CODEWITHSUNDEEP
android-room
live-love
live-love

Reputation: 52454

AndroidViewModel updating MutableLiveData object

I am having a problem initializing a boolean property in my ViewModel. I am not sure the right way to go about this.

I have a Switch control on the main activity, and if I change the switch I want to change the boolean startsWith value. Depending on the boolean value I will call the corresponding Dao function.

I am trying to initialize the value, but not sure how to do this. Should I observe the boolean value, should I use two way binding, should this property be MutableLiveData? 

wordListViewModel = ViewModelProviders.of(this).get(WordListViewModel.class);
wordListViewModel.setStartsWith(true);

I get this error, cannot even start Activity:

Attempt to invoke virtual method 'boolean java.lang.Boolean.booleanValue()' on a null object reference

Code:

public class WordListViewModel extends AndroidViewModel {

    final MutableLiveData<String> searchText = new MutableLiveData<>();
    final MutableLiveData<Boolean> startsWith = new MutableLiveData<>();

    private final LiveData<List<WordEntity>> list;

    private AppDatabase appDatabase;

    public WordListViewModel(Application application) {
        super(application);

        appDatabase = AppDatabase.getDatabase(this.getApplication());

        if (startsWith.getValue() == true)
            list = Transformations.switchMap(searchText, searchText -> {
                return appDatabase.wordDao().getWordsStartingWith(searchText);
            });
        else
            list = Transformations.switchMap(searchText, searchText -> {
                return appDatabase.wordDao().getWordsLike(searchText);
            });

    }

Upvotes: 0

Views: 2525

Answers (1)

live-love
live-love

Reputation: 52454

I think I figured it out. The check has to be inside the switchMap function. The rest of the code only runs when the model is initialized.

I changed my code and it worked:

    if (startsWith.getValue() == null)
        startsWith.setValue(true);

    list = Transformations.switchMap(searchText, searchText -> {
        if (startsWith.getValue() == true)
            return appDatabase.dictWordDao().getWordsStartingWith(searchText);
        else
            return appDatabase.dictWordDao().getWordsLike(searchText);
    });

Upvotes: 1

Related Questions