Building applications for Android

Building Applications

Building .apk files from Qt Applications requires a cross-compiling toolchain, which is hard to setup. To simplify this, there is a ready-to-use Docker container for building KDE applications.

This documentation only applies to applications that have a Craft blueprint in the craft-blueprints-kde repository. If the application you want does not have such a blueprint yet, have a look at the documentation.

The container can be initialized with

mkdir craft-kde-android
docker run -ti --rm -v $PWD/craft-kde-android:/home/user/CraftRoot kdeorg/android-qt515 bash
python3 -c "$(curl https://raw.githubusercontent.com/KDE/craft/master/setup/CraftBootstrap.py)" --prefix ~/CraftRoot

Craft will prompt you for the desired target architecture (arm32, arm64, x86_32 or x86_64) and possible other prompts.

To build an application you first need to enter the container using

docker run -ti --rm -v $PWD/craft-kde-android:/home/user/CraftRoot kdeorg/android-qt515 bash

and source the Craft environment with

source ~/CraftRoot/craft/craftenv.sh

Now run Craft commands like craft <appname> to build an application and craft --package <appname> to package it as apk.

Inside the Craft environment, the blueprints can be found by running cs craft-blueprints-kde and can be edited there to quickly test changes.

The source folder for an application or library can be found the same way by running cs <projectname>; the build folder can be found by running cb <projectname>.

You can quickly iterate on patches for a project by editing it in the source folder, followed by calling ninja install in the build folder and creating an apk file using craft --package <appname>.

There are much more Craft commands, take a look at the Craft documentation to learn about them.

The .apk file can be found at /home/user/CraftRoot/tmp. This folder is also available as craft-kde-android/tmp on the host system. Craft does not sign the apks, so you need to do that yourself before being able to install it onto a device. For signing an apk, you need to create a signing key first, which can be done using

keytool -genkey -noprompt -keystore key.keystore -keypass 123456  -dname "CN=None, OU=None, O=None, L=None, S=None, C=XY" -alias mykey -keyalg RSA -keysize 2048 -validity 10000 -storepass 123456

This key can be reused to sign all of your development apks.

Before signing the apk, it might be needed to align it. This can be done using

zipalign -p -f -v 4 <app>.apk <app>.signed.apk

You can finally sign the aligned apk with your key using

apksigner sign -verbose -ks key.keystore <app>.signed.apk

The zipalign and apksigner binaries can be found at /opt/android-sdk/build-tools/<version>/ inside the Craft container environment.