# Python for Android
These instructions are only needed if you're planning to compile Python for
-Android yourself. Most users should *not* need to do this. If you're looking to
-use Python on Android, one of the following tools will provide a much more
-approachable user experience:
-
-* [Briefcase](https://briefcase.readthedocs.io), from the BeeWare project
-* [Buildozer](https://buildozer.readthedocs.io), from the Kivy project
-* [Chaquopy](https://chaquo.com/chaquopy/)
+Android yourself. Most users should *not* need to do this. Instead, use one of
+the tools listed in `Doc/using/android.rst`, which will provide a much easier
+experience.
## Prerequisites
The test suite can usually be run on a device with 2 GB of RAM, though for some
configurations or test orders you may need to increase this. As of Android
Studio Koala, 2 GB is the default for all emulators, although the user interface
-may indicate otherwise. The effective setting is `hw.ramSize` in
-~/.android/avd/*.avd/hardware-qemu.ini, whereas Android Studio displays the
-value from config.ini. Changing the value in Android Studio will update both of
-these files.
+may indicate otherwise. Locate the emulator's directory under `~/.android/avd`,
+and find `hw.ramSize` in both config.ini and hardware-qemu.ini. Either set these
+manually to the same value, or use the Android Studio Device Manager, which will
+update both files.
Before running the test suite, follow the instructions in the previous section
to build the architecture you want to test. Then run the test script in one of
repository's `Lib` directory will be picked up immediately. Changes in C files,
and architecture-specific files such as sysconfigdata, will not take effect
until you re-run `android.py make-host` or `build`.
+
+
+## Using in your own app
+
+See `Doc/using/android.rst`.
+++ /dev/null
-.. include for modules that don't work on WASM or iOS
-
-.. availability:: not WASI, not iOS.
-
- This module does not work or is not available on WebAssembly platforms, or
- on iOS. See :ref:`wasm-availability` for more information on WASM
- availability; see :ref:`iOS-availability` for more information on iOS
- availability.
--- /dev/null
+.. include for modules that don't work on WASM or mobile platforms
+
+.. availability:: not Android, not iOS, not WASI.
+
+ This module is not supported on :ref:`mobile platforms <mobile-availability>`
+ or :ref:`WebAssembly platforms <wasm-availability>`.
designed to match the API of ncurses, an open-source curses library hosted on
Linux and the BSD variants of Unix.
-.. include:: ../includes/wasm-ios-notavail.rst
+.. include:: ../includes/wasm-mobile-notavail.rst
.. note::
is a `third party interface <https://www.jcea.es/programacion/pybsddb.htm>`_ to
the Oracle Berkeley DB.
-.. include:: ../includes/wasm-ios-notavail.rst
-
.. exception:: error
A tuple containing the exceptions that can be raised by each of the supported
The files created by :mod:`dbm.sqlite3` can thus be opened by :mod:`sqlite3`,
or any other SQLite browser, including the SQLite CLI.
+.. include:: ../includes/wasm-notavail.rst
+
.. function:: open(filename, /, flag="r", mode=0o666)
Open an SQLite database.
The file formats created by :mod:`dbm.gnu` and :mod:`dbm.ndbm` are incompatible
and can not be used interchangeably.
+.. include:: ../includes/wasm-mobile-notavail.rst
+
.. exception:: error
Raised on :mod:`dbm.gnu`-specific errors, such as I/O errors. :exc:`KeyError` is
when storing values larger than this limit. Reading such corrupted files can
result in a hard crash (segmentation fault).
+.. include:: ../includes/wasm-mobile-notavail.rst
+
.. exception:: error
Raised on :mod:`dbm.ndbm`-specific errors, such as I/O errors. :exc:`KeyError` is raised
:pep:`453`: Explicit bootstrapping of pip in Python installations
The original rationale and specification for this module.
-.. include:: ../includes/wasm-ios-notavail.rst
+.. include:: ../includes/wasm-mobile-notavail.rst
Command line interface
----------------------
This module provides access to the Unix group database. It is available on all
Unix versions.
-.. availability:: Unix, not WASI, not iOS.
+.. availability:: Unix, not WASI, not Android, not iOS.
Group database entries are reported as a tuple-like object, whose attributes
correspond to the members of the ``group`` structure (Attribute field below, see
operating system.
* If not separately noted, all functions that claim "Availability: Unix" are
- supported on macOS and iOS, both of which build on a Unix core.
+ supported on macOS, iOS and Android, all of which build on a Unix core.
* If an availability note contains both a minimum Kernel version and a minimum
libc version, then both conditions must hold. For example a feature with note
.. _Pyodide: https://pyodide.org/
.. _PyScript: https://pyscript.net/
+.. _mobile-availability:
.. _iOS-availability:
-iOS
----
+Mobile platforms
+----------------
-iOS is, in most respects, a POSIX operating system. File I/O, socket handling,
+Android and iOS are, in most respects, POSIX operating systems. File I/O, socket handling,
and threading all behave as they would on any POSIX operating system. However,
-there are several major differences between iOS and other POSIX systems.
-
-* iOS can only use Python in "embedded" mode. There is no Python REPL, and no
- ability to execute binaries that are part of the normal Python developer
- experience, such as :program:`pip`. To add Python code to your iOS app, you must use
- the :ref:`Python embedding API <embedding>` to add a Python interpreter to an
- iOS app created with Xcode. See the :ref:`iOS usage guide <using-ios>` for
- more details.
-
-* An iOS app cannot use any form of subprocessing, background processing, or
- inter-process communication. If an iOS app attempts to create a subprocess,
- the process creating the subprocess will either lock up, or crash. An iOS app
- has no visibility of other applications that are running, nor any ability to
- communicate with other running applications, outside of the iOS-specific APIs
- that exist for this purpose.
-
-* iOS apps have limited access to modify system resources (such as the system
+there are several major differences:
+
+* Mobile platforms can only use Python in "embedded" mode. There is no Python
+ REPL, and no ability to use separate executables such as :program:`python` or
+ :program:`pip`. To add Python code to your mobile app, you must use
+ the :ref:`Python embedding API <embedding>`. For more details, see
+ :ref:`using-android` and :ref:`using-ios`.
+
+* Subprocesses:
+
+ * On Android, creating subprocesses is possible but `officially unsupported
+ <https://issuetracker.google.com/issues/128554619#comment4>`__.
+ In particular, Android does not support any part of the System V IPC API,
+ so :mod:`multiprocessing` is not available.
+
+ * An iOS app cannot use any form of subprocessing, multiprocessing, or
+ inter-process communication. If an iOS app attempts to create a subprocess,
+ the process creating the subprocess will either lock up, or crash. An iOS app
+ has no visibility of other applications that are running, nor any ability to
+ communicate with other running applications, outside of the iOS-specific APIs
+ that exist for this purpose.
+
+* Mobile apps have limited access to modify system resources (such as the system
clock). These resources will often be *readable*, but attempts to modify
those resources will usually fail.
-* iOS apps have a limited concept of console input and output. ``stdout`` and
- ``stderr`` *exist*, and content written to ``stdout`` and ``stderr`` will be
- visible in logs when running in Xcode, but this content *won't* be recorded
- in the system log. If a user who has installed your app provides their app
- logs as a diagnostic aid, they will not include any detail written to
- ``stdout`` or ``stderr``.
+* Console input and output:
+
+ * On Android, the native ``stdout`` and ``stderr`` are not connected to
+ anything, so Python installs its own streams which redirect messages to the
+ system log. These can be seen under the tags ``python.stdout`` and
+ ``python.stderr`` respectively.
+
+ * iOS apps have a limited concept of console output. ``stdout`` and
+ ``stderr`` *exist*, and content written to ``stdout`` and ``stderr`` will be
+ visible in logs when running in Xcode, but this content *won't* be recorded
+ in the system log. If a user who has installed your app provides their app
+ logs as a diagnostic aid, they will not include any detail written to
+ ``stdout`` or ``stderr``.
- iOS apps have no concept of ``stdin`` at all. While iOS apps can have a
- keyboard, this is a software feature, not something that is attached to
- ``stdin``.
+ * Mobile apps have no usable ``stdin`` at all. While apps can display an on-screen
+ keyboard, this is a software feature, not something that is attached to
+ ``stdin``.
- As a result, Python library that involve console manipulation (such as
- :mod:`curses` and :mod:`readline`) are not available on iOS.
+ As a result, Python modules that involve console manipulation (such as
+ :mod:`curses` and :mod:`readline`) are not available on mobile platforms.
--------------
-.. include:: ../includes/wasm-ios-notavail.rst
+.. include:: ../includes/wasm-mobile-notavail.rst
Introduction
------------
* On VxWorks, os.popen, os.fork, os.execv and os.spawn*p* are not supported.
-* On WebAssembly platforms, and on iOS, large parts of the :mod:`os` module are
- not available or behave differently. API related to processes (e.g.
+* On WebAssembly platforms, Android and iOS, large parts of the :mod:`os` module are
+ not available or behave differently. APIs related to processes (e.g.
:func:`~os.fork`, :func:`~os.execve`) and resources (e.g. :func:`~os.nice`)
are not available. Others like :func:`~os.getuid` and :func:`~os.getpid` are
emulated or stubs. WebAssembly platforms also lack support for signals (e.g.
the groups of which the specified username is a member, plus the specified
group id.
- .. availability:: Unix, not WASI.
+ .. availability:: Unix, not WASI, not Android.
.. versionadded:: 3.2
Set the current process's effective group id.
- .. availability:: Unix, not WASI.
+ .. availability:: Unix, not WASI, not Android.
.. function:: seteuid(euid, /)
Set the current process's effective user id.
- .. availability:: Unix, not WASI.
+ .. availability:: Unix, not WASI, not Android.
.. function:: setgid(gid, /)
Set the current process' group id.
- .. availability:: Unix, not WASI.
+ .. availability:: Unix, not WASI, not Android.
.. function:: setgroups(groups, /)
Set the current process's real and effective group ids.
- .. availability:: Unix, not WASI.
+ .. availability:: Unix, not WASI, not Android.
.. function:: setresgid(rgid, egid, sgid, /)
Set the current process's real, effective, and saved group ids.
- .. availability:: Unix, not WASI.
+ .. availability:: Unix, not WASI, not Android.
.. versionadded:: 3.2
Set the current process's real, effective, and saved user ids.
- .. availability:: Unix, not WASI.
+ .. availability:: Unix, not WASI, not Android.
.. versionadded:: 3.2
Set the current process's real and effective user ids.
- .. availability:: Unix, not WASI.
+ .. availability:: Unix, not WASI, not Android.
.. function:: getsid(pid, /)
Set the current process's user id.
- .. availability:: Unix, not WASI.
+ .. availability:: Unix, not WASI, not Android.
.. placed in this section since it relates to errno.... a little weak
Change the root directory of the current process to *path*.
- .. availability:: Unix, not WASI.
+ .. availability:: Unix, not WASI, not Android.
.. versionchanged:: 3.6
Accepts a :term:`path-like object`.
.. audit-event:: os.exec path,args,env os.execl
- .. availability:: Unix, Windows, not WASI, not iOS.
+ .. availability:: Unix, Windows, not WASI, not Android, not iOS.
.. versionchanged:: 3.3
Added support for specifying *path* as an open file descriptor
for technical details of why we're surfacing this longstanding
platform compatibility problem to developers.
- .. availability:: POSIX, not WASI, not iOS.
+ .. availability:: POSIX, not WASI, not Android, not iOS.
.. function:: forkpty()
threads, this now raises a :exc:`DeprecationWarning`. See the
longer explanation on :func:`os.fork`.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. function:: kill(pid, sig, /)
documentation for more powerful ways to manage and communicate with
subprocesses.
- .. availability:: not WASI, not iOS.
+ .. availability:: not WASI, not Android, not iOS.
.. note::
The :ref:`Python UTF-8 Mode <utf8-mode>` affects encodings used
``os.POSIX_SPAWN_CLOSEFROM`` is available on platforms where
:c:func:`!posix_spawn_file_actions_addclosefrom_np` exists.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. function:: posix_spawnp(path, argv, env, *, file_actions=None, \
setpgroup=None, resetids=False, setsid=False, setsigmask=(), \
.. versionadded:: 3.8
- .. availability:: POSIX, not WASI, not iOS.
+ .. availability:: POSIX, not WASI, not Android, not iOS.
See :func:`posix_spawn` documentation.
There is no way to unregister a function.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. versionadded:: 3.7
.. audit-event:: os.spawn mode,path,args,env os.spawnl
- .. availability:: Unix, Windows, not WASI, not iOS.
+ .. availability:: Unix, Windows, not WASI, not Android, not iOS.
:func:`spawnlp`, :func:`spawnlpe`, :func:`spawnvp`
and :func:`spawnvpe` are not available on Windows. :func:`spawnle` and
.. audit-event:: os.system command os.system
- .. availability:: Unix, Windows, not WASI, not iOS.
+ .. availability:: Unix, Windows, not WASI, not Android, not iOS.
.. function:: times()
:func:`waitstatus_to_exitcode` can be used to convert the exit status into an
exit code.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. seealso::
Otherwise, if there are no matching children
that could be waited for, :exc:`ChildProcessError` is raised.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. versionadded:: 3.3
:func:`waitstatus_to_exitcode` can be used to convert the exit status into an
exit code.
- .. availability:: Unix, Windows, not WASI, not iOS.
+ .. availability:: Unix, Windows, not WASI, not Android, not iOS.
.. versionchanged:: 3.5
If the system call is interrupted and the signal handler does not raise an
:func:`waitstatus_to_exitcode` can be used to convert the exit status into an
exitcode.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. function:: wait4(pid, options)
:func:`waitstatus_to_exitcode` can be used to convert the exit status into an
exitcode.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. data:: P_PID
* :data:`!P_PIDFD` - wait for the child identified by the file descriptor
*id* (a process file descriptor created with :func:`pidfd_open`).
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. note:: :data:`!P_PIDFD` is only available on Linux >= 5.4.
:func:`waitid` causes child processes to be reported if they have been
continued from a job control stop since they were last reported.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. data:: WEXITED
The other ``wait*`` functions always report children that have terminated,
so this option is not available for them.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. versionadded:: 3.3
This option is not available for the other ``wait*`` functions.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. versionadded:: 3.3
This option is not available for :func:`waitid`.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. data:: WNOHANG
:func:`waitid` to return right away if no child process status is available
immediately.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. data:: WNOWAIT
This option is not available for the other ``wait*`` functions.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. data:: CLD_EXITED
These are the possible values for :attr:`!si_code` in the result returned by
:func:`waitid`.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. versionadded:: 3.3
:func:`WIFEXITED`, :func:`WEXITSTATUS`, :func:`WIFSIGNALED`,
:func:`WTERMSIG`, :func:`WIFSTOPPED`, :func:`WSTOPSIG` functions.
- .. availability:: Unix, Windows, not WASI, not iOS.
+ .. availability:: Unix, Windows, not WASI, not Android, not iOS.
.. versionadded:: 3.9
This function should be employed only if :func:`WIFSIGNALED` is true.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. function:: WIFCONTINUED(status)
See :data:`WCONTINUED` option.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. function:: WIFSTOPPED(status)
done using :data:`WUNTRACED` option or when the process is being traced (see
:manpage:`ptrace(2)`).
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. function:: WIFSIGNALED(status)
Return ``True`` if the process was terminated by a signal, otherwise return
``False``.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. function:: WIFEXITED(status)
by calling ``exit()`` or ``_exit()``, or by returning from ``main()``;
otherwise return ``False``.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. function:: WEXITSTATUS(status)
This function should be employed only if :func:`WIFEXITED` is true.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. function:: WSTOPSIG(status)
This function should be employed only if :func:`WIFSTOPPED` is true.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
.. function:: WTERMSIG(status)
This function should be employed only if :func:`WIFSIGNALED` is true.
- .. availability:: Unix, not WASI, not iOS.
+ .. availability:: Unix, not WASI, not Android, not iOS.
Interface to the scheduler
allowable constructs of that file, and the capabilities of the
Readline library in general.
-.. include:: ../includes/wasm-ios-notavail.rst
+.. include:: ../includes/wasm-mobile-notavail.rst
.. note::
.. audit-event:: socket.sethostname name socket.sethostname
- .. availability:: Unix.
+ .. availability:: Unix, not Android.
.. versionadded:: 3.3
:pep:`324` -- PEP proposing the subprocess module
-.. include:: ../includes/wasm-ios-notavail.rst
+.. include:: ../includes/wasm-mobile-notavail.rst
Using the :mod:`subprocess` Module
----------------------------------
Use :func:`clock_settime_ns` to avoid the precision loss caused by the
:class:`float` type.
- .. availability:: Unix.
+ .. availability:: Unix, not Android, not iOS.
.. versionadded:: 3.3
Similar to :func:`clock_settime` but set time with nanoseconds.
- .. availability:: Unix.
+ .. availability:: Unix, not Android, not iOS.
.. versionadded:: 3.7
`Python Packaging User Guide: Creating and using virtual environments
<https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/#create-and-use-virtual-environments>`__
-.. include:: ../includes/wasm-ios-notavail.rst
+.. include:: ../includes/wasm-mobile-notavail.rst
Creating virtual environments
-----------------------------
python -m webbrowser -t "https://www.python.org"
-.. include:: ../includes/wasm-notavail.rst
+.. availability:: not WASI, not Android.
The following exception is defined:
--- /dev/null
+.. _using-android:
+
+=======================
+Using Python on Android
+=======================
+
+Python on Android is unlike Python on desktop platforms. On a desktop platform,
+Python is generally installed as a system resource that can be used by any user
+of that computer. Users then interact with Python by running a :program:`python`
+executable and entering commands at an interactive prompt, or by running a
+Python script.
+
+On Android, there is no concept of installing as a system resource. The only unit
+of software distribution is an "app". There is also no console where you could
+run a :program:`python` executable, or interact with a Python REPL.
+
+As a result, the only way you can use Python on Android is in embedded mode – that
+is, by writing a native Android application, embedding a Python interpreter
+using ``libpython``, and invoking Python code using the :ref:`Python embedding
+API <embedding>`. The full Python interpreter, the standard library, and all
+your Python code is then packaged into your app for its own private use.
+
+The Python standard library has some notable omissions and restrictions on
+Android. See the :ref:`API availability guide <mobile-availability>` for
+details.
+
+Adding Python to an Android app
+-------------------------------
+
+These instructions are only needed if you're planning to compile Python for
+Android yourself. Most users should *not* need to do this. Instead, use one of
+the following tools, which will provide a much easier experience:
+
+* `Briefcase <https://briefcase.readthedocs.io>`__, from the BeeWare project
+* `Buildozer <https://buildozer.readthedocs.io>`__, from the Kivy project
+* `Chaquopy <https://chaquo.com/chaquopy>`__
+* `pyqtdeploy <https://www.riverbankcomputing.com/static/Docs/pyqtdeploy/>`__
+* `Termux <https://termux.dev/en/>`__
+
+If you're sure you want to do all of this manually, read on. You can use the
+:source:`testbed app <Android/testbed>` as a guide; each step below contains a
+link to the relevant file.
+
+* Build Python by following the instructions in :source:`Android/README.md`.
+
+* Add code to your :source:`build.gradle <Android/testbed/app/build.gradle.kts>`
+ file to copy the following items into your project. All except your own Python
+ code can be copied from ``cross-build/HOST/prefix/lib``:
+
+ * In your JNI libraries:
+
+ * ``libpython*.*.so``
+ * ``lib*_python.so`` (external libraries such as OpenSSL)
+
+ * In your assets:
+
+ * ``python*.*`` (the Python standard library)
+ * ``python*.*/site-packages`` (your own Python code)
+
+* Add code to your app to :source:`extract the assets to the filesystem
+ <Android/testbed/app/src/main/java/org/python/testbed/MainActivity.kt>`.
+
+* Add code to your app to :source:`start Python in embedded mode
+ <Android/testbed/app/src/main/c/main_activity.c>`. This will need to be C code
+ called via JNI.
.. toctree::
:numbered:
+ :maxdepth: 2
cmdline.rst
unix.rst
configure.rst
windows.rst
mac.rst
+ android.rst
ios.rst
editors.rst
-----------------------------
The Python standard library has some notable omissions and restrictions on
-iOS. See the :ref:`API availability guide for iOS <iOS-availability>` for
+iOS. See the :ref:`API availability guide for iOS <mobile-availability>` for
details.
Binary extension modules
* :pep:`730`: Apple's iOS is now an :ref:`officially supported platform
<whatsnew313-platform-support>`, at :pep:`tier 3 <11#tier-3>`.
- Official Android support (:pep:`738`) is also in the works.
+* :pep:`738`: Android is now an :ref:`officially supported platform
+ <whatsnew313-platform-support>`, at :pep:`tier 3 <11#tier-3>`.
* ``wasm32-wasi`` is now supported as a :pep:`tier 2 <11#tier-2>` platform.
* ``wasm32-emscripten`` is no longer an officially supported platform.
(PEP written and implementation contributed by Russell Keith-Magee in
:gh:`114099`.)
-:pep:`738`: Android support is being actively worked on,
-but the platform is not yet officially supported.
+:pep:`738`: Android is now a :pep:`11` supported platform, with the
+``aarch64-linux-android`` and ``x86_64-linux-android`` targets at tier 3.
+The 32-bit targets ``arm-linux-androideabi`` and ``i686-linux-android``
+are not tier 3 supported platforms, but will have best-effort support.
(PEP written and implementation contributed by Malcolm Smith in
:gh:`116622`.)
(:ref:`PEP 730 <whatsnew313-platform-support>` written
and implementation contributed by Russell Keith-Magee in :gh:`114099`.)
+* ``aarch64-linux-android`` and ``x86_64-linux-android`` are both
+ now :pep:`11` tier 3 platforms.
+ (:ref:`PEP 738 <whatsnew313-platform-support>` written
+ and implementation contributed by Malcolm Smith in :gh:`116622`.)
+
* ``wasm32-wasi`` is now a :pep:`11` tier 2 platform.
(Contributed by Brett Cannon in :gh:`115192`.)
Eric V. Smith
Ethan H. Smith
Gregory P. Smith
+Malcolm Smith
Mark Smith
Nathaniel J. Smith
Roy Smith
--- /dev/null
+Add an Android platform guide, and flag modules not available on Android.