Write Android apps in Google Go
github.com
github.com
And while I'm complaining about it, it sure would be nice if they would include POSIX support by default. It's not like the code to do it isn't largely already written and freely available.
Edit: clojure works on android now but it needed additional porting efforts
http://clojure-android.blogspot.com/2013/06/state-of-clojure...
Too much time is spent on hacking an half working solution and in the end the vendor offers no support if the problem is to be found outside the SDK. Or even if it is in the SDK, non supported languages offer a nice excuse to avoid giving support.
A mobile app has a far richer interface, and needs to interact with the system in more deep and meaningful ways. Memory is tight and application lifecycles can be hectic.
Heck on Android there isn't such a thing as an Application in the traditional sense - ie there is no entry point/main function. Instead the "application" is actually a mashup of components such as Activities (screens/ui), services (processing), content providers (data) and broadcast receivers (async updates)[1]. The Android system itself is then a mashup of those. Again there is a lot of scaffolding to make the different parts of the different apps all work together with bidirectional communication.
Using a different language means all that scaffolding has to be duplicated in each language. That is a heck of a lot of work and then requires ongoing maintenance. Dalvik essentially provides all that for Java like bytecode with JNI for calling out to native code. You'd need to duplicate what is in Dalvik to do a good language environment for Android. (Or generate Dalvik bytecode ahead of time.)
[1] That is how a well written app is structured for Android. You can ignore all that and put everything into a single Activity (iOS ports often do this) but it won't interoperate well with the system, and users will notice. With the increasing RAM and CPU these days you are increasingly likely to get away with it. The first Android phone had 192MB of RAM.
I'm not clear how this is different than it is for the variety of embedded Linux devices that natively support multiple languages. You can run Debian (sans X-Windows) with under 64MB of RAM.
>Using a different language means all that scaffolding has to be duplicated in each language.
Not really. I would be plenty happy if they would just provide a native C API like GNU/Linux does, which manages to support most of the major languages because almost everything has near-seamless support for calling C API functions.
For example the canonical way to structure a music app would be an activity (gui) for visuals, a content provider to provide the library and a service to play the actual audio. There is no requirement for these to be in the same app/process and it is pretty much immaterial to the code. But if your activity is communicating with the service (eg to send play/pause/next in one direction and getting the current play position and file in the other) then Android does housekeeping to make sure the right thing happens such as what happens when either side crashes or exits.
Android can do memory management within a process - for example if you switch to your email app, the music playing service can keep going, and the activity can be terminated (it is usually told).
This isn't remotely the same thing as swapping out pages as is done by the kernel. Additionally a whole bunch of the pieces have no kernel representation (eg a content provider). There is an IPC mechanism (binder) that has both kernel and user space components working in harmony.
To have something analogous in C, your "app" would be a large number of shared libraries (dozens), and they would be dynamically loaded and unloaded. They would talk to each other and shared libraries in other processes. There would be garbage collection, lifetime management and possibly reference counting. Calls into them could be asynchronous, as well as calls out. Managing all that would be non-trivial "scaffolding".
> ... almost everything has near-seamless support for calling C API functions
Dalvik already has that - using JNI. The pattern is to implement your interface to Android in Java and then call through to C when you need to.
The problem with Go is that it isn't designed to play well with others. It doesn't support dynamically linking, and expects to own the process - being in charge. The work the posting is about is some toolchain hacks that make it so a dynamically loadable binary is produced instead of an executable. There is then work to make the Android API available which is non-trivial, and Java flavoured.
> I would be plenty happy if they would just provide a native C API like GNU/Linux does
The "native" API it would provide would need to be analogous to libc, glib, X (and extensions like xrandr), gnome, systemd/udev, dbus, sdl, ibus, garbage collection, shm, reference counting etc all combined (in addition to whatever I forgot). There is no "just providing" that!
It sounds like you could do it a lot more easily by just having separate processes or threads for each activity/service/whatever.
>This isn't remotely the same thing as swapping out pages as is done by the kernel.
It seems to be almost identical to the OS sending SIGTERM and then SIGKILL to the process in question however.
>The "native" API it would provide would need to be analogous to libc, glib, X (and extensions like xrandr), gnome, systemd/udev, dbus, sdl, ibus, garbage collection, shm, reference counting etc all combined (in addition to whatever I forgot).
Are you assuming the necessity of a one to one mapping between Java API functions and C API functions? I don't care about something "analogous" to libc, just give me libc and you don't have to do any work. That solves most of what's on your list and obviates the need for garbage collection or reference counting.
The real trouble is the UI API because there isn't anything to lift it from since Android has a totally independent UI from Desktop Linux. But that doesn't mean it isn't worth doing -- and even if that isn't worth doing, why can't I have the rest of it? If I'm trying to port a Linux daemon into a service then I don't much care about a lack of GUI functions but I most certainly could use a full POSIX implementation.
Do you know much memory is used for a thread? Or for a process? The answer for either is not zero. In fact it is possible (but not used) for the same Dalvik process to host multiple apps.
> It seems to be almost identical to the OS sending SIGTERM and then SIGKILL to the process in question however.
Not even close. With swapping the kernel has to operate in units of 4kb pages. Dalvik can use a compacting garbage collector to reduce memory consumption. Signals are trivial. They are a single number, and not come even remotely close to interprocess resources. Think something closer to dbus, plus a bunch of code built on top of it.
> don't care about something "analogous" to libc, just give me libc and you don't have to do any work
Android already includes that (bionic). You can compile elf binaries that work just fine. Heck you'll even find 'ls' etc on the system done that way. But your binary won't be able to examine the clipboard.
Note the posting was about writing Android applications in Go, not about trivial binaries. Applications means all the crud you are dismissing.
> Are you assuming the necessity of a one to one mapping between Java API functions and C API functions?
Nope. But those functions only have a Dalvik hosted Java centric implementation. If you want to work with them then they all have to be reimplemented in a compatible manner, or you need to call from the native code back into Dalvik using JNI. Either way is a lot of work.
Your example of porting a Linux daemon to a service won't work as is. Being a service means the system has expectations of you - how you are started, how data is provided and returned and how it is stopped. (There is also other stuff such as permissions and process hosting.) The canonical way of doing this is to write the service front end in Java, and then use JNI to load native code you need. But it does mean your native code needs to play well with others in the same process - something that isn't Go's sweet spot.
In your scenario there are several SSH servers available. Most are delivered as a single "app", but behind the scenes consist of an sshd binary, plus Java authored code to provide a UI (start/stop/status/configuration) and manage lifecycle.
The desire from most folk is for Go authored apps to be first class citizens, and not require using any other language. That is what is a lot of duplicate work.
Most bindings (on Linux) to bigger frameworks are custom made with glue code (vs direct ffi calls to C ABI), and require significant effort to maintain and often some clever metaprogramming. Look Python/Ruby/Perl bindings to Gnome or Win32. They're still "3rd party" status so they may break when the wrapped API changes in a way that they fail to model.
A simple linux distribution as a base (as with Android), with posix. They could still lock-down app installation for normal users, have an app store, and all the other things that make current mobile platforms attractive to consumers.
Hooks for any popular languages to control the UI via simple glue libraries, all implementing the same API, with the ability to add more easily because the UI API could be really quite simple (and should remain so) if built off the work already done for the web. They could add C, C++, Golang, Java, C#, even ObjC to the mix this way. There's no chance they'll do this for their current API, so they'd need to have a radical rethink of just what a mobile OS should provide.
A web-based stack for the UI based on an improved webkit (a la webOS). Most apps have very simple needs (specify a UI, adjust the UI, listen for UI events) that could easily be dealt with by message passing between the view and app rather than binary interfaces. Webgl and css animations etc could be utilised for performance where required. Crucially this wouldn't tie developers into one complete stack from language to tools to UI - the UI should be separate and not tied intimately to the back-end language as it is currently on iOS and Android.
A base OS that is non-negotiable and non-modifiable by carriers/manufacturers, and upgrades from a central point (a consortium led by Google), that are not phone-specific. Carriers can add apps etc but there's no reason they have to adjust the base OS, and both should negotiate with Google for inclusion of new drivers, not hold up upgrades because they want to sell newer hardware/contracts.
Far stricter permissions for apps with far less access (more like web-apps), and individual prompts on first use of info like phone no, addresses etc. to discourage overuse.
It's a shame that our mobile devices are typically tied to one platform, one language, one UI, when they have so much potential as portable computing devices.
http://developer.android.com/about/dashboards/index.html and no, fragmentation's not an issue for anyone with the Play Store and the compatibility kit (and maybe sherlock).
I mean, are you not aware of Firefox OS which bootstrap(ed/s) itself on top of Android? Or that Ubuntu for Phones is coming out with phones to support it?
Or of the Nexus program? Or the pseudo-Nexus program with devices with unlocked bootloaders.
OH and webOS still exists, and is open source and runs on some Android devices.
What more do you want, sounds like your needs are being met. Take the android kernel and write a new UI. Then you can run it on one of the what, hundred different devices that CM supports?
>They could add C, C++, Golang, Java, C#, even ObjC to the mix this way.
lol, you think writing and supporting all of the Android APIs for all of those languages is feasible? Or you want some kind of bindings or what exactly?
>Carriers can add apps etc but there's no reason they have to adjust the base OS, and both should negotiate with Google for inclusion of new drivers
and you don't seem to actually know who controls the distribution of the drivers
Ubuntu OS looks interesting but has no traction right now, I'll be keeping an eye on that though. I'm afraid WebOS is dead at the moment - choice of which platforms to target is more political than technical unfortunately, which is why it'd be great to see Google pushing a more open system which lets people use any language they want for development. They have enough clout to make that happen and not many do. I'm aware it's very unlikely as I said in the post above - There's no chance they'll do this for their current API, so they'd need to have a radical rethink of just what a mobile OS should provide.
Please don't take this as some sort of attack on Google or Android.
What more do you want, sounds like your needs are being met. Take the android kernel and write a new UI. Then you can run it on one of the what, hundred different devices that CM supports?
That is of course a huge amount of work for one person and likely doomed to failure. To be clear that I'm not blaming Google or demanding that they change, just agreeing with the OP that I'd like to see more options, but pointing out that that requires a fundamental rethink of the entanglement between UI and API. I've written a few iOS apps which use HTML views extensively and make little use of the UI toolkits using urls etc to pass actions and move screen, so I'm well aware this is possible using the current system, but it's currently a pain to try to use another language as your core language for an app.
And devs get backporting of most apis via the Play Store so it's not like fragmentation is an issue very often at all.
The hardware is out there. The software is out there. You could port Firefox OS to the SGS4, you would have basically /everything/ on your checklist, and you can buy a 100% unlocked GSM SGS4 from Google and put Firefox OS, or port webOS, or whatever OS you want.
Are you simply lamenting that you can't walk into a store and buy that combo? I guess I don't care when I can follow the steps to do it myself (of course, now I'm starting to download stuff to play around with porting Firefox OS to my SGS4)
>requires a fundamental rethink of the entanglement between UI and API
Heh, I actually know of a platform that allows you to write web apps and from them invoke native code that conforms to their spec. And their vision is to have that platform spread across all device sizes. Do you know who it is? :)
http://channel9.msdn.com/Events/Lang-NEXT/Lang-NEXT-2012/The...
Sadly, non-free. But yes, you can write projections for your own language. I've thought it would be cool to try to write one for Go.
In practice this means that apps that do not make use of the Dalvik runtime are limited to special purpose apps such as games written mostly on top of OpenGL. Even those might end up being wrapped in a Dalvik VM runtime app to access things like accounts, sharing, etc.
A realistic step would be to add one or more JVM languages as first class citizens of the toolchain. Clojure would be very welcome.
Android really is an OS with a very intimate relationship with a VM that implements Java semantics, though not Java bytecodes.
https://github.com/mozilla/rust/wiki/Doc-building-for-androi...
http://sourceforge.net/mailarchive/message.php?msg_id=290363...
Quite a few languages are available for Android development now that the NDK allows native code.
http://code.google.com/p/android/issues/detail?id=39482
If the Android team wanted to give proper support for Go, I think it would have done it already, instead of changing tooling between IDEs.
The same goes for disabling the Objective-C support on gcc and clang toolchains.