精灵简单缓动效果

1.构建小球精灵

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.构建缓动动画

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

    public class Earsing extends Sprite
    {
        private var ball:Ball;
        private var earsing:Number=0.2;
        private var targetX:Number=stage.stageWidth/2;
        private var targetY:Number=stage.stageHeight/2;

        public function Earsing ()
        {
            Init ();
        }
        public function Init ():void
        {
            ball=new Ball(20,0xFF0000);
            ball.x=0;
            ball.y=0;
            addChild (ball);
            ball.addEventListener (MouseEvent.MOUSE_DOWN,MouseDown);
            addEventListener (Event.ENTER_FRAME,EnterFrame);
        }
        public function MouseDown (e:MouseEvent):void
        {
            stage.addEventListener (MouseEvent.MOUSE_UP,MouseUp);
            removeEventListener (Event.ENTER_FRAME,EnterFrame);
            ball.startDrag ();
        }
        public function MouseUp (e:MouseEvent):void
        {
            stage.removeEventListener (MouseEvent.MOUSE_UP,MouseUp);
            addEventListener (Event.ENTER_FRAME,EnterFrame);
            ball.stopDrag ();
        }
        public function EnterFrame (e:Event):void
        {
            var dx:Number=targetX-ball.x;
            var dy:Number=targetY-ball.y;
            var distance:Number=Math.sqrt(dx*dx+dy*dy);
            //停止缓动
            if (distance<1)
            {
                targetX=ball.x;
                targetY=ball.y;
                removeEventListener (Event.ENTER_FRAME,EnterFrame);
            }
            else
            {
                ball.x+=dx*earsing;
                ball.y+=dy*earsing;
            }
        }
    }
}