PoC for a translation layer that would execute the abolute minimum of android-specific code necessary in order to run an android app on a Linux system

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build instructions:

1. compile and install https://gitlab.com/Mis012/dalvik_standalone (art branch) (you can run it from builddir, but it requires some additional env variables)
2. mkdir builddir
3. meson builddir
4. ninja -C builddir

then, to run from builddir:
cd builddir
and
RUN_FROM_BUILDDIR= LD_LIBRARY_PATH=./ ANDROID_APP_DATA_DIR=../test_apks/example_data_dir/ ./android-translation-layer ../test_apks/org.happysanta.gd_29.apk -l org/happysanta/gd/GDActivity
(for an example of a full game working that can be distributed along this) or
RUN_FROM_BUILDDIR= LD_LIBRARY_PATH=./ ANDROID_APP_DATA_DIR=../test_apks/example_data_dir/ ./android-translation-layer ../test_apks/gles3jni.apk -l com/android/gles3jni/GLES3JNIActivity
(for a sample app using OpenGL from native code to do it's rendering) (note: the lib in test_apks/example_data_dir/gles3jni.apk/lib/ is for x86_64, make sure you extract the lib for your architecture from the apk)

to install:
meson install

to run after installataion:
ANDROID_APP_DATA_DIR=[data dir] android-translation-layer [path to apk] -l [activity to launch]
or just
android-translation-layer [path to apk] -l [activity to launch]
to use the default data dir of ~/.local/share/android_translation_layer/

NOTE: for apps which use the built-in NativeActivity mechanism, simply specify -l android/app/NativeActivity
if android.app.lib_name is set in the manifest, you currently need to rename the lib to libmain.so, which is the default. in cases where there's alread a different lib with that name, you need to add a way to pass the lib name to the NativeActivity class
if android.app.func_name is set in the manifest, then you need to add a way to pass this to the NativeActivity class (currently, the default of ANativeActivity_onCreate is always used, which works for all apps using android_native_app_glue)
TODO: figure out a mechanism for passing these to the NativeActivity class TODO_LONGTERM: parse AndroidManifest.xml

NOTE: some apps don't like runtime changes to resolution, and currently GLSurfaceView will stretch instead of changing resolution
to sidestep this, we allow for specifying the initial resolution, which will currently always get passed as the screen resolution to the app and to GLSurfaceView even when you resize the window. example with custom width/height: android-translation-layer path/to/org.happysanta.gd_29.apk -l org/happysanta/gd/GDActivity -w 540 -h 960

NOTE: you might need to copy some files out from the apk under ANDROID_APP_DATA_DIR (defaults to ~/.local/share/android_translation_layer/), e.g the assets folder;
additionally, resources (res) currently need to be "decompiled" (e.g. by apktool, though this additionally replaces hex IDs with string names, which then needs to be manually reversed; android studio's inspect apk feature is known to keep the integers)
NOTE: on X11, Gtk might decide to use GLX, which completely messes up our EGL-dependent code. If you have a debug build of Gtk, you can use GDK_DEBUG=gl-egl to force the use of EGL
NOTE: we don't currently handle signed apks; simply remove the META-INF folder from an apk to skip signature verification

when it doesn't work:
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 which is extremely simple since it's
currently displaying an image-not-found icon instead of the actual image) to see how to implement a
widget such that it shows up as a Gtk Widget. for layout widgets, you can cheat by duplicating
LinearLayout or RelativeLayout, which are currently implemented in an extremely simplistic manner
(it might not look correctly, but it should work)

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

screenshot:

Roadmap:

• fix issues mention above

• fix ugly hacks

  • don't assume apps only have one (relevant) activity
  • figure out a way to dynamically change the resolution of a GLSurfaceView

• 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"