缩放粒子

除了可以改变粒子的运动速度之外，还可以改变它的大小，通过设置它的growX和growY属性就可以达到目的。

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

	[SWF(width="800",height="600",backgroundColor="0xffffff",frameRate="31")]
	public class ParticleGrow extends Sprite{
		private var numbers:Number = 20;
		private var particles:Array;

		public function ParticleGrow(){
			particles=new Array();
			stage.addEventListener(Event.ENTER_FRAME, onEnterFrame);
		}

		private function onEnterFrame(e:Event):void{
			if(particles.length &lt; numbers){
				var ball:Ball=new Ball(12, 0x00ff00, 1, 0x000000, 1);
				addChild(ball);
				ball.xVelocity=Math.random() * 20 - 10;
				ball.yVelocity=Math.random() * 20 - 10;
				ball.gravity=0.9;
				ball.growX = 1.05;
				ball.growY = 1.05;
				ball.x=stage.stageWidth/2;
				ball.y=stage.stageHeight/4;
				particles.push(ball);
			}
			for (var i:int=0; i &lt; particles.length; i++){
				var particle:Ball=particles[i];
				particle.update();
				if (particle.x - particle.radius &gt; stage.stageWidth || particle.x + particle.radius &lt; 0 || particle.y - particle.radius &gt; stage.stageHeight || particle.y + particle.radius &lt; 0){
					particle.xVelocity=Math.random() * 20 - 10;
					particle.yVelocity=Math.random() * 20 - 10;
					particle.x=stage.stageWidth / 2;
					particle.y=stage.stageHeight / 4;
					particle.scaleX = particle.scaleY = 1;
				}
			}
		}
	}
}

代码将ball粒子的growX和growY设置为1.05，从而实现逐帧放大的效果。当超过环境边界之后，再将它的scaleX和scaleY设置设置为1，恢复它原始的大小。