adobe flash cs5 on demand part 58 doc

ptg 354 Chapter 14 A function is a block of ActionScript code that can be reused anywhere in a SWF file. If you pass values as parameters to a function, the function will operate on those values. A func- tion can also return values. Flash contains built-in functions that let you access certain information and perform certain tasks, such as getting the version number of Flash Player hosting the SWF file (getVersion()). Functions that belong to an object are called methods. Functions that don't belong to an object are called top-level functions and are found in the Functions category of the Actions panel. Each function has its own characteristics, and some functions require you to pass cer- tain values. If you pass more parameters than the function requires, the extra values are ignored. If you don't pass a required parame- ter, the empty parameters are assigned the undefined data type, which can cause errors when you export a script. To call a function, it must be in a frame that the playhead has reached. To call a function, simply u s e the function name and pass any required parameters. The following code describes a common syntax for creating functions: function firstFunction (x, y, z) { // place all actions here; } Using Functions Calling a Function Functions begin with the word function, fol- lowed by the name of the function (user- defined). The area enclosed by parenthesis is used for passing parameters to the function actions. If the parameters are left blank, you're essentially creating a generic function that will function the same way every time it's called. If the function contains parameters, it will perform in a unique way each time it's called. When you call a function, you're instructing Flash to execute all of the actions within that function. Therefore, if firstFunction contained 20 actions, all of them would be executed by using a single line of script. To call a function, simply add this line to the action: myFunction (); Passing Parameters to a Function If the function has been defined to accept parameter information, you can use the fol- lowing line of script: myFunction (parameter 1, parameter2); Once a Function is defined, it can be called anytime it's needed. Therefore, it's a good practice to define all of your functions in frame 1 of the active Flash document. That way they can be called anytime after that. From the Library of Wow! eBook ptg Chapter 14 Using Basic ActionScripts 355 Conditional statements in ActionScript are a critical part of interactivity. They let you pro- gram a script based on any number of condi- tions. For example, in the morning, you say good day, or good morning to someone you meet. In doing so, you made a conditional choice. ActionScript does the same thing. You can create an ActionScript that checks the time of day. If it's before noon, Flash responds with a Good Morning message. If it's from noon to 5, Flash says Good Afternoon, or from 5 till mid- night, Flash says Good Evening. This type of condition is known as an if/else condition. If this happens, do this… else do that. Since a variable can be almost anything you can measure on a computer, and a conditional statement is made up of two or more vari- ables, ActionScript can be taken to a point where it almost thinks for itself. The previous example could be expressed in flow charting the following way: Typically, when you're creating a condi- tional statement, you're comparing one ele- ment against another using operators. The following operators are available to create conditional statements: ◆ == Checks for equality between two values (is time of day equal to 5). ◆ != Checks for inequality between two values. ◆ < Checks for less than (is value A less than value B). ◆ > Checks for greater than (is value A greater than value B). ◆ <= Checks for less than or equal to between two values. ◆ >= Checks for greater than or equal to between two values. ◆ && Checks for a logical AND (if day == "Friday" && time > 5). ◆ || Checks for a logical OR (if day == "Saturday" || day == "Sunday"). Using these operators to check between two or more values, you can create complex ActionScripts that react differently based on the available data. To create a dynamic field that checks the time, and responds with the appropriate answer, you would enter the fol- lowing code: if (time > "0000 && time < 1200) { response = "Good Morning"; } else if (time >1200 && time < 1700) { response = "Good Afternoon"; }else if (time > 1700 && time < 2400); response = "Good Evening" } Using Conditional Statements From the Library of Wow! eBook ptg 356 Chapter 14 Attaching a mouse event to a button is probably the easiest of all the event handlers. For example, you have a movie clip of a dog that con- tains a barking audio file. When the movie clip plays, the dog barks. The trick is to have the dog bark when the visitor rolls their mouse over the dog’s face. To do this, you will need to create an invisible button and then attach the mouse event to the invisible button. Attaching a Mouse Event to a Button Attach an Event to a Button Click the Insert menu, and then click New Symbol. Select the Button type, and then name the symbol. Click OK. Create a blank keyframe in the Hit state of the button, and then create a shape. Leave the Up, Over, and Down states blank. Exit the Symbol editing mode, and then return to the Stage. Drag a movie clip onto the Stage. Create a new layer, and then name the layer. Drag the invisible button onto the Stage, and then place it over the area of the image you want to use as a button. Enter the script (ActionScript 2.0) as shown in the illustration. ◆ ActionScript 3.0 example files are available on the Web at www.perspection.com . When the visitor rolls into or out of the invisible button, the rollOver or rollOut event handlers will trigger the playing or stopping of the dog movie clip. Click the Control menu, point to Test Movie, and then click Test. 10 9 8 7 6 5 4 3 2 1 7 8 9 6 3 2 From the Library of Wow! eBook ptg Chapter 14 Using Basic ActionScripts 357 Frame event handlers are easy to understand. When an action is attached to a frame, the action is triggered when the play head hits the frame. For example, you want to create a frame event that swaps images on the Stage, and you want the images to swap every 40 frames. You can attach an ActionScript that swaps the image, and place the action every 40 frames. When the play head hits the frame, the action executes. When you attach an ActionScript to a frame, you’ll need a blank keyframe on the Timeline, and it is strongly recommended that you always place ActionScripts in a separate layer from access and control. In addition, if you're planning to swap images in a Flash movie, it's always best to use a blank movie clip (called a placeholder) to hold the images. Working with Frame Events Attach an ActionScript to a Frame Drag a blank movie clip onto the Stage, and then select the clip. Give the movie clip a unique instance name in the Properties panel. Create a new layer, and then name the layer. Create blank keyframes at frame numbers 1, 21, 41, and 61. Select a frame, click the Insert menu, point to Timeline, and then click Blank Keyframe. Select frame 1, and then enter the script (ActionScript 2.0) as shown in the illustration. ◆ ActionScript 3.0 example files are available on the Web at www.perspection.com . Select frames 21, 41, and 61, and then repeat the script, except change the name of the image you want to load (image_b.jpg, image_c.jpg, image_d.jpg). Click the Control menu, point to Test Movie, and then click Test. 8 7 6 5 4 3 2 1 6 4 3 2 1 From the Library of Wow! eBook ptg 358 Chapter 14 on(press) { trace("The button has been pressed."); } You can specify two or more events for each on() handler, separated by commas. The ActionScript in a handler executes when one of the events specified by the handler occurs. For example, the following on() handler attached to a button will execute whenever the mouse rolls over or out of the button. on(rollOver, rollOut) { trace("mouse rolled in or out"); } If you want different scripts to run when different events occur, you have the option to attach more than one handler to an object. You can attach onClipEvent() handler s to the same movie clip instance. The first would exe- cute when the movie clip first loads (or appears on the Stage); the second executes when the movie clip is unloaded from the Stage. onClipEvent(load) { trace("loaded"); } onClipEvent (unload) { trace("unloaded"); If you’re working with ActionScript 2.0 (not supported in ActionScript 3.0), you can attach clip events to movie clips, which triggers an action specified in the onClipEvent handler. Event handlers, also known as event listen- ers, control when events in Flash occur. When you create a script, some event will be invoked to trigger that particular action. You might want a specific movie clip to stop play- ing when another movie clip loads on the Stage, or when the user clicks or moves their mouse. The Clip Event is one of a series of event handlers that Flash uses to create actions within a Flash movie. You can attach event handlers directly to a button or movie clip instance by using the onClipEvent() or the on() handlers. The onClipEvent() handles movie clip events, and on() handles button events. To use an on() or onClipEvent() han- dler, attach it directly to an instance of a but- ton or movie clip on the Stage, and then specify the event you want to handle for that instance. For example, the following on() event handler executes whenever the user clicks the button the handler is attached to. Working with Clip Events Assigning a Clip Event using the Behaviors panel. Assigning a Clip Event directly in the Actions panel. From the Library of Wow! eBook ptg Chapter 14 Using Basic ActionScripts 359 For ActionScript 2.0, you can only attach an onClipEvent() to a movie clip instance that has been placed on the Stage. You can't attach an onClipEvent() to a movie clip instance that is created at runtime; for example, using the attachMovie() method. However, you can still attach multiple event handlers. Using different event handlers within the same Flash document do not conflict with each other. You could have a but- ton with an on(press) handler that tells the SWF file to play, and the same button can have an onPress method, for which you define a func- tion that tells an object on the Stage to rotate. When the button is clicked, the SWF file plays, and the object will rotate. Being able to consolidate different event handlers with a single instance gives you greater control, as well as less Stage clutter. Attaching a Clip Event to a Movie Clip Attach an onClipEvent to a Movie Clip Create or open a Flash document (ActionScript 2.0), place a movie clip on the Stage, and then select the movie clip. Give the movie clip a unique instance name in the Properties panel. Move down the Timeline and add a keyframe at frame 80. Click the Insert menu, point to Timeline, and then click Keyframe. Add a second movie clip to the Stage, and then select the second movie clip. Enter the script as shown in the illustration. Click the Control menu, point to Test Movie, and then click Test. When the playhead hits frame 80 it loads the second movie clip. The loading of the movie will trigger the onClipEvent handler, and stop the playing of the movie clip with the unique instance name of movie2. 7 6 5 4 3 2 1 3 5 6 1 From the Library of Wow! eBook . functions: function firstFunction (x, y, z) { // place all actions here; } Using Functions Calling a Function Functions begin with the word function, fol- lowed by the name of the function (user- defined) Functions that belong to an object are called methods. Functions that don't belong to an object are called top-level functions and are found in the Functions category of the Actions panel. Each. message. If it's from noon to 5, Flash says Good Afternoon, or from 5 till mid- night, Flash says Good Evening. This type of condition is known as an if/else condition. If this happens, do