Problems with ItemStack References

Discussion in 'Plugin Development' started by ndvenckus1, Nov 11, 2014.

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    For my plugin, I need to schedule a task to check if an item is still in a player's inventory after several ticks, and I'm running into more trouble than expected.

    Here's the method I created to check if the specified inventory contains the specified ItemStack:
    1. public static boolean itemInInventory(ItemStack item, Inventory inv) {
    2. for(int i = 0; i < inv.getSize(); i++) {
    3. if(inv.getItem(i) == item) //If ItemStack in inventory references the same object as item...
    4. return true;
    5. }
    7. return false;
    8. }

    And here's where I use it:
    1. @EventHandler(priority=EventPriority.HIGHEST, ignoreCancelled=true)
    2. public void onPlayerInteract(PlayerInteractEvent e) {
    3. final Player player = e.getPlayer();
    4. final ItemStack item = player.getItemInHand();
    6. Bukkit.getScheduler().runTaskLater(plugin, new Runnable() {
    7. @Override
    8. public void run() {
    9. if(!Util.itemInInventory(item, player.getInventory())) { //If item is no longer in player's inventory...
    10. player.sendMessage("Item is no longer in your inventory!");
    11. }
    12. }
    13. }, 5L);
    14. }

    The player right clicks, a reference to getItemInHand() is stored, and 5 ticks later, the itemInInventory method loops the player's inventory to see if it still contains a reference to the object specified. The problem is, itemInInventory always seems to return false, even when the player doesn't switch items. In testing, I also found that this code:
    1. player.getItemInHand() == player.getItemInHand();

    returns false. Yet I can operate directly on the ItemStack returned by the method, like so:
    1. player.getItemInHand().setType(Material.IRON_INGOT);

    and the code works... Could anyone explain this strange behavior to me?
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    I'm not trying to figure out if the ItemStacks have the same data attached to them; I'm trying to figure out if their variables reference the same object, which is precisely what the == operator is for.

    Can anyone explain this behavior?

    EDIT by Moderator: merged posts, please use the edit button instead of double posting.
    Last edited by a moderator: Jun 13, 2016
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    Have you tried using DJSkepter 's method? That could at least isolate the problem
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    That the ItemStack is created when you request it from the player, and a reference to it is not maintained between calls to retrieve it from the inventory.
    tangster132 likes this.
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    Ah, that makes sense. Thanks! I was under the impression that all ItemStacks on the server already existed in memory, and that when you made calls to retrieve them a reference was returned rather than a new object. With this being the case, I guess there's no way to get the inventory an ItemStack is located in, which is unfortunate.
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    I could certainly see where that idea comes from, and that's likely the way we'll do it in Trident. You could attach unique metadata to the item I believe, that would allow you to keep track of it.
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