User Guide

630 Chapter 6: Components Dictionary
Usage 2:
listenerObject = new Object();
listenerObject.click = function(eventObject){
...
}
radioButtonGroup.addEventListener("click", listenerObject)
Description
Event; broadcast to all registered listeners when the mouse is clicked (pressed and released) over
the radio button or if the radio button is selected by means of the arrow keys. The event is also
broadcast if the Spacebar or arrow keys are pressed when a radio button group has focus, but none
of the radio buttons in the group are selected.
The first usage example uses an
on() handler and must be attached directly to a RadioButton
instance. The keyword
this, used inside an on() handler attached to a component, refers to the
component instance. For example, the following code, attached to the radio button
myRadioButton, sends “_level0.myRadioButton” to the Output panel:
on(click){
trace(this);
}
The second usage example uses a dispatcher/listener event model. A component instance
(
radioButtonInstance) dispatches an event (in this case, click) 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. The event object has properties that contain
information about the event. You can use these properties to write code that handles the event.
Finally, you call the
EventDispatcher.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.
For more information, see “EventDispatcher class” on page 415.
Example
This example, written on a frame of the Timeline, sends a message to the Output panel when a
radio button in
radioGroup is clicked. The first line of code creates a listener object called form.
The second line defines a function for the
click event on the listener object. Inside the function
is a
trace() statement that uses the event object (eventObj) that is automatically passed to the
function to generate a message. The
target property of an event object is the component that
generated the event. You can access instance properties from the
target property (in this
example, the
RadioButton.selection property is accessed). The last line calls
EventDispatcher.addEventListener() from radioGroup and passes it the click event and
the
form listener object as parameters.
form = new Object();
form.click = function(eventObj){
trace("The selected radio instance is " + eventObj.target.selection);