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private final static String manasia_notification_channel = "Manasia Event Reminder";

// Create the NotificationChannel, but only on API 26+ because
// the NotificationChannel class is new and not in the support library
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
  //define the importance level of the notification
  int importance = NotificationManager.IMPORTANCE_DEFAULT;

  //build the actual notification channel, giving it a unique ID and name
  NotificationChannel channel = 

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//create an intent to open the event details activity
Intent intent = new Intent(getApplicationContext(), EventDetail.class);

//put together the PendingIntent
PendingIntent pendingIntent = 
  PendingIntent.getActivity(getApplicationContext(), 1, intent, FLAG_UPDATE_CURRENT);

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  private final static String manasia_notification_channel = "Manasia Event Reminder";  

  //get latest event details
  String notificationTitle = "Manasia event: " + event.getTitle();
  String notificationText = event.getDate() + " at Stelea Spatarul 13, Bucuresti";

  //build the notification
  NotificationCompat.Builder notificationBuilder = 
    new NotificationCompat.Builder(getApplicationContext(), manasia_notification_channel)
   .setSmallIcon(R.drawable.ic_manasia_small)

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public class NotifyWorker extends Worker {
    public NotifyWorker(@NonNull Context context, @NonNull WorkerParameters params) {
        super(context, params);
    }

    @NonNull
    @Override
    public Result doWork() {
        // Method to trigger an instant notification
        triggerNotification();

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//we set a tag to be able to cancel all work of this type if needed
public static final String workTag = "notificationWork";

//store DBEventID to pass it to the PendingIntent and open the appropriate event page on notification click
Data inputData = new Data.Builder().putInt(DBEventIDTag, DBEventID).build();
// we then retrieve it inside the NotifyWorker with:
// final int DBEventID = getInputData().getInt(DBEventIDTag, ERROR_VALUE);

OneTimeWorkRequest notificationWork = new OneTimeWorkRequest.Builder(NotifyWorker.class)
  .setInitialDelay(calculateDelay(event.getDate()), TimeUnit.MILLISECONDS)

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WorkManager.getInstance(context).enqueue(notificationWork);

//alternatively, we can use this form to determine what happens to the existing stack
// WorkManager.getInstance(context).beginUniqueWork(workTag, ExistingWorkPolicy.REPLACE, notificationWork);

//ExistingWorkPolicy.REPLACE - Cancel the existing sequence and replace it with the new one
//ExistingWorkPolicy.KEEP - Keep the existing sequence and ignore your new request
//ExistingWorkPolicy.APPEND - Append your new sequence to the existing one, 
                            //running the new sequence's first task after the existing sequence's last task finishes

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//firstly, we create a new piece of LiveData to pass the remote URL to the 
// Worker, and for that we define the REMOTE_URL String and initialize it
// by calling the getRemoteURL() method in our app
Data remoteUrl = new Data.Builder().putString(REMOTE_URL, getRemoteURL()).build();

//then, we create a new OneTimeWorkRequest since we don't need it to be 
//periodic, and set InputData to what we defined above, and add a work
//tag just in case we want to cancel this work
OneTimeWorkRequest getEventJson = new OneTimeWorkRequest
  .Builder(UpdateEventsWorker.class)

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//we create a class that extends Worker
public class UpdateEventsWorker extends Worker {
  //here we define the constants for the remote URL LiveData tag and 
  //the filename of the file we'll be exporting the JSON to
  private static final String REMOTE_URL = "REMOTE_URL";
  private static final String JSON_RESULT = "JSON_STRING";
  
 public UpdateEventsWorker(@NonNull Context context, @NonNull WorkerParameters params) {
  super(context, params);
 }

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//WARNING: this code is no longer valid as of WorkManager-alpha-10, please
//refer to this post for more details: https://medium.com/p/8e49c463cbf7

//finally, we get the status from the WorkManager by id since we still have
//a reference, otherwise we could do it by tag, and create an observer which
//checks whether the Worker has succeeded (i.e. returned Worker.Result.SUCCESS)
WorkManager.getInstance()
  .getStatusById(getEventJson.getId())
  .observe(MainActivity.this, workStatus -> {
    if (workStatus != null && workStatus.getState().equals(State.SUCCEEDED)) {

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//build an immediate OneTimeWorkRequest to fetch events from remote
OneTimeWorkRequest getEventJson = new OneTimeWorkRequest
  .Builder(UpdateEventsWorker.class)
  .setInputData(remoteUrl)
  .addTag(EVENTS_JSON_WORK_TAG)
  .build();

//we get a ListenableFuture<Void> from enqueue() which we can use below
//using beginUniqueWork to prevent re-enqueuing the same task while it is already running
ListenableFuture<Void> listenableFuture = WorkManager.getInstance().beginUniqueWork(EVENTS_JSON_WORK_TAG,