アイテムの属性値の動的変更例

package ak.sampleMod;

import cpw.mods.fml.common.registry.GameRegistry;
import net.minecraft.entity.SharedMonsterAttributes;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraft.item.ItemSword;
import net.minecraft.nbt.NBTTagCompound;
import net.minecraft.nbt.NBTTagList;
import net.minecraft.world.World;

import javax.annotation.Nonnull;

/**
 * 攻撃力可変ソードクラス
 */
public class SampleVariableSword extends ItemSword {
    /** 属性保存のキー */
    private static final String NBT_ATTRIBUTE_MODIFIERS_KEY = "AttributeModifiers";
    /** 属性値名称保存キー */
    private static final String NBT_ATTRIBUTE_MODIFIERS_NAME = "Name";
    /** 属性名キー */
    private static final String NBT_ATTRIBUTE_MODIFIERS_NAME_KEY = "AttributeName";
    /** 属性値double valueキー */
    private static final String NBT_ATTRIBUTE_MODIFIERS_AMOUNT = "Amount";
    /** 属性値Opキー */
    private static final String NBT_ATTRIBUTE_MODIFIERS_OPERATION = "Operation";
    /** 攻撃力の属性値の名称 */
    private static final String NBT_ATTRIBUTE_MODIFIERS_NAME_WEAPON = "Weapon modifier";
    /** UUIDMostを表すlong値用のキー */
    private static final String NBT_ATTRIBUTE_MODIFIERS_UUID_MOST = "UUIDMost";
    /** UUIDLeastを表すlong値用のキー */
    private static final String NBT_ATTRIBUTE_MODIFIERS_UUID_LEAST = "UUIDLeast";

    public SampleVariableSword(ToolMaterial toolMaterial) {
        super(toolMaterial);
        GameRegistry.registerItem(this, "sample_variable_sword");
    }

    @Override
    public ItemStack onItemRightClick(ItemStack itemStack, World world, EntityPlayer player) {
        if (!world.isRemote) {
            int randAttack = world.rand.nextInt(100);
            this.setAttribute(itemStack, player, SharedMonsterAttributes.attackDamage.getAttributeUnlocalizedName(),
                    NBT_ATTRIBUTE_MODIFIERS_NAME_WEAPON, randAttack, 0);
        }
        return super.onItemRightClick(itemStack, world, player);
    }

    /**
     * 武器の属性変更メソッド
     * @param itemStack 変更したい武器のItemStack
     * @param player 所有プレイヤー
     * @param attributeKey 属性のMultiMap上でのKey文字列
     * @param attributeName 属性のAttributeModifierName
     * @param amount 属性の値
     * @param op 属性のOp
     */
    protected void setAttribute(@Nonnull ItemStack itemStack, @Nonnull EntityPlayer player, @Nonnull String attributeKey,
                                @Nonnull String attributeName, @Nonnull double amount, @Nonnull int op) {
        NBTTagList nbtTagList;
        NBTTagCompound nbtTagCompound;
        if (!itemStack.hasTagCompound()) {
            itemStack.setTagCompound(new NBTTagCompound());
        }
        if (itemStack.getTagCompound().hasKey(NBT_ATTRIBUTE_MODIFIERS_KEY, 9)) {
            nbtTagList = itemStack.getTagCompound().getTagList(NBT_ATTRIBUTE_MODIFIERS_KEY, 10);
            for (int tagIndex = 0; tagIndex < nbtTagList.tagCount(); tagIndex++) {
                nbtTagCompound = nbtTagList.getCompoundTagAt(tagIndex);
                if (attributeKey.equals(nbtTagCompound.getString(NBT_ATTRIBUTE_MODIFIERS_NAME_KEY))
                        && attributeName.equals(nbtTagCompound.getString(NBT_ATTRIBUTE_MODIFIERS_NAME))) {
                    nbtTagCompound.setDouble(NBT_ATTRIBUTE_MODIFIERS_AMOUNT, amount);
                    break;
                }
            }
        } else {
            nbtTagList = new NBTTagList();
            nbtTagCompound = new NBTTagCompound();
            nbtTagCompound.setLong(NBT_ATTRIBUTE_MODIFIERS_UUID_MOST, Item.field_111210_e.getMostSignificantBits());
            nbtTagCompound.setLong(NBT_ATTRIBUTE_MODIFIERS_UUID_LEAST, Item.field_111210_e.getLeastSignificantBits());
            nbtTagCompound.setString(NBT_ATTRIBUTE_MODIFIERS_NAME_KEY, attributeKey);
            nbtTagCompound.setString(NBT_ATTRIBUTE_MODIFIERS_NAME, attributeName);
            nbtTagCompound.setDouble(NBT_ATTRIBUTE_MODIFIERS_AMOUNT, amount);
            nbtTagCompound.setInteger(NBT_ATTRIBUTE_MODIFIERS_OPERATION, op);
            nbtTagList.appendTag(nbtTagCompound);
            if (!itemStack.hasTagCompound()) {
                itemStack.setTagCompound(new NBTTagCompound());
            }
            itemStack.getTagCompound().setTag(NBT_ATTRIBUTE_MODIFIERS_KEY, nbtTagList);
        }

        player.getAttributeMap().applyAttributeModifiers(itemStack.getAttributeModifiers());
    }
}