Question

1. 调度员

public interface EventDispatcher {
    <T> EventListener<T> addEventListener(EventListener<T> l);
    <T> void removeEventListener(EventListener<T> l);
}

执行

public class DefaultEventDispatcher implements EventDispatcher {

@SuppressWarnings("unchecked")
private Map<Class, Set<EventListener>> listeners = new HashMap<Class, Set<EventListener>>();

public void addSupportedEvent(Class eventType) {
    listeners.put(eventType, new HashSet<EventListener>());
}

@Override
public <T> EventListener<T> addEventListener(EventListener<T> l) {
    Set<EventListener> lsts = listeners.get(T); // ****** error: cannot resolve T
    if (lsts == null) throw new RuntimeException("Unsupported event type");
    if (!lsts.add(l)) throw new RuntimeException("Listener already added");
    return l;
}

@Override
public <T> void removeEventListener(EventListener<T> l) {
    Set<EventListener> lsts = listeners.get(T); // ************* same error
    if (lsts == null) throw new RuntimeException("Unsupported event type");
    if (!lsts.remove(l)) throw new RuntimeException("Listener is not here");
}

}

使用

    EventListener<ShapeAddEvent> l = addEventListener(new EventListener<ShapeAddEvent>() {
        @Override
        public void onEvent(ShapeAddEvent event) {
            // TODO Auto-generated method stub

        }
    });
    removeEventListener(l);

我用上文(执行中)的评论标明了两个错误。是否有办法及时获取这些信息?

Answer 1

无,你可以暂时提一下T。

rel=“nofollow noretinger”>http://java.sun.com/docs/books/tutorial/java/generics/erasure.html

update
But something like this would achieve similar effect

abstract class EventListener<T> {
    private Class<T> type;
    EventListener(Class<T> type) {
        this.type = type;
    }
    Class<T> getType() {
        return type;
    }

    abstract void onEvent(T t);
}

创建听众

EventListener<String> e = new EventListener<String>(String.class) {
    public void onEvent(String event) {
    }
};
e.getType();

Answer 2

You can t do it in the approach you are trying, due to erasure. However, with a little change in the design I believe you can achieve what you need. Consider adding the following method to EventListener interface:

public Class<T> getEventClass();

每次活动的执行都必须说明它所从事活动的类别(我假设T是某种事件)。现在,你可以在你的添加方法中使用这种方法,并确定操作时间的类型。

友情链接