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Your first item

This lesson registers an item in your bundle and finds it in the creative tab. It assumes you finished Your first bundle and have a bundle that loads.

You will learn the smallest amount of Groovy you need to register content: classes, methods, and a builder.

Where content gets registered​

Content is registered when the bundle loads. Inside onLoad(), you build the content with a builder, then hand it to the registry.

A builder is a class that describes one piece of content with chained method calls. Each call returns the builder again, so you keep adding to the same description.

The id helper​

Every item needs a unique name: an Identifier with a namespace and a path, written namespace:path. A bundle with the id mybundle uses mybundle:magic_gem.

Add this helper to your entrypoint so you can write id("magic_gem") instead of the full name:

import net.minecraft.resources.Identifier

static Identifier id(String path) {
    return Identifier.fromNamespaceAndPath("mybundle", path)
}

The static keyword means you can call id(...) without creating an instance. It is a small helper that turns a short path into a full name.

Build an item​

Import the item builder and the registry event, then build an item in onLoad():

import de.luckymcdev.foundryengine.common.builder.item.ItemBuilder
import de.luckymcdev.foundryengine.common.event.BundleEvents

@Override
void onLoad() {
    def gem = ItemBuilder.create(id("magic_gem"))
            .stacksTo(16)

    BundleEvents.registry {
        it.items(gem)
    }
}

Two pieces of Groovy syntax to know:

  • def gem = ... declares a variable named gem that holds whatever the builder produced. def lets Groovy figure out the type.
  • BundleEvents.registry { it.items(gem) } passes a block of code to the registry event. The block runs when the registry is ready. Inside it, it is the object that can register content, and it.items(gem) registers your item.

Give the item a texture​

The item needs a texture or it renders as the missing texture checkerboard. Place the texture in your bundle's assets folder:

  1. Create FoundryEngine/bundles/mybundle/assets/mybundle/textures/item/magic_gem.png.
  2. Put a 16 by 16 pixel image there, named exactly magic_gem.png. The path must match the item's path: item id("magic_gem") looks for textures/item/magic_gem.png.

The model that points the item at the texture is generated for you by the data generator. You only supply the texture.

Run the game​

Run the game from your launcher. When it loads, open the creative tab and search for magic_gem. It appears with your texture.

What you built​

You registered an item with a texture. The builder described the item, the registry event registered it, and the texture made it visible.

Next, add a block and a recipe to give it a place in the world.