打造自定义物品

先制作可读的罗盘 · 位置见本节说明

ItemStack item = new ItemStack(Material.COMPASS);
var meta = item.getItemMeta();
meta.displayName(Component.text("矿工罗盘"));
meta.lore(List.of(Component.text("主手右键查看课堂任务")));
item.setItemMeta(meta);

故意漏掉最后一步 · 故意错误，先预测再修复

// 若忘了setItemMeta，检查名称和说明是否真的保存。

为本插件创建一个键 · 位置见本节说明

compassKey = new NamespacedKey(this, "miner_compass");

写入类型明确的标记 · 位置见本节说明

meta.getPersistentDataContainer().set(
    compassKey, PersistentDataType.BYTE, (byte) 1);

完整CompassItems.java · 完整文件

package de.teacherma.lesson37;

import java.util.List;
import net.kyori.adventure.text.Component;
import org.bukkit.Material;
import org.bukkit.NamespacedKey;
import org.bukkit.inventory.ItemStack;
import org.bukkit.persistence.PersistentDataType;

public final class CompassItems {
    private CompassItems() { }
    public static ItemStack create(NamespacedKey key) {
        ItemStack item = new ItemStack(Material.COMPASS);
        var meta = item.getItemMeta();
        meta.displayName(Component.text("矿工罗盘"));
        meta.lore(List.of(Component.text("主手右键查看课堂任务")));
        meta.getPersistentDataContainer().set(key, PersistentDataType.BYTE, (byte) 1);
        item.setItemMeta(meta);
        return item;
    }
    public static boolean isOurs(ItemStack item, NamespacedKey key) {
        if (item == null || item.getType() != Material.COMPASS || !item.hasItemMeta())
            return false;
        Byte marker = item.getItemMeta().getPersistentDataContainer()
                .get(key, PersistentDataType.BYTE);
        return Byte.valueOf((byte) 1).equals(marker);
    }
}

安全比较可能为空的值 · 位置见本节说明

Byte marker = meta.getPersistentDataContainer()
        .get(compassKey, PersistentDataType.BYTE);
boolean ours = Byte.valueOf((byte) 1).equals(marker);

删除自定义身份的片段 · 位置见本节说明

meta.getPersistentDataContainer().remove(compassKey);
item.setItemMeta(meta);

先筛选主手 · 位置见本节说明

if (event.getHand() != EquipmentSlot.HAND) return;

两种右键都允许 · 位置见本节说明

Action action = event.getAction();
if (action != Action.RIGHT_CLICK_AIR
        && action != Action.RIGHT_CLICK_BLOCK) return;

只读观察方法的入口 · 位置见本节说明

@EventHandler(priority = EventPriority.MONITOR)
public void onUse(PlayerInteractEvent event) {
    // 主手、动作、物品都匹配后，只发送任务文字。
}

不要为提示解封保护 · 故意错误，先预测再修复

event.setCancelled(false); // 本课不要这样做

完整plugin.yml · 完整文件

name: BlockAcademyL37
version: 1.0.0
main: de.teacherma.lesson37.CompassPlugin
api-version: '1.21.11'
author: TeacherMa
website: https://www.teacher-ma.de
commands:
  minercompass:
    description: 领取课堂矿工罗盘
    usage: /minercompass
permissions:
  blockacademy.compass.give:
    default: op

完整项目中的Java文件 · 完整文件

src/main/java/de/teacherma/lesson37/
  CompassItems.java
  CompassPlugin.java

主类第1部分 · 顺序接在同一源文件

package de.teacherma.lesson37;

import java.util.Objects;
import net.kyori.adventure.text.Component;
import org.bukkit.NamespacedKey;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.EventPriority;
import org.bukkit.event.Listener;
import org.bukkit.event.block.Action;
import org.bukkit.event.player.PlayerInteractEvent;
import org.bukkit.inventory.EquipmentSlot;
import org.bukkit.plugin.java.JavaPlugin;

public final class CompassPlugin extends JavaPlugin implements Listener {
    private NamespacedKey compassKey;
    @Override
    public void onEnable() {
        compassKey = new NamespacedKey(this, "miner_compass");
        Objects.requireNonNull(getCommand("minercompass")).setExecutor(this);
        getServer().getPluginManager().registerEvents(this, this);
    }

主类第2部分 · 顺序接在同一源文件

    @Override
    public boolean onCommand(CommandSender sender, Command command,
                             String label, String[] args) {
        if (!(sender instanceof Player p)) {
            sender.sendMessage("请在游戏中领取罗盘"); return true;
        }
        if (!p.hasPermission("blockacademy.compass.give")) {
            p.sendMessage("请老师授权后领取"); return true;
        }
        if (args.length != 0) { p.sendMessage("用法: /minercompass"); return true; }
        var left = p.getInventory().addItem(CompassItems.create(compassKey));
        left.values().forEach(item -> p.getWorld().dropItemNaturally(p.getLocation(), item));
        p.sendMessage(left.isEmpty() ? "罗盘已入包，主手右键试试" : "罗盘在脚边");
        return true;
    }
    @EventHandler(priority = EventPriority.MONITOR)
    public void onUse(PlayerInteractEvent event) {
        if (event.getHand() != EquipmentSlot.HAND) return;
        Action action = event.getAction();
        if (action != Action.RIGHT_CLICK_AIR && action != Action.RIGHT_CLICK_BLOCK) return;
        if (!CompassItems.isOurs(event.getItem(), compassKey)) return;
        event.getPlayer().sendMessage(Component.text("课堂任务：准备工具，参加矿石冲刺赛！"));
    }
}