Using flint and steel as a lighter for a custom portal

I want to have my portal activated by flint and steel, but I don't know how to add this to regular flint and steel

	public static class ModTrigger extends Item {
		/*public ModTrigger() {
			super();
			this.maxStackSize = 1;
			setMaxDamage(64);
			setCreativeTab(null);
		}*/

		@Override
		public EnumActionResult onItemUse(EntityPlayer entity, World world, BlockPos pos, EnumHand hand, EnumFacing facing, float hitX, float hitY,
				float hitZ) {
			pos = pos.offset(facing);
			ItemStack itemstack = entity.getHeldItem(hand);
			if (!entity.canPlayerEdit(pos, facing, itemstack)) {
				return EnumActionResult.FAIL;
			} else {
				if (world.isAirBlock(pos))
					portal.portalSpawn(world, pos);
				itemstack.damageItem(1, entity);
				return EnumActionResult.SUCCESS;
			}
		}
	}