How to make shape rotation at it's center point?

Question

I draw a shape,like follows:
var shape1:Shape;
shape1=draw();
addChild(shape1);
shape1.rotation=50;
private function draw():Shape{
   var shape:Shape = new Shape();
   shape.graphics.beginFill(0x00FFFF);
   shape.graphics.moveTo(200,200);
   shape.graphics.lineTo(300, 202);
   shape.graphics.lineTo(200, 204);
   shape.graphics.lineTo(100, 202);
   shape.graphics.lineTo(200, 200);
   return shape;
Then I want to rotate the shape at it's center point(200,202) by using shape1.rotation=50,but I find the shape don't rotate at the the center of it's shape. How to realize the function which make shape rotate at its center point?
Thanks

Answer 1

Here is a sample to make it rotate from center:
var sprite:Sprite=new Sprite();
sprite.graphics.lineStyle(3,0x00ff00);
sprite.graphics.beginFill(0x0000FF);
sprite.graphics.moveTo(0,0);
sprite.graphics.lineTo(100,0);
sprite.graphics.lineTo(100,100);
sprite.graphics.lineTo(0,100);
sprite.graphics.lineTo(0,0);
sprite.graphics.endFill();
var mc:Sprite=new Sprite();
mc.addChild(sprite);
//This will make the sprite to center
mc.getChildAt(0).x=-(mc.getChildAt(0).width/2);
mc.getChildAt(0).y=-(mc.getChildAt(0).height/2);
addChild(mc);
mc.x=200;
mc.y=300;
//Now it rotates from the center.
mc.rotation=20;