Android - filter data from database in an adapter

Question

I am learning Kotlin and am trying to filter some data coming straight from a (room) database into my adapter to display them.

Here's my code (from within the fragment, containing a recycleview with adapter):

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        val adapter = LatestReleaseListAdapter {
        }
        binding.recyclerView.layoutManager = LinearLayoutManager(this.context)
        binding.recyclerView.adapter = adapter

        viewModel.allItems.observe(this.viewLifecycleOwner) { items ->
            //Here I'd like to remove the items that has been seen already
            items.filter { item -> !item.hasBeenSeen }
            items.let {
                adapter.submitList(it)
            }
        }  

The code is quite straight forward as you can see. I am simply trying to filter the element of the list where the boolean "hasBeenSeen"is true. I only want to show the ones where the boolean "hasBeenSeen"is false. How can I achieve that?

Answer 1

The call to filter will filter the items and return a new collection that will contain just the filtered items. So you could do something like this

val filteredItems = items.filter { item -> !item.hasBeenSeen }
adapter.submitList(filteredItems)

Or keep it short

adapter.submitList(items.filter { item -> !item.hasBeenSeen })