Template for when I try to implement filters for categories in Tachiyomi.

LibraryNavigationView.kt

inner class CategoryGroup : Group {

        private val categories = List<Category>(0)

        override val items = categories.map { category -> Item.TriStateGroup( category.id, this) }

        override val header = Item.Header(R.string.categories)

        override val footer = Item.Separator()

        override fun initModels() {
            items.forEach{ it.state = STATE_IGNORE }
        }

        override fun onItemClicked(item: Item) {
            item as Item.TriStateGroup
            val prevState = item.state

            item.state = when (prevState) {
                STATE_IGNORE -> STATE_INCLUDE
                STATE_INCLUDE -> STATE_EXCLUDE
                STATE_EXCLUDE -> STATE_IGNORE
                else -> throw Exception("Unknown state")
            }
            
            adapter.notifyItemChanged(item)
        }
    }

This doesn't work for the following major reasons:

1. Line 3: I don't know how to get a list of all categories.
2. Line 5: Item.TriStateGroup(.) requires a resource ID