Room DataSource.Factory with multiple view RecyclerView

Question

I have the following SELECT on the DAO

@Query("SELECT * FROM todo ORDER BY time DESC")
abstract DataSource.Factory<Integer, TodoItem> getAll();

I have a repository that just returns the above. And in the model I have

PagedList.Config config = new PagedList.Config.Builder()
            .setEnablePlaceholders(false)
            .setInitialLoadSizeHint(40)
            .setPageSize(20)
            .build();

todos = new LivePagedListBuilder<>(todoRepository.getAll(), config).build();

The Fragment simply observes the above todos and calls adapter.submitList(items) on new updates.

I just recently switched to using the androidx.paging , before I was getting all the data and populating the RecyclerView with it.

The above code works fine for what it currently is. The problem is that I need support for multiple views. More exactly, I need to add the date on top of the first element with that date. Prior to the upgrade, I was looping the items and adding DateHeader items where needed (and handling multiple view types in the Adapter), but with this new method I cannot edit what DataSource.Factory provides.

Using ItemDecoration or adding the date in every item and changing its visibility are not an option.

I have the date saved in the database as well, so I can group by and get the item count by date if that can be of any help.

Is there a way to solve this? Just for reference, there is no network communication here, everything is local and saved only in the database.

Answer 1

Seems like there is currently no support for adding additional items to the list that DAO's DataSource.Factory returns.

Since all I needed was to add the date on top of the first item with that date I ended up solving this using SQLite.

Here is the query if it may help somebody:

select * from (
    select tDate.*, 0 as type from todos as tDate group by date having max(time) 
  UNION 
    select tItem.*, 1 as type from todos tItem
  ) as tView 
order by tView.time desc, tView.type asc

I defined the above query as a DatabaseView .

Thankfully PagedListAdapter just like a regular Adapter has support for multiple views, in case the type is 0 from above I print a date item, otherwise I print a regular item.

This is not the best solution, but it's the only one I managed to make it work just like a regular RecycleView with multiple types.