Android Room LiveData select query parameters

Question

I decided to teach myself Java and Android by doing a simple database app. I already implemented some functionality the \"lazy\" way - all selects are done on the main threa

Answer 1

I think your solution is a Transformations.switchMap. The simplest example how it may works in the case from codelab

public class WordViewModel extends AndroidViewModel {
    private WordRepository mRepository;
    private LiveData<List<Word>> mAllWords;
    private LiveData<List<Word>> searchByLiveData;
    private MutableLiveData<String> filterLiveData = new MutableLiveData<>();

    public WordViewModel (Application application) {
        super(application);
        mRepository = new WordRepository(application);
        mAllWords = mRepository.getAllWords();
        searchByLiveData = Transformations.switchMap(filterLiveData, 
                                                     v -> mRepository.searchBy(v));
    }

    LiveData<List<Word>> getSearchBy() { return searchByLiveData; }
    void setFilter(String filter) { filterLiveData.setValue(filter); }
    LiveData<List<Word>> getAllWords() { return mAllWords; }
    public void insert(Word word) { mRepository.insert(word); }
}

So, when you set filter value, it will change value of searchByLiveData

I hope this helps you.