MACROMEDIA FLASH MX 2004 - ACTIONSCRIPT - Using Button and Movie Clip Event Handlers

Using button and movie clip event handlers 87
Using button and movie clip event handlers
You can attach event handlers directly to a button or movie clip instance by using the
onClipEvent() and on() handlers. The onClipEvent() handler handles movie clip events, and
the
on() handler handles button events. You can also use on() with movie clips to create movie
clips that receive button events. For more information, see “Creating movie clips with button
states” on page 88.
To u se a n
on() or onClipEvent() handler, attach it directly to an instance of a button or movie
clip on the Stage and specify the event you want to handle for that instance. For example, the
following
on() event handler executes whenever the user clicks the button that the handler is
attached to.
on(press) {
trace("Thanks for pressing me.");
}
You can specify two or more events for each on() handler, separated by commas. The
ActionScript in a handler executes when either of the events specified by the handler occurs. For
example, the following
on() handler attached to a button executes whenever the mouse rolls over
out of the button.
on(rollOver, rollOut) {
trace("You rolled over, or rolled out");
}
You can also attach more than one handler to an object if you want different scripts to run when
different events occur. For example, you could attach the following
onClipEvent() handlers to
the same movie clip instance. The first executes when the movie clip first loads (or appears on the
Stage); the second executes when the movie clip is unloaded from the Stage.
onClipEvent(load) {
trace("I've loaded");
}
onClipEvent (unload) {
trace("I've unloaded");
}
For a complete list of events supported by the on() and onClipEvent() event handlers, see on()
on page 583 and
onClipEvent() on page 584.
Event handling through
on() and onClipEvent() doesn’t conflict with event handling through
event handler methods that you define. For example, suppose you have a button in a SWF file;
the button can have an
on(press) handler that tells the SWF file to play, and the same button
can have an onPress method, for which you define a function that tells an object on the Stage to
rotate. When the button is clicked, the SWF file plays and the object rotates. Depending on your
preference, you can use
on() and onClipEvent(), event handler methods, or both types of event
handling. However, the scope of variables and objects in on() and onClipEvent() handlers is
different than in event handler and event listeners. (See “Event handler scope” on page 88.)
You can attach
onClipEvent() and on() only to movie clip instances that have been placed on
the Stage during authoring. You cannot attach
onClipEvent() or on() to movie clip instances
that are created at runtime (using the
attachMovie() method, for example). To attach event
handlers to objects created at runtime, use event handler methods or event listeners. (See “Using
event handler methods” on page 83 and “Using event listeners” on page 85.)