childrenの重なり順を変える

/**
 * Copyright tepe ( http://wonderfl.net/user/tepe )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/zHrn
 */

package {
    import flash.display.*;
    import flash.events.*;
    import flash.text.*;
    
    public class FlashTest extends Sprite {
        private var tf:TextField = new TextField();
        public function FlashTest() {
            // write as3 code here..
            
            this.graphics.beginFill(0xffffff);
            this.graphics.drawRect(0,0,455,455);
            this.graphics.endFill();
            stage.addEventListener(MouseEvent.MOUSE_DOWN,add);
            addChild(tf);
            tf.text = "test";
        }
        private function add(e:MouseEvent):void{
            if(_sw)return;
            tf.text = mouseX.toString();
            var s:Sprite = new Sprite();
            stage.addChild(s);
            s.addEventListener(MouseEvent.MOUSE_OVER,onOver);
            s.addEventListener(MouseEvent.MOUSE_OUT,rollOut);
            s.addEventListener(MouseEvent.MOUSE_DOWN,onDrag);
            s.addEventListener(MouseEvent.MOUSE_UP,onDrop);
            s.x = this.mouseX;
            s.y = this.mouseY;
            s.graphics.lineStyle(1,0); 
            s.graphics.beginFill(Math.random()*0xffffff);
            s.graphics.drawCircle(0,0,30);
            s.graphics.endFill();
            var s2:Sprite = new Sprite();
            s.addChild(s2);
            s2.graphics.beginFill(0x0);
            s2.graphics.drawCircle(0,0,10);
            s2.graphics.endFill();
            _sw=true;
            
        }
        private var _sw:Boolean;
        private function onOver(e:MouseEvent):void{
            _sw=true;
            tf.text = e.currentTarget.name;
            
        }
        private function rollOut(e:MouseEvent):void{
            _sw=false;
        }

    

        
    private function onDrag(e:MouseEvent):void{
        e.currentTarget.startDrag();
        tf.text = e.currentTarget.parent.getChildIndex(e.currentTarget);

        //this.startDrag();
        e.currentTarget.parent.setChildIndex(e.currentTarget,e.currentTarget.parent.numChildren-1); //並べ替え
        //var s:DisplayObject = stage.getChildByName(e.currentTarget.name);//ディスプレイオブジェクト取得
        //stage.setChildIndex(s,stage.numChildren-1); //並べ替え
        tf.appendText(" -> "+e.currentTarget.parent.getChildIndex(e.currentTarget));
    }
    private function onDrop(e:MouseEvent):void{
        e.currentTarget.stopDrag();
    }


    }
}