模拟喷泉粒子

 

1.用ball构建单个粒子

package 
{
    import flash.display.Sprite;

    public class Ball extends Sprite
    {
        public var radius:Number;
        public var color:uint;
        public var vx:Number=0;
        public var vy:Number=0;

        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.构建喷泉粒子发射

 

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

    public class Fountain extends Sprite
    {
        private var count:int=300;
        private var gravity:Number=0.5;
        private var balls:Array;

        public function Fountain ()
        {
            Init ();
        }
        public function Init ():void
        {
            stage.scaleMode=StageScaleMode.NO_SCALE;
            stage.align=StageAlign.TOP_LEFT;
            balls=new Array();
            for (var i:int=0; i<count; i++)
            {
                var ball:Ball=new Ball(2,Math.random() * 0xffffff);
                InitPosition(ball);
                InitSpeed (ball);
                addChild (ball);
                balls.push (ball);
            }
            addEventListener (Event.ENTER_FRAME,Active);
        }
        private function Active (e:Event):void
        {
            for (var i:int =0; i<balls.length; i++)
            {
                var ball:Ball=Ball(balls[i]);//var ball:Ball=balls[i];也可以
                ball.vy+=gravity;
                ball.x+=ball.vx;
                ball.y+=ball.vy;

               //边界再生
                if (ball.x-ball.radius>stage.stageWidth || 
                    ball.x+ball.radius<0 ||
                    ball.y-ball.radius>stage.stageHeight || 
                    ball.y+ball.radius<0)
                 {
                    InitPosition(ball);
                    InitSpeed (ball);
                 }
            }
        }
        private function InitPosition(ball:Ball):void
        {
            ball.x=stage.stageWidth/2;
            ball.y=stage.stageHeight;
        }
        private function InitSpeed (ball:Ball):void
        {
            ball.vx=Math.random() *6-3;
            ball.vy=(-10)*Math.random() -10;
        }
    }
}