动态地将舞台上的MovieClip实例放在舞台上（AS3）

Question

我试图在舞台上动态地放置MovieClip的实例。 收到一个错误：

TypeError: Error #2007: Parameter child must be non-null. 
    at flash.display::DisplayObjectContainer/addChild() 

的ActionScript：

  // properties in class ---------- 
     var circle_ary:Array = new Array; 
     var circ_num:int;//number of circles on the stage 

     // dynamically place MovieClip instances on the stage ---------- 
     // inside Constructor function of class 
     var circ_num:int=20;//number of circles on the stage 

     for(var i=0; i<circ_num; i++) { 
      circle_ary[i] = new Circle(); //linkage in the library 
      addChild(Circle[i]); 
     } 

Answer 1

应该

addChild(circle_ary[i]);