Return arraylist populated inside Callback

Question

I'm trying to use an arraylist of Tweets that has been populated inside a callback but I can't figure out how to return the built list. Whenever I try to use the built list it's empty.

I got some code from this post

public  ArrayList<Tweet> tweetList() { 
   final ArrayList<Tweet> tweets = new ArrayList<>();
   final UserTimeline userTimeline = new UserTimeline.Builder()
           .screenName("xxxxxxxx")
           .build();
   userTimeline.next(null, new Callback<TimelineResult<Tweet>>() {
       @Override
       public void success(Result<TimelineResult<Tweet>> result) {
           for(Tweet tweet : result.data.items){
               tweets.add(tweet);
           }
           Log.d("Finished Tweet List", String.valueOf(tweets));
           //  when this is printed I can see the ArrayList and all tweets are there
       }
       @Override
       public void failure(TwitterException exception) {
           exception.printStackTrace();
       }
   });
   Log.d("Tweet list returned", String.valueOf(tweets));
   // the value of tweets is empty here for some reason

   return tweets;
}

Answer 1

Instead of returning the empty ArrayList of Tweets, you can modify your method so another ArrayList of Tweets is updated when the response from the Callback succeeds.

So I suggest modifying your method as follows:

private ArrayList<Tweet> tweetList = new ArrayList<>();

public void tweetList() { 
   final ArrayList<Tweet> tweets = new ArrayList<>();
   final UserTimeline userTimeline = new UserTimeline.Builder()
           .screenName("xxxxxxxx")
           .build();
   userTimeline.next(null, new Callback<TimelineResult<Tweet>>() {
       @Override
       public void success(Result<TimelineResult<Tweet>> result) {
           for(Tweet tweet : result.data.items){
               tweets.add(tweet);
           }

           this.tweetList = tweets;

           // execute the next sequence of instructions in your program here
           // and make use of tweetList instead of tweets

       }

       @Override
       public void failure(TwitterException exception) {
           exception.printStackTrace();
       }
   });
}