Significantly changed the menu creation mechanism.

src/main/java/org/mineacademy/fo/menu/AdvancedMenu.java

@@ -29,20 +29,14 @@
  * Basic advanced menu.
  * Supports adding items, buttons and filling locked slots with wrapper item.
  * Also contains some ready buttons (Menu, ReturnBack, Refresh, etc.).<br><br>
- * DO NOT FORGET to add {@link #init()} method in the end of the constructor
- * if you make any changes in your menu (like setting the locked slots or adding new buttons).
+ * To get started, override {@link #setup} method and customize your menu inside it.
  */
 public abstract class AdvancedMenu extends Menu {
 
     /**
      * The player watching the menu.
      */
     private final Player player;
-    /**
-     * The menu which is opened from {@link #getReturnBackButton}.
-     */
-    @Getter
-    private final Class<? extends AdvancedMenu> parentMenu;
     /**
      * Contains buttons and their slots.
      */
@@ -61,6 +55,10 @@ public abstract class AdvancedMenu extends Menu {
      */
     @Getter
     protected List<Integer> lockedSlots = new ArrayList<>();
+    /**
+     * The menu which is opened from {@link #getReturnBackButton}.
+     */
+    private Class<? extends AdvancedMenu> parentMenu = getClass();
     /**
      * The material of the wrapper item.
      * See {@link #wrapperItem} for more info.
@@ -78,16 +76,12 @@ public abstract class AdvancedMenu extends Menu {
     private ItemStack wrapperItem = ItemCreator.of(wrapperMaterial, "").build().make();
 
     public AdvancedMenu(Player player){
-        this(player, null);
-    }
-
-    public AdvancedMenu(Player player, Class<? extends AdvancedMenu> parent){
         this.player = player;
-        this.parentMenu = (parent == null ? getClass() : parent);
     }
 
     /**
-     * Add button to the menu.
+     * Add button to the menu.<br>
+     * <b>Use it only inside {@link #setup} method to avoid errors!</b><br>
      * @param slot the slot the button should be displayed on
      * @param btn the button
      */
@@ -96,7 +90,8 @@ protected void addButton(Integer slot, Button btn){
     }
 
     /**
-     * Add custom item with no behavior to the menu.
+     * Add custom item with no behavior to the menu.<br>
+     * <b>Use it only inside {@link #setup} method to avoid errors!</b><br>
      * If you want item to have behavior use {@link #addButton}.
      * @param slot the slot the item should be placed on
      * @param item the item
@@ -105,18 +100,10 @@ protected void addItem(Integer slot, ItemStack item){
         items.put(slot, item);
     }
 
-    /**
-     * Actions to be taken when opening or updating the menu.<br>
-     * It automatically runs when the menu opens. But if you make some changes after calling super()
-     * in your child class you must call init() manually in the constructor after all changes.
-     */
-    protected void init(){}
-
     /**
      * Redraw the menu without moving the cursor to the center.
      */
     protected void refreshMenu(){
-        init();
         redraw();
     }
 
@@ -127,10 +114,25 @@ public final Player getPlayer(){
         return this.player;
     }
 
+    /**
+     * Get the {@link #parentMenu}.
+     */
+    protected final Class<? extends AdvancedMenu> getParentMenu(){
+        return this.parentMenu;
+    }
+
+    /**
+     * Set the {@link #parentMenu}.
+     */
+    protected final void setParent(Class<? extends AdvancedMenu> parent){
+        this.parentMenu = parent;
+    }
+
     /**
      * Display this menu to the player given in the constructor.
      */
-    public final void display(){
+    public void display(){
+        setup();
         displayTo(getPlayer());
     }
 
@@ -145,7 +147,9 @@ protected Button getReturnBackButton(){
     /**
      * Get the button that returns player to the parent menu given in the constructor.
      * If the parent is not given it will return player to the same menu.
-     * If item is not given, it will get its item from {@link MenuUtil#defaultReturnBackItem}.<br>
+     * If item is not given, it will get its item from {@link MenuUtil#defaultReturnBackItem}.<br><br>
+     * <b>NOTE</b> that this button returns player to the non-personalized menu.
+     * To use personalized menus, use {@link #getMenuButton}.<br><br>
      * You can override this button and add some your logic.
      * @return the return button
      */
@@ -194,15 +198,49 @@ public ItemStack getItem() {
     }
 
     /**
-     * Does the same as {@link #getMenuButton(ItemStack, Class)}.
+     * <b>Attention! Please use {@link #getMenuButton(Class)} if possible because it is much more efficient!
+     * Use this method only if your menu constructor is custom or the menu must be created by instance
+     * (and not by class).</b><br><br>
+     * Does the same as {@link #getMenuButton(ItemStack, AdvancedMenu)}.
      * Uses the default button from {@link MenuUtil#defaultMenuItem}.
      */
+    protected Button getMenuButton(AdvancedMenu to){
+        return getMenuButton(MenuUtil.defaultMenuItem, to);
+    }
+
+    /**
+     * <b>Attention! Please use {@link #getMenuButton(ItemStack, Class)} if possible because it is much more efficient!
+     * Use this method only if your menu constructor is custom or the menu must be created by instance
+     * (and not by class).</b><br><br>
+     * Create a new button which opens a given menu instance.
+     * @param item how the button should look like
+     * @param to what menu the player should be sent to
+     * @return the button
+     */
+    protected Button getMenuButton(ItemStack item, AdvancedMenu to){
+        return new Button() {
+            @Override
+            public void onClickedInMenu(Player player, AdvancedMenu menu, ClickType click) {
+                to.display();
+            }
+
+            @Override
+            public ItemStack getItem() {
+                return item;
+            }
+        };
+    }
+
+    /**
+     * Does the same as {@link #getMenuButton(ItemStack, Class)}.
+     * Uses default item from {@link MenuUtil#defaultMenuItem}.
+     */
     protected Button getMenuButton(Class<? extends AdvancedMenu> to){
         return getMenuButton(MenuUtil.defaultMenuItem, to);
     }
 
     /**
-     * Get the button that displays new menu to the player.
+     * Create a new button which opens a new menu instance created from a given class.
      * @param item how the button should look like
      * @param to what menu the player should be sent to
      * @return the button
@@ -226,15 +264,12 @@ public ItemStack getItem() {
      */
     private AdvancedMenu newInstanceOf(Player player, Class<? extends AdvancedMenu> menu){
         try{
-            return menu.getDeclaredConstructor(Player.class).newInstance(player);
+            AdvancedMenu am = menu.getDeclaredConstructor(Player.class).newInstance(player);
+            am.setParent(menu);
+            return am;
         }
         catch (NoSuchMethodException | InstantiationException | IllegalAccessException | InvocationTargetException e){
-            try{
-                return menu.getDeclaredConstructor(Player.class, Class.class).newInstance(player, null);
-            }
-            catch (NoSuchMethodException | InstantiationException | IllegalAccessException | InvocationTargetException e1){
-                e1.printStackTrace();
-            }
+            e.printStackTrace();
         }
         throw new NullPointerException("Could not create a new instance of " + menu.getName() + " class. " +
                 "Please create a constructor with only Player argument.");
@@ -382,18 +417,19 @@ protected final void setLockedSlots(String figure){
         }
     }
 
-    @Override
-    protected void onButtonClick(Player player, int slot, InventoryAction action, ClickType click, Button button) {
-        super.onButtonClick(player, slot, action, click, button);
-    }
-
     @Override
     protected void onMenuClick(Player player, int slot, InventoryAction action, ClickType click, ItemStack cursor, ItemStack clicked, boolean cancelled) {
         if (getButtons().containsKey(slot)){
             getButtons().get(slot).onClickedInMenu(player, this, click);
         }
     }
 
+    /**
+     * Override this method and customize your menu here.
+     * This method is automatically started just before displaying a menu to a player.
+     */
+    protected void setup(){}
+
     @Override
     public ItemStack getItemAt(int slot) {
         if (getItems().containsKey(slot)){

src/main/java/org/mineacademy/fo/menu/AdvancedMenuPagged.java

@@ -19,15 +19,9 @@
 /**
  * Menu with pages.<br>
  * Supports previous and next buttons.<br><br>
- * DO NOT FORGET to add {@link #init()} method in the end of the constructor
- * if you make any changes in your menu (like setting the locked slots or adding new buttons).
+ * To get started, override {@link #setup} method and customize your menu inside it.
  */
 public abstract class AdvancedMenuPagged<T> extends AdvancedMenu {
-    /**
-     * Shows if the constructor of MenuPaginated was initialized at least once.
-     */
-    private final boolean isInitialized;
-
     /**
      * Slots and their raw {@link #elements}.
      */
@@ -76,27 +70,19 @@ public abstract class AdvancedMenuPagged<T> extends AdvancedMenu {
     private ItemStack nextButtonItem = ItemCreator.of(CompMaterial.TIPPED_ARROW, "&7Next page").build().make();
 
     public AdvancedMenuPagged(Player player){
-        this(player, null);
-    }
-
-    public AdvancedMenuPagged(Player player, Class<? extends AdvancedMenu> parent){
-        super(player, parent);
-        init();
-        isInitialized = true;
+        super(player);
     }
 
     /**
-     * Actions to be taken when opening or updating the menu.<br>
-     * It automatically runs when the menu opens. But if you make some changes after calling super()
-     * in your child class you must call init() manually in the constructor after all changes.
+     * Updating paged menu elements.<br>
+     * It automatically runs when the menu opens.
      */
-    @Override
-    protected void init(){
+    private void updateElements(){
         resetCursorAt();
         setElements();
         setElementsItems();
         setElementsSlots();
-        if (isInitialized) addPrevNextButtons(getPreviousButtonSlot(), getNextButtonSlot());
+        addPrevNextButtons(getPreviousButtonSlot(), getNextButtonSlot());
     }
 
     /**
@@ -244,6 +230,25 @@ private void resetCursorAt() {
         this.cursorAt = (currentPage - 1) * getAvailableSlotsSize();
     }
 
+    /**
+     * Redraw the menu without moving the cursor to the center.
+     */
+    @Override
+    protected void refreshMenu(){
+        updateElements();
+        redraw();
+    }
+
+    /**
+     * Display this menu to the player given in the constructor.
+     */
+    @Override
+    public void display(){
+        updateElements();
+        setup();
+        displayTo(getPlayer());
+    }
+
     /**
      * Display items on their slots.
      * This method already has a good working implementation, so try not to override it.

src/main/java/org/mineacademy/fo/menu/AdvancedMenuTools.java

@@ -13,18 +13,12 @@
 /**
  * The semi-ready implementation of paged menu with all tools.
  * You only have to set the size, title and locked slots.<br><br>
- * DO NOT FORGET to add {@link #init()} method in the end of the constructor
- * if you make any changes in your menu (like setting the locked slots or adding new buttons).
+ * To get started, override {@link #setup} method and customize your menu inside it.
  */
 public abstract class AdvancedMenuTools extends AdvancedMenuPagged<Tool> {
 
     public AdvancedMenuTools(Player player) {
-        this(player, null);
-    }
-
-    public AdvancedMenuTools(Player player, Class<? extends AdvancedMenu> parent){
-        super(player, parent);
-        init();
+        super(player);
     }
 
     @Override