Android List of primitives (RealmList)


Example

Realm currently does not support storing a list of primitives. It is on their todo list (GitHub issue #575), but for the meantime, here is a workaround.

Create a new class for your primitive type, this uses Integer, but change it for whatever you want to store.

public class RealmInteger extends RealmObject {
    private int val;

    public RealmInteger() {
    }

    public RealmInteger(int val) {
        this.val = val;
    }

    // Getters and setters
}

You can now use this in your RealmObject.

public class MainObject extends RealmObject {

    private String name;
    private RealmList<RealmInteger> ints;

    // Getters and setters
}

If you are using GSON to populate your RealmObject, you will need to add a custom type adapter.

Type token = new TypeToken<RealmList<RealmInteger>>(){}.getType();
Gson gson = new GsonBuilder()
        .setExclusionStrategies(new ExclusionStrategy() {
            @Override
            public boolean shouldSkipField(FieldAttributes f) {
                return f.getDeclaringClass().equals(RealmObject.class);
            }

            @Override
            public boolean shouldSkipClass(Class<?> clazz) {
                return false;
            }
        })
        .registerTypeAdapter(token, new TypeAdapter<RealmList<RealmInteger>>() {

            @Override
            public void write(JsonWriter out, RealmList<RealmInteger> value) throws IOException {
                // Empty
            }

            @Override
            public RealmList<RealmInteger> read(JsonReader in) throws IOException {
                RealmList<RealmInteger> list = new RealmList<RealmInteger>();
                in.beginArray();
                while (in.hasNext()) {
                    list.add(new RealmInteger(in.nextInt()));
                }
                in.endArray();
                return list;
            }
        })
        .create();