小球回弹模拟

 1.构建小球

Ball.as

package 
{
    import flash.display.Sprite;

    public class Ball extends Sprite
    {
        public var radius:Number;
        public var color:uint;

        public function Ball (radius:Number,color:uint)
        {
            this.radius=radius;
            this.color=color;
            Init ();
        }
        public function Init ():void
        {
            graphics.beginFill (color);
            graphics.drawCircle (0,0,radius);
            graphics.endFill ();
        }
    }
}

 

2.构建回弹动画

Bouncing.as
package 
{
    import flash.events.Event;
    import flash.display.Sprite;
    import flash.display.StageScaleMode;
    import flash.display.StageAlign;

    public class Bouncing extends Sprite
    {
        private var ball:Ball;
        private var vx:Number;
        private var vy:Number;
        private var radius:Number=20;

        public function Bouncing ()
        {
            Init ();
        }
        public function Init ():void
        {
            stage.scaleMode=StageScaleMode.NO_SCALE;
            stage.align=StageAlign.TOP_LEFT;

            ball=new Ball(radius,0xff0000);
            ball.x=stage.stageWidth/2;
            ball.y=stage.stageHeight/2;
            vx=20*Math.random()-10;
            vy=20*Math.random()-10;
            addChild (ball);
            addEventListener (Event.ENTER_FRAME,Active);
        }
        private function Active (e:Event):void
        {
            ball.x+=vx;
            ball.y+=vy;

            if (ball.x<radius)
            {
                ball.x=radius;
                vx*=-1;
            }
            if (ball.x>stage.stageWidth-radius)
            {
                ball.x=stage.stageWidth-radius;
                vx*=-1;
            }
            if (ball.y<radius)
            {
                ball.y=radius;
                vy*=-1;
            }
            if (ball.y>stage.stageHeight-radius)
            {
                ball.y=stage.stageHeight-radius;
                vy*=-1;
            }
        }
    }
}