as3中textField输入字符时，一次性过长后自动换行

     txt_show.text = showStr;

     var str:String = txt_show.text;
     var strlen:int = str.length;
     var len:int = 0;
     for (var i:int = 0; i < strlen; i++)
     {
         len += txt_show.textField.getCharBoundaries(i).width;
         if(len > txt_show.textField.width - 5)
         {
             var temp:String = str.charAt(i - 1) + "\n";
             txt_show.textField.replaceText(i - 1, i, temp);
             len = 0;
         }
     }

     txt_show.textField.width = 210;