How to refresh my RecyclerView with another Room-DAO Query - android-recyclerview

Question

I have a RecyclerView with an AAC in my Fragment.
ViewModel --> Repository --> DAO with some custom Queries and a getAllItems.
I want to use a Filter FAB or a Spinner to call getOrderItemList or getWhereItemList queries but i dont know how must i do it.
I have a Repository Filter for my SearchView but is a different thing, now i want to change list order (alphabetical, year...) and create a WhereCondition with a lot of checkbox that i have in a Dialog (example: i check "complete" and "Action" checkbox and creates the String whereCondition = "(status = 'complete' and genre like '%Action%')" ).
How can i call getWhereItemList and getOrderItemList queries from my Fragment to change my RecyclerView content?
ItemDAO:
#Query("SELECT * from item_table ")
<List<Item>> getItemList();
#Query("SELECT * from item_table ORDER by :order DESC")
<List<Item>> getOrderItemList(String order);
#Query("SELECT * from item_table WHERE :whereCondition")
<List<Item>> getWhereItemList(String whereCondition);
My Fragment fills the RecyclerView with getAllItems:
private ItemViewModel myItemViewModel;
RecyclerView myRecyclerView = findViewById(R.id.recyclerview);
final ItemListAdapter myAdapter = new ItemListAdapter(this);
myRecyclerView.setAdapter(myAdapter);
myRecyclerView.setLayoutManager(new LinearLayoutManager(this));
myItemViewModel = ViewModelProviders.of(this).get(ItemViewModel.class);
myItemViewModel.getAllItems().observe(this, new Observer<List<Item>>() {
#Override
public void onChanged(#Nullable final List<Item> items) {
myAdapter.setItems(items);
}
ItemListAdapter:
private List<Item> myItems;
void setItems(List<Item> items){
myItems = items;
notifyDataSetChanged();
}
ItemViewModel:
private ItemRepository myRepository;
private LiveData<List<Item>> myAllItems;
public ItemViewModel (Application application) {
super(application);
myRepository = new ItemRepository(application);
myAllItems = myRepository.getAllItems();
}
LiveData<List<Item>> getAllItems() { return myAllItems; }
Thanks.

Answer 1

The idea is to have two LiveData instances:
one that keeps track of the current filter type. You may set its initial value.
one that emits List<Item>. This also should react to the other LiveData change and get new List<Item> if necessary.
You can use Transformations.SwitchMap to implement LiveData2. What it does is it basically returns a LiveData instance that can switch to a different source in response to another LiveData object.
ItemViewModel:
private ItemRepository myRepository;
/**
* Keep track of the current filter type.
* In this example the initial value is set to Filter.ALL, which
* represents the non-filtered list.
*/
private MutableLiveData<Filter> itemFilter = new MutableLiveData<>(Filter.ALL);
/**
* Emits list of items
*/
private LiveData<List<Item>> myItems = Transformations.switchMap(itemFilter, filter -> {
// Everytime itemFilter emits a new value, this piece of code
// will be invoked. You are responsible for returning the
// LiveData instance according to the filter value.
switch(filter.type) {
case ALL:
return myRepository.getAllItems();
case ORDER_BY:
return myRepository.getOrderItemList(filter.query);
case WHERE:
return myRepository.getWhereItemList(filter.query);
}
});
public ItemViewModel (Application application) {
super(application);
myRepository = new ItemRepository(application);
}
public LiveData<List<Item>> getItems() { return myItems; }
/**
* View should call this method in order to switch to different
* filter.
*/
public void changeFilter(Filter itemFilter) {
this.itemFilter.setValue(filter);
}
Define this custom filter class:
public class Filter {
public enum Type {
ALL,
ORDER_BY,
WHERE
}
final public Type type;
final public String query;
public Filter(Type type, String query) {
this.type = type;
this.query = query;
}
}