<ActionScript 3 Bible 2nd>读书笔记(13，14，16，21)

Binary Types in ActionScript

A read-only stream, like a  URLStream, would only implement  IDataInput. A read-write stream, like Socket, implements both.

Read   or  write  an  ActionScript  object using  AMF    encoding.    Specify   AMF0  or AMF3  using  the  objectEncoding  parameter. 

In Flash Player 10 and later, you can clear out a  ByteArray with the  clear() method.  

position determines where objects will be read starting from, and read operations will automatically advance the position to the end of the last read object.
length reports, in bytes, the total size of the  ByteArray.

have an exact duplicate of the original object, not merely another reference 

     import flash.utils.ByteArray; 
           var arrayA:Array = new Array("a", "b", "c", "d";); 
           var byteArray:ByteArray = new ByteArray(); 
           byteArray.writeObject(arrayA); 
           byteArray.position = 0; 
           var arrayB:Array = byteArray.readObject(); 
           arrayB.push("e", "", "g", "h"); 
           trace(arrayA.join(" "));           //a b c d 
           trace(arrayB.join(" "));           //a b c d e f g h 
         }

There is one important consideration when you arecopying objects of custom types. Byte arrays write data using AMF, which natively supports standard ActionScript data types, butnot custom classes. (AMF is the Action Message Format, a binary protocol) That means that, by default, if you write an object of a custom type, it is written to the byte array correctly, but it isstored as a generic object. Therefore,when you retrieve it from a byte array you cannot cast it back to the correct type. You can fix this by using the  registerClassAlias() function.

Note 
The AIR runtime can have multiple stages because every top-level window has its own display list.  

交换两个显示对象的深度

 	stage.setChildIndex(apple, 0); 
       stage.setChildIndex(carrot, 1); 
       //now carrot is definitively on top of apple 
       stage.swapChildren(apple, carrot); //now apple is on top 
       stage.swapChildren(apple, carrot); //now carrot is back on top 
       //note that swapping again puts things the way they were 
       stage.swapChildrenAt(0, 1); 

You can investigate the contents and organization of a display list. You can test whether one display object contains another: 

       carrot.addChild(sprouts); 
       trace(carrot.contains(sprouts)); //true 

 wmodeGPU— In Flash Player 10.0.32 and later, this read-only Boolean flag indicates whether the GPU is performing compositing. This property will be true only if GPU compositing is actively in use: if you’ve indicated that the GPU wmode should be used in your embed parameters or at SWF publish time, and if it is supported by the hardware Flash Player is running  on. When this is true, you may be able to crank up the graphics without dropping frame rate.  If you have this graphics-intensive of an application, you would do well to keep track of other  performance metrics while you adjust. 

Using Assets from a SWF 

   package { 
      import com.actionscriptbible.Example; 
      import flash.display.DisplayObject; 
      import flash.display.Loader; 
      import flash.events.Event; 
      import flash.net.URLRequest; 
      import flash.system.ApplicationDomain; 
      public class ch16ex1 extends Example { 
        protected var loader:Loader; 
        public function ch16ex1() { 
          trace("Loading assets..."); 
           loader = new Loader(); 
           loader.load(new URLRequest( 
             "http://actionscriptbible.com/files/ch16assets.swf")); 
           loader.contentLoaderInfo.addEventListener(Event.COMPLETE, onLoad); 
        } 
        protected function onLoad(event:Event):void { 
          try { 
             var assetsDomain:ApplicationDomain = 
               loader.contentLoaderInfo.applicationDomain; 
             var FishingCatClass:Class = 
               Class(assetsDomain.getDefinition("assets.FishingCat")); 
             var cat:DisplayObject = new FishingCatClass(); 
             cat.y = 100; 
             addChild(cat); 
             trace("added fishing cat!"); 
           } catch (error:Error) { 
             trace(error); 
           } 
        } 
      } 
   } 

double clicking

double-clicks is off by default.

     doubleClickEnabled = true; 
     addEventListener(MouseEvent.DOUBLE_CLICK, onDoubleClick);