java - Java 新手 - 自定义事件处理程序

Question

在此示例中(来自 Oracle Site):

// Notify all listeners that have registered interest for
// notification on this event type.  The event instance 
// is lazily created using the parameters passed into 
// the fire method.

protected void fireFooXXX() {
 // Guaranteed to return a non-null array
 Object[] listeners = listenerList.getListenerList();
 // Process the listeners last to first, notifying
 // those that are interested in this event
 for (int i = listeners.length-2; i>=0; i-=2) {
     if (listeners[i]==FooListener.class) {
         // Lazily create the event:
         if (fooEvent == null)
             fooEvent = new FooEvent(this);
         ((FooListener)listeners[i+1]).fooXXX(fooEvent);
     }
 }
}

这是做什么的

listeners[i]==FooListener.class

比较吗？它让我有点失望，因为它似乎将类的实例与类的类型进行了比较。如果它说类似的话，我就能理解它

listeners[i].getClass() == Foolistener.class

但它没有...有人可以在这里启发我吗？提前致谢!

Answer 1

因为 getListenerList() 的文档就是这么说的。

public Object[] getListenerList()

Passes back the event listener list asan array of ListenerType-listenerpairs. Note that for performancereasons, this implementation passesback the actual data structure inwhich the listener data is storedinternally! This method is guaranteedto pass back a non-null array, so thatno null-checking is required in firemethods. A zero-length array of Objectshould be returned if there arecurrently no listeners. WARNING!!!Absolutely NO modification of the datacontained in this array should be made-- if any such manipulation is necessary, it should be done on a copyof the array returned rather than thearray itself.

数组是成对的Type和Instance。因此，索引 0 是在索引 1 处找到的实际监听器的类(或父类(super class))，索引 2 是在 3 处找到的实际监听器的类，依此类推。