488 ActionScript classes
You must first create a generic object that has two properties, x and y. These x and y values
(and they must be called x and y) are called the local coordinates because they relate to the
top-left corner of the movie clip. The x property represents the horizontal offset from the top-
left corner of the movie clip. In other words, it represents how far to the right the point lies.
For example, if x = 50, the point lies 50 pixels to the right of the top-left corner. The y
property represents the vertical offset from the top-left corner of the movie clip. In other
words, it represents how far down the point lies. For example, if y = 20, the point lies 20 pixels
below the top-left corner. The following code creates a generic object with these coordinates.
var myPoint:Object = new Object();
myPoint.x = 50;
myPoint.y = 20;
Alternatively, you can create the object and assign the values at the same time with a literal
Object value.
var myPoint:Object = {x:50, y:20};
After you create a point object with local coordinates, you can convert the coordinates to
global coordinates. The
localToGlobal() method doesn't return a value because it changes
the values of x and y in the generic object that you send as the parameter. It changes them
from values relative to a specific movie clip (local coordinates) to values relative to the Stage
(global coordinates).
For example, if you create a movie clip that is positioned at the point (_x:100, _y:100), and
you pass a local point representing a point near the top-left corner of the movie clip (x:10,
y:10) to the
localToGlobal() method, the method should convert the x and y values to
global coordinates, which in this case is (x:110, y:110). This conversion occurs because the x
and y coordinates are now expressed relative to the top-left corner of the Stage rather than the
top-left corner of your movie clip.
The movie clip coordinates were expressed using
_x and _y, because those are the MovieClip
properties that you use to set the x and y values for MovieClips. However, your generic object
uses
x and y without the underscore. The following code converts the x and y coordinates to
global coordinates:
var myPoint:Object = {x:10, y:10}; // create your generic point object
this.createEmptyMovieClip("myMovieClip", this.getNextHighestDepth());
myMovieClip._x = 100; // _x for movieclip x position
myMovieClip._y = 100; // _y for movieclip y position
myMovieClip.localToGlobal(myPoint);
trace ("x: " + myPoint.x); // output: 110
trace ("y: " + myPoint.y); // output: 110
You can extend the methods and event handlers of the MovieClip class by creating a subclass.
Availability: ActionScript 1.0; Flash Lite 2.0
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