Cant pass sprite

when I pass a sprite variable to a class to place images in it the spite doesnt display all the image as it should. It is unstable.


canvas1=new Sprite();
 addChild(canvas1);
mybackground=new ClassBackGroundtile(canvas1);
 
canvas1.addChild(mybackground);
///////////
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classbackgroundTile
private var canvas1:Sprite; 
public function ClassBackGroundTile(ccanvas1:Sprite...) {
canvas1=ccanvas1;
.....
//addChild(img1);
 canvas1.addChild(img1); //this causes the problem