createjs - Why can't create Bitmap in LoadQueue's fileload event? -

i tryting create bitmap , add stage, doesn't work.

this.queue.on("fileload", function(event) {     if(event.item.id == "bg") {     var bg = new createjs.bitmap(this.queue.getresult("bg"));// doesn't work here！  }       }, this);

however, if in complete handler works:

 this.queue.on("complete", function(event) {     var bg = new createjs.bitmap(this.queue.getresult("id"));     this.stage.addchild(bg); //works out , no error   }, this);

thanks helping me!!