viewmodel.java

public class MyViewModel extends ViewModel {
    private MutableLiveData<List<Article>> articles;
    public LiveData<List<Article>> getArticles() {
        if (articles == null) {
            articles = new MutableLiveData<List<Article>>();
            loadArticles();
        }
        return articles;
    }

    private void loadArticles() {
        // do async operation to fetch articles
    }
}