Added closeHandlers in Window

InvUI/src/main/java/de/studiocode/invui/window/Window.java

@@ -123,6 +123,18 @@ public interface Window extends GUIParent {
      */
     void handleVirtualInventoryUpdate(VirtualInventory virtualInventory);
     
+    /**
+     * Adds a close handler that will be called when this window gets closed.
+     * @param closeHandler The close handler to add
+     */
+    void addCloseHandler(Runnable closeHandler);
+    
+    /**
+     * Removes a close handler that has been added previously.
+     * @param closeHandler The close handler to remove
+     */
+    void removeCloseHandler(Runnable closeHandler);
+    
     /**
      * Removes the {@link Window} from the {@link WindowManager} list.
      * If this method is called, the {@link Window} can't be shown again.

InvUI/src/main/java/de/studiocode/invui/window/impl/BaseWindow.java

@@ -39,6 +39,8 @@ public abstract class BaseWindow implements Window {
     private boolean closeable;
     private boolean closed;
     
+    private final ArrayList<Runnable> closeHandlers = new ArrayList<>();
+    
     public BaseWindow(UUID viewerUUID, BaseComponent[] title, int size, boolean closeable, boolean closeOnEvent) {
         this.viewerUUID = viewerUUID;
         this.title = title;
@@ -142,6 +144,7 @@ public abstract class BaseWindow implements Window {
         if (closeable) {
             if (closeOnEvent) close(false);
             handleClosed();
+            closeHandlers.forEach(Runnable::run);
         } else {
             if (player.equals(getViewer()))
                 Bukkit.getScheduler().runTaskLater(InvUI.getInstance().getPlugin(), this::show, 0);
@@ -225,6 +228,16 @@ public abstract class BaseWindow implements Window {
         changeTitle(TextComponent.fromLegacyText(title));
     }
     
+    @Override
+    public void addCloseHandler(Runnable closeHandler) {
+        closeHandlers.add(closeHandler);
+    }
+    
+    @Override
+    public void removeCloseHandler(Runnable closeHandler) {
+        closeHandlers.remove(closeHandler);
+    }
+    
     @Override
     public Player getCurrentViewer() {
         List<HumanEntity> viewers = getInventories()[0].getViewers();