Flash: ActionScript Language Reference- P4

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Flash: ActionScript Language Reference- P4

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  1. CHAPTER 2 ActionScript Language Reference for Availability Flash Player 5. Usage for(init; condition; next) { statement(s); } Parameters init An expression to evaluate before beginning the looping sequence; usually an assignment expression. A var statement is also permitted for this parameter. condition An expression that evaluates to true or false. The condition is evaluated before each loop iteration; the loop exits when the condition evaluates to false. next An expression to evaluate after each loop iteration; usually an assignment expression using the increment (++) or decrement (--) operators. statement(s) An instruction or instructions to execute within the body of the loop. Description Statement; evaluates the init (initialize) expression once and then starts a looping sequence. The looping sequence begins by evaluating the condition expression. If the condition expression evaluates to true, statement is executed and the next expression is evaluated. The looping sequence then begins again with the evaluation of the condition expression. The curly braces ({}) used to enclose the block of statements to be executed by the for statement are not necessary if only one statement will execute. Example The following example uses for to add the elements in an array: var my_array:Array = new Array(); for (var i:Number = 0; i
  2. The following example shows that curly braces ({}) are not necessary if only one statement will execute: var sum:Number = 0; for (var i:Number = 1; i
  3. CHAPTER 2 ActionScript Language Reference for..in Availability Flash Player 5. Usage for(variableIterant in object){ statement(s); } Parameters variableIterant The name of a variable to act as the iterant, referencing each property of an object or element in an array. object The name of an object to be iterated. statement(s) An instruction to execute for each iteration. Returns Nothing. Description Statement; iterates over the properties of an object or elements in an array and executes the statement for each property or element. Methods of an object are not enumerated by the for..in action. Some properties cannot be enumerated by the for..in action. For example, movie clip properties, such as _x and _y, are not enumerated. In external class files, static members are not enumerable, unlike instance members. The for..in statement iterates over properties of objects in the iterated object’s prototype chain. Properties of the object are enumerated first, then properties of its immediate prototype, then properties of the prototype’s prototype, and so on. The for..in statement does not enumerate the same property name twice. If the object child has prototype parent and both contain the property prop, the for..in statement called on child enumerates prop from child but ignores the one in parent. The curly braces ({}) used to enclose the block of statements to be executed by the for..in statement are not necessary if only one statement will execute. If you write a for..in loop in a class file (an external AS file), then instance members are not available for the loop, but static members are. However, if you write a for..in loop in a FLA file for an instance of the class, then instance members are available but static ones are not. Examples The following example shows using for..in to iterate over the properties of an object: var myObject:Object = {name:"Tara", age:27, city:"San Francisco"}; for (var name in myObject) { trace("myObject."+name+" = "+myObject[name]); } for..in 303
  4. //output myObject.name = Tara myObject.age = 27 myObject.city = San Francisco The following example shows using for..in to iterate over the elements of an array: var myArray:Array = new Array("one", "two", "three"); for (var index in myArray) trace("myArray["+index+"] = " + myArray[index]); // output: myArray[2] = three myArray[1] = two myArray[0] = one The following example uses the typeof operator with for..in to iterate over a particular type of child: for (var name in this) { if (typeof (this[name]) == "movieclip") { trace("I have a movie clip child named "+name); } } Note: If you have several movie clips, the output consists of the instance names of those clips. The following example enumerates the children of a movie clip and sends each to Frame 2 in their respective Timelines. The RadioButtonGroup movie clip is a parent with several children, _RedRadioButton_, _GreenRadioButton_, and _BlueRadioButton. for (var name in RadioButtonGroup) { RadioButtonGroup[name].gotoAndStop(2); } 304 Chapter 2: ActionScript Language Reference
  5. CHAPTER 2 ActionScript Language Reference fscommand() Availability Flash Player 3. Usage fscommand("command", "parameters") Parameters command A string passed to the host application for any use, or a command passed to Flash Player. parameters A string passed to the host application for any use, or a value passed to Flash Player. Returns Nothing. Description Function; lets the SWF file communicate with either Flash Player or the program hosting Flash Player, such as a web browser. You can also use the fscommand() function to pass messages to Macromedia Director, or to Visual Basic, Visual C++, and other programs that can host ActiveX controls. Usage 1: To send a message to Flash Player, you must use predefined commands and parameters. The following table shows the values you can specify for the command and parameters parameters of the fscommand() function to control a SWF file playing in Flash Player, including projectors. Command Parameters Purpose quit None Closes the projector. fullscreen true or false Specifying true sets Flash Player to full-screen mode. Specifying false returns the player to normal menu view. allowscale true or false Specifying false sets the player so that the SWF file is always drawn at its original size and never scaled. Specifying true forces the SWF file to scale to 100% of the player. showmenu true or false Specifying true enables the full set of context menu items. Specifying false dims all the context menu items except About Flash Player. exec Path to Executes an application from within the projector. application trapallkeys true or false Specifying true sends all key events, including accelerator keys, to the onClipEvent(keyDown/keyUp) handler in Flash Player. fscommand() 305
  6. The exec command can contain only the characters A–Z, a–z, 0–9, period (.), and underscore (_). The exec command runs in the subdirectory fscommand only. In other words, if you use the fscommand exec command to call an application, the application must reside in a subdirectory named fscommand. Usage 2: To use the fscommand() function to send a message to a scripting language such as JavaScript in a web browser, you can pass any two parameters in the command and parameters parameters. These parameters can be strings or expressions and are used in a JavaScript function that handles, or catches, the fscommand() function. In a web browser, the fscommand() function calls the JavaScript function moviename_DoFScommand in the HTML page containing the SWF file. The moviename is the name of the Flash Player as assigned by the NAME attribute of the EMBED tag or the ID property of the OBJECT tag. If you assign the Flash Player the name myDocument, the JavaScript function called is myDocument_DoFScommand. Usage 3: The fscommand() function can send messages to Macromedia Director that are interpreted by Lingo (Director’s scripting language) as strings, events, or executable Lingo code. If the message is a string or an event, you must write the Lingo code to receive the message from the fscommand() function and carry out an action in Director. For more information, see the Director Support Center at www.macromedia.com/support/director. Usage 4: In Visual Basic, Visual C++, and other programs that can host ActiveX controls, the fscommand() function sends a VB event with two strings that can be handled in the environment’s programming language. For more information, use the keywords Flash method to search the Flash Support Center at www.macromedia.com/support/flash. Example In the following example, the fscommand() function sets Flash Player to scale the SWF file to the full monitor screen size when the fullscreen_btn button or unfullscreen_btn is released: this.fullscreen_btn.onRelease = function() { fscommand("fullscreen", true); }; this.unfullscreen_btn.onRelease = function() { fscommand("fullscreen", false); }; The following example uses the fscommand() function applied to a button in Flash to open a JavaScript message box in an HTML page. The message itself is sent to JavaScript as the fscommand parameter. You must add a function to the HTML page that contains the SWF file. This function, myDocument_DoFSCommand, sits in the HTML page and waits for an fscommand() function in Flash. When an fscommand is triggered in Flash (for example, when a user presses the button), the command and parameter strings are passed to the myDocument_DoFSCommand function. You can use the passed strings in your JavaScript or VBScript code in any way you like. In this example, the function contains a conditional if statement that checks to see if the command string is "messagebox". If it is, a JavaScript alert box (or “message box”) opens and displays the contents of the parameters string. 306 Chapter 2: ActionScript Language Reference
  7. function myDocument_DoFSCommand(command, args) { if (command == "messagebox") { alert(args); } } In the Flash document, add the fscommand() function to a button: fscommand("messagebox", "This is a message box called from within Flash.") You can also use expressions for the fscommand() function and parameters, as in the following example: fscommand("messagebox", "Hello, " + name + ", welcome to our website!") To test the SWF file, select File > Publish Preview > HTML. Note: If you publish your SWF file using the Flash with FSCommand template in the HTML tab of the Publish Settings dialog box, the myDocument_DoFSCommand function is inserted automatically. The SWF file’s NAME and ID attributes will be the filename. For example, for the file myDocument.fla, the attributes would be set to myDocument. fscommand() 307
  8. CHAPTER 2 ActionScript Language Reference function Availability Flash Player 5. Usage function functionname ([parameter0, parameter1,...parameterN]){ statement(s) } function ([parameter0, parameter1,...parameterN]){ statement(s) } Parameters functionname The name of the new function. This parameter is optional. parameter An identifier that represents a parameter to pass to the function. This parameter is optional. statement(s) Any ActionScript instruction you have defined for the body of the function. Returns Usage 1: Nothing. Usage 2: A reference to the anonymous function. Description Statement; comprises a set of statements that you define to perform a certain task. You can define a function in one location and invoke, or call, it from different scripts in a SWF file. When you define a function, you can also specify parameters for the function. Parameters are placeholders for values on which the function operates. You can pass different parameters to a function each time you call it so you can reuse a function in different situations. Use the return statement in a function’s statement(s) to cause a function to generate, or return, a value. You can use this statement to define a function with the specified functionname, parameters, and statement(s). When a script calls a function, the statements in the function’s definition are executed. Forward referencing is permitted; within the same script, a function may be declared after it is called. A function definition replaces any prior definition of the same function. You can use this syntax wherever a statement is permitted. You can also use this statement to create an anonymous function and return a reference to it. This syntax is used in expressions and is particularly useful for installing methods in objects. For additional functionality, you can use the arguments object in your function definition. Some common uses of the arguments object are creating a function that accepts a variable number of parameters and creating a recursive anonymous function. 308 Chapter 2: ActionScript Language Reference
  9. Example The following example defines the function sqr, which accepts one parameter and returns the Math.pow(x, 2) of the parameter: function sqr(x:Number) { return Math.pow(x, 2); } var y:Number = sqr(3); trace(y); // output: 9 If the function is defined and used in the same script, the function definition may appear after using the function: var y:Number = sqr(3); trace(y); // output: 9 function sqr(x:Number) { return Math.pow(x, 2); } The following function creates a LoadVars object and loads params.txt into the SWF file. When the file successfully loads, variables loaded traces: var myLV:LoadVars = new LoadVars(); myLV.load("params.txt"); myLV.onLoad = function(success:Boolean) { trace("variables loaded"); } function 309
  10. CHAPTER 2 ActionScript Language Reference Function class Availability Flash Player 6. Description Both user-defined and built-in functions in ActionScript are represented by Function objects, which are instances of the Function class. Method summary for the Function class Method Description Function.apply() Invokes the function represented by a Function object, with parameters passed in through an array. Function.call() Invokes the function represented by a Function object. 310 Chapter 2: ActionScript Language Reference
  11. Function.apply() Availability Flash Player 6. Usage myFunction.apply(thisObject:Object, argumentsArray:Array) Parameters thisObject The object to which myFunction is applied. argumentsArray An array whose elements are passed to myFunction as parameters. Returns Any value that the called function specifies. Description Method; specifies the value of this to be used within any function that ActionScript calls. This method also specifies the parameters to be passed to any called function. Because apply() is a method of the Function class, it is also a method of every Function object in ActionScript. The parameters are specified as an Array object, unlike Function.call(), which specifies parameters as a comma-delimited list. This is often useful when the number of parameters to be passed is not known until the script actually executes. Example The following function invocations are equivalent: Math.atan2(1, 0) Math.atan2.apply(null, [1, 0]) The following simple example shows how apply() passes an array of parameters: function theFunction() { trace(arguments); } // create a new array to pass as a parameter to apply() var firstArray:Array = new Array(1,2,3); theFunction.apply(null,firstArray); // outputs: 1,2,3 // create a second array to pass as a parameter to apply() var secondArray:Array = new Array("a", "b", "c"); theFunction.apply(null,secondArray); // outputs a,b,c The following example shows how apply() passes an array of parameters and specifies the value of this: // define a function function theFunction() { Function.apply() 311
  12. trace("this == myObj? " + (this == myObj)); trace("arguments: " + arguments); } // instantiate an object var myObj:Object = new Object(); // create arrays to pass as a parameter to apply() var firstArray:Array = new Array(1,2,3); var secondArray:Array = new Array("a", "b", "c"); // use apply() to set the value of this to be myObj and send firstArray theFunction.apply(myObj,firstArray); // output: // this == myObj? true // arguments: 1,2,3 // use apply() to set the value of this to be myObj and send secondArray theFunction.apply(myObj,secondArray); // output: // this == myObj? true // arguments: a,b,c See also Function.call() 312 Chapter 2: ActionScript Language Reference
  13. Function.call() Availability Flash Player 6. Usage myFunction.call(thisObject:Object, parameter1, ..., parameterN) Parameters thisObject An object that specifies the value of this within the function body. parameter1 A parameter to be passed to the myFunction. You can specify zero or more parameters. parameterN Returns Nothing. Description Method; invokes the function represented by a Function object. Every function in ActionScript is represented by a Function object, so all functions support this method. In almost all cases, the function call (()) operator can be used instead of this method. The function call operator produces code that is concise and readable. This method is primarily useful when the this parameter of the function invocation needs to be explicitly controlled. Normally, if a function is invoked as a method of an object, within the body of the function, this is set to myObject, as shown in the following example: myObject.myMethod(1, 2, 3); In some situations, you might want this to point somewhere else; for example, if a function must be invoked as a method of an object, but is not actually stored as a method of that object: myObject.myMethod.call(myOtherObject, 1, 2, 3); You can pass the value null for the thisObject parameter to invoke a function as a regular function and not as a method of an object. For example, the following function invocations are equivalent: Math.sin(Math.PI / 4) Math.sin.call(null, Math.PI / 4) Example The following example uses Function.call() to make a function behave as a method of another object, without storing the function in the object: function myObject() { } function myMethod(obj) { trace("this == obj? " + (this == obj)); } Function.call() 313
  14. var obj:Object = new myObject(); myMethod.call(obj, obj); The trace() statement displays: this == obj? true See also Function.apply() 314 Chapter 2: ActionScript Language Reference
  15. CHAPTER 2 ActionScript Language Reference get Availability Flash Player 6. Usage function get property() { // your statements here } Note: To use this keyword, you must specify ActionScript 2.0 and Flash Player 6 or later in the Flash tab of your FLA file’s Publish Settings dialog box. This keyword is supported only when used in external script files, not in scripts written in the Actions panel. Parameters property The word you use to refer to the property that get accesses; this value must be the same as the value used in the corresponding set command. Returns Nothing. Description Keyword; permits implicit getting of properties associated with objects based on classes you have defined in external class files. Using implicit get methods lets you access properties of objects without accessing the property directly. Implicit get/set methods are syntactic shorthand for the Object.addProperty() method in ActionScript 1. For more information, see “Implicit getter/setter methods” in Using ActionScript in Flash. Example In the following example, you define a Team class. The Team class includes get/set methods that let you retrieve and set properties within the class: class Team { var teamName:String; var teamCode:String; var teamPlayers:Array = new Array(); function Team(param_name:String, param_code:String) { this.teamName = param_name; this.teamCode = param_code; } function get name():String { return this.teamName; } function set name(param_name:String):Void { this.teamName = param_name; } } get 315
  16. Enter the following ActionScript in a frame on the Timeline: var giants:Team = new Team("San Fran", "SFO"); trace(giants.name); giants.name = "San Francisco"; trace(giants.name); /* output: San Fran San Francisco */ When you trace giants.name, you use the get method to return the value of the property. See also Object.addProperty(), set 316 Chapter 2: ActionScript Language Reference
  17. CHAPTER 2 ActionScript Language Reference getProperty() Availability Flash Player 4. Usage getProperty(my_mc:Object, property:Object) : Object Parameters my_mc The instance name of a movie clip for which the property is being retrieved. property A property of a movie clip. Returns The value of the specified property. Description Function; returns the value of the specified property for the movie clip my_mc. Example The following example creates a new movie clip someClip_mc and shows the alpha value (_alpha) for the movie clip someClip_mc in the Output panel: this.createEmptyMovieClip("someClip_mc", 999); trace("The alpha of "+getProperty(someClip_mc, _name)+" is: "+getProperty(someClip_mc, _alpha)); getProperty() 317
  18. CHAPTER 2 ActionScript Language Reference getTimer() Availability Flash Player 4. Usage getTimer() : Number Parameters None. Returns The number of milliseconds that have elapsed since the SWF file started playing. Description Function; returns the number of milliseconds that have elapsed since the SWF file started playing. Example In the following example, the getTimer() and setInterval() functions are used to create a simple timer: this.createTextField("timer_txt", this.getNextHighestDepth(), 0, 0, 100, 22); function updateTimer():Void { timer_txt.text = getTimer(); } var intervalID:Number = setInterval(updateTimer, 100); 318 Chapter 2: ActionScript Language Reference
  19. CHAPTER 2 ActionScript Language Reference getURL() Availability Flash 2. The GET and POST options are available only in Flash Player 4 and later versions. Usage getURL(url:String [, window:String [, "variables":String]]) : Void Parameters url The URL from which to obtain the document. window An optional parameter specifying the window or HTML frame into which the document should load. You can enter the name of a specific window or select from the following reserved target names: • _self specifies the current frame in the current window. • _blank specifies a new window. • _parent specifies the parent of the current frame. • _top specifies the top-level frame in the current window. variables A GET or POST method for sending variables. If there are no variables, omit this parameter. The GET method appends the variables to the end of the URL, and is used for small numbers of variables. The POST method sends the variables in a separate HTTP header and is used for sending long strings of variables. Returns Nothing. Description Function; loads a document from a specific URL into a window or passes variables to another application at a defined URL. To test this function, make sure the file to be loaded is at the specified location. To use an absolute URL (for example, http://www.myserver.com), you need a network connection. Example This example loads an image into a movie clip. When the image is clicked, a new URL is loaded in a new browser window. var listenerObject:Object = new Object(); listenerObject.onLoadInit = function(target_mc:MovieClip) { target_mc.onRelease = function() { getURL("http://www.macromedia.com/software/flash/flashpro/", "_blank"); }; }; var logo:MovieClipLoader = new MovieClipLoader(); logo.addListener(listenerObject); logo.loadClip("http://www.macromedia.com/images/shared/product_boxes/159x120/ 159x120_box_flashpro.jpg", this.createEmptyMovieClip("macromedia_mc", this.getNextHighestDepth())); getURL() 319
  20. In the following example, getURL() is used to send an e-mail message: myBtn_btn.onRelease = function(){ getURL("mailto:you@somedomain.com"); }; In the following ActionScript, JavaScript is used to open an alert window when the SWF file is embedded in a browser window: myBtn_btn.onRelease = function(){ getURL("javascript:alert('you clicked me')"); }; You can also use GET or POST for sending variables. The following example uses GET to append variables to a URL: var firstName:String = "Gus"; var lastName:String = "Richardson"; var age:Number = 92; myBtn_btn.onRelease = function() { getURL("http://www.macromedia.com", "_blank", "GET"); }; The following ActionScript uses POST to send variables in the HTTP header. Make sure you test your documents in a browser window, because otherwise your variables are sent using GET: var firstName:String = "Gus"; var lastName:String = "Richardson"; var age:Number = 92; getURL("http://www.macromedia.com", "_blank", "POST"); See also loadVariables(), XML.send(), XML.sendAndLoad(), XMLSocket.send() 320 Chapter 2: ActionScript Language Reference
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