CODEWITHSUNDEEP
javaandroidarraylist
keyoshi998
keyoshi998

Reputation: 89

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

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());

}

Upvotes: 0

Views: 90

Answers (1)

Tim Biegeleisen
Tim Biegeleisen

Reputation: 521008

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.

Upvotes: 3

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