何时使用EventListenerList而不是一般的收听器集合 [英] When to use EventListenerList instead of a general collection of listeners

问题描述

当我学习如何在Java中触发事件时，我熟悉了EventListenerList。当我创建自己的监听器时，我编写监听器，所以它扩展了EventListener，我将它们存储在一个EventListenerList中，我的fire方法将通过这样的事件监听器：

When I learned how to fire events in Java, I became familiar with EventListenerList. When I create my own listeners, I write the listener so it extends EventListener, I store them in an EventListenerList, and my fire method would go through the event listeners like this:

protected void fireChangeOccurred(Change change) {
    Object[] listeners = listenerList.getListenerList();
    for (int i = listeners.length-2; i>=0; i-=2) {
        if (listeners[i]==ChangeListener.class) {
            ((ChangeListener)listeners[i+1]).changeOccurred(change);
        }
    }
}

现在我正在审核代码只要将侦听器放入HashMap（可以是任何集合），监听器接口就不会扩展EventListener，并且fire方法如下所示：

Now I'm reviewing code that simply puts listeners into a HashMap (could be any collection), the listener interface does not extend EventListener, and the fire method looks like this:

protected void fireChangeOccurred(Change change) {
    for (ChangeListener listener : listeners) {
        listener.changeOccurred(change);
    }
}

替代使用EventListenerList有什么好处？只是维护我自己的监听器列表？它是否真的只关心监听器是否在一个Swing组件 - 事件调度线程是否重要？

What are the advantages of using EventListenerList instead of just maintaining my own list of listeners? Does it really only matter if the listeners are in a Swing component - does it matter for the Event Dispatch Thread?

推荐答案

对我来说， EventListenerList 的主要优点是如果类具有（或可能拥有）多个类型的监听器。许多Swing组件都做;你正在审查的一个可能不是。第二个例子较短，但它具有隐式设计限制。

To me, the major advantage of EventListenerList is if the containing class has (or may have) more than one type of listener. Many Swing components do; the one you're reviewing may not. The second example is shorter, but it has that implicit design limitation.

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