Framework Fundamentals

1
Framework Fundamentals

• Web 2.0 and Rich Internet Applications
• Prof. Suthikshn Kumar

2
Flex Framework Fundamentals

• Understanding the Flex Application Life Cycle
• Differentiating between Flash Player and
  Framework
  
• Bootstrapping Flex Applications
• Loading on Flex Application into another Flex
  Application
  
• Understanding Application Domains
• Understanding the Preloader

3
Flex Application Life Cycle

• A good understanding of the Flex Application Life
  cycle will enable you to build better
  applications because you will know where to
  optimally run the code.
• Example If you need to ensure that some code
  runs during a preloader, you need to know where
  to place the code for that event.
  
• An understanding of the application life cycle
  helps you to create applications that will
  deliver an optimal user experience.

4
SystemManager

• Flex applications are basically Flash
  applications that use the Flex Framework
  
• The root of a Flex application is typically
  SystemManager, which is a subclass of
  flash.display.MovieClip, a Flash player object
  type.
• A movie clip is a display object type that
  supports frames, which are units of a timeline.
  
• SystemManager has two frames.
• The .swf format is a progressive download format
  which means that Flash player can access content
  on frames as they download without having to wait
  for the entire file to download.

5
Basic Application Startup Event FLow
SystemManager
timeline
Frame1 Preloader
Frame2 Application framework used by application
6
SystemManager First Frame

• The first frame is used to display a progress
  indicator while the application loads.
  
• This frame is lightweight in terms of file size
  so that it can download and run almost
  immediately, and it does not house much of the
  flex framework.

7
Second Frame

• The second frame is the one in which the
  application itself housed.
  
• It contains the majority of the Flex Framework
  utlized by the application.
  
• Once the SystemManager instance for a Flex
  application has advanced to second frame, it
  creates an instance of the main application class
  for the flex application.

8
Internal Life cycle events

• Preinitialize The application has been
  instantiated but has not yet created any child
  components.
  
• Initialize The application has created child
  components but has not yet laid out those
  components.
  
• creationComplete The application has been
  completely instantiated and has laid out all
  components.
  

9
SystemManager

• The systemManager instance for the Flex
  application instance is initialized and runs
  through its own startup procedure.
  
• Once the application has completed its internal
  startup procedure, it notifies SystemManager
  which dispatches an applicationComplete event.
  
• From that point, application is ready to run.
• SystemManager also manages all things that are
  displayed in front of the application content.
  This means all pop ps, cursors, and tool tips are
  placed within the SystemManager instance.
• SystemManager has property called
  topLevelSystemManager. This is a reference to the
  SystemManager instance that is at the root of
  everything running in Flahs Player at that time.

10
Differentiating between Flash Player and Framework

• Flash player is a runtime environment for Flash
  and Flex applications.
  
• It can run .swf file which contains the bytecode
  that communicate with flash player, instructing
  to perform operations such as loading images,
  drawing graphics, making HTTP requests and so
  on.
• Flash and Flex application can do only what Flash
  player allows them to do.
  
• Flex consists of compiler that is capable of
  compiling MXML and ActionScript. It provides a
  layer of abstraction.
  
• The Flex Framework consists of many thousands of
  line of code, all of which ultimately run
  instructions that Flash player can understand.
  
• Compiler will include necessary libraries in the
  .swf file.
  
• Thus you can rapidly develop applications.
• The tradeoff of using the framework is that the
  file size of the .swf increases.
  

11
Differntiation between Flash player and Flex
Framework classes

• If the class is in a package starting with flash
  ( ex flash.net.URLLoader), it is a part of flash
  player
  
• If the class is in a package starting with
  letters mx ( ex mx.controls.Button), it is a part
  of flex framework
  
• MXML tags almost always correspond to Flex
  Framework classes.

12
Bootstrapping Flex Applications.

• Default root object is mx.managers.SystemManager
• Flash.display.Movieclip class is a display object
  type which allows you to programmatically work
  with timeline.
  
• Timelines are a feature used in flash
  applications because Flash authoring.
  
• Timelines are not used frequently in Flex
  applications
  

13
Timeline

• A timeline is composed of frames
• Frame represents a point in time during the
  playback of timeline.
  
• SystemManager consists of two frames.
• The Flex application to have a preloader that
  indicates download progress to the user
  
• The preloader must exist in the first frame and
  Flex application must exist in the second.
  
• Flex automatically handles all the bootstrapping,
  and initialization.

14
Loading One Flex application into Another.

• What is the path to the loaded application
  relative to the SWFLoader used to load the
  application?
  
• When has the loaded application actually
  initialized?
  
• Init event
• Event listener for applicationComplete event for
  the SystemManager

15
Application Domain

• They are critically important to how Flex
  applications function.
  
• An application domain is the partition within
  which an application runs in Flash player.
  
• If one application is running, there is one
  application domain.
  
• When additional .swf files are loaded into an
  existing application, you create additional
  application domains.

16
When .swf is loaded

• The loaded application runs in a new application
  domain that is completely partitioned from all
  other application domains.
  
• The loaded .swf runs in a new application domain
  that is a child of an existing application
  domain.
  
• The loaded .swf runs in an existing application
  domain.
  

17
Application domains.

• All flex and flash applications are composed of
  collections of classes
  
• An application domain holds the collections of
  classes for an application (s)
  
• When you load an additional .swf file, there is
  more possibility that it will contain a
  definition for a class by the same name as one
  that is already loaded from another .swf file.
• An application domain ensures that within the
  domain, there is only one definition for each
  class.
  
• Therefore it has a set of rules for determining
  how to choose between conflicting definitions if
  such a scenerio presents itself.
  

18
Preloader

• Preloader provides progress bar
• This preloader is a lightweight class that is
  created on the first frame of the systemManager
  
• The preloader dispatches a series of events that
  the progress bar then handles.
  
• Typically the progress bar registers one or more
  listeners for events dispatched by the preloader
  object.
  
• Once the complete event occurs, SystemManager
  progresses to second frame.
  

19
Events for Preloaders

• Progress Indicates download progress
• Complete
• rslError indicates that a runtime shared library
  could not load
  
• rslProgress indicates download progress for rsl
• rslComplete
• initProgress indicates that the application is
  initializing
  
• initComplete indicates that the application has
  initialized.