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My guide to 1.12.2 modding


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There are a ton of guides, and I felt like I just needed to make one of how I mod using 1.12.2.


Table of Contents:

1. Getting Started

2. Registries

3. Proxies

3. Basic Block/Item

4. GUIs

(There will be more coming, I am writing this as I learn.)


Getting Started:


Download Forge mdk

Unzip it

Run gradlew setupDecompWorkspace

for Eclipse:

Run gradlew eclipse in cmd.exe

for Intellij:

Run gradlew setupDevWorkspace ideaModule

Import build.gradle as a project

Go to File -> Project Structure -> Modules

Click '+' and click import, choose (folder name).iml. (There is only one in the folder)

Close intellij

run gradlew genIntellijruns

Open Intellij

Run -> Profile -> Edit Configurations

Choose server/client

Set "Use classpath of module" to (folder name)_main





Registries are Forge's way of injecting instances of your classes into the game.


Basic setup:


You need a class annotated with EventBusSubscriber

From there you add methods annotated with EventHandler to register blocks.


public static void registerBlocks(RegistryEvent.Register<Block> event) {

blocks is a List of all blocks in the mod.


Note: When registering blocks, you also have to register an ItemBlock.

To do this use the Item registry event, and register a new instance of ItemBlock(you have to set its registry name).


Registering models:

(This may need to be client side only, if it is please tell me)

public static void registerModels(ModelRegistryEvent event) {
    for (Block block : blocks) {
        if (block.getRegistryName() != null)
            ModelLoader.setCustomModelResourceLocation(Item.getItemFromBlock(block), 0, new ModelResourceLocation(block.getRegistryName(),"inventory"));

Pretty simple, nothing too hard.




What is ObjectHolder?

ObjectHolder is used to get instances of your block.


public class ModBlocks {
    public static final Block MOD_BLOCK = null;

After the block is registered, an instance of it will be injected into MOD_BLOCK.




Minecraft runs on 2 sides. Client and server.

Certain things are only client side, some are only server side.


Setting up proxies:


Proxies require 2 classes, Client and Server.

The SidedProxy annotation requires 2 arguments, the path to your client and server proxy (ex. "com.author.mod.proxies.ClientProxy")

Then you can use the SidedProxy annotation with the argument saying what side it is to tell Forge to run that code on a certain side.

If you want to check what side a method is, use world.isRemote(), true means client side, false means server side.




This is pretty simple, just make a class extend Block/Item, put in the necessary methods and constructors (setRegistryName() is a big one).

Then register an instance of that block/item in the appropriate registry.


When making a texture/model, you need to have the appropriate files. (BlockState for a block, block model for blocks, item model for blocks and items, and textures)

I suggest looking at the default MC asset files when making textures. I won't get too much into detail here because it's not that hard to do.




GUIs are a bit harder.

A GUI can either be a container, or a screen.


A GUI requires 2-3 classes bare minimum, depending on what type it is.


Simple screen:


Create a class that implements IGuiHandler.

That class needs 2 overrided methods.




public Object getServerGuiElement(int ID, EntityPlayer player, World world, int x, int y, int z) {
    return new Container(player.inventory, world);

public Object getClientGuiElement(int id, EntityPlayer player, World world, int x, int y, int z) {
    return new Gui(new Container(player.inventory, world));


Now you gotta register it in your main class's init method:

NetworkRegistry.INSTANCE.registerGuiHandler(instance, new WorkbenchGuiHandler());

(instance is the instance of your main class)

Note: the instance should be obtained by making a variable and annotating it with the Instance annotation, and your modid as an argument.


Now, we have to make the actual GUI. For my example I am going to be making a custom crafting table.


Here is the GUI screen with the crafting table background:


 GuiScreen(Container inventorySlotsIn) {

//This is for everything behind the items
protected void drawGuiContainerBackgroundLayer(float partialTicks, int mouseX, int mouseY) {
    GlStateManager.color(1.0F, 1.0F, 1.0F, 1.0F);
    //Makes the background darker like in a normal craftring table
    //Size of the GUI image
    int i = (this.width - this.xSize) / 2;
    int j = (this.height - this.ySize) / 2;
    //Load the default crafting GUI texture
    this.mc.getTextureManager().bindTexture(new ResourceLocation("textures/gui/container/crafting_table.png"));
    //Draw it
    this.drawTexturedModalRect(i, j, 0, 0, this.xSize, this.ySize);

//Now for on top of the items
protected void drawGuiContainerForegroundLayer(int mouseX, int mouseY) {
    //Draw the name at the top, getting the name from the lang file.
    this.fontRenderer.drawString(I18n.format("gui.custom_workbench.name"), 28, 6, 4210752);


Now we need a container to contain all of the items. the container has to draw the player's inventory, the inventory, listen for click events, etc...


just saying, this one's a big class.


Commented code is code for making the inventory a crafting table


public class GUIContainer extends Container {
    private World world;
    private InventoryCrafting matrix;
    private InventoryCraftResult result;
    private EntityPlayer player;

    GUIContainer(InventoryPlayer playerInventory, World world) {
        //matrix = new InventoryCrafting(this, 3, 3);
        player = playerInventory.player;
        this.world = world;
        //result = new InventoryCraftResult();

        int index = 1;
        Output slot, code down below.
        addSlotToContainer(new CraftResultSlot(matrix, 0, 124, 35));
        Crafting matrix
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                addSlotToContainer(new Slot(matrix, index, 30 + j * 18, 17 + i * 18));
                index += 1;
        //Player's inventory
        for (int k = 0; k < 3; k++) {
            for (int i = 0; i < 9; i++) {
                addSlotToContainer(new Slot(playerInventory, index, 8 + i * 18, 84 + k * 18));
                index += 1;
		//Player's hotbar
        for (int i = 0; i < 9; i++) {
            addSlotToContainer(new Slot(playerInventory, i, 8 + i * 18, 142));
    //Checking if player can open the inventory
    public boolean canInteractWith(EntityPlayer playerIn) {
        Code to check if it is a custom crafting table
        Getting the block the player is looking at, with a max distance of 6
        RayTraceResult ray = playerIn.rayTrace(6, 1.0f);
        if (ray == null) return false;
        //Get the position of the block
        BlockPos pos = ray.getBlockPos();
        //Get the world
        World world = playerIn.getEntityWorld();
        //And the block
        Block block = world.getBlockState(pos).getBlock();
        //Check if it is our block
        return block.equals(ModBlocks.CUSTOM_WORKBENCH);
        return true;

    public void onContainerClosed(EntityPlayer playerIn) {

        drop the items in the crafting grid
        if (!world.isRemote) {
            for (int i = 0; i < 9; ++i) {
                ItemStack itemstack = matrix.removeStackFromSlot(i);

                if (!itemstack.isEmpty()) {
                    playerIn.dropItem(itemstack, false);

    //Code when item is shift clicked
    public ItemStack transferStackInSlot(EntityPlayer playerIn, int index) {
        ItemStack itemstack = ItemStack.EMPTY;
        Slot slot = inventorySlots.get(index);

        if (slot != null && slot.getHasStack()) {
            ItemStack currentItem = slot.getStack();
            itemstack = currentItem.copy();

            if (index == 0) {
                currentItem.getItem().onCreated(currentItem, world, playerIn);
                if (!mergeItemStack(currentItem, 37, 46, false)) {
                    return ItemStack.EMPTY;
                slot.onSlotChange(currentItem, itemstack);
            if (index >= 11 && index < 38) {
                //if (!mergeItemStack(currentItem, 37, 46, false)) {
                    //if (recipe != null)
                        //Put correct output in output slot
                        //putStackInSlot(0, recipe.output);
                    //return ItemStack.EMPTY;
                //This might not work!
                if(!mergeItemStack(currentItem, 0, 8, false)) {
                    return ItemStack.EMPTY;
            } //else if (index >= 38 && index < 46) {
                //if (!mergeItemStack(currentItem, 10, 37, false)) {
                    //return ItemStack.EMPTY;
            //} else if (!mergeItemStack(currentItem, 10, 46, false)) {
                //return ItemStack.EMPTY;

            if (currentItem.isEmpty()) {
            } else {

            if (currentItem.getCount() == itemstack.getCount()) {
                return ItemStack.EMPTY;
            slot.onTake(playerIn, currentItem);

        return itemstack;

    public boolean canMergeSlot(ItemStack stack, Slot slotIn) {
        return /*slotIn.inventory != result && */super.canMergeSlot(stack, slotIn);

    public void onCraftMatrixChanged(IInventory in) {
        IRecipe recipe = CraftingManager.findMatchingRecipe(matrix, world);
        if (recipe != null)
              putStackInSlot(0, recipe.getRecipeOutput());


If you want the CraftResultSlot code, here it is:

public class CraftResultSlot extends Slot {
    public CraftResultSlot(InventoryCrafting matrix, int index, int x, int y) {
        super(matrix, index, x, y);

    //Disable items getting put in the slot
    public boolean isItemValid(ItemStack stack) {
        return false;


Please comment anything i missed, things I should add, errors, etc...


I will expand this soon!

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