[英]When a listener is removed, is it okay that the event be called on that listener one more time?
Most people use a ConcurrentLinkedQueue or CopyOnWriteArrayList to collect listeners and notify them when something happens. 大多数人使用ConcurrentLinkedQueue或CopyOnWriteArrayList来收集侦听器,并在发生事件时通知它们。 The drawback of that is that it is possible that a listener can get a notification while it already unregistered himself.
这样做的缺点是,监听者可能会在自己未注册的情况下获得通知。 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.
如果管理器(集合,...,给它命名)正在迭代侦听器的集合并且某些侦听器在该迭代期间注销了自己,则会发生这种情况。
So, the 'remove listener' contract is broken. 因此,“删除侦听器”合同被打破。 Would you consider that as a problem?
您认为这是一个问题吗?
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. 即使您检查了侦听器是否仍已注册,在多线程环境中,您仍不确定在调用它之前仍在注册它。 Even for non-multithreaded situations, the standard implementation is to work on a copy.
即使在非多线程情况下,标准实现也是在副本上工作。
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