as3使用scrollRect来实现内容滚动

package {

import flash.display.Sprite;
import flash.geom.Rectangle;
import flash.events.MouseEvent;
import flash.events.Event;

public class SampleScrollRect extends Sprite {
private var circle : Sprite;
private var slider : Sprite;

public function SampleScrollRect() {
circle = new Sprite();
circle.graphics.beginFill(0xFFCC00);
circle.graphics.drawCircle(200, 200, 200);
circle.scrollRect = new Rectangle(0, 0, 200, 200);
addChild(circle);

slider = new Sprite();
slider.graphics.beginFill(0xff0000);
slider.graphics.drawRect(0, 0, 10, 30);
slider.graphics.endFill();
addChild(slider);
slider.x = 300;

slider.addEventListener(MouseEvent.MOUSE_DOWN, _down);
slider.addEventListener(MouseEvent.MOUSE_UP, _up);
}

private function _down(e : MouseEvent) : void {
stage.addEventListener(MouseEvent.MOUSE_MOVE, _move);
stage.addEventListener(MouseEvent.MOUSE_UP, _up);

}

private function _up(e : MouseEvent) : void {
stage.removeEventListener(MouseEvent.MOUSE_MOVE, _move);
stage.removeEventListener(MouseEvent.MOUSE_UP, _up);

}

private function _move(event : MouseEvent) : void {

var rect : Rectangle = circle.scrollRect;
trace(mouseY);
rect.y = mouseY;
slider.y = mouseY;
trace(rect);
circle.scrollRect = rect;
}
}
}