A translation layer that allows running Android apps on a Linux system

Build

see build documentation

Run in builddir

cd builddir

For an example of a full game working that can be distributed along this:

RUN_FROM_BUILDDIR= LD_LIBRARY_PATH=./ ./android-translation-layer /path/to/test_apks/org.happysanta.gd_29.apk -l org/happysanta/gd/GDActivity

Or for a sample app using OpenGL from native code to do it's rendering:

RUN_FROM_BUILDDIR= LD_LIBRARY_PATH=./ ./android-translation-layer path/to/test_apks/gles3jni.apk -l com/android/gles3jni/GLES3JNIActivity

Note: the test apks are available at https://gitlab.com/android_translation_layer/atl_test_apks.

Run after installation

cd builddir
meson install

To run with the default data dir ~/.local/share/android_translation_layer/:

android-translation-layer [path to apk] [-l activity to launch]

For custom data dir:

ANDROID_APP_DATA_DIR=[data dir] android-translation-layer [path to apk] [-l activity to launch]

App data

As mentioned, the default data dir is ~/.local/share/android_translation_layer/. The data for each app is then stored in ~/.local/share/android_translation_layer/[apk-name]_. What this means in practice is that:

• we pass this directory to the app where AOSP would pass /data/data/[app-id], and extract native libs in lib/
• we pass this directory to the app where AOSP would pass /storage/emulated/0 (this means OBBs will be under Android/obb/[app-id]/, and various litter that the app would happily dump on the "sdcard" on AOSP will end up here as well)
• we pass this directory as an additional resource directory to libandroidfw, so you can for example put something in assets/file.txt and if the app tries to load assets/file.txt from it's apk file, it will be preferentially loaded from here instead (do note that some apps read files from the apk by themselves, and some apps do weird things like only load the file in order to find it's offset in the apk to then read it out by themselves, so not only will this not always work but you will sometimes find out by having the app crash)
• we extract some additional files from the apk here for our purposes

The reason that we don't use [app-id] for the directory name is simply that we don't have access to the app id at an early enough point. However, this also allows you to have multiple versions of the same app not clash. Feel free to rename the apk to [app-id]_[version].apk, or simply [app-id].apk if you wish to replace it with a different version later and reuse the data dir.

"install" an apk

You can pass --install on the cmdline to "install" an apk instead of launching it. This will copy the apk to _installed_apks_ in the data dir (~/.local/share/android_translation_layer/ by default), and use the xdp portal to install a .desktop file.

Tweaks

Resolution Changes

Some apps don't like runtime changes to resolution. To sidestep this, we allow for specifying the initial resolution. example with custom width/height:

android-translation-layer path/to/org.happysanta.gd_29.apk -l org/happysanta/gd/GDActivity -w 540 -h 960

Potential issues

• On X11, Gtk might decide to use GLX, which completely messes up our EGL-dependent code. Use GDK_DEBUG=gl-egl to force the use of EGL.
• On Apple Silicon, the page size is non-standard. Upstream ART is only recently getting patches to support such non-standard page size, so the version we use obviously doesn't have any. While there will probably still be some issues with native libraries, you can work around the issue of AOT-compiled code not working by adding -X '-Xnoimage-dex2oat' -X '-Xusejit:false' to the atl cmdline, which will force the use of an interpreter. Make sure to clear ~/.cache/art/ since AOT-compiled oat files will still be used if they were generated previously.

Contribute

If you are trying to launch a random app, chances are that we are missing implementations for some stuff that it needs, and we also don't have (sufficiently real looking) stubs for the stuff it says it needs but doesn't really.

The workflow is basically to see where it fails (usually a Class or Method was not found) and to create stubs which sufficiently satisfy the app so that it continues trying to launch.

Once the app launches, you may find that some functionality (UI elements, ...) is missing. To enable such functionality, you need to convert the relevant stubs to actual implementation. You can look at simple widgets (e.g. TextView, or ImageView) to see how to implement a widget such that it shows up as a Gtk Widget.

For more specific instructions, see doc/QuickHelp.md.
For general description of the architecure, see doc/Architecture.md.

If you want to contribute, and find the codebase overwhelming, don't hesitate to open an issue so we can help you out and possibly write more documentation.

Roadmap

• fix issues mentioned above

• fix ugly hacks

• implement more stuff (there is a lot of it, and it won't get done if nobody helps... ideally pick a simple-ish application and stub/implement stuff until it works)

• explore using bubblewrap to enforce the security policies that google helpfully forces apps to comply with (and our own security policies, like no internet access for apps which really shouldn't need it and are not scummy enough to refuse to launch without it)

Tips

• the correct format for changing verbosity of messages going through android's logging library is ANDROID_LOG_TAGS=*:v (where * is "all tags" and v is "verbosity verbose or lesser"
  (note that specifying anything other than * as the tag will not work with the host version of liblog)