Ouch, it hurts when i do that
As promised, here are the slides for "Ouch! It hurts when i do that." presentation first delivered at 360Flex San Jose, March 10th, 2010.
Flex 4 for Flex 3 developers
Today, I presented my Flex 4 for Flex 3 developers presentation at FlashCamp Chicago. For those that wanted the slide deck, you can find it here.
In this, I discuss a number of differences between flex 3 and flex 4, and what an existing Flex 3 developer will need to know to start being productive in Flex 4.
Flex 360 tickets selling fast
Down to the last 5 (Cheap) tickets left for 360|Flex. Register now, save $100 and get the same awesome content for a little less coin. Act fast, these last tickets won't last. When they're gone, the regular price of $599 kicks in.
Come on out and hear me give advice how not to hurt yourself with code, in my "Ouch, it hurts when i do that" talk.
Wanna know more about how not to code flex apps?
I'll be presenting my freshly revised "How Not To Code Flex Applications" twice in the next few days. Tomorrow, in the boston area at RIA-Unleashed and then next week at Flash Camp Wall Street.
c'mon by and see us at one, if not both of these great events
Free Flex 4 Training in Chicago
I'll be giving a free full-day, hands-on training session, where experienced ColdFusion Developers can learn how to build their first Flex application using the latest Flash Builder 4 beta software. This training is designed to help experienced ColdFusion developers get started in understanding how to add rich UI to existing and new ColdFusion applications.
Date / Time
Thursday, November 19
Hyatt Regency Chicago on the River Walk,
151 East Wacker Drive,
Chicago, IL 60601
Registration: 8:30am
Registration
http://www.adobe.com/go/flextrainingforcfdevelopers
Fun with custom preloaders in Flex
As you probably know, its pretty easy to use a custom preloader in flex to replace the built in preloader shown as a flex application loads. There are a few tricks to remember with a custom preloader though, remember that the preloader is built to be displayed until the flex framework is done downloading. As such, the preloader won't display until all the classes needed by the preloader are done downloading. For this reason, its really important to remember that your custom preloader class doesn't make use of the flex framework, because if it does, the users will see nothing until enough of the framework has been loaded to display the preloader, and the preloader will only be displayed while the remainder of the framework is downloaded.
Fortunately, the DownloadProgressBar class makes little use of the flex framework, as it extends Sprite, instead of UIComponent, and only utilizes a few event classes from flex, which don't require any additional framework classes. A quick google search can show you dozens of examples on subclassing DownloadProgressBar to create a preloader which matches your application.
A larger challenge is faced when you have additional needs from a preloader. Frequently, we are tasked with writing a preloader which is shown during the initial download, as well as remaining displayed until some startup procedures are complete within the application. Some might try to approach by referencing Application.application within the preloader, to listen for a custom event indicating that the startup procedures are complete. Of course, this is not an ideal solution, as referencing the Application class will link in the mx.core.Applicaiton class, which in turn links in around 170k worth of the Flex framework.
A better approach is to create a new class, which is not linked to the flex framework, which can act as an event bus between the main application and the preloader. If this class is built as a singleton, you can be assured that both the main application and the preloader are accessing the same instance, allowing for a simple and convenient mechanism for the preloader to listen to the main application, without needing any reference to the application or the flex framework.
package net.digitalprimates.preload
{
public class PreloadEventBus extends EventDispatcher
{
public var isReady:Boolean = false;
private static var _instance:PreloadEventBus;
public static const READY:String = "READY";
public static function getInstance():PreloadEventBus
{
if (!_instance)
{
_instance = new PreloadEventBus(new SingletonEnforcer());
}
return _instance;
}
public function PreloadEventBus(singletonEnforcer:SingletonEnforcer)
{
if (!singletonEnforcer)
{
throw new Error("PreloadEventBus is a singleton class, use getInstance() instead");
}
}
}
}
class SingletonEnforcer {}
{
public class PreloadEventBus extends EventDispatcher
{
public var isReady:Boolean = false;
private static var _instance:PreloadEventBus;
public static const READY:String = "READY";
public static function getInstance():PreloadEventBus
{
if (!_instance)
{
_instance = new PreloadEventBus(new SingletonEnforcer());
}
return _instance;
}
public function PreloadEventBus(singletonEnforcer:SingletonEnforcer)
{
if (!singletonEnforcer)
{
throw new Error("PreloadEventBus is a singleton class, use getInstance() instead");
}
}
}
}
class SingletonEnforcer {}
With this class, when the main application is done with its startup procedure, it's a simple process to get a reference to the PreloadEventBus, set isReady to true, and dispatch an event.
protected function applicationCustomStartupDone(event:Event)
{
var bus:PreloadEventBus = PreloadEventBus.getInstance();
bus.isReady = true;
bus.dispatchEvent( new Event ( PreloadEventBus.READY );
}
{
var bus:PreloadEventBus = PreloadEventBus.getInstance();
bus.isReady = true;
bus.dispatchEvent( new Event ( PreloadEventBus.READY );
}
In the custom preloader, you can override the set preload method, and instead of listening for the complete event as the base class does, listen for the INIT_COMPLETE event, which indicates that the application has loaded, and had its initialize event dispatched. In the event handler for this method, you will get a reference to the PreloadEventBus, check if the application has already set the isReady flag to true, and if not, listen for the READY event.
private function bus:PreloadEventBus = PreloadEventBus.getInstance();
override public function set preloader( value:Sprite ):void
{
preloader.addEventListener( FlexEvent.INIT_COMPLETE , initComplete);
}
override public function set preloader( value:Sprite ):void
{
preloader.addEventListener( FlexEvent.INIT_COMPLETE , initComplete);
}
An important thing to note is the lack of call to super.preloader in this overridden setter. If the base classes setter is allowed to run, the preloader will act as initially intended, such that it disappears when the application is done downloading. As the purpose of this preloader is to allow for the application to determine when to hide the preloader and start the app, its important we override this functionality. You may find that you need to listen for other events here, such as ProgressEvent.PROGRESS, FlexEvent.INIT_PROGRESS or Event.COMPLETE. This example shows the bare minimum you would need to make use of the preloader
private function initComplete( event:Event ):void
{
if (bus.isReady)
{
completePreloader(event)
}
else
{
bus.addEventListener(PreloadEventBus.READY, completePreloader);
}
}
{
if (bus.isReady)
{
completePreloader(event)
}
else
{
bus.addEventListener(PreloadEventBus.READY, completePreloader);
}
}
While its not expected that the application will be done with its initialization procedures before the INIT_COMPLETE, but, based on how the application is built, it is possible. To avoid this race condition, the isReady property of the PreloadEventBus is used, so that the preloader only listens for the READY event if the application is not already done with its startup.
Last but not least is the completePreloader method, which is called when the preloader has determined that the application is ready. With the logic in initComplete, this same method will be used, regardless whether the state of the application was determined by the isReady property, or by listening for the PreloadEventBus.READY event.
private function completePreloader(event:Event):void
{
dispatchEvent( new Event( Event.COMPLETE ) );
}
{
dispatchEvent( new Event( Event.COMPLETE ) );
}
Event.COMPLETE is used, as this is the event for which the system manager listens, to know that the preloader is done with its job. By preventing its normal mechanism of dispatching, and only dispatching it when the application determines it is ready, you have a nice clean approach to allow the the preloader to display as long as it needs to.
I'll be speaking at Adobe MAX again this year
For the 9th year of the last decade I'll be speaking at Adobe MAX, being held this year in Los Angeles, between October 3rd and October 7th. This time, adobe has asked me to present two sessions, one an "Intro to Flex 4," and the other a session on "How not to code Flex Applications." You can find information on registration and everything else at max.adobe.com
If the schedule stands as planned, I'll present my "How not to code" 10/6 at 3pm, and my "Intro to Flex 4" 10/5 at 11:30am
In case you are wondering, here is what I have spoken on in years past...
- 2009 - Los Angeles - How Not To Code Flex, Intro to Flex 4
- 2008 - San Francisco - Intro to Flex 3
- 2007 - Chicago - Intro to Adobe AIR / Building Desktop applications with HTML and AIR
- 2006 - Las Vegas - Getting Started with Flex Development
- 2005 - Anaheim - Creating Better Performing Flex Applications
- 2004 - New Orleans - Using ColdFusion to Power Flex and Flash Applications
- 2003 - Salt Lake City - XML in ColdFusion / Building Components in Flash
- 2002 - Orlando - Styling a Flash Application
- 2001 - Orlando - Did not speak
- 2000 - Washington DC - Planning a Spectra Application
FlexUnit 4 feature overview
Flex Unit 4 Feature Overview
View more presentations from jefftapper.
More details available on Labriola's blog and openSource.adobe
How not to code Flex Applications
How Not To Code Flex Applications
View more presentations from jefftapper.
Flex Camp Chicago
I'm speaking today and tomorrow at Flex Camp Chicago. Today, I'm covering for Mike Nimer (who is recovering from some dental work), and presenting his "Flex for ColdFusion Developers" session. For those of you looking for the presentation or source code, you can find it on Nimers blog.
Tomorrow, I'll be presenting my Unit Testing with Fluint session. You can find the code and preso for this session here
