1 Flash Actionscript Adding Interactive Actions Variables

2 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.

3 Adding an Interactive Action Start a new movie with File -> 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.

4 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.

5 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;

6 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.

7 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.

8 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.

9 ActionScript Variables ActionScript is supposed to be a programming language. Program => 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

10 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 can’t remember any of its input … merely respond immediately. I think we need some variables!

11 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).

12 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.

13 Variables and Data Types ActionScript has the following basic data types: Boolean int uint Null Number Object String Void

14 ActionScript Variables Declaring a variable: var catName:String; You can then assign a value - done using an assignment statement which uses the assignment operator which, conveniently, is an = sign. catName = "Pirate Eye";

15 ActionScript Variables Or you can do both together: So for example the following are all valid: var hisName:String = “Pete”; var hisAge:int = 32; var gameOver:Boolean = true;

16 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.

17 ActionScript Variables Expressions We can also generate values for variables by using mathematical expressions e.g. var myAge:int = 42; var myResult:int = myAge - 10; myAge = myAge+1; var newVar:int = myResult * myAge; We can also add variables which hold things other than numbers e.g. var firstPart:String=“This is ”; var secondPart:String =“a sentence.”; var sentence:String = firstPart + secondPart; Don’t mix types in expressions though!

18 ActionScript Variables Let’s 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.

19 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. Let’s now make an output box to make sure this is happening. 4.Create a new layer and call it actions. 5.Select Frame 1 of the actions layer and open the actions panel. 6.Type in: var myTextVar:String = In1.text;

20 ActionScript Variables So we have told Flash to display the contents of in1 in the output textbox. Test the movie – why doesn’t it work? 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. 6.With the Text tool, add a new text field directly below the existing one. Give this one the instance name Out1. 7.Select frame 1 of the actions layer and open the actions panel. 8.Add the following to the existing code: Out1.text = myTextVar;

21 ActionScript Variables 10.Add a a frame to layer 1 and keyframe to frame 2 of your actions layer. 11.Select the keyframe and open the actions panel 12.Type in the following code: gotoAndPlay(1);

22 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.

23 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.

24 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 strGlobal:String = "Global"; function scopeTest() { trace(strGlobal); // Global } scopeTest(); trace(strGlobal); // Global

25 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.

26 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 strLocal:String = "local"; } localScope(); trace(strLocal); // error because strLocal is //not defined globally

27 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.

28 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 str1:String = "Global"; function scopeTest () { var str1:String = "Local"; trace(str1); // Local } scopeTest(); trace(str1); // Global

29 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.