PySide for Android guide

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PySide for Android

This guide describes:

  • how to build Shiboken & PySide for Android using the Necessitas SDK
  • how to use the resulting libraries
  • and how to bundle them with your Python program in a standalone APK

NOTE: If you just want to run you Python & PySide programs on Android, you can skip the Building PySide section and go directly to PySide for Android example application [qt.io] & Example project for the Necessitas Qt Creator [qt.io] .

See Links [qt.io] for source code [qt.io] & pre-built binaries [qt.io].

Building PySide

Prerequisites

Necessitas SDK Make sure to get the latest Necessitas alpha 4 SDK – older version might not work correctly with the build script (incompatible libraries, different paths, etc.).

Download & run the Necessitas SDK installer

Once the installer starts -> don’t forget to install Android API 14 !!

  • on the Select components page go to * Miscellaneous ->Android SDK* and select API 14 for installation
  • to make sure you have the Android SDK platform/API 14 installed in the Necessitas SDK (can be done after SDK installation):
    - run 
    SDKMaintenanceTool
    select Package manager and in Miscantelous->Android SDK check if you have API 14 installed
    - PySide should probably compile even against a lower API, but that has not been tested yet

Other prerequisites

  • system-wide installed Shiboken
  • system-wide installed Python 2.7
  • Python 2.7 compiled for Android
  • cmake
  • git

This command should probably fetch most of the prerequisites on Ubuntu:

If you find some are is missing or if you wan’t to provide similar command for other distributions, add them ! :)

Then clone the Android-pyside-build-scripts project and cd to it’s directory:

Now run the prepare.sh script:
It clones Android-modified Shiboken & PySide and creates some folders needed for the build.

And that’s it, you are ready to start the build. :)

Build

To start the build, just run the main build script, called build.sh:
It first builds Shiboken, followed by PySide. The script is fully automatic, but waits for the user to press any key:

  • after Shiboken is configured for build
  • after PySide is configured for build
    Like this you can easily check for any errors during configuration.

Also note, that when running the script, it clears any previous build results before building.

You can also run the build_shiboken.sh and build_pyside.sh scripts manually, just always make sure to run the Shiboken one before running the PySide one.

Build issues

If you have any issues during the PySide build, the first thing you should do is to check the PySide for Android build scripts repository if it was not updated since you cloned it, as it might already contain a fix for you issue.

arm-linux-androideabi-g++: Internal error: Killed (program cc1plus)

This error seems to be caused by low system resources during build and/or running the compilation in multiple threads on some machines. If you are experiencing this error, try to set 

<span class="caps">BUILD</span>_THREAD_COUNT

in 

env.sh

to 1.

Results

The resulting PySide libraries compiled for Android are located in the stage/lib folder.

See the Example project for the Necessitas Qt Creator, Modifying the project [qt.io], section Replacing PySide libraries for how the PySide libraries can be used as a part of a self-contained Android application.

PySide for Android example application

This is an example, that demonstrates a fully functional standalone Android application that uses Python, PySide and Qt Components.

example application in ladscape example application in portrait example application showing the tools menu

more screenshots [modrana.org]

Ready-to-install APK

A ready-to-install standalone APK is available here:

http://modrana.org/platforms/android/pyside_example/PySideExample_1.2.apk

Just install it and press the PySideExample icon.

First start

If you haven’t yet installed any Ministro using Qt application on your Android device, you will be redirected to the Play store to install the Ministro application. Ministro is a manager & updater for the Qt libraries for Android. The example application requires to be installed to run.
So just install Ministro and everything else will be handled automatically. You might need to press the PySideExample icon again once Ministro is installed.

Once Ministro is installed and does it’s work, the example might still take some time to start, as it is unpacking Python, Qt Components, theme for Qt Components and the example program to it’s working directory. Once the unpacking is finished, the example application will be started.

The unpacking is done only once on the first application start, following starts are very fast, at least when tested on my device (HP Touchpad with CM9).

What the example application demonstrates

  • sending data to Python and back * the content of the entry field is sent to Python, where it is painted on the PySide image and returned to QML using ImageProvider * the date is retrieved in Python and shown in QML
  • working text entry with the Android virtual keyboard
  • working screen rotation
  • correct Portrait/Landscape orientation switching * in both normal & inverted orientations
  • working notifications (InfoBanner)
  • working ToolBar
  • working Menu
  • “tools” menu with rotation & opacity sliders for the PySide image

Source code

Available from Github under BSD licence:
https://github.com/M4rtinK/expyside/tree/android

Size of the APK

The example APK has about 16 MB. This is because it needs to bundle quite a lot of
libraries and related files. Big part of it is actually not used by the example in any way.

For normal applications it should be possible to make the resulting APK much smaller by:

  • including only the PySide libraries that are actually used
  • removing unused Python modules
  • cutting down the Qt Components theme from all graphics & icons that are not used

Example project for the Necessitas Qt Creator

This project has been used to generate the above mentioned application example APK.

Using the project

Using the project to build your own project is very easy. Just install the Necessitas SDK and clone the example project from git:
Then just open the PySideExample.pro with the Necessitas Qt Creator.

To generate a new APK, just click the green run arrow in the lower left – Qt Creator should rebuild the the APK and deploy it either to the simulator or to any connected Android device that has debugging enabled.

Build & deployment issues

The example fails to start when deployed to device

First check you have the latest clone of the project.

Then check for which ARM architecture are you building by clicking on Projects. The available architecture targets are:

  • Necessitas Qt 4.8.2 for Android armv5
  • Necessitas Qt 4.8.2 for Android armv7a

The currently used architecture dark, the unused is white-grey. The build architecture needs to correspond to what the CPU of your device is using. If not sure, just try both and stick with the one that works. :)

Cannot find ELF information

This error is harmless and can be safely ignored.

How does it work ?

The project contains various components, that together enable the creation of fully standalone Python & PySide application APK, while also allowing to bundle any arbitrary libraries and files needed by the application.

The example project is called 

PySideExample

and uses the 

org.modrana.PySideExample

unique name. This means, that when it’s APK is installed on and Android device, it gets installed to this directory:
This path is important, as the application needs to set a couple of environmental variables during startup, pointing to libraries and themes that reside in this directory.

C++ wrapper

The 

main.cpp

and 

main.h

files are used to build a C++ Python wrapper. This wrapper is build against the the Android-compiled python libraries in 

build_dependencies/python

by Necessitas. Once the APK is deployd to the device and started, this wrapper is run. It initializes it’s build-in Python interpreter, which tries to start the 

/data/data/org.modrana.PySide.Example/files/main.py

Python file. This Python code then imports PySide, instantiates a QApplication and starts the main loop.

Behind the scenes, Necessitas handles wrapping the QApplication to an Android activity and showing it on the screen. It also handles other stuff like keyboard input & Qt Mobility.

main.h

This file contains important paths for the C++ wrapper. 

  • <span class="caps">MAIN</span>_PYTHON_FILE
    – path to the main Python file to run once the application is started
  • <span class="caps">PYTHON</span>_HOME

  • LD_LIBRARY_PATH
    – : separated list of paths used to look for libraries when loading them
  • <span class="caps">PATH</span>
    – search path for executables
  • <span class="caps">THEME</span>_PATH
    – path to the main themes folder for Qt Components
  • <span class="caps">QML</span>_IMPORT_PATH
    – path to the Qt Components 
    imports
    folder
main.cpp

This is the C++ wrapper, it contains the embedded Python interpreter that is used to start the application and also sets some important environmental variables specified through 

main.h

.

The example Python application

The example in 

main.py

inside 

my_python_project.zip

is basically a normal PySide application, it imports PySide, instantiates QApplication and starts the main loop. There is only one main difference in this piece of code: Due to some not yet identified bug, unless 

libshiboken.so

& 

libpyside.so

are manually loaded to memory like this, importing any PySide module fails.

So make sure this piece of code is somewhere in your application and is executed before import of any PySide module takes place.

Regarding the 

<span class="caps">PYSIDE</span>_APPLICATION_FOLDER

environmental variable, it is set by the 

main.cpp

wrapper and can be configured in 

main.h

.

Bundling

The example project bundles all files needed by the application inside the standalone APK. This section describes how the bundling works.

Modified QtActivity.java

Another mportant file is the main Android activity located in 

android/src/org/kde/necessitas/origo/QtActivity.java

This is actually the first thing that is started once you press the application icon on android. It basically works as a glue between Android, Qt and in our case, Python & PySide.

The basic activity file that is part of every Necessitas Qt Creator project has been modified by the android_python27 project, to look for two specific zip archives in the installation folder at startup ant to decompress them & then remover the archives.

This way bundling of arbitrary files (libraries, executables, code, themes, etc.) inside the application APK has been achieved.

NOTE: Necessitas Qt Creator might sometimes want to update the pre-generated *.java files with a new version. If this happens, check if the update didn’t break or remove the bundling code in 

QtActivity.java

.

GlobalConstants.java

The file 

android/src/org/kde/necessitas/origo/GlobalConstants.java

contains variables for the main 

QtActivity

file.

It looks like this:

As you can see, you can use it to set various variables, such as name of the bundling archives or logging prefix (does this actually work ?).

my_python_project.zip

The first archive, located in 

android/res/raw/my_python_project.zip

in the project contains the Python application code. On first application start, it’s contents are unpacked into: 

/data/data/org.modrana.PySide.Example/files/
python27.zip

This file is located 

android/res/raw/python_27.zip

in the project and it’s content is unpacked to: 

/data/data/org.modrana.PySide.Example/files/python

The paths set in 

main.h

expect this and point the corresponding environmental variables to the 

bin

, 

lib

, 

imports

and 

themes

folders in this directory.

Modifying the project

When you want to use the example project as basis for your Python application for Android, you just need to rename it and replace the example application.

But just in case I’ve also documented replacing all the other components.

Renaming

Names

There are actually two names – the project/application name and the unique application name.

For the example project, they project name is 

PySideExample

and the unique name is 

org.modrana.PySideExample

. As you can see, the project name is also a suffix for the unique name. (You probably can use a project name that differs from the suffix, but I rather make them the same to avoid needless confusion).

The unique name is very important:

  • it has to be unique so it dosn’t clash with other applications * for this reason, it is mostly based on a domain name you control or some other string with low possibility of being used by another developer
  • the unique name is used for path to the installation folder * the example project uses the 
    org.modrana.PySideExample
    and it is installed into 
    /data/data/org.modrana.PySideExample
    as a result * the path to the installation folder is used when setting important environmental variables, so make sure to change all the corresponding paths when changing the unique name
Project rename script

You can also run this combined script from the project directory, which should do all the needed renaming:
Just change 

<span class="caps">NEW</span>_NAME

and 

<span class="caps">NEW</span>_UNIQUE_NAME

to values matching you application and you are set. :)

What the rename script does

Lets say we want to rename the example project from 

PySideExample

to 

BarApp

and from 

org.modrana.PySideExample

to 

foo.foomatic.BarApp
  • rename the project file:
  • replace the name inside the project file:
  • replace all unique names in 
    main.h
    :
  • replace all unique names in the 
    QtActivity
    :
  • replace all names in the Android manifest file:
  • and the last is in the 
    android/res/strings.xml
    and 
    android/build.xml
    file:

NOTE: Some of these names can be changed from the Necessitas Qt Creator GUI or of course also by using an editor.

To verify that you have really changed all of the original names or if there are still some left, you can use this command:

Replacing the application

The application is located in: 

android/res/raw/my_python_project.zip

This file is decompressed into the 

/data/data/org.modrana.PySide.Example/files/

folder on first start after installation. Then 

/data/data/org.modrana.PySide.Example/files/main.py

is run by Python. To replace the example application, just replace the contents of 

my_python_project.zip

, if you want to start other file than 

main.py

, just change the MAIN_PYTHON_FILE path in 

main.h

.

Replacing Python

The project contains two Python “bundles”, one is used to compile the application wrapper and is located in 

build_dependencies/python

, the other one is in 

android/res/raw/python_27.zip

and is deployed on first start after installation into 

/data/data/org.modrana.PySide.Example/files/python

with all other bundled libraries and files in this archive.

When replacing Python, you should probably replace both bundles with the same Android-compiled Python version, or at least use the same series (2.7 & 2.7 not 2.7 & 2.6).

Replacing PySide libraries

The PySide libraries are located in 

android/res/raw/python_27.zip

archive inside the lib folder. This folder is deployed to 

/data/data/org.modrana.PySide.Example/files/python/lib

on the Android device.

When replacing PySide, you need to replace the libshiboken and libpyside:

Replacing Qt Components

The Qt Components are packed in the 

android/res/raw/python_27.zip

in the 

imports

directory, the theme is in 

themes

. These to folders are deployed like this after installation:
So to replace Qt Components and/or their theme, just replace the content of the imports and/or themes folders in the 

python_27.zip

archives.

Adding files, libraries & executables

Files

Arbitrary files needed by you application should probably go to the 

my_python_project.zip

, to be deployed together with your application to the main instalation folder.

Libraries & executables

Libraries should be added to 

python_27.zip

to the 

lib

folder, exectuables to the 

bin

folder. Like this they will be deployed to a folder that is listed in 

$LD_LIBRARY_PATH

and 

$PATH

respectively.

NOTE: I haven’t yet tested if running executables through subprocess actually works.

Ideas for improvement

There is definitely still room for improvement, such as:

  • customizes Necessitas Qt Creator PySide projects
  • building APKs from command line only without Qt Creator
  • show a progress bar when the bundled libs are unpacked on first start
  • modified bundling that doesn’t unpack the files during startup bud during installation * this could speed up the first start quite a bit
  • compiling the many Qt Components files & images to a single resource file ?
  • documenting how to use Android specific APIs from Python
  • videos

Links

Source code listing

A convenient listing of sources for all the components used for the PySide & co port to Android. :)

Shiboken for Android
https://github.com/M4rtinK/shiboken-android/tree/android

PySide for Android
https://github.com/M4rtinK/pyside-android/tree/android

PySide for Android build scripts
https://github.com/M4rtinK/android-pyside-build-scripts

Qt Components
https://qt.gitorious.org/~martink/qt-components/martinks-ineans-qt-components/commits/android

Example program
https://github.com/M4rtinK/expyside/tree/android

Example project for Necessitas QtCreator
https://github.com/M4rtinK/android-pyside-example-project

Binary listing

List of relevant pre-built binaries

PySide libraries
http://modrana.org/platforms/android/pyside/

PyQt libraries
http://modrana.org/platforms/android/pyqt4/

Python 2.7 compiled for android – libs, executables & headers
http://www.modrana.org/platforms/android/python2.7/python2.7_for_android_v1.zip

Qt Components for Android
http://modrana.org/platforms/android/qt_components/qt_components_v1.zip

Cut-down Qt Components theme
http://modrana.org/platforms/android/qt_components/qt_components_theme_mini_v1.zip

Example application APK
http://modrana.org/platforms/android/pyside_example/PySideExample_1.2.apk

Acknowledgement

As usual with open source development, I haven’t done all of this single handedly, but built on work done by others before me. So I’d like to both acknowledge on which work this is build upon and also provided links to the sources I’ve used:

  • THPs PySide for Android [thp.io] – showing that this is possible
  • Adrià Cereto-Massagué – integrated & improved THPs patches for Shiboken [github.com] and PySide [github.com]
  • The Android-Python2.7 project [code.google.com] – solved the APK bundling issue, provides Android-buildable Python 2.7
  • the BlackBerry-Py Building PySide guide [hg.microcode.ca] PySide – I’ve used this as a base when making the Android build scripts
  • the Necessitas project [necessitas.kde.org] – made Qt on Android possible * also provides the Necessitas Qt Creator used for by the example project for building standalone APKs
  • Qt-Project [qt.io] – provides the GUI toolkit :)
  • PySide [qt.io] – provides the Python-Qt bindings
  • Ineans Qt Components [gitorious.org] – with small modifications used in the example application & project

Thanks a lot – without you, this would not be possible! :)

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