Pagination

All GUI objects should have a special pagination manager.

TL;DR

Allows you to show tons of items part by part. Just copy the code blocks.

How to use

Define Pagination Manager of the GUI

public class TestGUI extends GUI {
    private final PaginationManager pagination = new PaginationManager(this);

}

Registering Page Slots

this.pagination.registerItemSlots(10, 11, 12, 13, 14, 15);
//or
this.pagination.registerSlotsBetween(10, 15);

this.pagination.getSlots();

Registering Icons

You must add all icons for all pages.

for (Material material : Material.values()) {
	this.pagination.addItem(new Icon(material));
}

Show

this.pagination.update(); // puts page icons
		
this.pagination.goFirstPage(); // sets page to 0
this.pagination.goLastPage(); // sets page to last page
this.pagination.isFirstPage();
this.pagination.isLastPage();
this.pagination.goNextPage(); // sets page to page+1 
this.pagination.goPreviousPage(); // sets page to page-1
this.pagination.setPage(3); // sets page to 3
this.pagination.getPage();
this.pagination.getLastPage();
this.pagination.getItems();

Example Gif

Real World Example

• XMaterials.
• Page navigators.
• Custom gui titles.
• Formatted lores and display names.

package mc.obliviate.supershops.gui;

import mc.obliviate.inventory.Gui;
import mc.obliviate.inventory.Icon;
import mc.obliviate.inventory.pagination.PaginationManager;
import mc.obliviate.supershops.product.ShopProduct;
import mc.obliviate.supershops.shop.category.Category;
import mc.obliviate.supershops.user.ShopUser;
import mc.obliviate.supershops.utils.XMaterial;
import mc.obliviate.supershops.utils.message.MessageUtils;
import mc.obliviate.supershops.utils.message.placeholder.PlaceholderUtil;
import org.bukkit.Material;
import org.bukkit.enchantments.Enchantment;
import org.bukkit.entity.Player;
import org.bukkit.event.inventory.InventoryOpenEvent;
import org.bukkit.inventory.ItemFlag;

public class CategoryGUI extends Gui {

	private final PaginationManager paginationManager = new PaginationManager(this);
	private final Category category;
	private final ShopUser user;

        //handles initialization of the gui. registers gui title and pagination slots.
	public CategoryGUI(Player player, Category category) {
		super(player, "category-gui", category.getShop().getShopDisplayName() + " > " + category.getName(), 6);
		this.category = category;
		this.user = ShopUser.getUser(player.getUniqueId());
		paginationManager.registerPageSlotsBetween(9, 44);
	}


        //handles onOpen event and inserts static items like stained glasses.
	@Override
	public void onOpen(InventoryOpenEvent event) {
		fillRow(new Icon(XMaterial.GRAY_STAINED_GLASS_PANE.parseItem()), 0);
		fillRow(new Icon(XMaterial.BLACK_STAINED_GLASS_PANE.parseItem()), 5);
		calculateAndUpdatePagination();
		if (paginationManager.getCurrentPage() != 0) {
			addItem(0, new Icon(XMaterial.ARROW.parseItem()).setName("§aPrevious").onClick(e -> {
				paginationManager.goPreviousPage();
				calculateAndUpdatePagination();
			}));
		}
		if (!paginationManager.isLastPage()) {
			addItem(8, new Icon(XMaterial.ARROW.parseItem()).setName("§aNext").onClick(e -> {
				paginationManager.goNextPage();
				calculateAndUpdatePagination();
			}));
		}
		putStackSizeIcons();
	}

  
        // makes glowed selected stack size icon.
	private void putStackSizeIcon(int slot, int stackSize) {
		final Icon icon = new Icon(XMaterial.CHEST_MINECART.parseItem()).onClick(e -> {
					user.setStackSize(stackSize);
					open();
				})
				.setName(MessageUtils.formatName(new PlaceholderUtil().add("{stack}", stackSize + ""), "stack-size-selector"))
				.setLore(MessageUtils.formatLore(new PlaceholderUtil().add("{stack}", stackSize + ""), "stack-size-selector"))
				.setAmount(stackSize);

		if (user.getStackSize() == stackSize) {
			icon.enchant(Enchantment.PROTECTION_ENVIRONMENTAL, 1);
			icon.hideFlags(ItemFlag.HIDE_ENCHANTS);
		}

		addItem(slot, icon);
	}

        //updates stack size bar.
	private void putStackSizeIcons() {
		putStackSizeIcon(2, 1);
		putStackSizeIcon(3, 8);
		putStackSizeIcon(4, 16);
		putStackSizeIcon(5, 32);
		putStackSizeIcon(6, 64);
	}

        //calculates content of the shop gui.
	private void calculateProducts() {
		paginationManager.getItems().clear();
		for (final ShopProduct product : category.getProducts()) {
			Icon icon = new Icon(product.getIconItem(user.getStackSize()));
			int amount = Math.min(user.getStackSize(), icon.getItem().getMaxStackSize());
			paginationManager.addItem(new Icon(product.getIconItem(user.getStackSize())).setAmount(amount).onClick(e -> {
				if (product.isBuyable() && !product.isSellable()) {
					product.buy(player, amount);
				} else if (!product.isBuyable() && product.isSellable()) {
					product.sell(player, amount);
				} else if (product.isSellable() && product.isBuyable()) {
					if (e.isLeftClick()) {
						product.buy(player, amount);
					} else if (e.isRightClick()) {
						product.sell(player, amount);
					}
				}
			}));
		}
	}
        
        // calculates and updates content of the shop gui.
	private void calculateAndUpdatePagination() {
		calculateProducts();
		paginationManager.update();
	}
}