The ActionScript Drawing API, introduced
in
Flash MX, allows you to draw inside movie clips at runtime. The
handful of primitive Drawing API methods let you draw almost any
imaginable shape, as demonstrated in this chapter’s
recipes. The Drawing API uses a pen
metaphor,
akin to a CAD line plotter, in which an imaginary pen is moved around
the drawing canvas. The pen’s stroke attributes can
be customized, and the pen can draw lines or curves. Shapes can be
empty or filled. Note that the coordinates are relative to the movie
clip’s registration point. Use the
MovieClip.
_x
and
MovieClip.
_y
properties
to reposition the entire clip on the Stage.
The Drawing API is a subset
of
the methods of the MovieClip
class, and
therefore most of the recipes in this chapter are implemented as
custom methods of the MovieClip
class. You
should add these custom methods to an ActionScript file named
DrawingMethods.as (or download
the final version from the URL cited in the Preface) and include it in your own projects.
All paths and shapes drawn
with the
Drawing API are drawn inside the movie clip from which the methods
are invoked. For this reason the createEmptyMovieClip(
)
method is often used in conjunction
with any runtime drawing. The
createEmptyMovieClip( )
method does just what
its name implies—it creates a new, empty movie clip nested
within the movie clip on which it is invoked:
// Create a new movie clip named myMovieClip_mc
with a depth of 1 inside of _root.
_root.createEmptyMovieClip("myMovieClip_mc", 1);
You can specify the pen
style
with the MovieClip
class’s lineStyle( )
method and
draw lines and curves with
the lineTo( )
and curveTo( )
methods.
The pen can be repositioned without drawing
anything
by
calling
the
moveTo( )
method.
Many of these
recipes use the
custom Math.degToRad( )
method from Recipe 5.12 to convert angles from degrees to
radians. Your DrawingMethods.as
file should
include Math.as
from Chapter 5 by using this statement on the first line:
#include "Math.as"
Also see Recipe 5.13 and Recipe 5.14 for an explanation of how to calculate X and Y coordinates using trigonometry, which is called for in some of this chapter’s recipes.
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