Multiple pages

GuiMenu gui = xaGui.createMenu("&a&lExample", 3, 2);
 
gui.getCurrentPage();      // 1      (first page)
gui.getCurrentPageIndex(); // 0      (first page but indexed from 0)
 
gui.setSlot(1, Material.COAL); // The page here is not set, so it will be set to the current page which is 1 (0 indexed)
gui.setSlot(0, 2, Material.COAL); // Same as above, but slot 2 instead of 1
 
gui.setSlot(1, 0, Material.COAL); // Now we set COAL to slot 0 on page 2 (1 indexed)
gui.setSlot(1, 1, Material.CHARCOAL); // Now we set COAL to slot 0 on page 2 (1 indexed)
 
// Pages are indexed from 0 in all methods, such as .setSlot, .switchPage, etc.
gui.setSlot(0, 26, new GuiButton(new ItemStack(Material.ARROW)).setName("&aNext page").withListener((event) -> {
    try {
        gui.switchPage(gui.getCurrentPageIndex() + 1, (Player) event.getWhoClicked());
    } catch (PageOutOfBoundException e) {
        // IGNORE
    }
}));
 
gui.setSlot(1, 18, new GuiButton(new ItemStack(Material.ARROW)).setName("&cGo back").withListener((event) -> {
    try {
        gui.switchPage(gui.getCurrentPageIndex() - 1, (Player) event.getWhoClicked());
    } catch (PageOutOfBoundException e) {
        // IGNORE
    }
}));
 
gui.setOnPageSwitch((data) -> {
    data.getPlayer().sendMessage("You switched to page " + data.getPage() + " from page " + data.getOldPage());
});
 
gui.open(player);