Continue Service even if application is cleared from Recent app

Just follow these scenarios, your service and processes (Threads run inside your service) will remain continuous.

1. Create service and use START_STICKY as return value in onStartCommand method like below:

   @Override
   public int onStartCommand(final Intent intent, 
                             final int flags,
                             final int startId) {
   
       //your code
       return START_STICKY;
   }  
   

2. Above code will Restart the service if destroyed and always remain running but the process(Threads) run from the service will stop working if your app is removed from the recent apps. To ensure that your processes(Threads) remains always in running condition you have to Override onTaskRemoved() method and add code to restart Tasks like below.

   @Override
   public void onTaskRemoved(Intent rootIntent){
       Intent restartServiceTask = new Intent(getApplicationContext(),this.getClass());
       restartServiceTask.setPackage(getPackageName());    
       PendingIntent restartPendingIntent =PendingIntent.getService(getApplicationContext(), 1,restartServiceTask, PendingIntent.FLAG_ONE_SHOT);
       AlarmManager myAlarmService = (AlarmManager) getApplicationContext().getSystemService(Context.ALARM_SERVICE);
       myAlarmService.set(
               AlarmManager.ELAPSED_REALTIME,
               SystemClock.elapsedRealtime() + 1000,
               restartPendingIntent);
   
       super.onTaskRemoved(rootIntent);
   }
   

3. Start service like below

startService(new Intent(this, YourService.class));