Added BackgroundItem

src/main/java/de/studiocode/invgui/item/impl/customtexture/BackgroundItem.java

@@ -0,0 +1,24 @@
+package de.studiocode.invgui.item.impl.customtexture;
+
+import de.studiocode.invgui.item.impl.SimpleItem;
+import de.studiocode.invgui.item.itembuilder.ItemBuilder;
+import de.studiocode.invgui.resourcepack.ForceResourcePack;
+import org.bukkit.Material;
+
+public class BackgroundItem extends SimpleItem {
+    
+    private static final BackgroundItem INSTANCE = new BackgroundItem();
+    
+    static {
+        ForceResourcePack.getInstance(); // initializes ForceResourcePack which automatically activates forced resource packs (if not disabled)
+    }
+    
+    private BackgroundItem() {
+        super(new ItemBuilder(Material.POPPY).setDisplayName("§f").setCustomModelData(10000000));
+    }
+    
+    public static BackgroundItem getInstance() {
+        return INSTANCE;
+    }
+    
+}

src/main/java/de/studiocode/invgui/resourcepack/ForceResourcePack.java

@@ -0,0 +1,77 @@
+package de.studiocode.invgui.resourcepack;
+
+import de.studiocode.invgui.InvGui;
+import org.bukkit.Bukkit;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerJoinEvent;
+import org.bukkit.event.player.PlayerResourcePackStatusEvent;
+import org.bukkit.scheduler.BukkitTask;
+
+import java.util.HashMap;
+
+import static org.bukkit.event.player.PlayerResourcePackStatusEvent.Status.DECLINED;
+
+public class ForceResourcePack implements Listener {
+    
+    private static final ForceResourcePack INSTANCE = new ForceResourcePack();
+    
+    private final HashMap<Player, BukkitTask> tasks = new HashMap<>();
+    
+    private String resourcePackUrl = "https://github.com/NichtStudioCode/InvGuiRP/releases/download/v0.1/InvGuiRP.zip";
+    private boolean activated = true;
+    
+    private ForceResourcePack() {
+        Bukkit.getPluginManager().registerEvents(this, InvGui.getInstance().getPlugin());
+        Bukkit.getOnlinePlayers().forEach(this::sendResourcePack);
+    }
+    
+    public static ForceResourcePack getInstance() {
+        return INSTANCE;
+    }
+    
+    @EventHandler
+    public void handleJoin(PlayerJoinEvent event) {
+        if (activated) sendResourcePack(event.getPlayer());
+    }
+    
+    @EventHandler
+    public void handleResourcePackStatus(PlayerResourcePackStatusEvent event) {
+        if (activated) {
+            Player player = event.getPlayer();
+            if (tasks.containsKey(player)) {
+                if (event.getStatus() == DECLINED) kickPlayer(player);
+                else tasks.get(player).cancel();
+                tasks.remove(player);
+            }
+        }
+    }
+    
+    private void sendResourcePack(Player player) {
+        player.setResourcePack(resourcePackUrl);
+        tasks.put(player, Bukkit.getScheduler().runTaskLater(InvGui.getInstance().getPlugin(),
+            () -> kickPlayer(player), 20 * 5));
+    }
+    
+    private void kickPlayer(Player player) {
+        player.kickPlayer("§cPlease accept the custom resource pack");
+    }
+    
+    public String getResourcePackUrl() {
+        return resourcePackUrl;
+    }
+    
+    public void setResourcePackUrl(String resourcePackUrl) {
+        this.resourcePackUrl = resourcePackUrl;
+    }
+    
+    public boolean isActivated() {
+        return activated;
+    }
+    
+    public void setActivated(boolean activated) {
+        this.activated = activated;
+    }
+    
+}

src/main/java/de/studiocode/invgui/window/Window.java

@@ -2,6 +2,7 @@ package de.studiocode.invgui.window;
 
 import de.studiocode.invgui.animation.Animation;
 import de.studiocode.invgui.gui.GUI;
+import de.studiocode.invgui.gui.SlotElement.ItemStackHolder;
 import de.studiocode.invgui.item.Item;
 import de.studiocode.invgui.item.itembuilder.ItemBuilder;
 import de.studiocode.invgui.virtualinventory.VirtualInventory;
@@ -16,6 +17,7 @@ import org.bukkit.inventory.Inventory;
 import org.bukkit.inventory.ItemStack;
 
 import java.util.UUID;
+import java.util.function.Predicate;
 
 /**
  * A window is the way to show a player a GUI.
@@ -126,8 +128,9 @@ public interface Window {
      * Plays an animation.
      *
      * @param animation The animation to play.
+     * @param filter    The filter that selects which Items should be animated.
      */
-    void playAnimation(Animation animation);
+    void playAnimation(Animation animation, Predicate<ItemStackHolder> filter);
     
     /**
      * Gets if the player is able to close the {@link Inventory}.

src/main/java/de/studiocode/invgui/window/impl/BaseWindow.java

@@ -20,8 +20,7 @@ import org.bukkit.inventory.Inventory;
 import org.bukkit.inventory.ItemStack;
 
 import java.util.*;
-import java.util.stream.Collectors;
+import java.util.function.Predicate;
-import java.util.stream.IntStream;
 
 public abstract class BaseWindow implements Window {
     
@@ -187,24 +186,25 @@ public abstract class BaseWindow implements Window {
     }
     
     @Override
-    public void playAnimation(Animation animation) {
+    public void playAnimation(Animation animation, Predicate<ItemStackHolder> filter) {
         if (getViewer() != null) {
             this.animation = animation;
             
+            List<Integer> slots = new ArrayList<>();
+            for (int i = 0; i < size; i++) {
+                ItemStackHolder holder = itemsDisplayed[i];
+                if (holder != null && filter.test(holder)) {
+                    slots.add(i);
+                    inventory.setItem(i, null);
+                }
+            }
+            
             animation.setBounds(getGui().getWidth(), getGui().getHeight());
             animation.setPlayer(getViewer());
             animation.addShowHandler((frame, index) -> redrawItem(index, itemsDisplayed[index], false));
             animation.addFinishHandler(() -> this.animation = null);
-            animation.setSlots(IntStream.range(0, size)
+            animation.setSlots(slots);
-                .filter(i -> {
-                    ItemStackHolder element = itemsDisplayed[i];
-                    return !(element == null || (element instanceof VISlotElement
-                        && !((VISlotElement) element).getVirtualInventory().hasItem(((VISlotElement) element).getIndex())));
-                })
-                .boxed()
-                .collect(Collectors.toCollection(ArrayList::new)));
             
-            clearItemStacks();
             animation.start();
         }
     }
@@ -221,10 +221,6 @@ public abstract class BaseWindow implements Window {
         }
     }
     
-    private void clearItemStacks() {
-        for (int i = 0; i < inventory.getSize(); i++) inventory.setItem(i, null);
-    }
-    
     @Override
     public Player getViewer() {
         return Bukkit.getPlayer(viewerUUID);