Programming Android apps in jython

Question

The other day I came across a Python implementation called Jython.
With Jython you can write Java applications with Python and compile them to pure Java.

I was wondering: Android programming is done with Java.
So, is it possible to make Android apps with Jython?

Kloman

Python do not have awesome interoperability with java. If you want native and nice ui, you are forced to use java/scala. If you are ok with non native ui, you can use qt for android + python wrapper + write code in python. – Dominations

I see... So you can't do anything you can do in java with jython? – Kloman

@tabbykitten that interop between Python and Java is exactly what Jython does provide. – Angevin

can you create Jython class which extends android.app.Activity? – Dominations

@tabbykitten for clarity, its better to ask that as: does Jython allow you to write Python subclasses of Java classes (or, of that specific Java class)? And, yes. Yes, it does. "Writing a Jython class" is a little ambiguous, since Jython is just a Python implementation (not a dialect as the OP says), so it could mean a class that forms part of jython itself (which trivially can subclass Java classes, since Jython is written in Java). – Angevin

are you sure that jython extend Java class? There are post that says another groups.google.com/d/msg/android-developers/uFSnwuUJZvY/… . I'am python user, not jython. Perhaps you know more about it. – Dominations

@tabbykitten that post seems to suggest that Python classes extending Java classes don't quite behave properly when passed to Java APIs - I've never tried that specifically, but that seems to be anomalous to everything else I can find about this - eg, stackoverflow.com/questions/11071525 has a Python class implement Runnable in order to use Java thread management APIs. If it is a problem (maybe an extends vs implements difference?), you can always code some Java glue to make it work - Jython is just Python for the JVM; you can mix other JVM languages without problem. – Angevin

I agree that jython code can be written and used, but you have to write some Java glue. Android Application Framework has some frame and require "extend" too often. – Dominations

The actual issue, at least with current Jython is totally missed in this whole thread, including the accepted answer: Jython also generates and loads bytecode at runtime. Inherently. Even if it could do this as dexed bytecode or somehow dex it at runtime, Android does not permit loading new bytecode at runtime (AFAIK). Without a significant redesign, Jython on Android is currently not feasible, unfortunately. See sourceforge.net/p/jython/mailman/message/36752389 – Coup

Answer 1

Jython doesn't compile to "pure java", it compiles to java bytecode - ie, to *.class files. To develop for Android, one further compiles java bytecode to Dalvik bytecode. This means that, yes, Jython can let you use Python for developing Android, subject to you getting it to play nice with the Android SDK (I haven't personally tried this, so I don't know how hard it actually is) - you do need to make sure you don't depend on any Java APIs that Android doesn't provide, and might need to have some of the Android API .class files around when you run jython. Aside from these niggles, your core idea should work - Jython does, indeed, let write code in Python that interacts with anything else that runs on the JVM.

Angevin

according to wiki.python.org/jython/JythonFaq/… jython requires JME instead of JSE and that there is no port to the former yet. So is this answer pure theory or has this actually been done by anyone? – Electrify

@TobiasKienzler the answer is largely theoretical - I do say in the answer that I haven't tried this, and that getting Jython and the Android tools to work together could be a problem. That said, I don't think the JME/JSE difference matters here, since the Python->Java bytecode step would be done on the development machine, not on the Android device. Java SE is available on every platform supported by the Android SDK, and the newer Android Studio. – Angevin

thanks for your reply - incidentally I was hoping to use jython for native android development... – Electrify

Android is not the same as Java Micro Edition. JME was used on the 'pre-smartphone phones', like your average Nokia from the early 2000's. Android is an entirely different thing, the FAQ item on the Jython page is misleading on this subject. – Pierre

Answer 2

I specially like Kivy

Scripting Layer for Android (SL4A) brings scripting languages to Android by allowing you to edit and execute scripts and interactive interpreters directly on the Android device.

Stela

Is it easy to package this into an *.apk? – Debutant

Answer 3

As long as it compiles to pure java (with some constraints, as some APIs are not available), but I doubt that python will be of much use in development of android-specific stuff like activities and UI manipulation code.

You also have to take care of application size - that is serious constraint for mobile developement.

Roborant

Considering that the javac based output of the jython code does not include a python runtime, but only jvm code, how so? Talking in terms of application size. – Peekaboo

Answer 4

Yes and no. With jython you can use java classes to compile for the JVM. But Android use the DVM (Dalvik Virtual Machine) and the compiled code is different. You have to use tools to convert from JVM code to DVM.

Attributive

Answer 5

Yes, you can.

Test your python code on your computer and, when it is ok, copy to your Android device.

Install Pydroid from Google Play Store and compile your code again inside the application and you will get your App ready and running.

Use pip inside Pydroid to install any dependencies.

PS: You will need to configure your Android device to install APKs from outside Play Store.

Pegu

Answer 6

It's not possible. You can't use jython with android because the DVM doesn't understand it. DVM is not JVM.

Englebert

Thanks @Burhan Khalid I'll be careful about these little but important things in my future postings with-in StackOverFlow. – Englebert

I already admitted my English writing mistakes yet somebody down voting me even now. :( To err is human, important is to learn from your mistakes. – Englebert

Those application are using "jythonroid" i.e. Jython for Android... How come; somebody comes just out of no where and down-votes you for something he knows nothing... hehehe :-p. – Englebert

Bro You really need to work hard on your findings. First no where is written there that the app is using jython... second They are using python... and You can run python/jython in android as I told you but you need to apply some different treatment to android and last There is a hug difference between python and jython. – Englebert

Answer 7

sadly No.

Mobile phones only have Java ME (Micro Edition) but Jython requires Java SE (Standard Edition). There is no Jython port to ME, and there is not enough interest to make it worth the effort.

Behoof

This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post - you can always comment on your own posts, and once you have sufficient reputation you will be able to comment on any post. – Concerning

@A.J. The question is "is it possible to run Jython in Android". So, it IS an answer. With absolutely incorrect explanation, yes, but an answer it is. – Hypostasize

@Gangnus, to be honest, that close vote is quite general, I was more so saying it because there is no evidence or reasoning, it could easily be encapsulated in a comment, which the OP cannot make, hence the close vote. – Concerning

Android is NOT using Java ME. – Clupeoid