Objects added to stage with coordinates 0,0 appear near the middle...why?

Question

I'm using Flash Builder to build an flash-web application, and whenever I try to add objects to the stage, they appear near the center even if their coordinates are set at 0,0. I've tried track the mouse movement to see what the coordinates of the upper left corner are, and they are always a negative number.

Strangely, the stage coordinates and position of the children change based on how large the flash object is. For example, if the flash object is 500 pixels wide, the top left corner of the stage is at about -130 and if the flash object is 800 pixels wide, its at about -200. Why is the coordinate system wrong? Do I have to alter an anchor point or something like that?

Here is a sample of an object I'm trying to position at 0,0:

var square:Sprite = new Sprite();
addChild(square);
square.graphics.lineStyle(3,0x00ff00);
square.graphics.beginFill(0x0000FF);
square.graphics.drawRect(0,0,100,100);
square.graphics.endFill();
square.x = 0;
square.y = 0;

This shows up near the center and I can't figure out why.

Unknown Unknown · Accepted Answer · 2012-12-28T11:07:34

Is the object you are using a MovieClip or Sprite? If so then your registration point could be in an incorrect position.

Usually registration points are placed right in the middle of the object instead of lets say the top left as you would want it. So the co-ordinates would be different to the stage.

Objects added to stage with coordinates 0,0 appear near the middle...why?

2 Answers