mediator-live-data-gist-3

BooksViewModel.kt

class BooksViewModel(bookDao: BookDao) : ViewModel() {

    private val booksAscending = bookDao.booksAscending()
    private val booksDescending = bookDao.booksDescending()

    val books = MediatorLiveData<List<Book>>()

    private var currentOrder = ASCENDING    

    init {
        books.addSource(booksAscending) { result ->
            if (currentOrder == ASCENDING) {
                result?.let { books.value = it }
            }
        }
        books.addSource(booksDescending) { result ->
            if (currentOrder == DESCENDING) { 
                result?.let { books.value = it }
            }
        } 
    }

    fun rearrangeBooks(order: BooksOrder) = when (order) {
       ASCENDING -> booksAscending.value?.let { books.value = it }
       DESCENDING -> booksDescending.value?.let { books.value = it }
    }.also { currentOrder = order }
}

this is what i did in my java code :

public void InitMediation(MvvmAdapter mvvmAdapter)
{
mediatorLiveData.addSource(getSortAlphabetically(), new Observer<List>() {
@OverRide
public void onChanged(List list) {
mvvmAdapter.UpdateRecycler(list);

        }
    });
}

** and this code in my main activity which supposdly should sort the data :
public void OrderATOZ() {
viewModel.InitMediation(mvvmAdapter);
}

i m working on todolist app with mvvm architecture , i would like to get the data sorted alphabetically when the user click on navigation drawer item , so when the user clicks , firstly the order data gets updated in the recycler and also to be shown order next launch