When you create a movie clip instance
in a Flash Professional document, the movie clip
has its own timeline. Every movie clip symbol has its own timeline.
The movie clip’s timeline is nested inside the main timeline of
the document. You can also nest a movie clip instance inside another
movie clip symbol.
When a movie clip is created
inside a Flash Professional document, or nested inside
another movie clip, it becomes a child of that document or movie
clip, which becomes the parent. Relationships between nested movie
clips are hierarchical: modifications made to the parent affect
the child. The root Timeline for each level is the parent of all
the movie clips on its level, and because it is the top-most Timeline,
it has no parent. In the Movie Explorer panel, you can view the hierarchy
of nested movie clips in a document by choosing Show Symbol Definitions
from the panel menu.
To understand movie clip hierarchy,
consider the hierarchy on a computer: the hard disk has a root directory
(or folder) and subdirectories. The root directory is analogous
to the main (or root) Timeline of a Flash Professional document:
it is the parent of everything else. The subdirectories are analogous
to movie clips.
You can use the movie clip hierarchy in Flash Professional to
organize related objects. For example, you could create a Flash Professional document containing a car that
moves across the Stage. You can use a movie clip symbol to represent the
car and set up a motion tween to move it across the Stage.
To add wheels that rotate, you can create a movie clip for a
car wheel, and create two instances of this movie clip, named frontWheel and backWheel.
Then you can place the wheels on the car movie clip’s Timeline—not
on the main Timeline. As children of car, frontWheel and backWheel are
affected by any changes made to car; they move
with the car as it tweens across the Stage.
To make both wheel instances spin, you can set up a motion tween
that rotates the wheel symbol. Even after you change frontWheel and backWheel,
they continue to be affected by the tween on their parent movie
clip, car; the wheels spin, but they also move
with the parent movie clip car across the Stage.