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.

 
AAPL
$106.98
Apple Inc.
+0.00
MSFT
$46.05
Microsoft Corpora
+0.00
GOOG
$550.31
Google Inc.
+0.00

MacTech Search:
Community Search:

Software Updates via MacUpdate

Dropbox 2.10.44 - Cloud synchronization...
Dropbox is an application that creates a special Finder folder that automatically syncs online and between your computers. It allows you to both backup files and keep them up-to-date between systems... Read more
Sandvox 2.9.2 - Easily build eye-catchin...
Sandvox is for Mac users who want to create a professional looking website quickly and easily. With Sandvox, you don't need to be a Web genius to build a stylish, feature-rich, standards-compliant... Read more
Cocktail 8.0.1 - General maintenance and...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
LibreOffice 4.3.3.2 - Free Open Source o...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
VMware Fusion 7.0.1 - Run Windows apps a...
VMware Fusion allows you to create a Virtual Machine on your Mac and run Windows (including Windows 8.1) and Windows software on your Mac. Run your favorite Windows applications alongside Mac... Read more
OneNote 15.3.2 - Free digital notebook f...
OneNote is your very own digital notebook. With OneNote, you can capture that flash of genius, that moment of inspiration, or that list of errands that's too important to forget. Whether you're at... Read more
Audio Hijack Pro 2.11.4 - Record and enh...
Audio Hijack Pro drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio with Audio Hijack... Read more
Iridient Developer 3.0.0 beta 3 - Powerf...
Iridient Developer (was RAW Developer) is a powerful image conversion application designed specifically for OS X. Iridient Developer gives advanced photographers total control over every aspect of... Read more
TextWrangler 4.5.11 - Free general purpo...
TextWrangler is the powerful general purpose text editor, and Unix and server administrator's tool. Oh, and also, like the best things in life, it's free. TextWrangler is the "little brother" to... Read more
NeoFinder 6.6 - Catalog your external me...
NeoFinder (formerly CDFinder) rapidly organizes your data, either on external or internal disks, or any other volumes. It catalogs all your data, so you stay in control of your data archive or disk... Read more

Latest Forum Discussions

See All

Night Sky Pro™ (Reference)
Night Sky Pro™ 3.0.1 Device: iOS Universal Category: Reference Price: $2.99, Version: 3.0.1 (iTunes) Description: Night Sky Pro™Wonder No More™ Night Sky Pro™ is the ultimate stargazing experience. From the creators of the original... | Read more »
Audio Defence : Zombie Arena (Games)
Audio Defence : Zombie Arena 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: A zombie shooter audio game. Made from gut-wrenching 3D binaural sound, for a new kind of weird immersion. You... | Read more »
RPG Asdivine Hearts (Games)
RPG Asdivine Hearts 1.1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.1.0 (iTunes) Description: SPECIAL PRICE50% OFF (USD 7.99 -> USD 3.99)!!! Travel alongside four companions and a cat in the adventure of a... | Read more »
Haunt the House: Terrortown (Games)
Haunt the House: Terrortown 1.0.1 Device: iOS Universal Category: Games Price: $.99, Version: 1.0.1 (iTunes) Description: 66.6% OFF! SPECIAL SPOOKY HALLOWEEN LAUNCH PRICE! 66.6% OFF! ...What was that sound? Is somebody there? | Read more »
SAS: Zombie Assault 4 Review
SAS: Zombie Assault 4 Review By Jennifer Allen on October 30th, 2014 Our Rating: :: FLAWED SHOOTERUniversal App - Designed for iPhone and iPad Shoot everything that moves in this fun, if flawed, twin-stick shooter.   | Read more »
Naailde the Witch Review
Naailde the Witch Review By Amy Solomon on October 30th, 2014 Our Rating: :: PITCH-PERFECT STORYTELLINGUniversal App - Designed for iPhone and iPad Marvelous storytelling, narration, and moving illustrations make this storybook... | Read more »
1st & Goal Review
1st & Goal Review By Andrew Fisher on October 30th, 2014 Our Rating: :: FOR THE D&D LOVING QBUniversal App - Designed for iPhone and iPad 1st & Goal is a board gamer’s football game, a football fan’s board game, and... | Read more »
French Developer Pated Unveils Seashine
French Developer Pated Unveils Seashine Posted by Ellis Spice on October 30th, 2014 [ permalink ] French one-man studio Pated has unveiled Seashine, “a poetic journey into the abyss.” Players take on the role of a jellyfish strugglin | Read more »
Agents of Storm: Tips, Tricks, and Strat...
Calling all agents: Would you like to see what we thought of this rather pretty base builder? Check out our Agents of Storm review! Have you downloaded Agents of Storm, been bowled over by the graphics, and aren’t quite sure what to do next? Never... | Read more »
Any.DO 2.0 Hopes to Help Manage Producti...
Any.DO 2.0 Hopes to Help Manage Productivity Posted by Ellis Spice on October 30th, 2014 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »

Price Scanner via MacPrices.net

Apple Regains Momentum As Windows Stutters An...
The latest smartphone sales data from Kantar Worldpanel ComTech, for the three months to March 2014, shows Apple performing strongly in the first quarter of the year, with sales bouncing back in... Read more
Worldwide Smartphone Shipments Increase 25.2%...
New smartphone releases and an increased emphasis on emerging markets drove global smartphone shipments above 300 million units for the second consecutive quarter, according to preliminary data from... Read more
Apple now offering refurbished 2014 15-inch M...
The Apple Store is now offering Apple Certified Refurbished 2014 15″ Retina MacBook Pros for up to $400 off the cost of new models. An Apple one-year warranty is included with each model, and... Read more
Apple drops prices on refurbished 2013 Retina...
The Apple Store has dropped prices on 2013 Apple Certified Refurbished 13″ and 15″ Retina MacBook Pros, with Retina models now available starting at $999. Apple’s one-year warranty is standard, and... Read more
New 2.8GHz Mac mini on sale for $949, save $5...
Abt Electronics has the new 2.8GHz Mac mini in stock and on sale for $949.05 including free shipping. Their price is $50 off MSRP, and it’s the lowest price available for this model from any reseller... Read more
Sale! 3.7GHz Quad Core Mac Pro available for...
 B&H Photo has the 3.7GHz Quad Core Mac Pro on sale for $2649 including free shipping plus NY sales tax only. Their price is $350 off MSRP, and it’s the lowest price for this model from any... Read more
Mujjo Steps Up The Game With Refined Touchscr...
Netherlands based Mujjo have just launched their Refined Touchscreen Gloves, stepping up their game. The gloves feature a updated elegant design that takes these knitted gloves to the next level. A... Read more
Sale! Preorder the new 27-inch 5K iMac for $2...
 Abt Electronics has the new 27″ 3.5GHz 5K iMac on sale and available for preorder for $2374.05 including free shipping. Their price is $125 off MSRP, and it’s the lowest price available for this... Read more
Simplex Solutions Inc. Brings Secure Web Surf...
New York based Simplex Solutions Inc. has announced the release and immediate availability of Private Browser 1.0, its revolutionary new secure web browser developed for iPhone, iPad and iPod touch... Read more
Save up to $180 off MSRP with an Apple refurb...
The Apple Store has Apple Certified Refurbished 2014 MacBook Airs available for up to $180 off the cost of new models. An Apple one-year warranty is included with each MacBook, and shipping is free.... Read more

Jobs Board

Position Opening at *Apple* - Apple (United...
**Job Summary** Every day, business customers come to the Apple Store to discover what powerful, easy-to-use Apple products can do for them. As a Business Leader, Read more
Sr. Manager, *Apple* Deployment Programs fo...
**Job Summary** Apple is seeking candidates for a new position on the Education Content and Technology team. iPad and Mac is in the hands of millions of teachers and Read more
*Apple* Solutions Consultant (ASC) - Apple I...
…important role that the ASC serves is that of providing an excellent Apple Customer Experience. Responsibilities include: * Promoting Apple products and solutions Read more
*Apple* Solutions Consultant (ASC) - Apple I...
…important role that the ASC serves is that of providing an excellent Apple Customer Experience. Responsibilities include: * Promoting Apple products and solutions Read more
*Apple* Solutions Consultant (ASC) - Apple I...
…important role that the ASC serves is that of providing an excellent Apple Customer Experience. Responsibilities include: * Promoting Apple products and solutions Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.