Posted on

python-for-android status update

It’s been a while since Kivy’s python-for-android project was revamped, so here’s a quick status update.

There have since been well over 200 commits from 15 different contributors, cleaning up the missing pieces of the new toolchain and adding new features that weren’t previously possible. Thanks to everyone who has contributed.

These fixes include progress on the remaining major goals of the python-for-android revamp. In particular, compilation is now supported for multiple target architectures - in principle anything targeted by the Android SDK (i.e. ARM, ARMv7a, x86, x86_64 and MIPS options), though I’ve tested only with the ARM and x86 ones. This means that Kivy applications, or other Python projects built with these tools, can be built for devices with e.g. intel atom processors. Even without this compilation it was often possible to run Kivy apps as many devices include libhoudini, but directly targeting them means such apps should now always work. A further advantage is that Kivy apps can be built for and tested on the Android emulator, which was not previously possible.

The architecture target support does need some more work to create fully multiarch APKs (i.e. including .so files for each target, so a single APK can work on different types of device). The problem here is that we need to duplicate as little as possible, as Kivy APKs are already made large by including the python interpreter, and it is undesirable to include two or more copies of everything. Using a single python installation and loading the .so dependencies as appropriate should be possible but needs more work. However, this is not a problem if uploading an APK to a store like Google Play; in this case you can include multiple APKs, one for each arch target, and the user will receive one that is appropriate.

Another important feature that I’ve worked on, but unfortunately unsuccessfully so far, is support for python3 APKs. The problem to be solved is to patch the interpreter to compile for Android (it cannot do so by default, due to problems with the Android platform like poor locale support), to modify the python-for-android bootstrap to load it correctly (it builds things a little differently to python2), and to modify the initialisation code to have it start successfully. I’ve only partially succeeded with the first two of these; using patches from the SL4A python-for-android tools (plus extras for our own modifications to python loading) allows the interpreter to be built, but it fails during Py_Initialize when run on the device, apparently raising an exception when calculating the python install path. Work on this will continue, but it’s hard to know how long it might take to resolve this error. If you know of any other projects patching python3.4+ for Android, I’d love to heard about it to compare their methods.

Posted on

python-for-android revamp replaces master

This post is to announce that the revamped python-for-android toolchain, introduced in this previous post, has now been merged into python-for-android’s master branch. This is now the master branch going forward.

The revamp project is largely (but not quite) feature complete with the old toolchain, supporting almost all the same options when building pygame-based APKs. It also supports a new and much better SDL2 backend, which Kivy will move to in the future, but which also supports other kinds of python projects such as Vispy as described in the previous post.

We’ve done our best to minimise problems arising from this change. The old toolchain (with distribute.sh and build.py) is still available in the old_toolchain branch. Issues and PRs relating to this branch are still accepted, though existing PRs will need to be retargeted or merged manually (we’ll try to do what’s easiest case by case, if necessary).

If you use buildozer, this now pulls from the old_toolchain branch and so will work exactly as before. However, you will need to install the latest version from pypi or github (at least version 0.30) for this to work. Older versions of buildozer will continue to build APKs fine with existing projects, but if you create a new one they will download the new and incompatible python-for-android master. The revamp includes a fake distribute.sh executable giving these same instructions, so if this happens the problem and solution should be clearly displayed.

The new toolchain is currently documented (temporarily) here. We’ll push the new documentation to the normal readthedocs site as soon as possible, which will also include the legacy doc for the old toolchain so nothing is lost.

In the slightly longer term, the new toolchain will receive an official release and hopefully be released itself on pypi; unlike the old toolchain, it behaves as a fully installable python module with an improved command line interface.

Posted on

python-for-android revamp replaces master

This post is to announce that the revamped python-for-android toolchain, introduced in this previous post, has now been merged into python-for-android’s master branch. This is now the master branch going forward.

The revamp project is largely (but not quite) feature complete with the old toolchain, supporting almost all the same options when building pygame-based APKs. It also supports a new and much better SDL2 backend, which Kivy will move to in the future, but which also supports other kinds of python projects such as Vispy as described in the previous post.

We’ve done our best to minimise problems arising from this change. The old toolchain (with distribute.sh and build.py) is still available in the old_toolchain branch. Issues and PRs relating to this branch are still accepted, though existing PRs will need to be retargeted or merged manually (we’ll try to do what’s easiest case by case, if necessary).

If you use buildozer, this now pulls from the old_toolchain branch and so will work exactly as before. However, you will need to install the latest version from pypi or github (at least version 0.30) for this to work. Older versions of buildozer will continue to build APKs fine with existing projects, but if you create a new one they will download the new and incompatible python-for-android master. The revamp includes a fake distribute.sh executable giving these same instructions, so if this happens the problem and solution should be clearly displayed.

The new toolchain is currently documented (temporarily) here. We’ll push the new documentation to the normal readthedocs site as soon as possible, which will also include the legacy doc for the old toolchain so nothing is lost.

In the slightly longer term, the new toolchain will receive an official release and hopefully be released itself on pypi; unlike the old toolchain, it behaves as a fully installable python module with an improved command line interface.

Posted on

python-for-android revamp replaces master

This post is to announce that the revamped python-for-android toolchain, introduced in this previous post, has now been merged into python-for-android’s master branch. This is now the master branch going forward.

The revamp project is largely (but not quite) feature complete with the old toolchain, supporting almost all the same options when building pygame-based APKs. It also supports a new and much better SDL2 backend, which Kivy will move to in the future, but which also supports other kinds of python projects such as Vispy as described in the previous post.

We’ve done our best to minimise problems arising from this change. The old toolchain (with distribute.sh and build.py) is still available in the old_toolchain branch. Issues and PRs relating to this branch are still accepted, though existing PRs will need to be retargeted or merged manually (we’ll try to do what’s easiest case by case, if necessary).

If you use buildozer, this now pulls from the old_toolchain branch and so will work exactly as before. However, you will need to install the latest version from pypi or github (at least version 0.30) for this to work. Older versions of buildozer will continue to build APKs fine with existing projects, but if you create a new one they will download the new and incompatible python-for-android master. The revamp includes a fake distribute.sh executable giving these same instructions, so if this happens the problem and solution should be clearly displayed.

The new toolchain is currently documented (temporarily) here. We’ll push the new documentation to the normal readthedocs site as soon as possible, which will also include the legacy doc for the old toolchain so nothing is lost.

In the slightly longer term, the new toolchain will receive an official release and hopefully be released itself on pypi; unlike the old toolchain, it behaves as a fully installable python module with an improved command line interface.

Posted on

Kivy – Interactive Applications and Games in Python, 2nd Edition Review

I was recently asked by the author to review the second edition of “Kivy – Interactive Applications in Python” from Packt Publishing. I had difficulty recommending the first edition mostly due to the atrocious editing – or lack thereof – that it had suffered. It really reflected badly on Packt, and since it was the only Kivy book available, I did not want that same inattention to quality to reflect on Kivy. Packt gave me a free ebook copy of this book in exchange for agreeing to do this review.

At any rate, the second edition is much improved over the first. Although a couple of glaring issues remain, it looks like it has been visited by at least one native English speaking editor. The Kivy content is good, and I can now recommend it for folks who know Python and want to get started with Kivy. The following is the review I posted to Amazon:

—

This second edition of “Kivy – Interactive Applications and Games in Python” is much improved from the first edition. The atrocious grammar throughout the first edition book has mostly been fixed, although it’s still worse than what I expect from a professionally edited book. The new chapters showcase current Kivy features while reiterating how to build a basic Kivy app, and the book covers an impressive amount material in its nearly 185 pages. I think this is due largely to the efficiency and power of coding in Python and Kivy, but also to the carefully-chosen projects the author selected for his readers to create. Despite several indentation issues in the example code and the many grammar issues typical of Packt’s books, I can now recommend this book for intermediate to experienced Python programmers who are looking to get started with Kivy.

Chapter one is a good, quick introduction to a minimal Kivy app, layouts, widgets, and their properties.

Chapter two is an excellent introduction and exploration of basic canvas features and usage. This is often a difficult concept for beginners to understand, and this chapter handles it well.

Chapter three covers events and binding of events, but is much denser and difficult to grok than chapter two. It will likely require multiple reads of the chapter to get a good understanding of the topic, but if you’re persistent, everything you need is there.

Chapter four contains a hodge-podge of Kivy user interface features. Screens and scatters are covered well, but gestures still feel like magic. I have yet to find a good in-depth explanation of gestures in Kivy, so this does not come as a surprise. Behaviors is a new feature in Kivy and a new section in this second edition of the book. Changing default styles is also covered in this chapter. The author does not talk about providing a custom atlas for styling, but presents an alternative method for theming involving Factories.

In chapter six the author does a good job of covering animations, and introduces sounds, the clock, and atlases. He brings these pieces together to build a version of Space Invaders, in about 500 lines of Python and KV. It ends up a bit code-dense, but the result is a fun game and a concise code base to play around with.

In chapter seven the author builds a TED video player including subtitles and an Android actionbar. There is perhaps too much attention paid to the VideoPlayer widget, but the resulting application is a useful base for creating other video applications.

—

Posted on

python-for-android revamped

I’ve recently been working on a significantly revamped version of python-for-android, the Kivy-project tools that take a Python program and package it - along with any dependencies and the Python interpreter itself - into an Android APK that can be run and distributed just like a normal Android app. This rewrite is driven by the problem that although the current python-for-android is fairly robust as far as the build process goes, it’s quite set in its ways and hard to modify to make large changes such as to support backends other than Kivy.

To this end, the revamp project has several major goals:

  • Rewrite python-for-android to a fully Python toolchain that can be more easily modified and extended.
  • Support multiple bootstrap targets for different kinds of Python scrips to run on Android, starting with a new SDL2 backend for Kivy applications.
  • Support Python 3 on Android.
  • Support some kind of binary distribution, enabling easier and cross-platform distribution…this should work on Windows!
  • Be a standalone PyPI module with a more convenient and standard interface, potentially interfacing with setuptools.
  • Support (less painfully) multiple Android architectures, or fat APKs supporting more than one.

Each of these is individually a popularly requested feature, and this is a great opportunity to go for all of them at once!

I’m making this post to announce that the python-for-android revamp project has reached a usable state, with several of these goals either implemented or significantly advanced, and all of them at least made much more accessible. The core change is that all of the original toolchain has been rewritten in Python, with the initial structure based on the recent Kivy-iOS rewrite. It’s also much lighter, all heavy pygame stuff is downloaded on demand instead of built in, and is designed to be accessed by a single set of commands and the new python-for-android executable rather than by the separate invocation of different scripts in different places. I won’t go into the technical details here, but you can find the (WIP) documentation temporarily hosted here. If anyone would like to test it you can try the instructions there, but the project is in an experimental state right now and it’s likely you may encounter bugs or missing features, the current focus is ironing these out. I’m very happy to discuss these on the kivy-users mailing list or #kivy irc channel on irc.freenode.net.

Another of the core goals of this rewrite was to support multiple app backends; in Kivy’s case in particular we want to move from Pygame to a new SDL2 bootstrap, but this could also include support for other Python module backends. As of now, the new python-for-android supports the old Pygame bootstrap mostly as before, but also implements an SDL2 based PythonActivity that works very well with Kivy - highly anecdotal testing found, amongst other things, app start time reduced to 60% of what it was with Pygame. It also simplifies maintenance as SDL2’s java components fulfil the same role as those maintained in the Pygame backend, but no longer require much special treatment as functionality such as touch interaction and pausing are now accessed with the SDL2 api just as on desktop platforms.

Further, python-for-android can now build non-Kivy apps! The first project with this support built in is the Vispy scientific visualisation library. This uses the same new SDL2 backend but Kivy is not involved, and the build process does not use Cython (unlike with Kivy); instead, SDL2 and OpenGL are called entirely with ctypes, using pysdl2 and Vispy’s own gloo wrapper respectively. I didn’t even have to patch things much for this, Vispy is mostly self contained and already quite platform independent, barring a couple of possible small bugs and a hack to avoid the lack of a supported font provider on Android. Vispy also uses numpy heavily, but this was already supported by python-for-android and seems to work fine. The Vispy support is itself quite experimental and there are some performance issues that will need resolving, but it was very simple to set up with the new toolchain. Here’s a screenshot of one of Vispy’s 3D examples running on Android - there are a few small visual artifacts, but I think these are small bugs in Vispy’s OpenGL ES 2 support that the Vispy team are actively addressing:

Image of Vispy running on Android

Support for binary distribution and multiple architectures are both partially implemented but (at the time of writing) not yet working. However, the toolchain is built around them, so there should be no major issues. The initial idea with binary distribution will be to simply make available a number of prebuilt distributions (i.e. Android projects with the Python interpreter) that include common dependencies, so that when the user adds modules as requirements when calling python-for-android they can automatically be checked and an appropriate choice downloaded, with this process being transparent to the user and not requiring any special options. This should not only make many builds faster but also work on Windows, one of our most requested features but something that was not possible when the toolchain required that everything be locally compiled. Likewise, the toolchain has semi-implemented support for multiple architectures internally, but none other than armeabi are yet supported and there will be bugs to work out when more are enabled. Still, these will (fingers crossed) be things to look forward to in the relatively near future.

I should note here that this model of binary distribution is what I initially targeted as a natural extension of python-for-android’s distribution system - although we never made much of it, the first step is already to build a standalone android package which later can be distributed separately and populated with app details by a user, and the above just involves making such prebuilt distributions available to download and use automatically. I found more recently the method of the pybee project/Toga toolkit’s Python-Android-template. This is a similar idea (built by a modified python-for-android) but implemented much better as a standalone project with app details populated by cookiecutter and the packaging of the user’s Python modules taken care of using ant itself, the normal APK build and deployment interface - I didn’t know this was even possible! This means that the user can just write their Python code, drop it in place, and run the APK build, a very neat process. It should be quite easy to modify python-for-android’s dist output to easily create such templates, its dist system is functionally the same thing with a different and less standard-Android interface, and I hope that doing so could make it even more convenient for users to build and distribute different kinds of Python apps.

This leaves the elephant in the room, support for Python 3 on Android, which is perhaps the most requested feature for Kivy itself. The new toolchain makes significant progress on this in a couple of ways. The first is by removing hardcoded use of Python 2, so that now (barring remaining bugs) a Python 3 build should be well behaved once a recipe and appropriate Android patch set are added. The second is that the old Kivy Android bootstrap probably needed significant changes to support Python 3, but this is sidestepped entirely by moving to the new SDL2 backend which should have no issues supporting Python3 more or less the same as on the desktop. However, the missing link here is still actually being able to compile Python 3 for Android, and I don’t yet know how to do this. Some of Kivy’s main Python 2 patches come from this site, but this has Python 3 patches only up to 3.2.2 and it would be ideal to target 3.4 or 3.5 (and to be able to support new versions as they appear). I’ve looked around and seen a few different discussions of this, but I’m not sure what’s the best direction to try. If anyone has any information about places to find more up to date patch sets I would be very interested. I can’t make any other predictions about this as I don’t know much about the Python compilation process or what difficulties might be involved in doing the work we need.

That’s all for now. I’ll note again that this is an initial announcement of the new toolchain; I hope that people may be interested to look and try it, and it should support most of what the old toolchain does when it comes to compiling Pygame APKs, but there are likely to be bugs and missing features particularly surrounding (but not limited to) the new additions. If you’re interested in making this toolchain work with other modules or backends, or just have any questions, comments or criticisms, let us know! If you want to keep informed, watch this space, I’ll make further announcements as things develop. If there is developer interest and people start switching from the old toolchain, I hope development will speed up a lot and quickly approach proper feature parity.

tl;dr (I was told I should have one): Kivy’s python-for-android build tools have been revamped to have a better interface, build apps based on SDL2, build non-Kivy apps (currently Vispy apps), and be more extensible. Further semi-complete features include binary distribution, Windows support, and multiple architecture targets. Python 3 is brought closer but needs direct compilation work.

Posted on

python-for-android revamped

I’ve recently been working on a significantly revamped version of python-for-android, the Kivy-project tools that take a Python program and package it - along with any dependencies and the Python interpreter itself - into an Android APK that can be run and distributed just like a normal Android app. This rewrite is driven by the problem that although the current python-for-android is fairly robust as far as the build process goes, it’s quite set in its ways and hard to modify to make large changes such as to support backends other than Kivy.

To this end, the revamp project has several major goals:

  • Rewrite python-for-android to a fully Python toolchain that can be more easily modified and extended.
  • Support multiple bootstrap targets for different kinds of Python scrips to run on Android, starting with a new SDL2 backend for Kivy applications.
  • Support Python 3 on Android.
  • Support some kind of binary distribution, enabling easier and cross-platform distribution…this should work on Windows!
  • Be a standalone PyPI module with a more convenient and standard interface, potentially interfacing with setuptools.
  • Support (less painfully) multiple Android architectures, or fat APKs supporting more than one.

Each of these is individually a popularly requested feature, and this is a great opportunity to go for all of them at once!

I’m making this post to announce that the python-for-android revamp project has reached a usable state, with several of these goals either implemented or significantly advanced, and all of them at least made much more accessible. The core change is that all of the original toolchain has been rewritten in Python, with the initial structure based on the recent Kivy-iOS rewrite. It’s also much lighter, all heavy pygame stuff is downloaded on demand instead of built in, and is designed to be accessed by a single set of commands and the new python-for-android executable rather than by the separate invocation of different scripts in different places. I won’t go into the technical details here, but you can find the (WIP) documentation temporarily hosted here. If anyone would like to test it you can try the instructions there, but the project is in an experimental state right now and it’s likely you may encounter bugs or missing features, the current focus is ironing these out. I’m very happy to discuss these on the kivy-users mailing list or #kivy irc channel on irc.freenode.net.

Another of the core goals of this rewrite was to support multiple app backends; in Kivy’s case in particular we want to move from Pygame to a new SDL2 bootstrap, but this could also include support for other Python module backends. As of now, the new python-for-android supports the old Pygame bootstrap mostly as before, but also implements an SDL2 based PythonActivity that works very well with Kivy - highly anecdotal testing found, amongst other things, app start time reduced to 60% of what it was with Pygame. It also simplifies maintenance as SDL2’s java components fulfil the same role as those maintained in the Pygame backend, but no longer require much special treatment as functionality such as touch interaction and pausing are now accessed with the SDL2 api just as on desktop platforms.

Further, python-for-android can now build non-Kivy apps! The first project with this support built in is the Vispy scientific visualisation library. This uses the same new SDL2 backend but Kivy is not involved, and the build process does not use Cython (unlike with Kivy); instead, SDL2 and OpenGL are called entirely with ctypes, using pysdl2 and Vispy’s own gloo wrapper respectively. I didn’t even have to patch things much for this, Vispy is mostly self contained and already quite platform independent, barring a couple of possible small bugs and a hack to avoid the lack of a supported font provider on Android. Vispy also uses numpy heavily, but this was already supported by python-for-android and seems to work fine. The Vispy support is itself quite experimental and there are some performance issues that will need resolving, but it was very simple to set up with the new toolchain. Here’s a screenshot of one of Vispy’s 3D examples running on Android - there are a few small visual artifacts, but I think these are small bugs in Vispy’s OpenGL ES 2 support that the Vispy team are actively addressing:

Image of Vispy running on Android

Support for binary distribution and multiple architectures are both partially implemented but (at the time of writing) not yet working. However, the toolchain is built around them, so there should be no major issues. The initial idea with binary distribution will be to simply make available a number of prebuilt distributions (i.e. Android projects with the Python interpreter) that include common dependencies, so that when the user adds modules as requirements when calling python-for-android they can automatically be checked and an appropriate choice downloaded, with this process being transparent to the user and not requiring any special options. This should not only make many builds faster but also work on Windows, one of our most requested features but something that was not possible when the toolchain required that everything be locally compiled. Likewise, the toolchain has semi-implemented support for multiple architectures internally, but none other than armeabi are yet supported and there will be bugs to work out when more are enabled. Still, these will (fingers crossed) be things to look forward to in the relatively near future.

I should note here that this model of binary distribution is what I initially targeted as a natural extension of python-for-android’s distribution system - although we never made much of it, the first step is already to build a standalone android package which later can be distributed separately and populated with app details by a user, and the above just involves making such prebuilt distributions available to download and use automatically. I found more recently the method of the pybee project/Toga toolkit’s Python-Android-template. This is a similar idea (built by a modified python-for-android) but implemented much better as a standalone project with app details populated by cookiecutter and the packaging of the user’s Python modules taken care of using ant itself, the normal APK build and deployment interface - I didn’t know this was even possible! This means that the user can just write their Python code, drop it in place, and run the APK build, a very neat process. It should be quite easy to modify python-for-android’s dist output to easily create such templates, its dist system is functionally the same thing with a different and less standard-Android interface, and I hope that doing so could make it even more convenient for users to build and distribute different kinds of Python apps.

This leaves the elephant in the room, support for Python 3 on Android, which is perhaps the most requested feature for Kivy itself. The new toolchain makes significant progress on this in a couple of ways. The first is by removing hardcoded use of Python 2, so that now (barring remaining bugs) a Python 3 build should be well behaved once a recipe and appropriate Android patch set are added. The second is that the old Kivy Android bootstrap probably needed significant changes to support Python 3, but this is sidestepped entirely by moving to the new SDL2 backend which should have no issues supporting Python3 more or less the same as on the desktop. However, the missing link here is still actually being able to compile Python 3 for Android, and I don’t yet know how to do this. Some of Kivy’s main Python 2 patches come from this site, but this has Python 3 patches only up to 3.2.2 and it would be ideal to target 3.4 or 3.5 (and to be able to support new versions as they appear). I’ve looked around and seen a few different discussions of this, but I’m not sure what’s the best direction to try. If anyone has any information about places to find more up to date patch sets I would be very interested. I can’t make any other predictions about this as I don’t know much about the Python compilation process or what difficulties might be involved in doing the work we need.

That’s all for now. I’ll note again that this is an initial announcement of the new toolchain; I hope that people may be interested to look and try it, and it should support most of what the old toolchain does when it comes to compiling Pygame APKs, but there are likely to be bugs and missing features particularly surrounding (but not limited to) the new additions. If you’re interested in making this toolchain work with other modules or backends, or just have any questions, comments or criticisms, let us know! If you want to keep informed, watch this space, I’ll make further announcements as things develop. If there is developer interest and people start switching from the old toolchain, I hope development will speed up a lot and quickly approach proper feature parity.

tl;dr (I was told I should have one): Kivy’s python-for-android build tools have been revamped to have a better interface, build apps based on SDL2, build non-Kivy apps (currently Vispy apps), and be more extensible. Further semi-complete features include binary distribution, Windows support, and multiple architecture targets. Python 3 is brought closer but needs direct compilation work.

Posted on

python-for-android revamped

I’ve recently been working on a significantly revamped version of python-for-android, the Kivy-project tools that take a Python program and package it - along with any dependencies and the Python interpreter itself - into an Android APK that can be run and distributed just like a normal Android app. This rewrite is driven by the problem that although the current python-for-android is fairly robust as far as the build process goes, it’s quite set in its ways and hard to modify to make large changes such as to support backends other than Kivy.

To this end, the revamp project has several major goals:

  • Rewrite python-for-android to a fully Python toolchain that can be more easily modified and extended.
  • Support multiple bootstrap targets for different kinds of Python scrips to run on Android, starting with a new SDL2 backend for Kivy applications.
  • Support Python 3 on Android.
  • Support some kind of binary distribution, enabling easier and cross-platform distribution…this should work on Windows!
  • Be a standalone PyPI module with a more convenient and standard interface, potentially interfacing with setuptools.
  • Support (less painfully) multiple Android architectures, or fat APKs supporting more than one.

Each of these is individually a popularly requested feature, and this is a great opportunity to go for all of them at once!

I’m making this post to announce that the python-for-android revamp project has reached a usable state, with several of these goals either implemented or significantly advanced, and all of them at least made much more accessible. The core change is that all of the original toolchain has been rewritten in Python, with the initial structure based on the recent Kivy-iOS rewrite. It’s also much lighter, all heavy pygame stuff is downloaded on demand instead of built in, and is designed to be accessed by a single set of commands and the new python-for-android executable rather than by the separate invocation of different scripts in different places. I won’t go into the technical details here, but you can find the (WIP) documentation temporarily hosted here. If anyone would like to test it you can try the instructions there, but the project is in an experimental state right now and it’s likely you may encounter bugs or missing features, the current focus is ironing these out. I’m very happy to discuss these on the kivy-users mailing list or #kivy irc channel on irc.freenode.net.

Another of the core goals of this rewrite was to support multiple app backends; in Kivy’s case in particular we want to move from Pygame to a new SDL2 bootstrap, but this could also include support for other Python module backends. As of now, the new python-for-android supports the old Pygame bootstrap mostly as before, but also implements an SDL2 based PythonActivity that works very well with Kivy - highly anecdotal testing found, amongst other things, app start time reduced to 60% of what it was with Pygame. It also simplifies maintenance as SDL2’s java components fulfil the same role as those maintained in the Pygame backend, but no longer require much special treatment as functionality such as touch interaction and pausing are now accessed with the SDL2 api just as on desktop platforms.

Further, python-for-android can now build non-Kivy apps! The first project with this support built in is the Vispy scientific visualisation library. This uses the same new SDL2 backend but Kivy is not involved, and the build process does not use Cython (unlike with Kivy); instead, SDL2 and OpenGL are called entirely with ctypes, using pysdl2 and Vispy’s own gloo wrapper respectively. I didn’t even have to patch things much for this, Vispy is mostly self contained and already quite platform independent, barring a couple of possible small bugs and a hack to avoid the lack of a supported font provider on Android. Vispy also uses numpy heavily, but this was already supported by python-for-android and seems to work fine. The Vispy support is itself quite experimental and there are some performance issues that will need resolving, but it was very simple to set up with the new toolchain. Here’s a screenshot of one of Vispy’s 3D examples running on Android - there are a few small visual artifacts, but I think these are small bugs in Vispy’s OpenGL ES 2 support that the Vispy team are actively addressing:

Image of Vispy running on Android

Support for binary distribution and multiple architectures are both partially implemented but (at the time of writing) not yet working. However, the toolchain is built around them, so there should be no major issues. The initial idea with binary distribution will be to simply make available a number of prebuilt distributions (i.e. Android projects with the Python interpreter) that include common dependencies, so that when the user adds modules as requirements when calling python-for-android they can automatically be checked and an appropriate choice downloaded, with this process being transparent to the user and not requiring any special options. This should not only make many builds faster but also work on Windows, one of our most requested features but something that was not possible when the toolchain required that everything be locally compiled. Likewise, the toolchain has semi-implemented support for multiple architectures internally, but none other than armeabi are yet supported and there will be bugs to work out when more are enabled. Still, these will (fingers crossed) be things to look forward to in the relatively near future.

I should note here that this model of binary distribution is what I initially targeted as a natural extension of python-for-android’s distribution system - although we never made much of it, the first step is already to build a standalone android package which later can be distributed separately and populated with app details by a user, and the above just involves making such prebuilt distributions available to download and use automatically. I found more recently the method of the pybee project/Toga toolkit’s Python-Android-template. This is a similar idea (built by a modified python-for-android) but implemented much better as a standalone project with app details populated by cookiecutter and the packaging of the user’s Python modules taken care of using ant itself, the normal APK build and deployment interface - I didn’t know this was even possible! This means that the user can just write their Python code, drop it in place, and run the APK build, a very neat process. It should be quite easy to modify python-for-android’s dist output to easily create such templates, its dist system is functionally the same thing with a different and less standard-Android interface, and I hope that doing so could make it even more convenient for users to build and distribute different kinds of Python apps.

This leaves the elephant in the room, support for Python 3 on Android, which is perhaps the most requested feature for Kivy itself. The new toolchain makes significant progress on this in a couple of ways. The first is by removing hardcoded use of Python 2, so that now (barring remaining bugs) a Python 3 build should be well behaved once a recipe and appropriate Android patch set are added. The second is that the old Kivy Android bootstrap probably needed significant changes to support Python 3, but this is sidestepped entirely by moving to the new SDL2 backend which should have no issues supporting Python3 more or less the same as on the desktop. However, the missing link here is still actually being able to compile Python 3 for Android, and I don’t yet know how to do this. Some of Kivy’s main Python 2 patches come from this site, but this has Python 3 patches only up to 3.2.2 and it would be ideal to target 3.4 or 3.5 (and to be able to support new versions as they appear). I’ve looked around and seen a few different discussions of this, but I’m not sure what’s the best direction to try. If anyone has any information about places to find more up to date patch sets I would be very interested. I can’t make any other predictions about this as I don’t know much about the Python compilation process or what difficulties might be involved in doing the work we need.

That’s all for now. I’ll note again that this is an initial announcement of the new toolchain; I hope that people may be interested to look and try it, and it should support most of what the old toolchain does when it comes to compiling Pygame APKs, but there are likely to be bugs and missing features particularly surrounding (but not limited to) the new additions. If you’re interested in making this toolchain work with other modules or backends, or just have any questions, comments or criticisms, let us know! If you want to keep informed, watch this space, I’ll make further announcements as things develop. If there is developer interest and people start switching from the old toolchain, I hope development will speed up a lot and quickly approach proper feature parity.

tl;dr (I was told I should have one): Kivy’s python-for-android build tools have been revamped to have a better interface, build apps based on SDL2, build non-Kivy apps (currently Vispy apps), and be more extensible. Further semi-complete features include binary distribution, Windows support, and multiple architecture targets. Python 3 is brought closer but needs direct compilation work.