Hello Im trying to get this function. Especially the offhand.hitentity to work.  Everytime I face a mob the item swings but doesn't hurt the mob and if I face away from the mob the game crashes.

 

@SubscribeEvent
    public static void dualweild(MouseEvent event)
    {
        EntityLivingBase target = (EntityLivingBase) Minecraft.getMinecraft().pointedEntity;
        EntityPlayer player = Minecraft.getMinecraft().player;

        ItemStack mainhand = player.getHeldItemMainhand();
        ItemStack offhand = player.getHeldItemOffhand();

//right mouse button is 1

        if (event.getButton() == 1)
        {
            if (offhand.getItem() instanceof ItemKnife)
            {
               
                    offhand.hitEntity(target, player);
                    offhand.damageItem(1, player);
                    player.swingArm(EnumHand.OFF_HAND);
                
            }
            else
            {
                return;
            }
        }

    }

If you crash, then please post the crash log. We cannot help you with what we cannot see.

Use pastebin.com or github gist, and link the url here.

 

I'm betting that you're getting a nullpointer exception. Your code runs on the belief that there is always an entity where you are looking... 95% of the time, that is incorrect.

We need the crashlog. But probably it's due to this:

 

EntityLivingBase target = (EntityLivingBase) Minecraft.getMinecraft().pointedEntity;

offhand.hitEntity(target, player);

You need to make sure that is not null. (As you mention, that would be the case when you not facing an entity) Now in Minecraft, you are able to swing weapons even without facing entities, so that's something you should look into.