Using Event Handler Methods

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Using Event Handler Methods
All standard event handlers have equivalent event handler methods (also called callback
functions or function callbacks). For example:

on (press) is buttonName_btn.onPress or movieClipName_mc.onPress



on (release) is buttonName_btn.onRelease or movieClipName_mc.onRelease



on (enterFrame) is movieClipName_mc.onEnterFrame


In addition, these event handler methods exist but have no standard event equivalents:
Buttons/Movie Clips

nameOfClipOrButton.onKillFocus

nameOfClipOrButton.onSetFocus


Sound Objects

nameOfSoundObject.onLoad

nameOfSoundObject.onSoundComplete

nameOfSoundObject.onID3


Text Fields

nameOfTextField.onChanged

nameOfTextField.onKillFocus

nameOfTextField.onScroller

nameOfTextField.onSetFocus


Stage Objects

Stage.onLoad


StyleSheet Objects

nameOfStyleSheet.onResize


ContextMenu Objects

nameOfContextMenu.onSelect

ContextMenuItem Objects

nameOfContextMenuItem.onSelect


LoadVars Objects

nameOfLoadVarsObject.onLoad


SharedObject Objects

nameOfSharedObject.onStatus


LocalConnection Objects

nameOfLocalConnection.allowDomain

nameOfLocalConnection.onStatus


NetConnection Objects

nameOfNetConnection.onStatus


NetStream Objects

nameOfNetStream.onStatus

XML Objects

nameOfXMLObject.onData

nameOfXMLObject.onLoad


XMLSocket Objects

nameOfXMLSocketObject.onClose

nameOfXMLSocketObject.onConnect

nameOfXMLSocketObject.onData

nameOfXMLSocketObject.onXML


You can use numerous events to trigger a script. Because some of these objects are
intangible (for example, Sound, LoadVars, and XML), defining event handler methods
on a keyframe of the timeline is the only way to execute a script when an event occurs in
relation to that object (in contrast to buttons and movie clip instances, which you can
select on the stage and to which you can directly attach scripts).
NOTE
We will discuss and use many of these event handler methods throughout this book. For
more information, see the ActionScript dictionary.

By attaching a script to a button or movie clip instance using a regular event handler, you

pretty much lock down not only what happens when an event occurs but also the events
that actually trigger execution of a script. For example:

on (press) {

gotoAndPlay(5);

}


If you were to attach this script to a button, the button would react only to the press event,
performing a single action when that event occurred. To give you an idea of the power
and flexibility of event handler methods, assume there's a button instance on the stage
named myButton_btn. By placing the following script on Frame 1 of the main timeline
(assuming the button exists at that frame), you define how that button will react to certain
events:

myButton_btn.onPress = function() {

stopAllSounds();

}

myButton_btn.onRelease = function() {

myMovieClip_mc._xscale = 50;

}

When pressed, the button will halt all sounds; when released, it will horizontally scale
myMovieClip_mc to 50 percent of its original size.
However, by moving that timeline to Frame 2—which contains the following script
(assuming the button exists at Frame 2)—you would change the button's function
completely:

myButton_btn.onPress = null

myButton_btn.onRelease = null

myButton_btn.onRollOver = function() {

stopAllSounds();

}

myButton_btn.onRollOut = function() {

myMovieClip_mc._xscale = 50;

}