Scrollable Menu by el_trueno

Example.java

    private static ScrollableMenuModel getModel(){
        ItemStack air = new ItemStack(Material.AIR);
        ItemStack nextpage = nolore(Material.ARROW, 1, 0, "§ePágina siguiente");
        ItemStack previouspage = nolore(Material.ARROW, 1, 0, "§ePágina anterior");
        ItemStack shop = nolore(Material.EMERALD, 1, 0, "§aVolver a la tienda");
        ScrollableMenuModel menumodel = new ScrollableMenuModel(54, air,
                  new ScrollableMenuSlot(ScrollableMenuSlot.SlotType.DECORATION, null, 0)
                , new ScrollableMenuSlot(ScrollableMenuSlot.SlotType.NEXT_PAGE, nextpage, 41)
                , new ScrollableMenuSlot(ScrollableMenuSlot.SlotType.PREVIOUS_PAGE, previouspage, 39)
                , new ScrollableMenuSlot(ScrollableMenuSlot.SlotType.ITEM, null, 10,11,12,13,14,15,16,19,20,21,22,23,24,25,28,29,30,31,32,33,34)
                , new ScrollableMenuSlot(ScrollableMenuSlot.SlotType.CUSTOM, shop, 49)
        );
        return menumodel;

    }

ScrollableMenu menu = new ScrollableMenu("Cajas", getModel(), items);
p.openInventory(menu.getPage(0).getInventory());

ScrollableMenu.java

public class ScrollableMenu {

    private String title;
    private ArrayList<ItemStack> items;
    private ScrollableMenuModel menumodel;

    private int pagescount;
    private ArrayList<ScrollableMenuPage> pages = new ArrayList<ScrollableMenuPage>();

    public ScrollableMenu(String title, ScrollableMenuModel menumodel, ArrayList<ItemStack> items){
        this.title = title;
        this.menumodel = menumodel;
        this.items = items;

        this.pagescount = (items.size()/this.menumodel.getSlotsByType(ScrollableMenuSlot.SlotType.ITEM).getSlots().length);
        if((items.size()%this.menumodel.getSlotsByType(ScrollableMenuSlot.SlotType.ITEM).getSlots().length) > 1 ){
            this.pagescount=this.pagescount+1;
        }
        if(this.pagescount==0){
            this.pagescount=1;
        }
        ArrayList<ItemStack> unuseditems = (ArrayList<ItemStack>) items.clone();
        int unusedindex = 0;
        for(int ipage=0; ipage<pagescount; ipage++){
            Inventory pageinv = Bukkit.createInventory(null, this.menumodel.getSize() ,this.title);
            ITEMS: for(int slot : menumodel.getSlotsByType(ScrollableMenuSlot.SlotType.ITEM).getSlots()){
                if(unusedindex<unuseditems.size()){
                    pageinv.setItem(slot, unuseditems.get(unusedindex));
                    unusedindex++;
                }else{
                    break ITEMS;
                }
            }
            if(this.items.isEmpty()){
                pageinv.setItem(this.getMenuModel().getNoItemReplace().getSlots()[0], this.getMenuModel().getNoItemReplace().getItem());
            }
            for(ScrollableMenuSlot scrslot : menumodel.getSlots()){
                if(scrslot.getSlotType()!= ScrollableMenuSlot.SlotType.ITEM){
                    if(ipage==0 && scrslot.getSlotType() == ScrollableMenuSlot.SlotType.PREVIOUS_PAGE){
                        for(int slot : scrslot.getSlots()){
                            pageinv.setItem(slot, this.menumodel.getPageReplace());
                        }
                    }else if( (ipage==(this.pagescount-(1))) && scrslot.getSlotType() == ScrollableMenuSlot.SlotType.NEXT_PAGE){
                        for(int slot : scrslot.getSlots()){
                            pageinv.setItem(slot, this.menumodel.getPageReplace());
                        }
                    }else{
                        for(int slot : scrslot.getSlots()){
                            pageinv.setItem(slot, scrslot.getItem());
                        }
                    }
                }
            }
            ScrollableMenuPage page = new ScrollableMenuPage(ipage, pageinv);
            this.pages.add(page);
        }
    }

    public void updateItems(ArrayList<ItemStack> items){
        boolean clear = false;
        if(this.items.size()>items.size() || this.items.isEmpty() && !items.isEmpty()){
            clear = true;
        }
        this.items = items;
        this.pagescount = (items.size()/this.menumodel.getSlotsByType(ScrollableMenuSlot.SlotType.ITEM).getSlots().length);
        if((items.size()%this.menumodel.getSlotsByType(ScrollableMenuSlot.SlotType.ITEM).getSlots().length) > 1 ){
            this.pagescount=this.pagescount+1;
        }
        if(this.pagescount==0){
            this.pagescount=1;
        }
        ArrayList<ItemStack> unuseditems = (ArrayList<ItemStack>) items.clone();
        int unusedindex = 0;
        for(ScrollableMenuPage page : this.pages){
            Inventory pageinv = page.getInventory();
            if(clear) {
                for (int slot : menumodel.getSlotsByType(ScrollableMenuSlot.SlotType.ITEM).getSlots()) {
                    pageinv.setItem(slot, new ItemStack(Material.AIR));
                }
            }
            ITEMS:
            for (int slot : menumodel.getSlotsByType(ScrollableMenuSlot.SlotType.ITEM).getSlots()) {
                if (unusedindex < unuseditems.size()) {
                    pageinv.setItem(slot, unuseditems.get(unusedindex));
                    unusedindex++;
                } else {
                    break ITEMS;
                }
            }
            if(this.items.isEmpty()){
                pageinv.setItem(this.getMenuModel().getNoItemReplace().getSlots()[0], this.getMenuModel().getNoItemReplace().getItem());
            }
            for (ScrollableMenuSlot scrslot : menumodel.getSlots()) {
                if (scrslot.getSlotType() != ScrollableMenuSlot.SlotType.ITEM) {
                    if (page.getPageId() == 0 && scrslot.getSlotType() == ScrollableMenuSlot.SlotType.PREVIOUS_PAGE) {
                        for (int slot : scrslot.getSlots()) {
                            pageinv.setItem(slot, this.menumodel.getPageReplace());
                        }
                    } else if( (page.getPageId()==(this.pagescount-(1))) && scrslot.getSlotType() == ScrollableMenuSlot.SlotType.NEXT_PAGE){
                        for (int slot : scrslot.getSlots()) {
                            pageinv.setItem(slot, this.menumodel.getPageReplace());
                        }
                    } else {
                        for (int slot : scrslot.getSlots()) {
                            pageinv.setItem(slot, scrslot.getItem());
                        }
                    }
                }
            }
        }
    }

    public ScrollableMenuPage getPage(int page){
        return this.pages.get(page);
    }

    public ArrayList<ScrollableMenuPage> getPages(){
        return this.pages;
    }

    public int getPagesCount(){
        return this.pagescount;
    }

    public String getTitle(){
        return this.title;
    }

    public ScrollableMenuSlot.SlotType getSlotType(int slot, int page){
        ScrollableMenuSlot.SlotType type = null;
        A: for(ScrollableMenuSlot scrslot : this.getMenuModel().getSlots()){
            B: for(int slotn : scrslot.getSlots()){
                if(slotn==slot){
                    if( (scrslot.getSlotType()== ScrollableMenuSlot.SlotType.NEXT_PAGE
                            || scrslot.getSlotType()== ScrollableMenuSlot.SlotType.PREVIOUS_PAGE)
                            && getPage(page).getInventory().getItem(slotn).equals(this.getMenuModel().getPageReplace())){
                        type = ScrollableMenuSlot.SlotType.DECORATION;
                    }else if(scrslot.getSlotType()== ScrollableMenuSlot.SlotType.ITEM && this.items.isEmpty()){
                        type = ScrollableMenuSlot.SlotType.DECORATION;
                    }else{
                        type = scrslot.getSlotType();
                    }
                    break A;
                }else continue;
            }
        }
        return type;
    }

    public ScrollableMenuModel getMenuModel(){
        return menumodel;
    }

}

ScrollableMenuModel.java

public class ScrollableMenuModel {

    private int size;
    private ScrollableMenuSlot[] slots;
    private ItemStack pagereplace;
    private ScrollableMenuSlot noitemreplace;

    public ScrollableMenuModel(int size, ItemStack pagereplace, ScrollableMenuSlot noitemreplace, ScrollableMenuSlot... items){
        this.slots = items;
        this.size = size;
        this.pagereplace = pagereplace;
        this.noitemreplace = noitemreplace;
    }

    public ScrollableMenuSlot[] getSlots() {
        return slots;
    }

    public int getSize(){
        return size;
    }

    public ScrollableMenuSlot getSlotsByType(ScrollableMenuSlot.SlotType type){
        ScrollableMenuSlot retslot = null;
        for(ScrollableMenuSlot slot : slots){
            if(slot.getSlotType()== ScrollableMenuSlot.SlotType.ITEM){
                retslot = slot;
                break;
            }
        }
        return retslot;
    }

    public ItemStack getPageReplace(){
        return this.pagereplace;
    }

    public ScrollableMenuSlot getNoItemReplace() {
        return noitemreplace;
    }
}

ScrollableMenuPage.java

public class ScrollableMenuPage {

    private int pageid;
    private Inventory formatedinv;

    public ScrollableMenuPage(int pageid, Inventory inventory){
        this.pageid = pageid;
        this.formatedinv = inventory;
    }

    public int getPageId(){
        return pageid;
    }

    public Inventory getInventory() {
        return formatedinv;
    }

}

ScrollableMenuSlot.java

public class ScrollableMenuSlot {

    public enum SlotType{
        DECORATION,
        NEXT_PAGE,
        PREVIOUS_PAGE,
        ITEM,
        CUSTOM
    }

    private SlotType type;
    private int[] slots;
    private ItemStack item;

    public ScrollableMenuSlot(SlotType type, ItemStack item, int... slots){
        this.type = type;
        this.slots = slots;
        this.item = item;
    }

    public int[] getSlots(){
        return this.slots;
    }

    public ItemStack getItem(){
        return this.item;
    }

    public SlotType getSlotType(){
        return this.type;
    }

}