Parsing a large JSON data in android and filtering it

Question

Context: I'm requesting large JSON data from my back-end which consists of a constantly updating JSON in a VPS.

I request my first JSON file which contains my movie release dates and the id of the movies; example:

[
  {
   "id": 101,
   "release_date": "2018-03-23",
  }, {...}  
]

The second JSON file I request contains the movie's general info like name and description, example;

[
  {
    "id": 101,
    "name": "PACIFIC RIM UPRISING",
    "description": "Here's a cool description",
    "genres:": [12, 11, 8]
  }, {...}  
]

Both files requested are saved in the user's phone.

Now on to parsing (the subject of this question). I first parse the release JSON in an ArrayList (Release is an object containing the movie ID and the release date), then I parse the movie info JSON in a HashMap (Integer is the id of the movie and Movie is the object containing the name, then genre lists and the description).

Now when I want to filter the releases by genres (user can filter the recyclerview/data by multiple genres at once) I use this code:

    Collections.sort(userGenres); // user chosen genres gotten from a shared pref
    ArrayList<Release> newReleases = new ArrayList<>(); // the list with only the movie the user wants by genre 
    for (Release release : mUpcomingReleases) {
        Movie movie = gameInfoHashMap.get(release.id); // gameInfoHashMap is the hashmap which contains our movie info (it has the genres list)
        ArrayList<Integer> releaseGenres = movie.genres; 
        Collections.sort(releaseGenres);
        if (!releaseGenres.equals(genres)) {
            // if they don't contain the same genres chosen by the user, get out
            break;
        } else {
            // add it to the list
            newReleases.add(release);
        }
    }

And now the problem is it doesn't seem efficient at all. You need to understand that my mUpcomingReleases contains like a thousand releases object, is there a better way to filter by genre(s)? My app feels slow. Or is there a better way to change the parsing of my app to make it more lightweight?

Answer 1

I think what you need to do is, you should not download all the data at once. Only parse like 50-60 objects at a time. Make your backend send you only parts of the complete result. Its the best practice to get only the required data ie only the parts which user can see at a time. As the user scrolls down the recyclerview load data simultaneously. Apps like IMDB and others do the same.

Hope this helps