Nifty inventory HUD extremely slow

Troubleshooting
1

I’m using Nifty GUI to populate my HUD. I’m trying to implement an inventory similar to minecraft’s item slots at the bottom of the screen.

Every time the player picks up a new item the frame rate gets slower and slower until it’s not playable at about 5 items. I have a HUDControl that is my ScreenController.

Here is my onStartScreen method:

   public void onStartScreen()
{
    screen = nifty.getCurrentScreen();
    
    for (int col = 0; col < INVENTORY_COLUMNS; col++)
    {
        panelBuilder = new PanelBuilder("");
        panelBuilder.id("hudItemColumn" + col);
        panelBuilder.childLayoutVertical();
        Element column = panelBuilder.build(nifty, screen, screen.findElementByName("hudItemSlots"));
        slotBuilder = new ControlBuilder("itemSlot");
        slotBuilder.id("itemSlot" + col);
        slotBuilder.build(nifty, screen, column);
    }        
}

Then in my controlUpdate method I populate the items from my Inventory data structure as follows:

    private void populateInventoryItems()
{
    List<InventoryItem> items = player.getInventory().getEquippedItems();
    for (int i = 0; i < items.size() && i < INVENTORY_COLUMNS; i++)
    {
        InventoryItem item = items.get(i);
        itemBuilder = new ControlBuilder("item");
        itemBuilder.id("item" + i);

        final int spriteIndex = item.getBlock().getSpriteIndex();
        Element e = itemBuilder.build(nifty, screen, screen.findElementByName("itemSlot" + i));
        ImageBuilder imageBuilder = new ImageBuilder()
        {
            {
                filename("Textures/minecraft-6.bmp");
                imageMode("sprite:16,16," + spriteIndex);
                width("50");
                height("50");

            }
        };
        imageBuilder.build(nifty, screen, e);
    }        
}

I’m sure a seasoned developer will know what is causing the problem. Should I have an InventoryListener that reports inventory changes to my HUDControl or am I going about this all wrong?

Thanks for the help!

2

Updating the gui like that every frame on update is your performance problem. You really only want to update when there is a change in your inventory.

3

Thanks @glh3586. That’s what I did.

I created an InventoryListener with an onInventoryChanged method that my HUDControl implements. It marks a dirty flag and rebuilds the inventory items when the flag is true.