Building Applications

Instead of (or as well as) including binary APKs from external sources in a repository, you can build them directly from the source code.

Using this method, it is is possible to verify that the application builds correctly, corresponds to the source code, and contains only free software. Unforunately, in the Android world, it seems to be very common for an application supplied as a binary APK to present itself as Free Software when in fact some or all of the following are true:

  1. The source code (either for a particular version, or even all versions!) is unavailable or incomplete.
  2. The source code is not capable of producing the actual binary supplied.
  3. The ’source code’ contains binary files of unknown origin, or with proprietary licenses.

For this reason, source-built applications are the preferred method for the main F-Droid repository, although occasionally for technical or historical reasons, exceptions are made to this policy.

When building applications from source, it should be noted that you will be signing them (all APK files must be signed to be installable on Android) with your own key. When an application is already installed on a device, it is not possible to upgrade it in place to a new version signed with a different key without first uninstalling the original. This may present an inconvenience to users, as the process of uninstalling loses any data associated with the previous installation.

The process for managing a repository for built-from-source applications is very similar to that described in the Simple Binary Repository chapter, except now you need to:

  1. Include Build entries in the metadata files.
  2. Run fdroid build to build any applications that are not already built.
  3. Run fdroid publish to finalise packaging and sign any APKs that have been built.

App data directory aka fdroiddata

To do anything, you’ll need at least one repository data directory. It’s from this directory that you run the fdroid command to perform all repository management tasks. You can either create a brand new one, or grab a copy of the data used by the main F-Droid repository:

git clone https://gitlab.com/fdroid/fdroiddata.git

Regardless of the intended usage of the tools, you will always need to set up some basic configuration details. This is done by creating a file called config.py in the data directory. You should do this by copying the example file (./examples/config.py) from the fdroidserver project to your data directory and then editing according to the instructions within.

Once configured in this way, all the functionality of the tools is accessed by running the fdroid command. Run it on its own to get a list of the available sub-commands.

You can follow any command with --help to get a list of additional options available for that command.

fdroid update --help

More about fdroid build

When run without any parameters, fdroid build will build any and all versions of applications that you don’t already have in the repo directory (or more accurately, the unsigned directory). There are various other things you can do. As with all the tools, the --help option is your friend, but a few annotated examples and discussion of the more common usage modes follows:

To build a single version of a single application, you could run the following:

fdroid build org.fdroid.fdroid:16

This attempts to build version code 16 (which is version 0.25) of the F-Droid client. Many of the tools recognise arguments as packages, allowing their activity to be limited to just a limited set of packages.

If the build above was successful, two files will have been placed in the unsigned directory:

org.fdroid.fdroid_16.apk
org.fdroid.fdroid_16_src.tar.gz

The first is the (unsigned) APK. You could sign this with a debug key and push it direct to your device or an emulator for testing. The second is a source tarball containing exactly the source that was used to generate the binary.

If you were intending to publish these files, you could then run:

fdroid publish

The source tarball would move to the repo directory (which is the directory you would push to your web server). A signed and zip-aligned version of the APK would also appear there, and both files would be removed from the unsigned directory.

If you’re building purely for the purposes of testing, and not intending to push the results to a repository, at least yet, the --test option can be used to direct output to the tmp directory instead of unsigned. A similar effect could by achieved by simply deleting the output files from unsigned after the build, but with the risk of forgetting to do so!

Along similar lines (and only in conjunction with --test, you can use --force to force a build of a Disabled application, where normally it would be completely ignored. Similarly a version that was found to contain ELFs or known non-free libraries can be forced to build. See also — scanignore= and scandelete= in the Build: section.

If the build was unsuccessful, you can find out why by looking at the output in the logs/ directory. If that isn’t illuminating, try building the app the regular way, step by step: android update project, ndk-build, ant debug.

Note that source code repositories often contain prebuilt libraries. If the app is being considered for the main F-Droid repository, it is important that all such prebuilts are built either via the metadata or by a reputable third party.

Running fdroid build in your app’s source

Another option for using fdroid build is to use a metadata file that is included in the app’s source itself, rather than in a metadata/ folder with lots of other apps. This metadata file should be in the root of your source repo, and be called .fdroid.json, .fdroid.xml, .fdroid.yaml, or .fdroid.txt, depending on your preferred data format: JSON, XML, YAML, or F-Droid’s .txt format.

Once you have that setup, you can build the most recent version of the app using the whole FDroid stack by running:

fdroid build

If you want to build every single version, then specify --all.

Direct Installation

You can also build and install directly to a connected device or emulator using the fdroid install command. If you do this without passing packages as arguments then all the latest built and signed version available of each package will be installed . In most cases, this will not be what you want to do, so execution will stop straight away. However, you can override this if you’re sure that’s what you want, by using --all. Note that currently, no sanity checks are performed with this mode, so if the files in the signed output directory were modified, you won’t be notified.