/briefcase-android-gradle-template

A template for generating Android Gradle projects with Briefcase

MIT LicenseMIT

Briefcase Android Gradle Template

A Cookiecutter template for building Python apps that will run under Android.

This repository branch contains a template for Python 3.9. Other Python versions are available by cloning other branches of repository.

Using this template

The easiest way to use this project is to not use it at all - at least, not directly. Briefcase is a tool that uses this template, rolling it out using data extracted from a pyproject.toml configuration file.

However, if you do want use this template directly...

  1. Install cookiecutter. This is a tool used to bootstrap complex project templates:

    $ pip install cookiecutter

  2. Run cookiecutter on the template:

    $ cookiecutter https://github.com/beeware/briefcase-android-gradle-template --checkout 3.9

    This will ask you for a number of details of your application, including the name of your application (which should be a valid PyPI identifier), and the Formal Name of your application (the full name you use to describe your app). The remainder of these instructions will assume a name of my-project, and a formal name of My Project.

  3. Download the Python support package for Android, and extract it into the My Project directory generated by the template. This will create app/libs and app/src/main/assets folders containing a self contained Python install.

    Alternatively, you can download the Python-Android-support project, and build your own version.

  4. Add your code to the template, into the My Project/app/src/main/assets/python/app directory. At the very minimum, you need to have an My Project/app/src/main/assets/python/app/<app name>/__main__.py file that instantiates an instance of org.beeware.android.IPythonApp, and then invokes org.beeware.android.MainActivity.setPythonApp(), providing the IPythonApp instance.

    If your code has any dependencies, they should be installed into the My Project/app/src/main/assets/python/app_packages directory.

If you've done this correctly, a project with a formal name of My Project, with an app name of my-project should have a directory structure that looks something like:

My Project/
    app/
        src/
            main/
                assets/
                    python/
                        app/
                            my_project/
                                __init__.py
                                __main__.py (declares IPythonApp)
                        app_packages/
                            ...
            cpp/
                ...
            java/
                ...
            res/
                ...
            AndroidManifest.xml
        build.gradle
        proguard-rules.pro
    briefcase.toml
    build.gradle
    gradle.properties
    gradlew
    gradlew.bat
    settings.gradle

You're now ready to run build and run your project! Set

$ ./gradlew installDebug

Next steps

Of course, running Python code isn't very interesting by itself - you'll be able to output to the console, and see that output in Gradle, but if you tap the app icon on your phone, you won't see anything - because there isn't a visible console on an Android.

To do something interesting, you'll need to work with the native Android system libraries to draw widgets and respond to screen taps. The Rubicon Java bridging library can be used to interface with the Android system libraries. Alternatively, you could use a cross-platform widget toolkit that supports Android (such as Toga) to provide a GUI for your application.

Regardless of whether you use Toga, or you write an application natively, the template project will run the __main__ module associated with the app name that you provided when you generated the tempalte. That Python code must define an instance of org.beeware.android.IPythonApp, and invoke org.beeware.android.MainActivity.setPythonApp() to set that instance as the active Python app. This app will coordinate provides the hooks into the Android application lifecycle (onCreate, onResume and so on); it's up to you what your code does with those lifecycle hooks. If setPythonApp is not set, an error will be logged, and the Python interpreter will be shut down.

If you have any external library dependencies (like Toga, or anything other third-party library), you should install the library code into the app_packages directory. This directory is the same as a site_packages directory on a desktop Python install.