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Events

Define and trigger events; create listeners that respond to events

Events are notices broadcast when some change or action occurs involving an object. Listeners define functions that execute when specific events occur. Classes can define and trigger events. MATLAB® can trigger predefined events when code accesses object properties.

Functions

eventsEvent names
handle.notifyNotify listeners that event is occurring
handle.addlistenerCreate event listener bound to event source
handle.listenerCreate event listener without binding to event source
event.hasListenerDetermine if listeners exist for event

Classes

event.EventDataBase class for event data
event.listenerClass defining listener objects
event.PropertyEventData for property events
event.proplistenerDefine listener object for property events

Topics

Events and Listeners

Overview Events and Listeners

Use events and listeners to send and respond to messages.

Event and Listener Concepts

Events broadcast notifications to all registered listener and pass event-specific data to listener callback functions.

Events and Listeners Syntax

These code examples show how to define events and listeners

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.

Implementing Listeners

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 handle.listener method instead of handle.addlistener.

Determine If Event Has Listeners

You can determine if there are listeners defined for a specific event and event source.

Property Listeners

Listen for Changes to Property Values

MATLAB defines pre and post set and get events for all properties.

Assignment When Property Value Unchanged

Prevent the triggering of property events when values do not change using the property AbortSet attribute.

Samples of Events and Listeners

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.

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