KV Application/Software development for Kindle

Maimun Ahmed · 02-25-2024, 09:43 AM

Hi there, mobileread family. I recently stumbled upon an e-reader application named "KOReader". I use a jailbroken Kindle Voyage and I am willing to make an open-source software like koreader as one of my personal projects.

Of course, I can develop my app over KOReader but then I will have to code in Lua and I am not familiar with it.

Is there any way I can make an application for kindle with another language (like Java or C++ or javascript or python). I am completely new to developing on kindle so I would be very thankful if you could explain it to me in detail. Appreciate your time.

Thank you.

fonix232 · 02-26-2024, 12:55 PM

Well, yes and no.

Kindles are generally quite locked down, and even apps like KOReader and KUAL need some hacky ways to work those limitations around.

First limitation is the launch approach. Kindles used to allow some limited apps called "kindlets" (which is how e.g. KUAL installed itself, and how KOReader's homescreen launcher worked), but it was recently removed. Kindlets, while limited, were much more portable than the other option - booklets. (sidenote: AFAIK the Voyage did not get the update that removes Kindlet support, so you should be able to use that approach).

Booklets are system-installed Java applications that, aside from a JAR file containing at least one final class extending Booklet/AbstractBooklet, and register it in a system-level SQL database (basically, an "install" process). The latest KUAL releases are now in this format.

Both of these formats are primarily Java, however do note that there isn't really a UI library for these approaches, and you'll need to handle the UI yourself.

My recommendation would be that you look into the KUAL sources, as well as the two KOReader Launcher approaches:

- KUAL (maintained by NiLuJe): https://github.com/NiLuJe/KUAL_Booklet
- KOL Booklet: https://github.com/yparitcher/KUAL_Booklet
- KOReader Booklet: https://github.com/koreader/kpvbooklet/

You'll also need a bunch of the framework files from your Kindle, mainly from /opt/amazon/ebook/lib and /opt/amazon/ebook/booklet. Primarily kaf.jar (which is the Kindle Application Framework).

There are some Python runtimes built for various Kindles in the Snapshots threads too, and IIRC NiLuJe maintains an fbink Python wrapper, which you can use for the UI.

Then, finally, you can do WAFs (Web Application Framework) - as Amazon moved towards a Chromium based frontend, they introduced these (much more limited) web apps, but getting third party ones into the system is quite hacky and semi-tethered.

Overall I think your best bet is trying a Java Booklet, but it all depends on what kind of app you're trying to build.

j.p.s · 02-26-2024, 01:22 PM

Quote:

Originally Posted by fonix232

AFAIK the Voyage did not get the update that removes Kindlet support, so you should be able to use that approach.

There were many firmware updates for the Voyage after kindlet support was removed.

Maimun Ahmed · 02-28-2024, 10:58 PM

Thank you for such quick answers. You guys are amazing.

However I ended up using Lua as I found the language very easy to learn and the KOReader source code was so properly commented / documented (I can't remember the exact term). Moreover, if you develop over KOReader's source code, you get a good safety that your device won't get stuck as if your code somehow crashes; it will exit into the kindle OS.

Thank you guys for your answers. Have a great day!

02-25-2024, 09:43 AM	#1
Maimun Ahmed Mr. Developer Posts: 19 Karma: 10 Join Date: Feb 2024 Device: Kindle Voyage	Application/Software development for Kindle Hi there, mobileread family. I recently stumbled upon an e-reader application named "KOReader". I use a jailbroken Kindle Voyage and I am willing to make an open-source software like koreader as one of my personal projects. Of course, I can develop my app over KOReader but then I will have to code in Lua and I am not familiar with it. Is there any way I can make an application for kindle with another language (like Java or C++ or javascript or python). I am completely new to developing on kindle so I would be very thankful if you could explain it to me in detail. Appreciate your time. Thank you.

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02-26-2024, 12:55 PM	#2
fonix232 Enthusiast Posts: 35 Karma: 102 Join Date: Jul 2016 Device: KOA4	Well, yes and no. Kindles are generally quite locked down, and even apps like KOReader and KUAL need some hacky ways to work those limitations around. First limitation is the launch approach. Kindles used to allow some limited apps called "kindlets" (which is how e.g. KUAL installed itself, and how KOReader's homescreen launcher worked), but it was recently removed. Kindlets, while limited, were much more portable than the other option - booklets. (sidenote: AFAIK the Voyage did not get the update that removes Kindlet support, so you should be able to use that approach). Booklets are system-installed Java applications that, aside from a JAR file containing at least one final class extending Booklet/AbstractBooklet, and register it in a system-level SQL database (basically, an "install" process). The latest KUAL releases are now in this format. Both of these formats are primarily Java, however do note that there isn't really a UI library for these approaches, and you'll need to handle the UI yourself. My recommendation would be that you look into the KUAL sources, as well as the two KOReader Launcher approaches: - KUAL (maintained by NiLuJe): https://github.com/NiLuJe/KUAL_Booklet - KOL Booklet: https://github.com/yparitcher/KUAL_Booklet - KOReader Booklet: https://github.com/koreader/kpvbooklet/ You'll also need a bunch of the framework files from your Kindle, mainly from /opt/amazon/ebook/lib and /opt/amazon/ebook/booklet. Primarily kaf.jar (which is the Kindle Application Framework). There are some Python runtimes built for various Kindles in the Snapshots threads too, and IIRC NiLuJe maintains an fbink Python wrapper, which you can use for the UI. Then, finally, you can do WAFs (Web Application Framework) - as Amazon moved towards a Chromium based frontend, they introduced these (much more limited) web apps, but getting third party ones into the system is quite hacky and semi-tethered. Overall I think your best bet is trying a Java Booklet, but it all depends on what kind of app you're trying to build.

02-28-2024, 10:58 PM	#4
Maimun Ahmed Mr. Developer Posts: 19 Karma: 10 Join Date: Feb 2024 Device: Kindle Voyage	Thank you for such quick answers. You guys are amazing. However I ended up using Lua as I found the language very easy to learn and the KOReader source code was so properly commented / documented (I can't remember the exact term). Moreover, if you develop over KOReader's source code, you get a good safety that your device won't get stuck as if your code somehow crashes; it will exit into the kindle OS. Thank you guys for your answers. Have a great day!

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