Passing value to LiveData in Android

Question

I'm new in development and I'm aware that stack isn't for 'full code requests'. But I'm stuck and can't find the solution.

I'm using Room database which has two columns - firstName and lastName. I'm loading the database with passed firstName parameter:

@Query("SELECT * FROM passenger WHERE firstName LIKE :firstName")
List<Passenger>getAllByName (String firstName);

It works as supposed.

But.. When I want to update Passenger, I need to populate data again, again, and again. There comes LiveData and observer.

But.. setValue in LiveData is private and I cannot send any parameters for Query line. There comes MutableLiveData, but how can I implement that?

You need to add some further explanation, because I don't fully understand what you are trying to achieve. — 476rick, Oct 15 '18 at 13:35

score -1 · Answer 1 · answered Oct 15 '18 at 20:00

@Eduardas Seems like you need to return LiveData instead:

LiveData<List<Passenger>> getAllByName (String name);

And you can write a transformation in the ViewModel or you can directly observe it from your Activity/Fragment.

In activity/fragment onCreate() or onResume():

YourDao.getAllByName(name).observe(this, new LiveData<List<Passenger>>(){
   @Override
   public void onChanged( @Nullable List<Passenger>) {
     // update your adapter if the list isn't null
   }
});

Something similar to above. You can add customization as per your use case.

Can you please add a comment as in why the answer was down voted? — theThapa, Sep 16 '19 at 21:07

Passing value to LiveData in Android

1 Answers1