How do I make a new creative tab without editing base files?

Make a new variable, which holds a new instance of your tab, like this:

public static CreativeTabs yourTab = new CreativeTabs("yourTab");

 

Add a title to this tab like this:

LanguageRegistry.instance().addStringLocalization("itemGroup.yourTab", "en_US", "My Custom Tab");

 

And last but not least, add your items to your custom tab, using the instance you've created, like this:

myItem.setCreativeTab(yourTab);

I figured it out, anyway 1 question.

 

Items that has hasEffect = true makes some tabs go purple and its weird, ive been getting this on achieves with this effect item too, the achieve screen goes white

I figured it out, anyway 1 question.

 

Items that has hasEffect = true makes some tabs go purple and its weird, ive been getting this on achieves with this effect item too, the achieve screen goes white

 

That might be a vanilla issue, due none of the items in the achievements nor those for the creative tabs have the effect. I encountered that, too.

Make a new variable, which holds a new instance of your tab, like this:

public static CreativeTabs yourTab = new CreativeTabs("yourTab");

 

Add a title to this tab like this:

LanguageRegistry.instance().addStringLocalization("itemGroup.yourTab", "en_US", "My Custom Tab");

 

And last but not least, add your items to your custom tab, using the instance you've created, like this:

myItem.setCreativeTab(yourTab);

 

what icon will this new tab have?

Make a new variable, which holds a new instance of your tab, like this:

public static CreativeTabs yourTab = new CreativeTabs("yourTab");

 

Add a title to this tab like this:

LanguageRegistry.instance().addStringLocalization("itemGroup.yourTab", "en_US", "My Custom Tab");

 

And last but not least, add your items to your custom tab, using the instance you've created, like this:

myItem.setCreativeTab(yourTab);

 

what icon will this new tab have?

 

I forgot to mention that you have to make a new class which extend CreativeTabs and override this method:

public ItemStack getIconItemStack() {
    return new ItemStack(Item.eyeOfEnder);
}

 

So this tab would have the Eye Of Ender item as icon.

 

And instead of initializate with the standard CreativeTabs class, you should do this:

public static CreativeTabs yourTab = new MyCustomTab("yourTab");

So would this tab overwrite one of the existing tabs? Or be alongside them?

So would this tab overwrite one of the existing tabs? Or be alongside them?

 

It will be a new tab alongside the others.

 

BTW, I made a wiki article about this whole creative tabs thingy here:

http://www.minecraftforge.net/wiki/Custom_Creative_Tabs