Actionscript 3 - Session 4 Core Concept

Computer Animation with Flash CS3 & ActionScript 3.0 National Polytechnic Institute of Cambodia Bachelor of IT, Year III, Semester 1 2007-2008 by Oum Saokosal, Head of IT Department

Core Concepts Computer Animation with Flash CS3 & ActionScript 3.0

Core Concepts (Brief only) Variable Data types Conditionals Loops Functions Objects Package Class Inheritance Overriding Methods Java and AS3 Comparisons Array

Variables In AS3, variables are originally untype. It means we can define variables without any data type. E.g.: var a, b = “Hi”, c = true; var d:*; However, we also can specify datatype to them. E.g.: var a:int, b:String = “Hi”; var c:Boolean = true;

Data Types String Numeric: Number : (float) int uint : (unsigned int) Boolean MovieClip : Movie Clip Symbol TextField : dynamic or input text field SimpleButton : button Symbol Date : Data and Time Example: var i:int = 5; var mv1:MovieClip = new MovieClip(); var d1:Date = new Date();

Conditionals if .. else if .. else if switch

Loops for for .. in for each .. in while do .. while

Functions Function = Methods Defining Function - function method1() {} // untype function - function method2():void {} //void function - function method3():int{ // return-var func. return 0; } - function method4(par1, par2:int):int{ //Parameter return 0; }

Objects (1) Look at MovieClip’s variable again: var mv1:MovieClip = new MovieClip(); In fact, mv1 is an object instantiated from MovieClip class. So after that, mv1 can have: properties methods events

Objects (2) properties mv1 .x = 20; Methods mv1 .gotoAndStop(1) ; Events mv1 .addEventListener (...); Note: Only AS3 supports Events features. Other OOPs including Java don’t support these.

Package Create package: package sample1 { public class SampleCode1 { } } Using packages: package sample2 { import sample1.*; public class SampleCode2{ } }

Classes Create Class: package { public class TestClass{ } }

Inheritance To inherit a superclass, please use extends. class C1{ } class C2 extends C1{ }

Overriding Methods Unlike Java, to override methods in AS3, we have to use override keyword. public class C1{ public function aMethod():void{ trace(“Hi”); } } class C2 extends C1{ override public function aMethod():void{ trace(“Good Morning”); } }

Java and AS3 Comparisons (1) Java: package abc; public class C1 extends C2{ private int v1; public C1(){ this.v1 = 5; } int method(int v1){ return v1; } } AS3.0: package abc { public class C1 extends C2{ private var v1 :int ; public function C1(){ this.v1 = 5; } function method( v1:int ): int { return v1; } } }

Java and AS3 (2) – Starting Point In Java Application, the main class has to have a main mathod, public static void main(String[] args) to start the program. public class Test{ public static void main(String[] args){ //starting point } }

Java and AS3 (3) – Starting Point In AS3, the main class starts the program from its non-arg constructor. Moreover, the class must inherit MovieClip or Sprite from flash.display package. Otherwise, compile error occurs. Sample: package{ import flash.display.*; public class Example extends MovieClip { public function Example(){ //the starting point of the program } public function Example(arg:int){ } } }

Array (1) Unlike other language, in AS3 Array is a class . You can store a variety of data types in an array element, including numbers, strings, objects, and even other arrays . You can create a multidimensional array by creating an indexed array and assigning to each of its elements a different indexed array.

Array – Creating (2) Creating Array: Array constructor can be used 3 ways. No argument: var arr1:Array = new Array(); arr1[0] = 5; arr1[1] = true; arr1[2] = “This is AS3”; arr1[3] = new MovieClip(); trace(“length:”+arr1.length); trace(arr1); //length: 4 //5,true, This is AS3, [object MovieClip]

Array – Creating (3) Length of Array: Note it must be unsigned integer number between 0 and 4,294,967,295 . var names:Array = new Array(10); trace(names[0]); //output: undefined trace(names[1]); //output: undefined names[0] = 2; names[2] = true; trace(names[0]); //output: 2 trace(names[1]); //output: undefined trace(names[2]); //output: true

Array – Creating (4) Initializing Array: The number of parameters can start from 2 elements. var arr3:Array = new Array(4, 5); trace(arr3.length); //output:2 trace(arr3); //output: 4, 5 var arr4:Array = new Array(2, true, “Hi”); trace(arr4); //output: 2,true, Hi Only one element could also be initializing value if it is not number. It can be String, Boolean, Object etc. var arr6:Array = new Array(“Hi”); trace(arr6); //output: Hi var arr5:Array = new Array(4.2); trace(arr5); //Compile Error

Array – Creating (5) Array Literals var arr:Array = [7.2,”Hi”, new MovieClip()]; trace(arr[0]); //output: 7.2 trace(arr.length); // output: 3 trace(arr); //7.2, Hi, [Object MovieClip] var arr2:Array = []; // No element is OK! trace(arr2[0]); //output: undefined trace(arr2); //output: (nothing) trace(arr2.length); //output: 0

Array – Inserting elements (6) After creating an array object, we can insert elements to it. E.g.: var arr:Array = new Array(2,”hi”); push(): appends elements to the end of arrays. arr.push(true, “Hello”); trace(arr);//output: 2,hi, true,Hello unshift(): inserts elements at the beginning of an array, which is always at index number 0. arr.unshift(“NPIC”,1.5); trace(arr);//output: NPIC,1.5 ,2,hi,true,Hello splice(): inserts any number of items at a specified index in the array. Note: set deleteCount = 0. theArray .splice ( startIndex , deleteCount , item1 , item2 ,... itemN ) arr.splice(2, 0 ,”Wow”); trace(arr); //output: NPIC,1.5,2, Wow ,hi,true,Hello

Array – Removing elements (6) We can also remove elements from arrays. E.g.: var arr:Array = new Array(2,”hi”, true, “Hello”); pop(): remove one last element of the array. arr.pop(); trace(arr);//output: 2,hi,true shift(): remove the first element of the array. arr.shift(); trace(arr);//output: hi,true splice(): delete any number of items at a specified index in the array. Note: specify deleteCount. theArray .splice ( startIndex , deleteCount , item1 , item2 ,... itemN ) arr.splice(1,1); trace(arr); //output: hi

Actionscript 3 - Session 4 Core Concept

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