Flash Actionscript Adding Interactive Actions Variables

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Flash Actionscript Adding Interactive
Actions Variables
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ActionScript 3.0

• ActionScript is the language you use to add
  interactivity to Flash applications, whether your
  applications are simple animated movies or more
  complex rich Internet applications.
• You don't have to use ActionScript to use Flash,
  but if you want to provide basic or complex user
  interactivity, work with objects other than those
  built into Flash (such as buttons and movie
  clips), or otherwise turn a SWF file into a more
  robust user experience, you'll probably want to
  use it.

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Adding an Interactive Action

• Start a new movie with File -gt New
• Create a blue circle, put it in the centre of the
  stage, and convert it to a movie clip symbol.
  Call the symbol circle_mc.
• With the circle still selected use the
  properties panel to give this instance of circle
  the name ball.

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Adding an Interactive Action

• So we have a symbol called circle with an
  instance of this symbol called ball.
• Now create a new layer and call it actions. Add a
  keyframe to the actions layer at frame 2 and add
  a new frame to the other layer (this is so that
  the first layer has two frames).
• We will then add actions to both of the frames on
  the actions layer.

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Adding an Interactive Action

• Call up the Frame Actions window for frame 1 of
  the actions layer (right click on frame 1 and
  select actions).
• Make sure Script Assist is turned off.
• Type the following into the actions window
• this.ball.x mouseX
• this.ball.y mouseY

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Adding an Interactive Action

• Put the following action into the Frame Actions
  window for frame 2 of the actions layer.
• gotoAndPlay (1)
• The second action means that the animation simply
  loops from 1 to 2 indefinitely.

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Adding an Interactive Action

• this.ball.x mouseX What does this mean?
• this is used to target the current timeline
• mouseX is the Flash way of referring to the
  current x coordinate of the mouse
• ball is the name we gave to the current instance
  of the circle symbol.
• x is the horizontal position property of that
  instance which we are assigning to the current
  value of the x position of the mouse.

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Adding an Interactive Action

• We are doing the same with the value of the y and
  hence the blue ball will simply follow the mouse
  around the screen when we run the animation.

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ActionScript Variables

• ActionScript is supposed to be a programming
  language.
• Program gt something which receives some input,
  performs some processing, and does some output.
• Our Flash animations are interactive
• input button presses, mouse events
• output graphics on screen

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ActionScript Variables

• So it is a programming language of sorts but so
  far not a very flexible one for two reasons
• 1. Forms of input are a bit limited
• 2. It cant remember any of its input merely
  respond immediately.
• I think we need some variables!

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ActionScript Variables

• A variable is a memory location in which a
  program can store data values.
• These values can change constantly when a
  program needs to find out the current value it
  just looks it up. In order to be able to look up
  the right one it associates a unique name with
  each variable (chosen by the programmer).

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Variables and Data Types

• You can explicitly declare the object type of a
  variable when you create the variable, which is
  called strict data typing.
• If you do not explicitly define an item as
  holding either a number, a string, or another
  data type, at runtime Flash Player will try to
  determine the data type of an item when it is
  assigned.
• Because data type mismatches trigger compiler
  errors, strict data typing helps you find bugs in
  your code at compile time and prevents you from
  assigning the wrong type of data to an existing
  variable.

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Variables and Data Types

• ActionScript has the following basic data types
• Boolean
• int
• uint
• Null
• Number
• Object
• String
• Void

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ActionScript Variables

• Declaring a variable
• var catNameString
• You can then assign a value - done using an
  assignment statement which uses the assignment
  operator which, conveniently, is an sign.
• catName "Pirate Eye"

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ActionScript Variables

• Or you can do both together
• So for example the following are all valid
• var hisNameString Pete
• var hisAgeint 32
• var gameOverBoolean true

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ActionScript Variables

• To view the value of a variable, use the trace()
  statement to send the value to the Output panel.
  Then, the value displays in the Output panel when
  you test the SWF file in the test environment.
• E.g., trace(hoursWorked) sends the value of the
  variable hoursWorked to the Output panel in the
  test environment.

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ActionScript Variables

• Expressions
• We can also generate values for variables by
  using mathematical expressions e.g.
• var myAgeint 42
• var myResultint myAge - 10
• myAge myAge1
• var newVarint myResult myAge
• We can also add variables which hold things other
  than numbers e.g.
• var firstPartStringThis is
• var secondPartString a sentence.
• var sentenceString firstPart secondPart

Dont mix types in expressions though!
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ActionScript Variables

• Lets look at an example of using variables to
  store text inputted from the screen.

1. Open a new movie and select the Text
Option. Select Input Text from the
drop-down menu and click once on the stage to
insert a textfield. 2. Give your textbox an
instance name in1. 3. Check the border box to
make Flash draw a box around the textfield.
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ActionScript Variables

• If we are going to read some text in from the
  screen we are going to need to store it somewhere
  (i.e. we need a variable)
• We get a box into which we can type stuff. That
  stuff can be referred to as In1.text. We have now
  asked Flash to store In1.text in the string
  variable myTextVar. Lets now make an output box
  to make sure this is happening.

• Create a new layer and call it actions.
• Select Frame 1 of the actions layer and open the
  actions panel.
• Type in
• var myTextVarString In1.text

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ActionScript Variables

• 5. Click on a blank part of the stage to
  deselect the input box. Click on the Text Option
• again and select Dynamic Text. Make sure
  border and Selectable are
• unchecked.
• With the Text tool, add a new text field directly
  below the existing one. Give this one
• the instance name Out1.
• Select frame 1 of the actions layer and open the
  actions panel.
• Add the following to the existing code
• Out1.text myTextVar

• So we have told Flash to display the contents of
  in1 in the output textbox.
• Test the movie why doesnt it work?

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ActionScript Variables

• Add a a frame to layer 1 and keyframe to frame 2
  of your actions layer.
• Select the keyframe and open the actions panel
• Type in the following code
• gotoAndPlay(1)

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Variables and Scope

• A variable's scope refers to the area in which
  the variable is known (defined) and can be
  referenced.
• A global variable is one that is defined in all
  areas of your code, whereas a local variable is
  one that is defined in only one part of your
  code.

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Variables and Scope

• In ActionScript 3.0, variables are always
  assigned the scope of the function or class in
  which they are declared.
• A global variable is a variable that you define
  outside of any function or class definition.

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Global Variables

• E.g., the following creates a global variable
  strGlobal by declaring it outside of any
  function.
• This shows that a global variable is available
  both inside and outside the function definition.

var strGlobalString "Global" function
scopeTest() trace(strGlobal) // Global
scopeTest() trace(strGlobal) // Global
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Local Variables

• You declare a local variable by declaring the
  variable inside a function definition.
• The smallest area of code for which you can
  define a local variable is a function definition.
  
• A local variable declared within a function will
  exist only in that function.

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Local Variables

• E.g., if you declare a variable named str2 within
  a function named localScope(), that variable will
  not be available outside the function.

function localScope() var strLocalString
"local" localScope() trace(strLocal) //
error because strLocal is //not defined globally
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Variable Scope

• If the variable name you use for your local
  variable is already declared as a global
  variable, the local definition hides (or shadows)
  the global definition while the local variable is
  in scope.
• The global variable will still exist outside of
  the function.

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Variable Scope

• E.g., the following creates a global string
  variable named str1, and then creates a local
  variable of the same name inside the scopeTest()
  function.

var str1String "Global" function scopeTest
() var str1String "Local" trace(str1)
// Local scopeTest() trace(str1) // Global
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Variable Scope

• The trace statement inside the function outputs
  the local value of the variable, but the trace
  statement outside the function outputs the global
  value of the variable.