package {
 
    import flash.display.Sprite;
    import flash.events.MouseEvent;
    import flash.events.Event;
 
    public class ArrayChain extends Sprite {
 
        var arrBall:Array;      
        var spring:Number=0.12;
        var firstBall:Ball;
        var gravity:Number=6;
        var friction:Number=0.8;
 
        public function ArrayChain() {          
            init();
        }
         
        private function init():void {
            arrBall=new Array(5);
            for (var i:uint=0,j:uint=arrBall.length; i<j; i++) {
                arrBall[i]=new Ball(10,Math.random()*0xffffff);
                addChild(arrBall[i]);
            }
            firstBall=arrBall[0];
            firstBall.x=Math.random()*stage.stageWidth;
            firstBall.y=Math.random()*stage.stageHeight;    
            addEventListener(Event.ENTER_FRAME,EnterFrameHandler);
        }
 
        private function EnterFrameHandler(e:Event):void {
            //第一个球以鼠标所在位置为目标做弹性运动
            firstBall.vx += (mouseX - firstBall.x) * spring;
            firstBall.vy += (mouseY - firstBall.y) * spring;
            firstBall.vy+=gravity;
            firstBall.vx*=friction;
            firstBall.vy*=friction;
            firstBall.x+=firstBall.vx;
            firstBall.y+=firstBall.vy;
 
            //准备画连线
            graphics.clear();
            graphics.lineStyle(0.2,0x666666);
            graphics.moveTo(mouseX,mouseY);
            graphics.lineTo(firstBall.x,firstBall.y);
 
            //后面的小球依次以前一个的位置为目标做弹性运动
            for (var i=1,j=arrBall.length; i<j; i++) {
                var ball:Ball=arrBall[i];
                ball.vx += (arrBall[i-1].x-ball.x)*spring;
                ball.vy += (arrBall[i-1].y-ball.y)*spring;
                ball.vy+=gravity;
                ball.vx*=friction;
                ball.vy*=friction;
                ball.x+=ball.vx;
                ball.y+=ball.vy;
                graphics.lineTo(ball.x,ball.y);//画出连线将各球连在一起
            }
        }
    }
 
}