Completely prevent moving items in inventory (click,drag,offhand swapping) during gameplay to stop a few exploits

src/main/java/nl/Steffion/BlockHunt/BlockHunt.java

@@ -110,6 +110,7 @@ public class BlockHunt extends JavaPlugin implements Listener {
 		getServer().getPluginManager().registerEvents(new OnFoodLevelChangeEvent(), this);
 		getServer().getPluginManager().registerEvents(new OnInventoryClickEvent(), this);
 		getServer().getPluginManager().registerEvents(new OnInventoryCloseEvent(), this);
+		getServer().getPluginManager().registerEvents(new OnPlayerSwapHandItemsEvent(), this);
 
 		// Removed - This is handled by WorldGuard now.
 		// getServer().getPluginManager().registerEvents(

src/main/java/nl/Steffion/BlockHunt/Listeners/OnInventoryClickEvent.java

@@ -25,12 +25,10 @@ public class OnInventoryClickEvent implements Listener {
 		Player player = (Player) event.getWhoClicked();
 
 		for (Arena arena : MemoryStorage.arenaList) {
-			if (arena.playersInArena.contains(player) && !arena.seekers.contains(player)) {
+			if (arena.playersInArena.contains(player)) {
-				if (event.getSlot() == 8 || event.getSlot() == 39) {
 				event.setCancelled(true);
 			}
 		}
-		}
 
 		Inventory inv = event.getInventory();
 		InventoryView invView = event.getView();

src/main/java/nl/Steffion/BlockHunt/Listeners/OnPlayerSwapHandItemsEvent.java

@@ -0,0 +1,25 @@
+package nl.Steffion.BlockHunt.Listeners;
+
+import nl.Steffion.BlockHunt.Arena;
+import nl.Steffion.BlockHunt.ArenaHandler;
+import nl.Steffion.BlockHunt.MemoryStorage;
+import org.bukkit.entity.Player;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
+import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerSwapHandItemsEvent;
+
+public class OnPlayerSwapHandItemsEvent implements Listener {
+    @EventHandler(priority = EventPriority.NORMAL, ignoreCancelled = true)
+    public void onPlayerSwapHandItemsEvent(PlayerSwapHandItemsEvent event) {
+        // Early exit if no one is in any arena
+        if (ArenaHandler.noPlayersInArenas()) return;
+
+        Player player = event.getPlayer();
+        for (Arena arena : MemoryStorage.arenaList) {
+            if (arena.playersInArena.contains(player)) {
+                event.setCancelled(true);
+            }
+        }
+    }
+}