事件

定义和触发事件；创建响应事件的侦听程序

事件是发生涉及对象的某些更改或操作时的通知广播。侦听程序定义在发生特定事件时执行的函数。类可以定义和触发事件。当代码访问对象属性时，MATLAB^® 可以触发预定义的事件。

函数

`event.EventData`	事件数据的基类
`event.ClassInstanceEvent`	`InstanceCreated` 和 `InstanceDestroyed` 事件的事件数据
`event.listener`	定义侦听程序对象的类
`event.PropertyEvent`	属性事件的数据
`event.proplistener`	定义属性事件的侦听程序对象

事件和侦听程序概述
使用事件和侦听程序发送和响应消息。
事件和侦听程序概念
事件向所有注册的侦听程序广播通知，并将特定于事件的数据传递给侦听程序回调函数。
事件和侦听程序语法
这些代码示例说明如何定义事件和侦听程序。
Event Access List
Specify a list of classes that can be notified of a specific event.
Event Attributes
Control access to events by setting event attributes.

Listener Callback Syntax
Specify listener callbacks using function handles.
Callback Execution
Errors in listener callbacks do not prevent execution of other listeners. However, the order of listener execution is not defined.
Listener Lifecycle
MATLAB manages the lifecycle of listeners. For greater control of listener lifecycle, constructor listener objects using the listener method instead of addlistener.
Determine If Event Has Listeners
You can determine if there are listeners defined for a specific event and event source.

侦听对属性值的更改
MATLAB 为所有属性定义了在执行 set 和 get 前后触发的事件。
Assignment When Property Value Is Unchanged
Prevent the triggering of property events when values do not change using the property AbortSet attribute.

Define Custom Event Data
Redefine the event data that MATLAB passes to listeners when an event is triggered.
Observe Changes to Property Values
Listeners can respond to changes in the value of properties using predefined property events.
Implement Property Set Listener
Listeners can respond to changes in property values before or after MATLAB assigns the value.
Techniques for Using Events and Listeners
This example shows how to enable and disable listener execution using context menus.
Restore Listeners
You can restore property listeners from the loadobj method.