realm.java

private <E extends RealmObject> Observable<List<E>> getCopiedObjects(Func1<Realm, RealmResults<E>> resultsHandler) {
        final HandlerThread handlerThread = new HandlerThread("RealmReadThread", Process.THREAD_PRIORITY_BACKGROUND);
        handlerThread.start();
        final Scheduler scheduler = AndroidSchedulers.from(handlerThread.getLooper());
        final AtomicReference<Realm> realmReference = new AtomicReference<>(null);
        return Observable.defer(() -> {
            final Realm realm = Realm.getDefaultInstance();
            realmReference.set(realm);
            return resultsHandler.call(realm).asObservable();
        })
                .filter(results -> results.isLoaded() && results.isValid())
                .map(results -> realmReference.get().copyFromRealm(results))
                .subscribeOn(scheduler)
                .unsubscribeOn(scheduler)
                .doOnUnsubscribe(() -> unsubscribeOnDbThread(handlerThread, realmReference.get()));
    }

    private <E extends RealmObject> Observable<E> getCopiedObject(Func1<Realm, E> objectHandler) {
        final HandlerThread handlerThread = new HandlerThread("RealmReadThread", Process.THREAD_PRIORITY_BACKGROUND);
        handlerThread.start();
        final Scheduler scheduler = AndroidSchedulers.from(handlerThread.getLooper());
        final AtomicReference<Realm> realmReference = new AtomicReference<>(null);
        return Observable.defer(() -> {
            final Realm realm = Realm.getDefaultInstance();
            realmReference.set(realm);
            final E object = objectHandler.call(realm);
            return object == null ? Observable.empty() : object.asObservable();
        })
                .filter(realmObject -> realmObject.isLoaded() && realmObject.isValid())
                .map(realmObject -> {
                    //noinspection unchecked
                    return realmReference.get().copyFromRealm((E) realmObject);
                })
                .subscribeOn(scheduler)
                .unsubscribeOn(scheduler)
                .doOnUnsubscribe(() -> unsubscribeOnDbThread(handlerThread, realmReference.get()));
    }

    private void unsubscribeOnDbThread(HandlerThread handlerThread, Realm realm) {
        final Handler handler = new Handler(handlerThread.getLooper());
        handler.post(() -> {
            realm.close();
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
                handlerThread.quitSafely();
            } else {
                handlerThread.quit();
            }
        });
    }