Tài liệu Understanding Multiple Timelines doc

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Understanding Multiple Timelines
Every project includes a main timeline. But projects also include movie clip instances
that have timelines of their own. You can use the loadMovie() action to add external
SWFs to a project, thereby adding even more timelines. Therefore, a single project can
have many separate timelines, all of which can act independently, with their own
variables, properties, objects, and functions.
However, these timelines can also work together: one timeline can control another. In
fact, any timeline present in a scene can tell another present timeline to do something.
(Timelines are considered present as long as they exist in the Player movie window. If a
movie clip instance appears in your movie for 40 frames, it's considered present—and
targetable—only during those 40 frames.)
The communication lines for these movie elements are provided by target paths—
addresses to objects (movie clip instances, for example) that describe the overall area in
which the object exists and narrow that area with each subsequent level. To better
understand this concept, take a look at the following example. The target path to one of
your authors would look something like this:

This target path contains four levels, separated by dots, with each subsequent level
smaller in size and scope until you reach the target: Derek Franklin. This is what's known
as an absolute path—the complete and absolute location of Derek Franklin here on Earth.
If someone in Australia wanted to communicate with Derek (using a hypothetical
communication system), he or she would use this absolute address.

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In addition to absolute target paths, there are also relative target paths—a slightly trickier
concept to understand, so let's consider an example. If someone in Bloomington wanted
to communicate with Derek (who is also in Bloomington), a lot of the information
included in the absolute path would be unnecessary (country, state, city) because both
people exist in a position relative to one another: Bloomington. The following relative
path would suffice:

DerekFranklin


Relative paths are powerful because they enable you to script a "chunk" of timelines to
work together, in a unique way, based on their relationship. As long as these timelines'
relative relationship remains the same, they'll continue to work together—even if you
move them to another location in your project, or to another project altogether.
Think of a Flash project as a hierarchy of movies, where timelines exist within other
timelines and where the main, or root, movie serves as the starting point (see the section
titled "Targeting the Main Movie
" on page 114). When timelines exist in a hierarchical
structure, as they do in Flash projects, it is critical that you understand how to address, or
target, a timeline using target paths.

You will use target paths not only to alter timelines but to access their data, functions,
objects, and so on.

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