ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Display programming
public function addShape(shapeName:String, len:Number):void
{
var newShape:GeometricSprite;
switch (shapeName)
{
case "Triangle":
newShape = new TriangleSprite(len);
break;
}
case "Square":
newShape = new SquareSprite(len);
break;
case "Circle":
newShape = new CircleSprite(len);
break;
}
newShape.alpha = 0.8;
this.addChild(newShape);
Each constructor method calls the drawShape() method, which uses the graphics property of the class (inherited
from the Sprite class) to draw the appropriate vector graphic. For example, the drawShape() method of the
CircleSprite class includes the following code:
this.graphics.clear();
this.graphics.lineStyle(1.0, this.lineColor, 1.0);
this.graphics.beginFill(this.fillColor, 1.0);
var radius:Number = this.size / 2;
this.graphics.drawCircle(radius, radius, radius);
The second to last line of the addShape() function sets the alpha property of the display object (inherited from the
DisplayObject class), so that each display object added to the canvas is slightly transparent, letting the user see the
objects behind it.
The final line of the addChild() method adds the new display object to the child list of the instance of the
DrawingCanvas class, which is already on the display list. This causes the new display object to appear on the Stage.
The interface for the application includes two text fields, selectedSpriteTxt and outputTxt. The text properties of
these text fields are updated with information about the GeometricSprite objects that have been added to the canvas
or selected by the user. The GeometricSprite class handles this information-reporting task by overriding the
toString() method, as follows:
public override function toString():String
{
return this.shapeType + " of size " + this.size + " at " + this.x + ", " + this.y;
}
The shapeType property is set to the appropriate value in the constructor method of each GeometricSprite subclass.
For example, the toString() method might return the following value for a CircleSprite instance recently added to
the DrawingCanvas instance:
Circle of size 50 at 0, 0
The describeChildren() method of the DrawingCanvas class loops through the canvas’s child list, using the
numChildren property (inherited from the DisplayObjectContainer class) to set the limit of the for loop. It generates
a string listing each child, as follows:
Last updated 6/6/2012
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