Adding objects to an arraylist in a for loop, but arraylist is empty after for loop is done?

Question

I'm a beginner so I feel like I might be making a silly mistake. Basically, I am running through a for loop and with each iteration, it is creating a new Event object and adding it to the arraylist called eventsList.

I have added a print statement at the bottom of each for loop iteration and it tells me that the size of eventsList is increasing: 1,2,3..

but for the second print statement, out of the for loop it tells me that the size is 0 (the second print statement which says: "size is...")

ListView eventsListView;
ArrayList<Event> eventList = new ArrayList<Event>();
Event event = null;

public void update() {

    ParseQuery<ParseObject> query = ParseQuery.getQuery("Events");

    query.findInBackground(new FindCallback<ParseObject>() {
        @Override
        public void done(List<ParseObject> objects, ParseException exception) {
            if (exception != null) {
                return
            }

            if (objects.size() == 0) {
                System.out.println("objects empty");
                return
            }

            System.out.println("objects size > 0");

            for (ParseObject object: objects) {

                String address = object.getString("address");
                String name = object.getString("name");
                String date = object.getString("date");
                String time = object.getString("time");
                String description = 
                object.getString("description");

                event = new Event(name, date, address);
                eventList.add(event);
                System.out.println(eventList.size());

            }
        }
    });

    System.out.println("The size is: " + eventList.size());

}

Use Log instead of print for debugging in android. Post your log after changing. — Abhimanyu
– Abhimanyu, Commented Jul 30, 2019 at 1:31

Tim Biegeleisen · Accepted Answer · 2019-07-30 01:32:11Z

3

There is nothing obviously wrong with your code, but the issue here is that when the The size is: print statement is hit, the background task which actually populates the event list may not yet have completed. So, the change you need to make to your code is a logical one, in which you only attempt to use the populated list after the background task has finished. The place to do that is in the done() method.

answered Jul 30, 2019 at 1:32

Tim Biegeleisen

526k32 gold badges323 silver badges399 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Adding objects to an arraylist in a for loop, but arraylist is empty after for loop is done?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related