- user events
Actions taken by the user (e.g., a mouseclick or a keystroke)
- system events
Things that happen as part of the internal playback of a movie (e.g.,
a movie clip appearing on stage or a series of variables loading from
an external file)
ActionScript does not distinguish syntactically between user events
and system events. An event triggered internally by a movie is no
less palpable than a user's mouseclick. While we might not
normally think of, say, a movie clip's removal from the Stage
as a noteworthy "event," being able to react to system
events gives us great control over a movie.
ActionScript events may also be categorized more practically
according to the object to which they pertain. All events happen
relative to some object in the Flash environment. That is, the
interpreter doesn't just say "The user clicked"; it
says, "The user clicked this button"
or "The user clicked while this movie clip
was on stage." And the interpreter doesn't say,
"Data was received"; it says, "This movie
clip received some data." We define the code that
responds to events on the objects to which the events relate.
The ActionScript objects that can receive events are:
As we'll see throughout this chapter, ActionScript actually has
two different event implementations: one for events that relate to
movie clips and buttons, and one for all other kinds of objects.
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10.2. Event-Based AsynchronousCode Execution |  | 10.4. Event Handlers |