentName = new 
ComponentName(getActivity().getBaseContext(),WallpaperJobService.class);
        JobInfo jobInfo = new JobInfo.Builder(777,componentName)

.setRequiresCharging(sharedPreferences.getBoolean("Charging",false))

.setRequiredNetworkType(sharedPreferences.getBoolean("Wifi",false) ? 
JobInfo.NETWORK_TYPE_UNMETERED : JobInfo.NETWORK_TYPE_ANY)
                .setPeriodic(sharedPreferences.getInt("Duration",15) * 60 * 
1000)
                .setPersisted(true)
                .build();

        JobScheduler scheduler = (JobScheduler) 
getContext().getSystemService(Context.JOB_SCHEDULER_SERVICE);
        scheduler.schedule(jobInfo);

My Job Service Class:

public class WallpaperJobService extends JobService {

private boolean jobCancelled;
private SharedPreferences sharedPreferences;
private SharedPreferences.Editor editor;

@Override
public boolean onStartJob(JobParameters params) {
    Log.i("WallpaperJobService", "Job started!");
    changeWallpaper(params);
    return true;
}

private void changeWallpaper(final JobParameters params) {
    final ArrayList<Image> images = (ArrayList<Image>) 
MainActivity.favoritesRoomDatabase.roomDao().getAllFavoriteWallpapers();
    sharedPreferences = getSharedPreferences("GridSize", MODE_PRIVATE);
    editor = sharedPreferences.edit();

    if (images != null && images.size() != 0) {
        if (sharedPreferences.getInt("Index", 0) == images.size()) {
            editor.putInt("Index", 0);
            editor.commit();
        }
        Picasso.get().load(Constants.domain + 
images.get(sharedPreferences.getInt("Index", 0)).getImage_url()).into(new 
Target() {
            @Override
            public void onBitmapLoaded(final Bitmap bitmap, 
Picasso.LoadedFrom from) {
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        if (jobCancelled) {
                            Log.i("WallpaperJobService","Returned");
                            return;
                        }
                        try {
                           //Doing some work here 

                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                        Log.i("WallpaperJobService", "Job finished!");
                        jobFinished(params, false);
                    }
                }).start();
            }

            @Override
            public void onBitmapFailed(Exception e, Drawable errorDrawable) 
{
                Log.i("WallpaperJobService", "Bitmap load failed " + 
e.getMessage());
            }

            @Override
            public void onPrepareLoad(Drawable placeHolderDrawable) {

            }
        });
    } else {
        Log.i("WallpaperJobService", "Favorite database is null!");
    }
}

@Override
public boolean onStopJob(JobParameters params) {
    Log.i("WallpaperJobService", "Job cancelled before completion!");
    jobCancelled = true;
    return true;
}


}

回答1:

When doing stuff periodically in the background — JobScheduler, WorkManager, AlarmManager, FCM push messages, etc. — you have to take into account that your process might not be around when it is time for you to do your work. Android will fork a process for you, but it is "starting from scratch". Anything that your UI might have set up in memory, such as a database, would have been for some prior process and might not be set up in the new process.

来源：https://stackoverflow.com/questions/54268524/how-can-i-keep-the-job-service-running-when-the-app-is-closed-from-recent-task-l