如何在 ViewModel 中对 MutableLiveData ArrayList 进行排序？

Question

I have an Android app (Java) that makes an api call for shows. After the shows are returned, I need to filter the show arraylist by season & then by episode. I'm currently sorting the list in my fragment because I haven't found a good solution on how to do this in my viewmodel.

This is my call in my vm:

public MutableLiveData<ArrayList<Titles>> getTitlesListLiveData(){
    return repository.getTitlesLiveData();
} 

And this is how I'm sorting it in my fragment:

    titlesViewModel.titlesListLiveData.observe(getViewLifecycleOwner(), titles -> {

        for (Titles title : titles) {
            titlesList.add(title);
        }
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            titlesList.sort(Comparator.comparing(Titles::getSeasonNumber).thenComparing(Titles::getEpisodeNumber));
        }
        binding.rvTitles.setAdapter(ShowTitlesAdapter);            
        ShowTitlesAdapter.setShowTitlesList(titlesList);

    });
    titlesViewModel.getAllTitles(ShowTag);

I find this but I don't understand how I would do it in Java or in my viewmodel. Can anyone help?

Answer 1

Just use the LiveData Transformations . In your case it could be something like this:

public LiveData<List<Titles>> getTitlesListLiveData()
{
    return Transformations.map( repository.getTitlesLiveData(), titles ->
            titles.sort(Comparator.comparing(Titles::getSeasonNumber).thenComparing(Titles::getEpisodeNumber))
    );
}

Also you don't have to set the adapter every time the data changes:

binding.rvTitles.setAdapter(ShowTitlesAdapter);

You can set it once, for example in the onCreate (when in Activity) or in onCreateView (when in Fragment). Then when the data changes you just call the setShowTitlesList to change the data in adapter