删除侦听器后，可以再在该侦听器上调用该事件一次吗? [英] When a listener is removed, is it okay that the event be called on that listener one more time?

问题描述

大多数人使用ConcurrentLinkedQueue或CopyOnWriteArrayList来收集侦听器，并在发生某些情况时通知他们.这样做的缺点是，侦听程序可能会在自己未注册的情况下获得通知.如果管理器(集合，...，给它命名)正在遍历侦听器的集合，并且在该迭代过程中某些侦听器取消了自己的注册，则会发生这种情况.

Most people use a ConcurrentLinkedQueue or CopyOnWriteArrayList to collect listeners and notify them when something happens. The drawback of that is that it is possible that a listener can get a notification while it already unregistered himself. This happens if the manager (collection, ..., give it a name) is iterating over the collection of listeners and some listener unregisters himself during that iteration.

因此，删除侦听器"合同被打破.您认为这是一个问题吗?

So, the 'remove listener' contract is broken. Would you consider that as a problem?

推荐答案

即使您已检查侦听器是否仍已注册，在多线程环境中，您仍无法确定在调用它时仍已注册该侦听器.即使在非多线程情况下，标准实现也是在副本上工作.

Even if you checked the listener was still registered, in a multithreaded environment you still couldn't be sure it was still registered by the time you call it. Even for non-multithreaded situations, the standard implementation is to work on a copy.

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