Multimedia Authoring COM315

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Multimedia Authoring COM315

• Week 9
• Actionscript

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Timetable weeks 9-10-11-12

• Week 9
• Lecture Actionscript
• Lab Flash
• Week 10
• Lecture Assignment 1 Feedback
• Lab Flash
• Week 11
• Lecture Assignment 1 feedback/ Class Test
  Revision /Web design
• Lab Flash/Actionscript
• Week 12
• Lecture Class test
• Lab Flash/Actionscript/Assignment help

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Submission Deadlines

• Assignment 2 11/12/09 (Week 12)
• Assignment 3 10/12/09 (Week 12)

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Introduction to Actionscript

• What is ActionScript?
• What is ActionScript good for?
• What ActionScript can't do
• Object orientated programming
• Elements of programming in Actionscript

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What Is ActionScript?

• ActionScript is the scripting language used in
  Adobe Flash to create advanced interactivity and
  animation.
• Allows the execution of different actions in a
  movie depending on what a user does or on what
  frame of the movie is being played.
• Similar in structure to Javascript

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Some uses of ActionScript

• Create multiplayer games.
• Create engaging, user-aware navigation.
• Send data to middleware, like PHP and Cold
  Fusion.
• Communicate with JavaScript.

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Benefits of using Actionscript

• Allow for a more responsive Web site.
• Allows inclusion of dynamic data
• Make your site more accessible to readers.

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ActionScript limitations

• ActionScript can't talk directly to a database.
  Middleware like PHP, Cold Fusion, or ASP is
  needed to do this.
• This functionality can now be achieved using
  Adobe Flash Remoting

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Actionscript limitations

• Can't use exception handling i.e. try, throw, or
  catch. (Error handling in Javascript)
• Exceptions provide error-handling capabilities
• for programs. An exception is an event that
• occurs during the execution of a program that
• disrupts the normal flow of instructions.

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Object-Oriented Scripting

• ActionScript is an object-oriented scripting
  language
• Scripting languages organize information into
  groups called classes.
• Classes and objects are just ways to group
  together chunks of information

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Terminology

• Class
• Instance
• Object

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Classes objects

• Classes are groups of objects that share
  characteristics, e.g. rectangles
• Shared characteristics allow you to create a
  blueprint for those objects.
• A software blueprint for an object is called a
  class.

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Object-Oriented Scripting

• You can create multiple instances of these
• classes, which are called objects.
• Real-world analogy Bicycle" class

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Classes objects

• You can have many objects of the same kind.
• E.g. A bicycle
• Your bicycle is just one of many bicycles in the
  world.
• Using object-oriented terminology, we say that
  your
• bicycle object is an instance of the class of
  objects
• known as bicycles.

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Object-oriented terminology
Class Defines the common characteristics of a
bicycle. Like a plan
Objects Physical manifestation of bicycle class.
Each object is a instance of the bicycle class
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Instances

• Using the bicycle class, you can create any
• number of bicycle objects from the class.
• When you create an instance of a class each
• instance gets its own copy of all the instance
• variables defined in the class.

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Instances
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Classes objects

• Bicycles have states (current gear)
• Bicycles have behaviors (change gears, brake) in
  common.
• However, each bicycle's state is independent of
• and can be different from that of other bicycles.

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Objects vs. Classes

• Objects and classes seem very similar.
• In the real world, it's obvious that classes are
  not themselves but the objects they describe
• A blueprint of a bicycle is not a bicycle

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Objects vs. Classes
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Class Instances in Flash
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Class Instance in Flash
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Classes objects

• Classes are groups of objects that share
  characteristics i.e. software blueprint
• Object is the physical manifestation of a class
• Each object is an instance of the class

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Actionscript Fundamentals

• Actionscript is a programming language
• Similar to lingo
• Subject to usual programming language constraints
• Has its own syntax and structure

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Action Script

• Script applied to an action
• Basic structure of an action
• whenSomethingHappens (input variables)
• do stuff

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Object and Frame Actions

• Two basic kinds of actions in Flash
• Object actions
• Frame actions

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Object Actions - Movie Clips

• Object actions are chunks of ActionScript code
  that are attached to an object
• Usually an object is a symbol that's either a
  button or a movie clip.
• Graphic symbols dont have actions

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Object and Frame Actions
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Object Actions

• An object action is associated with an instance
• of a symbol, not with the symbol itself.

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Object Actions

• Both shapes are instances of the same movie
• clip symbol, but only one of them has an action
• attached to it.
• The function is always attached to this object
• instance, no matter where in the movie it appears
  
• Object actions arent concerned with what frame
  the
• movie is currently on (as long as the object
  actually
• exists in the movie at that frame)

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Event handlers

• The function you saw was a onClipEvent
• and is known as an event handler
• An event is something that happens i.e. a
• movie loads, user presses a mouse button
• An event handler constantly looks for events
• and lets ActionScript know when one of them
  occurs.

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Event handlers
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Typical Event handler

• OnmouseDown refers to what the mouse button is
  doing.
• If mouse button was pressed, then
  onClip-Event(mouseDown) is called, and everything
  inside the first set of curly braces is executed.
  
• OnmouseDown
• startDrag(this)

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Object Actions Drag fish
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Methods

• startDrag is what's called a method.
• A method does something.
• In this case drag what was clicked.

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Methods

• A method is something an object can do or
  something
• you can do to an object. For example, here are
  some
• things methods can do
• Stop a movie clip
• Go to a certain frame and start playing there.
• See if a movie clip is over another movie clip.
• Hide the mouse cursor.
• Set the volume of a sound being played.

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Targets

• Notice that we didn't use startDrag(), but used
  startDrag(this).
• The startDrag method requires a target i.e., it
  needs to know what it should start dragging.

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this command

• The easiest way to reference the current object
  is just to call it this
• The other way to refer to the object is absolute
  i.e. startDrag(_root.drag_fish)
• Where drag_fish is the name of the instance of
  the fish symbol.
• The _root part means "start looking from the top
  of the movie hierarchy."

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Object actions onClipEvent

• Object actions on a movie clip have to be inside
  of an
• onClipEvent. Possible events are
• load
• unload
• enterFrame
• mouseMove
• mouseDown
• mouseUp
• keyDown
• keyUp

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Object Actions Buttons

• The only real difference between actions that
• are attached to buttons instead of movie clips is
• that the event handler for buttons is on
• instead of onClipEvent.
• Otherwise, they're pretty much the same.

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Object Actions Buttons

• The events for on are
• press
• release
• releaseOutside
• rollOver
• rollOut
• dragOver
• dragOut
• keyPress

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Object Actions Buttons
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Object Actions Buttons
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Frame Actions

• Frame actions are like object actions, except
  that the actions are associated with a certain
  spot in the timeline instead of an object.
• If a frame has some actions associated with it,
  those actions are carried when the playhead
  enters that frame.

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Frame Actions
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Frame Actions
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Frame Actions

• Frame actions only allowed on a keyframe!!!
• Hint Place all of your frame actions on a
• separate layerit makes organization easier

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Summary

• Two basic kinds of actions in Flash
• Object actions (Movie clips and buttons)
• Frame actions

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Actionscript Syntax

• ActionScript uses what is called dot syntax.
• For example, if you have a movie clip called
• red_shirt inside of the movie clip called
• santa_claus, then one way to access that
• object is
• _root.santa_claus.red_shirt

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Dot Syntax

• To write paths actionscript uses what is called
  dot syntax.
• E.g. to access the movie highlighted the path
  would be
• _root.movieClip_one.clip_a.square1

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Relative Absolute Paths
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Root Properties

• _root is the base of all Flash movies. If you
• want to find out where red_shirt is on the stage,
• you could use
• xPosition _root.santa_claus.red_shirt._x
• _x is a property that returns the horizontal
  position of the object.

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Root Properties

• Its analogous to an absolute URL You start at
• the top and specify your way down

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Properties

• A property is an attribute of an object. Movie
  clip
• examples include
• how wide it is (_width)
• where it is on the stage (_x and _y)
• what frame is currently being played
  (_currentframe)
• how transparent it is (_alpha)
• its name (_name)
• whether it's visible or not (_visible)

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Properties

• Most properties can be read or altered. For
• example, let's see how wide a movie clip called
• clue is
• _root.clue._width 110
• _root.clue._width 40

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underscore (_)

• All movie clip properties start with an
• underscore (_)
• That's just how Flash is

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Summary

• Actionscript is an object orientated programming
  language used in Flash.
• Applied to objects (movie clips buttons)
  frames
• Event driven

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Multimedia Authoring COM315

• Week 9
• Actionscript