多目标点弹性运动

package com.aswing2.cn
{
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.events.MouseEvent;

    public class MultiSpring extends Sprite
    {
        private var ball:Ball;
        private var handle:Array=[];
        public var numhandle:int=3;
        private var spring:Number=0.1;
        private var fri:Number=.8;


        public function MultiSpring()
        {
            super();
            init();
        }

        private function init():void
        {
            ball=new Ball;
            
            this.addChild(ball);
            
            for (var i:int=0; i < numhandle; i++)
            {
                var hand:Ball=new Ball;

                hand.x=Math.random() * stage.stageWidth;
                hand.y=Math.random() * stage.stageHeight;

                this.addChild(hand);
                handle.push(hand);

                hand.addEventListener(MouseEvent.MOUSE_DOWN, onDown);
            }

            addEventListener(Event.ENTER_FRAME, onEnterFrame);
            addEventListener(MouseEvent.MOUSE_UP, onUp);
        }

        private function onEnterFrame(e:Event):void
        {
            for (var i:int=0; i < numhandle; i++)
            {
                var hand:Ball=handle[i] as Ball;

                var dx:Number=hand.x - ball.x;
                var dy:Number=hand.y - ball.y;

                ball.vx+=dx * spring;
                ball.vy+=dy * spring;
            }

            ball.vx*=fri;
            ball.vy*=fri;

            ball.x+=ball.vx;
            ball.y+=ball.vy;

            graphics.clear();
            graphics.lineStyle(1);

            for (i=0; i < numhandle; i++)
            {
                graphics.moveTo(ball.x, ball.y);
                graphics.lineTo(handle[i].x, handle[i].y);
            }

        }

        private function onDown(e:MouseEvent):void
        {
            e.target.startDrag(true);
        }

        private function onUp(e:MouseEvent):void
        {
            e.target.stopDrag();
        }

    }
}