Objects that implement this interface can receive notification that an event has occurred, and they can respond to queries about the event.

实现此接口的对象可以接收事件已发生的通知，并且可以响应有关该事件的查询。

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This strategy means that the control does not need to maintain a list of target objects for event notification-the delegate handles all registration and notification.

此策略意味着控件不需要维护事件通知的目标对象列表——委托可处理所有的注册和通知。

youdao

This strategy means that the control does not need to maintain a list of target objects for event notification-the delegate handles all registration and notification.

此策略意味着控件不需要维护事件通知的目标对象列表——委托可处理所有的注册和通知。

youdao