User Guide

190 ComboBox component
Description
Event; broadcast to all registered listeners when the drop-down list is completely open.
Using the dispatcher/listener event model, a component instance (
comboBoxInstance)
dispatches an event (in this case,
open) and the event is handled by a function, also called a
handler, on a listener object (
listenerObject) that you create. You define a method with the
same name as the event on the listener object; the method is called when the event is
triggered. When the event is triggered, it automatically passes an event object (
eventObject)
to the listener object method. Each event object has properties that contain information about
the event. You can use these properties to write code that handles the event. For more
information, see “EventDispatcher class” on page 499.
Finally, you call the
addEventListener() method on the component instance that
broadcasts the event to register the listener with the instance. When the instance dispatches
the event, the listener is called.
Example
With a ComboBox component instance my_cb on the Stage, the following example sends a
message to the Output panel when the drop-down list opens or closes:
// Add Items to List.
my_cb.addItem({data:1, label:"First Item"});
my_cb.addItem({data:2, label:"Second Item"});
// Create Listener Object.
var cbListener:Object = new Object();
cbListener.open = function(evt_obj:Object) {
trace("The ComboBox has opened.");
}
cbListener.close = function(evt_obj:Object){
trace("The ComboBox has closed.");
}
// Add Listener.
my_cb.addEventListener("open", cbListener);
my_cb.addEventListener("close", cbListener);
// Open the combo box.
my_cb.open();
See also
ComboBox.close, EventDispatcher.addEventListener()