KotlinBukkitAPI Menu Pagination sample

GoldsMenu.kt

private val items = Array<ItemStack>(64) {
    item(Material.GOLD_INGOT, it).displayName("$it")
}.toMutableList()

private var menuCache: MenuDSL? = null
val goldsMenu: MenuDSL
    get() {
      if(menuCache == null)
        menuCache = generateMenUConfiguration()
    }

private fun generateMenuConfiguration() = menu("Golds Menu", 6) {
    val previousPage = slot(6, 1, item(Material.ARROW).displayName("Previous Page"))
    val nextPage = slot(6, 9, item(Material.ARROW).displayName("Next Page"))

    val pagination = pagination(
        ObservableList(items),
        nextPage, previousPage
    ) {
        slot {
            onRender { showingItem = it }
        }
        onPageChange {
            updateSlot(previousPageSlot, player)
            updateSlot(nextPageSlot, player)
        }
    }

    fun MenuPlayerInventorySlot.showItemWhenHasPage(hasPageLogic: () -> Boolean) {
        if(hasPageLogic()) {
            showingItem = nextPage.item
        } else {
            showingItem = null
        }
    }
    nextPage.onRender { showItemWhenHasPage { pagination.hasNextPage(player) } }
    nextPage.onUpdate { showItemWhenHasPage { pagination.hasNextPage(player) } }
    previousPage.onRender { showItemWhenHasPage { pagination.hasPreviousPage(player) } }
    previousPage.onUpdate { showItemWhenHasPage { pagination.hasPreviousPage(player) } }
}

MaterialsMenu.kt

private val MINECRAFT_MATERIALS = ObservableList(
    Material.values().toMutableList()
)

private var menuCache: MenuDSL? = null
val materialMenu: MenuDSL
    get() {
      if(menuCache == null)
        menuCache = generateMenuConfiguration()
      
      return menuCache!!
    }

private fun generateMenuConfiguration() = menu("Mercado", 6, true) {

    val previousPage = slot(6, 1, item(Material.ARROW).displayName("Previous Page"))
    val nextPage = slot(6, 9, item(Material.ARROW).displayName("Next Page"))

    val itemsAdapter: ItemsAdapter<Material> = { items ->
        val filter = getPlayerData(PICKAXE_FILTER_KEY) as Boolean? ?: false

        if(filter) items.filter {
            it.name.contains("PICKAXE")
        }
        else items
    }

    val pagination = pagination(
        MINECRAFT_MATERIALS,
        nextPage, previousPage,
        startLine = 2, endLine = 4,
        startSlot = 2, endSlot = 4,
        itemsAdapterOnOpen = itemsAdapter,
        itemsAdapterOnUpdate = itemsAdapter
    ) {
        slot {
            onRender { currentItem ->
                showingItem = currentItem?.asItemStack()
            }
        }

        onPageChange {
            updateSlot(nextPageSlot, player)
            updateSlot(previousPageSlot, player)
        }
    }

    fun MenuPlayerInventorySlot.showItemWhenHasPage(hasPageLogic: () -> Boolean) {
        if(hasPageLogic()) {
            showingItem = nextPage.item
        } else {
            showingItem = null
        }
    }
    nextPage.onRender { showItemWhenHasPage { pagination.hasNextPage(player) } }
    nextPage.onUpdate { showItemWhenHasPage { pagination.hasNextPage(player) } }
    previousPage.onRender { showItemWhenHasPage { pagination.hasPreviousPage(player) } }
    previousPage.onUpdate { showItemWhenHasPage { pagination.hasPreviousPage(player) } }

    slot(6, 5, item(Material.DIAMOND_PICKAXE).displayName("FILTER BY PICKAXE")) {
        onClick {
            canceled = true
            putPlayerData(PICKAXE_FILTER_KEY, true)
            pagination.updateItemsToPlayer(this)
        }
    }

    slot(6, 6, item(Material.STONE).displayName("REMOVE FILTER")) {
        onClick {
            putPlayerData(PICKAXE_FILTER_KEY, false)
            pagination.updateItemsToPlayer(this)
        }
    }

}