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Event API Reference

来自Minecraft插件百科
Tdiant讨论 | 贡献2016年8月15日 (一) 22:16的版本 基础
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介绍

服务器里发生的事情,服务器会用事件 来告诉你。 Bukkit中有各种各样的事件,例如 玩家的互动(玩家登录, 玩家点击了一个方块, 玩家死了,玩家重生...), 方块的动态(方块被放置, 方块被破坏, 方块附近的实体被改变...), 实体事件(一个怪物看上了你233, 一个苦力怕帮你收集土方块...), 世界事件 (一个世界被加载或卸载, 一个区块被加载或卸载)等等. 由于MC官方的一些原因,他们的JavaDocs都挂了= =

基础

为了保持简单易懂,这一节只讨论一种事件——PlayerLoginEnvent。让我们从创建一个监听器开始吧。

创建方法

为了让你的插件能够监听并处理该事件的回调,你需要为它创建一个方法,这个方法就是事件监听器

@EventHandler
public void onLogin(PlayerLoginEvent event) {
    // 你自己的代码...
}

你需要向Bukkit注册你的监听器,这样服务器才会在"PlayerLoginEvent"触发时调用该监听器。我们需要给监听器打上 @EventHandler 批注。

@EventHandler

"@EventHandler" 是一个能打在某个方法上的批注,就像这样:

@EventHandler // 优先级 默认为NORMAL级

这样一来,这所对应的方法就成为了一个 优先级 为NORMAL的监听器。

你可以设置EventHandler标签的EventPriority属性来自定义事件的优先级,例如:

@EventHandler(priority = EventPriority.HIGHEST) // 将优先级设为HIGHEST级
@EventHandler(priority = EventPriority.LOW) // 优先级设为LOW级

你的监听器应该看上去像是这样:

@EventHandler
public void onLogin(PlayerLoginEvent event) {
    // 你自己的代码...
}

添加监听器

为了让Bukkit能够注册你的监听器,你需要给你的监听器所在的类实现Listener接口(org.bukkit.event.Listener)。例如这样:

public final class MyPlayerListener implements Listener {
    @EventHandler
    public void onLogin(PlayerLoginEvent event) {
        // Your code here...
    }
}

监听器的方法名(例子中是“onlogin”的东西)并不重要;只要符合命名规则,起什么名字,你开心就好。 你可能想知道:“Bukkit怎么知道监听那个事件呢?”。Bukkit是通过上面例子中你定义的“PlayerLoginEvent”这个参数知道的。 Warning.png 一个监听器只能监听一个事件,否则Bukkit是不会注册它的! 你的插件的主类 (就是继承JavaPlugin的那个类) 也可以成为一个事件监听器。在你的插件非常小的时候,这样就很方便了。比如:

public class MyPlugin extends JavaPlugin implements Listener {
  @Override
  public void onEnable() {
    getServer().getPluginManager().registerEvents(this, this);
  }

  @EventHandler
  public void onLogin(PlayerLoginEvent event) {
    getLogger().log(Level.INFO, "Player " + event.getPlayer().getName() + " is logging in!");
  }
}

EventHandler的参数

@EventHandler 批注可以设置某些参数来改变监听器的某些作用等。在某些情况下,你可以设置这些参数:

名称 类型 默认值 描述
priority EventPriority EventPriority.NORMAL 设置监听器优先级
  • EventPriority.MONITOR
  • EventPriority.HIGHEST
  • EventPriority.HIGH
  • EventPriority.NORMAL
  • EventPriority.LOW
  • EventPriority.LOWEST
ignoreCancelled boolean false 如果设为true,在事件被其他监听器关闭的时候,你的监听器将监听不到这个事件
  • true
  • false


事件优先级

Bukkit中的监听器拥有六个优先级

  • EventPriority.LOWEST
  • EventPriority.LOW
  • EventPriority.NORMAL
  • EventPriority.HIGH
  • EventPriority.HIGHEST
  • EventPriority.MONITOR

每个插件可能会在一个事件触发时做出不同的相应,并且有的插件可能想更快的知道一个事件的发生。并且,有时候Bukkit传递事件给每个插件的时候,甚至这个事件已经被其他插件关闭了。某些情况下,其他插件刚把这个事件关掉,另外一个插件监听到了以后又把这个事件开开了。这样乱七八糟的冲突发生了以后,这就很尴尬了。

比如 方块放置 被触发了,LOWEST优先级的监听器将会最先对这个事件做出决定,比如关闭它什么的。然后LOW优先级的监听器将会被触发,这时候可以重写LOWEST级监听器刚刚做出的修改,以此类推。Eventually it hits monitor, and at this point nothing should change the outcome of the event. MONITOR级的监听器 should be used to see the outcome of an event, without changing any aspect of it. If we have three plugins enabled; one is a basic area protection plugin, one is a fancy plugin using signs, and another is a logging plugin. The protection plugin listens on Priority.LOWEST. It says they can't place blocks in this area, and cancels the event. The fancy sign plugin listens on Priority.NORMAL. It says they can place signs here, and uncancels the event. The log plugin listens on Priority.MONITOR. It sees that the event was actually allowed, and logs it.

If you want to change the outcome of an event, choose very carefully from LOWEST to HIGHEST. Suggested generalized protection plugins on lowest, more specific plugins on normal, and override plugins on high. If you want to act when an event happens, but not change the outcome, use MONITOR. It's really really important that you use MONITOR, or an event might get cancelled after you've acted on it, and it's even more important that you don't change the outcome of the event on MONITOR or it'll break other plugins.

中文简单解释

优先级越高的方法越早调用

优先级再高(除了MONITOR) setCanceled() 方法也不能阻止其它插件监听到它

在MONITOR上搞 setCanceled(false) 其它插件会给你玩死~

注册事件(监听器)

要注册你的方法,包含EventHandler的类必须是implent了Listenr类的

import org.bukkit.event.Listener;

public final class LoginListener implements Listener {
}

你只需要提供一个插件和一个监听器来在PluginManager里注册它们

getServer().getPluginManager().registerEvents(Listener, Plugin);

监听器示例

这个监听器包含两个EventHandlers,一个监听级别是HIGH并且另一个是NORMAL。

import org.bukkit.event.Listener;
import org.bukkit.event.EventHandler;
import org.bukkit.event.EventPriority;
import org.bukkit.event.player.PlayerLoginEvent;

public final class LoginListener implements Listener {
    @EventHandler
    public void normalLogin(PlayerLoginEvent event) {
        // Some code here
    }

    @EventHandler(priority = EventPriority.HIGH)
    public void highLogin(PlayerLoginEvent event) {
        // Some code here
    }
}

在插件中注册事件监听器

The registerEvents method requires a listener and a plugin. Luckily, we already have our LoginListener. Now for the LoginPlugin!

import org.bukkit.plugin.java.JavaPlugin;

public final class LoginPlugin extends JavaPlugin {
    public void onEnable() {
        getServer().getPluginManager().registerEvents(new LoginListener(), this);
    }
}


在实现监听器接口的插件中注册事件监听器

[1] You could even have the events in the main class, for example:

import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.event.Listener;
import org.bukkit.event.EventHandler;
import org.bukkit.event.player.PlayerLoginEvent;

public final class LoginPlugin extends JavaPlugin implements Listener {
    public void onEnable() {
        getServer().getPluginManager().registerEvents(this, this);
    }

    @EventHandler
    public void normalLogin(PlayerLoginEvent event) {
        // Some code here
    }
}

在监听器中注册事件监听器

There are many ways to register your events. Here's an example where you register them in your listener class.

import org.bukkit.event.Listener;
import org.bukkit.event.EventHandler;
import org.bukkit.event.EventPriority;
import org.bukkit.event.player.PlayerLoginEvent;

public final class LoginListener implements Listener {
    public LoginListener(LoginPlugin plugin) {
        plugin.getServer().getPluginManager().registerEvents(this, plugin);
    }

    @EventHandler
    public void normalLogin(PlayerLoginEvent event) {
        // Some code here
    }

    @EventHandler(priority = EventPriority.HIGH)
    public void highLogin(PlayerLoginEvent event) {
        // Some code here
    }
}

The LoginPlugin would look like this:

import org.bukkit.plugin.java.JavaPlugin;

public final class LoginPlugin extends JavaPlugin {
    public void onEnable() {
        new LoginListener(this);
    }
}

在监听器中注销事件监听器

You can un-register individual events, entire listener classes or all events registered by your plugin or even by other plugins!

注销特定的事件监听器

Each event class has the getHandlerList() static method, call that and then you can use .unregister() method. Example:

PlayerInteractEvent.getHandlerList().unregister(plugin);
// this will unregister all PlayerInteractEvent instances from the plugin
// you can also specify a listener class instead of plugin.

Now you know why you'll need the getHandlerList() in your custom events.

注销所有事件监听器

Using the HandlerList class and its unregisterAll() static method you can easily unregister events from listener classes or plugins. Example:

HandlerList.unregisterAll(plugin);
// this will unregister all events from the specified plugin
// you can also specify a listener class instead of plugin.

创建自定义事件

Creating custom events is very simple, you can use the same system that Bukkit uses without ruining performance.

There are two (2) things to keep in mind when you create a Custom Event. They are "extend Event" and "static handlers." With static handlers, you must input the following code into your custom event:

private static final HandlerList handlers = new HandlerList();

public HandlerList getHandlers() {
    return handlers;
}

public static HandlerList getHandlerList() {
    return handlers;
}

This block of code makes the EventHandlers contained inside your own event, keeping any unrelated events completely separated.

自定义事件示例

The following example shows how easy it is to create your own "CustomEvent."

import org.bukkit.event.Event;
import org.bukkit.event.HandlerList;

public final class CustomEvent extends Event {
    private static final HandlerList handlers = new HandlerList();
    private String message;

    public CustomEvent(String example) {
        message = example;
    }

    public String getMessage() {
        return message;
    }

    public HandlerList getHandlers() {
        return handlers;
    }

    public static HandlerList getHandlerList() {
        return handlers;
    }
}

调用你的自定义事件

You are in control of creating and calling your events, where you call it is completely up to you. Here's an example

// Create the event here
CustomEvent event = new CustomEvent("Sample Message");
// Call the event
Bukkit.getServer().getPluginManager().callEvent(event);
// Now you do the event
Bukkit.getServer().broadcastMessage(event.getMessage());

Remember: You are in control of your events. If you don't call it, and act upon it, it doesn't happen!

监听一个自定义事件

How do you listen to a custom event you say? Simple, the same way as listening to a normal event!

import org.bukkit.event.Listener;
import org.bukkit.event.EventHandler;

public final class CustomListener implements Listener {
    @EventHandler
    public void normalLogin(CustomEvent event) {
        // Some code here
    }
}

使得你的自定义事件具有可撤销性

If you ever want to make your event cancellable, remember one thing: "implements Cancellable." Just like you would import Listener. It's really that simple, let me show you an example!

import org.bukkit.event.Event;
import org.bukkit.event.HandlerList;
import org.bukkit.event.Cancellable;

public final class CustomEvent extends Event implements Cancellable {
    private static final HandlerList handlers = new HandlerList();
    private String message;
    private boolean cancelled;

    public CustomEvent(String example) {
        message = example;
    }

    public String getMessage() {
        return message;
    }

    public boolean isCancelled() {
        return cancelled;
    }

    public void setCancelled(boolean cancel) {
        cancelled = cancel;
    }

    public HandlerList getHandlers() {
        return handlers;
    }

    public static HandlerList getHandlerList() {
        return handlers;
    }
}

Afterwards, you would check if a plugin had cancelled the event in your code, before processing normally

// Create the event here
CustomEvent event = new CustomEvent("Sample Message");
// Call the event
Bukkit.getServer().getPluginManager().callEvent(event);
// Check if the event is not cancelled
if (!event.isCancelled()) {
    // Now you do the event
    Bukkit.getServer().broadcastMessage(event.getMessage());
}

视频教程

If you would prefer to watch a video tutorial version of this, please click here.

  1. 准确来说是在实现了监听器接口的继承了JavaPlugin的类中注册事件(笑