TweetFollow Us on Twitter

Macromedia Flash; Visual vs. Language-Based programming

Volume Number: 18 (2002)
Issue Number: 8
Column Tag: Reviews

Macromedia Flash; Visual vs. Language-Based programming

by Bradley Kaldahl and Jacob Kirk

Macromedia Flash has taken the web by storm and with it a new programming paradigm has evolved that we refer to as "Visual Programming." Non-traditional "Visual Programmers" are producing algorithms that are really quite intriguing. In some respects this new visual paradigm represents an opportunity to create algorithms based on visual logic, which is an interesting alternative to traditional language-based algorithms. Please read on to see if you agree.

In the traditional language-based programming paradigm, the developer relies almost completely on the programming code to accomplish the desired task. While several highly respected authors such as Grady Booch and Coad & Yourdon have created visual diagram-based models for OO development, ultimately the design is translated into code. On the other hand Flash allows both design and implementation in a visual environment. This visual style of programming obviously has a strong appeal to certain individuals, most notably creatives, designers, and those unfamiliar with traditional programming languages and conventions.

Any programmer called upon to work or consult on an ActionScript project should be aware of the issues and idiosyncrasies of this new trend in "Visual Programming" as they will likely encounter legacy code that has been developed using the visual paradigm.

Problem definition

To contrast the visual paradigm with the language-based approach we have defined a simple programming problem.

Using Macromedia Flash 5, animate an object to move across the stage. When the user rolls-over the object have it reverse direction.

If you are familiar with Flash and ActionScript then we hope that you will enjoy the contrast of these two disparate techniques. If you are new to ActionScript we hope you will benefit from our discussion of some of the programming anomalies you will encounter in Flash when using the language-based approach.

Anomalies in ActionScript

While ActionScript resembles JavaScript, it is helpful to remember that ActionScript must conform to the animation and encapsulation features found in Flash. One of the more noticeable programming differences you will encounter in Flash is that you cannot animate an object using a standard FOR or WHILE repeat loop. There has been some debate as to why this is the case. Some have suggested that it is because the computer can execute a repeat loop at a much faster rate than the screen can redraw. While on the surface this sounds plausible, it suggests that computer animation within a repeat loop cannot be accomplished. According to Michael Williams, Associate Product Manager at Macromedia: "The issue here is not the fact that FOR and WHILE execute too quickly, it is because ActionScript, on a frame, executes before the stage is updated. The stage is only updated after all scripts on that frame have been executed."

If you do attempt to use the FOR or WHILE repeat loop for animation you will most likely encounter the following alert.


Figure 1. Flash places a 15 second time-out limit on FOR and WHILE repeat loops.

Mr. Williams explains: "The Flash Player itself provides this option to abort the script. The Flash Player will do this when it plays a movie which contains a one-frame ActionScript loop which can repeat itself indefinitely or for too long. A movie with such a loop can tax the resources of the computer system playing it. Giving viewers the option to end the script helps the Flash Player prevent an SWF file from freezing the viewer's browser or system. To avoid creating a movie that triggers this error message when it is played in the Flash Player, create a loop that goes through frames. You can do this by evaluating a variable in an if statement and, if the variable conditionalizes as true, then have the movie break the loop by going to the next frame. If the variable does not conditionalize as true, then have the movie loop back to the first frame (usually two to three frames back) of the movie."

The question still remains: How can an object be animated and controlled with ActionScript?

As discussed by Mr. Williams: "Use ActionScript applied to a Movie Clip, also known as clipEvents. For example, you have a movieClip on stage named "circle" the following code will move the circle across the X axis 10 pixels once per frame:

onClipEvent(enterFrame) {
    _x += 10;
}

This is dependent on the frame rate of the movie. In the default case this will refresh 12 frames/sec, but this can be increased or decreased by changing the movies frame rate at authortime."

The Language-Based Solution

PsuedoCode

Move the object by 15 pixels per frame.
   If the object goes off the left edge of the stage 
      then place the object on the right side of the stage.
   If the object goes off the right side of the stage
      then place the object on the left side of the stage.
When the user rolls-over the object
   stop the object from moving.
When the user rolls-off the object
   reverse the direction of the object.

Listing 1: Language-Based MovieClip Script

Animate and wrap object.
/* onClipEvent(load) is being used to define some of the variables.
The variable moveAmount is the number of pixels the object will be animated.

ballLoc: (ball location) is used to define the location of the center point of the movieClip that 
encapsulates the ball-Button object. 

_parent: is a relative reference to the movieClip that encapsulates the ball object.*/

onClipEvent (load) {         
   moveAmount = 15;   
   ballLoc = _parent
               
}

/* The (enterFrame) clipEvent is the animation repeat loop used by Flash.
ballLoc._x += moveAmount will move the object by the moveAmount each time a new frame is called. The 
two IF statements (with the magic numbers) are checking to see if the object has exceeded the left or
right edge of the stage. They are set to create an object wrap so the object appears to leave one 
edge and return on the opposite edge of the stage. */

onClipEvent (enterFrame) {
   ballLoc._x += moveAmount;
   if (ballLoc._x>640) {
      ballLoc._x = 0;   
   }
   if (ballLoc._x<0) {
      ballLoc._x = 640;
   }
}

Listing 2: Language-Based Object Script

Reverse object direction.

/* This script is placed inside a button object on the stage. 
Both rollOver and rollOut use the this. reference which insures that only the object that received 
the event will have its variables altered. If multiple instances of the ball object were used without 
the this. parameter all the objects on the stage would reverse direction. storePosition is a global 
variable created on the fly. It holds the original moveAmount before temporarily setting the 
moveAmount to 0 to stop the object. rollOut restores the original moveAmount, then reverses the 
direction of the object by setting it to the opposite of its original value. */

   on (rollOver) {
      this.storePosition=moveAmount;
      this.moveAmount=0;
      }
   on (rollOut) {
      this.moveAmount = storePosition;
      this.moveAmount = moveAmount *-1;
      }

Since the programmer has taken control of the object with ActionScript, knowledge of the timeline is not needed. This animation takes place on a single frame. However, the developer does need to know how to create a button symbol since it is the only object that will respond to a rollOver event. Additionally the developer needs to know how to encapsulate the button in a movieClip symbol, since it is the only object that will accept a clipEvent.

In contrast the visual solution, presented below, utilizes the Flash timeline and its tweening capabilities to create the movement. The animation capabilities of Flash simplify the scripting.

The Visual Solution

Some might refer to the visual solution as a "designers approach" or a "non-programmers" solution, but to minimize it would be inappropriate as it demonstrates many of the features that programmers strive for when creating an algorithm. It is simple, elegant, fast and responsive, and with Flashs built-in encapsulation capabilities, it is easily reusable. Bradley Kaldahl refers to the visual algorithm presented below as "Equal Parallel Inverse Animation's," or EPI.

Description of the visual solution

Frame #            Frame #
1------------------------40 *      100-----------------140**
 >>>>>>>>>>>>>>>      <<<<<<<<<<<<<
Animate Left to Right      Animate right to left
   * = Script to loop back to frame 1
   ** = Script to loop back to frame 100

The object is animated to move from left to right (frame 1-40) using a motion tween. In frame 1 the object is on the LEFT side of the stage and in frame 40 the object is on the far RIGHT. When the animation playback-head reaches frame 40 it loops back to frame 1 using a simple "gotoAndPlay" navigation script placed on the timeline. An equal inverse animation is created further out on the timeline, in which the object is animated from right to left (frame 100-140). In frame 100 the object is on the RIGHT side of the stage and in frame 140 the object is on the LEFT. The two animation's are on the same timeline but move in opposite directions as shown in Figure 2.


Figure 2. The Animation Timeline

When the animation begins, the playback head is looping from frame 1-40, i.e., the object is moving from left to right. To capture the rollOver event and jump the playback-head to the inverse animation another simple navigation script is placed inside the object.

On RollOver
gotoAndPlay frame (x of the inverse animation)
End RollOver

It is important to note that there are two separate instances of the ball object shown in figure 2 above. Each instance of the ball object can have a different script. The first instance begins on frame 1, and the second instance begins on frame 100. (Technically speaking there are actually 4 instances of the ball because each keyframe on the timeline represents an instance. Frame 40 and frame 140 both display a one frame instance of the ball object. For the sake of discussion we will refer to the first animation as instance one and the second animation as instance two). To view the code in the first instance of the ball object you would click on frame 1 on the timeline then click on the ball object on the stage. To view the code in the second instance of the ball object, click on frame 100 on the timeline then click on the ball object on the stage.

The final question is: Which frame in the inverse animation will produce a smooth reverse?

Algorithm - Equal Parallel Inverse Animation's with Flash

Flash provides an easy-to-use property called _currentFrame, which provides the number of the frame when the event occurs. Using this property the following algorithm finds the inverse frame in the reverse animation.

    Inverse of first the first animation instance = Number of Frames in the Animation - Current Frame Number + Distance to the Reverse Animation or (NFA - CFN + D2RA = Inverse).

    Inverse of the second animation instance = Distance to the Reverse Animation - Current Frame Number + Number of Frames in the Animation or (D2RA - CFN + NFA = Inverse).

For example, using figure 2 and discussion above, if the user rolled over the object while it was on frame 23... NFA(40) - CFN(23) + D2RA(100) = Frame number 117.

By jumping the playback head to frame 117 the object appears unchanged with the exception of reversing direction of movement.

Listing 1: Visual Solution, first animation timeline loop script

Placed in frame 40 of the timeline
gotoAndPlay (1);

Listing 2: Visual Solution, second animation timeline loop script

Placed in frame 140 of the timeline
gotoAndPlay (100);

Listing 3: Visual Solution, first object instance script

Placed in the first instance of the object
// The Number of Frames in the Animation = 40;
// Distance to the Reverse Animation = 100;
on (rollOver) {
   stop ();
}
on (rollOut) {
   gotoAndPlay (40 - _currentFrame + 100 );
}

Listing 4: Visual Solution, second object instance script

Placed in the second instance of the object
on (rollOver) {
   stop ();
}
on (rollOut) {
   gotoAndPlay (100 - _currentframe + 40 );
}

Encapsulation

Encapsulation is what really makes Flash so powerful. Converting either the language or visual animation into a movieClip not only captures the animation but also encapsulates both Frame and Object scripts. Basically a movieClip becomes a self contained animated object that knows how it should behave to specific events. Once encapsulated as a movieClip multiple copies can be dropped on the stage and each plays independently. We have encapsulated and extended the code from this article to produce a couple of different web games. The games and source code can be found at www.hotFlashBook.com

Conclusion

While certain problems clearly require a language-based solution, such as score keeping in a game, a variety of other functions are more easily accomplished using the visual paradigm. To see two examples that appear fairly complex but were easily accomplished using the visual solution visit the web site listed below. The fact that these functions can be accomplished with little code and an aptitude for logical thinking makes it easy to see why many creatives are so excited about Flash. It is interesting that, when presented with a Flash problem, we both tend to look for code-based solutions first, yet on several occasions we have been delighted to discover simpler visual solutions that met our needs. One thing that is clear is that ActionScript programmers need to be familiar with Flash and its visual capabilities as well as the scripting language. An excellent resource for both novice and experienced Flash users is the book EZ Flash 5 by Bradley Kaldahl. It uses short 2-8 page hands-on projects to provide a wealth of both visual and code-based ideas and solutions. To find out more about the book EZ Flash 5 visit www.hotFlashbook.com

Acknowledgements

Special thanks to Michael Williams, from Macromedia, for your insight and information and to Suzy Ramirez, from Macromedia, for your wonderful assistance.


Bradley Kaldahl is a professor of Computer Publishing at Montgomery College and is author of the book EZ Flash 5. You can contact him through www.hotFlashBook.com

Jacob Kirk is a Designer, Teacher, Author and an all around Interactive Web "Whiz-kid". He specializes in using Macromedia Flash and Adobe LiveMotion. More information about what Jacob is up to can be found at www.EmazingMedia.com.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Bookends 12.8 - Reference management and...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
Apple iTunes 12.6 - Play Apple Music and...
Apple iTunes lets you organize and stream Apple Music, download and watch video and listen to Podcasts. It can automatically download new music, app, and book purchases across all your devices and... Read more
Default Folder X 5.1.4 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more
Amazon Chime 4.1.5587 - Amazon-based com...
Amazon Chime is a communications service that transforms online meetings with a secure, easy-to-use application that you can trust. Amazon Chime works seamlessly across your devices so that you can... Read more
CrossOver 16.2 - Run Windows apps on you...
CrossOver can get your Windows productivity applications and PC games up and running on your Mac quickly and easily. CrossOver runs the Windows software that you need on Mac at home, in the office,... Read more
Adobe Creative Cloud 4.0.0.185 - Access...
Adobe Creative Cloud costs $19.99/month for a single app, or $49.99/month for the entire suite. Introducing Adobe Creative Cloud desktop applications, including Adobe Photoshop CC and Illustrator CC... Read more
MegaSeg 6.0.2 - Professional DJ and radi...
MegaSeg is a complete solution for pro audio/video DJ mixing, radio automation, and music scheduling with rock-solid performance and an easy-to-use design. Mix with visual waveforms and Magic... Read more
Bookends 12.8 - Reference management and...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
Adobe Creative Cloud 4.0.0.185 - Access...
Adobe Creative Cloud costs $19.99/month for a single app, or $49.99/month for the entire suite. Introducing Adobe Creative Cloud desktop applications, including Adobe Photoshop CC and Illustrator CC... Read more
Default Folder X 5.1.4 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more

The best deals on the App Store this wee...
Deals, deals, deals. We're all about a good bargain here on 148Apps, and luckily this was another fine week in App Store discounts. There's a big board game sale happening right now, and a few fine indies are still discounted through the weekend.... | Read more »
The best new games we played this week
It's been quite the week, but now that all of that business is out of the way, it's time to hunker down with some of the excellent games that were released over the past few days. There's a fair few to help you relax in your down time or if you're... | Read more »
Orphan Black: The Game (Games)
Orphan Black: The Game 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Dive into a dark and twisted puzzle-adventure that retells the pivotal events of Orphan Black. | Read more »
The Elder Scrolls: Legends is now availa...
| Read more »
Ticket to Earth beginner's guide: H...
Robot Circus launched Ticket to Earth as part of the App Store's indie games event last week. If you're not quite digging the space operatics Mass Effect: Andromeda is serving up, you'll be pleased to know that there's a surprising alternative on... | Read more »
Leap to victory in Nexx Studios new plat...
You’re always a hop, skip, and a jump away from a fiery death in Temple Jump, a new platformer-cum-endless runner from Nexx Studio. It’s out now on both iOS and Android if you’re an adventurer seeking treasure in a crumbling, pixel-laden temple. | Read more »
Failbetter Games details changes coming...
Sunless Sea, Failbetter Games' dark and gloomy sea explorer, sets sail for the iPad tomorrow. Ahead of the game's launch, Failbetter took to Twitter to discuss what will be different in the mobile version of the game. Many of the changes make... | Read more »
Splish, splash! The Pokémon GO Water Fes...
Niantic is back with a new festival for dedicated Pokémon GO collectors. The Water Festival officially kicks off today at 1 P.M. PDT and runs through March 29. Magikarp, Squirtle, Totodile, and their assorted evolved forms will be appearing at... | Read more »
Death Road to Canada (Games)
Death Road to Canada 1.0 Device: iOS Universal Category: Games Price: $7.99, Version: 1.0 (iTunes) Description: Get it now at the low launch price! Price will go up a dollar every major update. Update news at the bottom of this... | Read more »
Bean's Quest Beginner's Guide:...
Bean's Quest is a new take on both the classic platformer and the endless runner, and it's free on the App Store for the time being. Instead of running constantly, you can't stop jumping. That adds a surprising new level of challenge to the game... | Read more »

Price Scanner via MacPrices.net

2.6GHz Mac mini on sale for $559, $140 off MS...
Guitar Center has the 2.6GHz Mac mini (MGEN2LL/A) on sale for $559 including free shipping. Their price is $140 off MSRP, and it’s the lowest price available for this model. Read more
SSD Speeder RAM Disk SSD Life Extender App Fo...
Fehraltorf, Switzerland based B-Eng has announced they are making their SSD Speeder app for macOS publicly available for purchase on their website. SSD Speeder is a RAM disk utility that prevents... Read more
iPhone Scores Highest Overall in Smartphone D...
Customer satisfaction is much higher among smartphone owners who use their device to operate other connected home services such as smart thermostats and smart appliances, according to the J.D. Power... Read more
Swipe CRM Free Photo-Centric CRM Sales DEal C...
Swipe CRM LLC has introduced Swipe CRM: Visual Sales 1.0 for iPad, an app for creating, managing, and sharing visually stunning sales deals. Swipe CRM is targeted to small-and-medium creative... Read more
13-inch 2.0GHz Apple MacBook Pros on sale for...
B&H has the non-Touch Bar 13″ 2.0GHz MacBook Pros in stock today and on sale for $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.0GHz MacBook Pro Space Gray (... Read more
15-inch Touch Bar MacBook Pros on sale for up...
B&H Photo has the new 2016 15″ Apple Touch Bar MacBook Pros in stock today and on sale for up to $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.7GHz Touch Bar... Read more
Apple’s iPhone 6s Tops Best-Selling Smartphon...
In terms of shipments, the iPhone 6s from Apple bested all competitors for sales in 2016, according to new analysis from IHS Markit, a world leader in critical information, analytics and solutions.... Read more
Logitech Rugged Combo Protective iPad Case an...
Logitech has announced its Logitech Rugged Combo, Logitech Rugged Case, and Logitech Add-on Keyboard for Rugged Case for Apple’s new, more affordable $329 9.7-inch iPad, a complete solution designed... Read more
T-Mobile To Offer iPhone 7 and iPhone 7 Plus...
T-Mobile has announced it will offer iPhone 7 and iPhone 7 Plus (PRODUCT)RED Special Edition in a vibrant red aluminum finish. The introduction of this special edition iPhone celebrates Apple’s 10... Read more
9-inch 128GB iPad Pros on sale for $50-$70 of...
B&H Photo has 9.7″ 128GB Apple WiFi iPad Pros on sale for up to $70 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 9″ Space Gray 128GB WiFi iPad Pro: $649 $50... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Fulltime aan de slag als shopmanager in een h...
Ben jij helemaal gek van Apple -producten en vind je het helemaal super om fulltime shopmanager te zijn in een jonge en hippe elektronicazaak? Wil jij werken in Read more
Starte Dein Karriere-Abenteuer in den Hauptst...
…mehrsprachigen Teams betreust Du Kunden von bekannten globale Marken wie Apple , Mercedes, Facebook, Expedia, und vielen anderen! Funktion Du wolltest schon Read more
*Apple* Retail - Multiple Positions- Chicago...
SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Fulltime aan de slag als shopmanager in een h...
Ben jij helemaal gek van Apple -producten en vind je het helemaal super om fulltime shopmanager te zijn in een jonge en hippe elektronicazaak? Wil jij werken in Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.