Amazon Kindle Application Development Tutorial – Part 3 Aasim Naseem, November 14, 2010 Kindle Application Lifecycle Hello everyone. Hope you are fine and doing good in your daily routine. Here is the 3rd part of my series of tutorial on Amazon Kindle Application Development. Note : So far we have discussed following topics in this category. Amazon Kindle :: An Introduction Amazon Kindle Tutorial – Part 1 :: Basic Concepts Amazon Kindle Tutorial – Part 2 :: Setting up Your System For Amazon Kindle Amazon Kindle Tutorial – Part 3 :: Kindle Application Lifecycle In this part I will describe some core concept that one must know before starting development on kindle plateform. It includes life cycle of kindle application and some other key points we have to care during code. Earlier i was going to start hello world tutorial but i felt these things should discuss first so that when one start writing his first program he/she should clear about whats going on at backend. So let start. I have bring my bowl of “fruit chaat” but my music player is silent today. I’m not in mood of listen any track, but while reading these lines; don’t forget to follow the traditions. You must have something to eat and listen, having relax seat in your chair … Orite here we go .. Active Content First of All we need to know what is “Active Content” are. Within the community of kindle developers you will hear this term time and again. Active contents are noting but the apps runs over kindle device. Simply the apps for kindle, here we called them “active content”. Simple it is. Kindlet Technically, kindlet is an interface in kdk (kindle development kit). We extends its subclass and write our code. At little abstract level, the main entrance of our kindle application is called kindlet. For example like any java program must have a class that contains main() method; to start application from that point (.i.e. via main() method) same in case of kindle app, there must be a class that must extend subclass of kindlet interface (AbstractKindlet class) and hence become entry point of our kindle app. Such class is normally refer as kindlet of our kindle app. In more concise words, if someone asks you where is your kindlet, then it means he/she is asking about the entry point of your kindle application, the class which extends the subclass of kindlet interface of kdk .i.e AbstractKindlet class. Lifecycle of Kindle application Like every application, active contents have also a defined life cycle. Our application move in between these life cycle phases during its execution and terminates from its exit point. There are four phases application move among. They are loaded ready to run running shutdown when application jumps into a phase, a specific method is called, defined in kindlet interface. These method calls and phase changes are very well defined until any unchecked exception is thrown, that causes the active content to die/shut down and user will see crash. Now as application crashed, there isn’t no surety whether the life cycle will complete normally or will terminate immediately. The kindlet method associates with above mentioned phases are create() start() stop() destroy() Refer the following image describing the phases and method calls during the life cycle of kindle application {src : kdk documentation} Lets discuss different phases of life cycle Loaded When we chose a kindle application to run, its kindlet initialized, along with other static initialization of application. Once this happened, its means kindlet object has been constructed and properly initialized, hence application has LOADED. At this stage, we don’t see any screen/user interface at user end. Its all occurred at backend. At developer lever, we don’t have access to persistent storage; we haven’t access to application environment/context. After loaded phase, there are two possible ways. Either application will enter in “ready to run” phase or will “shutdown”. In case of shutdown kindlet will not notified. Ready to run In case application are eligible for “ready to run” then a transition is occur via method called create() declaired in Kindlet interface. At this stage application gain access to kindle environment and we have a reference of KindletContext object. This object represents the Kindle application’s environment for a Kindlet and provides access to the Kindlet’s user interface, filesystem space, network connectivity and more. Once a Kindlet create method has finished, the Kindlet is considered “ready to run”. The application’s user interface is not visible while in the “ready to run” state and no user input will be received. be patient The next phase from “ready to run” is to “running”. During this start() method of kindlet interface will be called. Even at this point, the user interface is still not visible. “ready to run” to “shutdown” is also possible. If this occurs, destroy will be called. During destroy, the application should release any resources it has allocated. Running Phase The end of start() method moves the application in running state. At this point user interface become visible and application is said to be running state. User can start using application. Note: one thing need to know. When user plug usb cable to device, then the device goes to screen saver and its stop() method calls for current running application. You can’t use device when its plug with usb cable. The stop() method should pause any executing work, release any file or network resources, and prepare for the user interface to be made invisible. At this stage application move to “ready to run” state again. Shutdown State When use wants to quit the application, the application moves to shutdown state and stop () method is called. This pause any executing work, release any file or network resources, and prepare for the user interface to be made invisible. That’s was a theoretical concepts for life cycle of a kindle application. Let have a quick glance over life cycle methods of kindlet. create is the first step in the life cycle. A reference to the application’s environment is provided to this method. This method will only be called once during the life of the Kindlet instance. start indicates that the application is about to become active. Upon completion of the start method, the user interface will become visible and the application will start to receive events from the user. Unlike create, start may be called many times during the overall life of the Kindlet instance. For instance, entering and exiting the screensaver results in a stop event followed by a start event. Similar cases exist for USB and other system notifications. stop indicates that the application should stop. The user interface will become invisible shortly after this method completes. When the user interface becomes invisible any open option panes will be closed. Stop will be called on a running application when the Kindle enters USB mode, screensaver or exits the application. When an application is stopped, the file system may disappear. It is important for applications to close resources like files and re-open them on stop / start cycles, respectively. Additionally, any threads that are performing work should either shutdown or sleep. This includes network access, and all requests for connectivity may be cancelled on stop. destroy indicates that the Kindlet instance will not be used again. This permits the Kindlet to clean up resources and do any housekeeping that may be necessary on application exit. The device may choose to shutdown an application during screen saver or USB mode to preserve battery life. Its enough for today .. in next part, we will move to actual development, a hello world program. though i start working that part today but i felt we should discuss these things first so that while writing the code, we should know what actually going inside code and at backend of our application. feel free to ask any thing confusing here. i will try my best to make it more simple, easy to understand as per your kind suggestions. Be blessed. Have a nice day. Please follow and like us: Amazon Kindle Tips & Tutorials AbstractKindletActive ContentAmazon Kindle Application Development Tutorial – Part 3kdk application tutorialkdk create()kdk destroykdk life cyclekdk loadedkdk on javakdk ready to runkdk runningkdk shutdownkdk startskdk stopKindle Application Lifecyclekindle create()kindle distroykindle lifecyclekindle loadedkindle on javakindle phaseskindle ready to runkindle runningkindle shutdownkindle start()kindle stateskindle stopkindle tutorialKindletKindlet interfaceLifecycle of Kindle application
MonoTouch: Building iPhone Apps Using C# and .NET September 25, 2009March 27, 2024 Novell has released MonoTouch 1.0, what it claims is the industry’s first solution for developing applications for the iPhone and iPod Touch using the Microsoft .NET Framework, including C# and other .NET programming languages. Until now, developers primarily built iPhone applications using C and Objective-C. With MonoTouch, the creativity of millions of… Read More
Local history/revision of files in Xcode February 24, 2013 Hello friends .. hope things are going good on your desk .. Last night I was going through my tweets, and there I found something really interesting; I crawled it for few minutes and after reading some blog posts I came to know about a very useful but hidden feature that… Read More
Event Object :: JavaScript Tutorial July 23, 2010 Hello All … Hope enjoying most enjoyable activity .i.e development 🙂 i love it … really love it .. Today i will try to explain something related to javascript event object. By using JavaScript, we have the ability to create dynamic web pages. Events are actions that can be detected… Read More
@Athar A valid question. Many people has asked the same thing many times. According to them why to spend time (some of them use “waste of time”) on such dull old fashioned device where there isn’t anything to attract users to first buy it and then use different apps … they are correct … kindle seems like a thirty fourty year old invention in first look. No touch no color display (only 16 shades of grey) with eInk surface. In the age of apple’s iPad, samsung glaxy an upcoming dell due; kindle simply looks odd man out. So one must think before spending time to develop app for this platform. But there are few good aspects too for kindle …Kindle is backed by Amazon, a big name. Kindle was a best selling item for Amazon in last quarter and it holds a big market share in its domain (.i.e. ebook reading devices). Color e-ink display has also introduced and amazon is working on feasibility of introducing this feature in kindle. Might we have colored kindle after next year or so ..(Hanvon has implemented color display already) plus if we have touch over kindle then think about a device with such great display even in daylight with touch and color … !!! kindle’s future seems very bright to me .. ☺ Reply
Hello, I am trying to distribute kindles directly to our customers. We plan to develop applications for them and install them on kindle and then give the kindles to our customers. So, I wanted to know if it is possible to install applications directly on kindle without going the Kindle App Store way? Do we need to get a certification, from Amazon or some other place? Thanks, Mayank Reply
well Aasim, its not that bad as you are saying. I can see there are new things comming up here in UK for Kindle 3G so its getting into the market with new features. All I was just saying is to see that what kinda of other application you can develop rather than for reading only. Reply
i can but it will not work for you cuz it has signed with my account and device; you will not able to run/debug for at your end; Reply
Hi Ans, thanks for the tutorials! I found them to be the best intro to the idk topic on the net. I was hoping you would write a part 4 tutorial on a basic hello world program. Do you still intend to write it or can you recommend other resources on the net where I may get more idk advice? Thanks again for your work! Matthew scheer Reply
it`s very very nice post! thanks for sharing! you said in this post that “Its enough for today .. in next part, we will move to actual development, a hello world program” i have not find that post about hello world program.where the post url? by the way,your profile picture are very handsome! hehe! thanks! Reply