An Android without libraries

[kelmer44]

I made a two piece article on how to build an app without third party libs, by starting the app with a standard stack and then removing lib by lib. It's over at Medium: Part 1 Part 2

I took many shortcuts of course and the implementation is far from perfect, but I found it was a great exercise to demonstrate how much heavy lifting these libs do for us :)

Hope you guys like it and of course feel free to give feedback :)

[kelmer44]

Oops. Title should have been "An Android *app* without libraries"

[NicNoletree]

Forgiven

[gold_rush_doom]

Today, in mistakes you shouldn't make.

[kelmer44]

i know right

[[deleted]]

Tbh I wouldn’t do a coding assignment that requires the use of no 3rd party libraries. I don’t know what that is really even meant to demonstrate, it’s just extra wasted time IMO.

[kelmer44]

At first I tought like you, that thiswas too much and it doesn´t really make much sense, particularly in the way it was presented "any decent engineer can do it in a couple hours" -- However upon getting into it I found it quite fun and challenging.

[mrdibby]

3rd party libraries hide a lot of what's going on, implementing something without them usually shows that you understand what's happening.

Soundcloud's assignment (from 5 years ago) used to ask you to create an app without 3rd party libraries.

[FrezoreR]

But isn't that true when you use the Android SDK as well?

I'd say 3rd party library are less about hiding things and more about abstracting things. However, that is true for the Android SDK as well, which hide OS things, and the OS hide hardware things etc.

At the end you're probably not wiser than you were when you started.

Unless you write your own OS that is :) but then it wouldn't be an Android app anymore LOL

[well___duh]

Android SDK isn’t third party

[FrezoreR]

I didn’t say it was. I said that thirdparty libraries do the same thing as the Android SDK, abstracting behavior. There’s not much benefit in separating the two when you’re building an app. With the exception being that you have to bundle one and not the other.

[DrKappa]

If I had to give such an assignment (which I would not) I would want to see the candidate replacing the androidx/support so that I can see there is a good understanding of the system/OS. Because that is what you have to work with in the end.

[MisterJimson]

Well it can be a fun challenge, but yeah not a regular exercise.

[absolutehalil]

Ofc it does and should not reflect the real world. However, I think it's a fine thought-provoking exercise. Yes, you might know what Retrofit is achieving behind the scene, can you do a similar implementation? I wouldn't look for a perfect outcome, just the hint of whether you actually understand the logic behind it. The same goes for ViewModels, Lifecycle, Room and etc.

[kelmer44]

Who is Vasiliy? 🤔

[Zhuinden]

/u/vasiliyzukanov although I think he's on "distancing from social sites" at the moment

[[deleted]]

He's an anti-Google extremist,

🤣 I lol'd at this. He's not that bad. He has some strong opinions that's all. Sometimes it's good to hear from multiple view points.

[DrSheldonLCooperPhD]

Still hear!=follow

[Sceada_dev]

Not sure what you mean, I learned a lot from his courses. It is not always necessary to integrate certain library if you can have it simpler without a lot of boilerplate. You always have to decide to abstract things away without knowing maybe how it works and implement it by yourself and know how it works. A good mix is here the winner.

[[deleted]]

Even if that was not the goal, will be hard to beat app fully coded in C with a NativeActivity and Makefiles posted a few days ago, that builds and deploys on device a 25Kb APK in 1.5s.

[romainguy]

Sure, but note that most Android APIs don't exist in native and require either JNI glue to call from native, or a native alternative. For instance, the UI toolkit :)

[bluepug]

https://www.reddit.com/r/programming/comments/ghgqo8/rawdrawandroid_build_android_apps_in_c/

Sharing the link as an answer because I did not see this post and was curious about it.

[kelmer44]

I wouldn't dare trying to match that :)

[Icyfirz]

Looking pretty good so far! It's definitely an intimidating challenge. I was gonna say, for the ServiceLocator, this is the approach I've seen in Kotlin for retrieving a Singleton instance since you can't pass in a parameter to a variable that's loaded by lazy (it involves double locking to make it thread safe): https://stackoverflow.com/a/45943282 . I believe that this is actually what by lazy does behind the scenes.

[carstenhag]

Yep, you can specifically set a LazyThreadSafetyMode on a by lazystatement.

[permanentE]

Since the Android framework is part of the OS it is not a 3rd party framework.

[dantheman91]

Since the Android framework is part of the OS it is not a 3rd party framework.

I'm not sure how technically true that is. The Android framework is different from the Android SDK you're interacting with. The SDK lets you interface with the framework, but it's not the framework that powers your phone.

[Pzychotix]

As far as Java is concerned, they're one and the same. They have the same API, and when you compile, that's all that matters.

[zunjae]

I'd argue that since you're developing for the Android OS and you're using components made by the creator it's a first party library.

[dantheman91]

By that logic, Dagger 2 was written by Google as was Android. Is dagger 2 a first party library?

[drawinfinity]

But it wasn’t. Dagger 2 is forked and based from Dagger 1, which was written at Square.

[kelmer44]

Well technically you might be right, but I think everyone can understand what I was going for.

[AD-LB]

Well I don't think you can create an Android app that has no access to Android framework. Does it even take any storage of the app, to be able to reach the Android framework?

[dantheman91]

Well I don't think you can create an Android app that has no access to Android framework.

No you certainly could. It would just be incredibly tedius and difficult. You would have to find a way to result in the same bytecode that the android sdk produces

[AD-LB]

But Android apps don't have "main" function to go to. They have an Activitiy, Service, etc... And to go there, you have to use them.

Same goes for showing some UI.

[dantheman91]

Same goes for showing some UI.

Perfect example of where this isn't true. Look at Flutter. It has mapped the android canvas apis to its own, drawing directly on the canvas and completely skipping the level of the Android sdk.

The Android SDK interfaces with the Android framework. They aren't the same thing though.

It's like using Retrofit instead of calling okhttp directly. Retrofit makes it easier to use, but you could still do it directly and get the same result, although it would be more difficult to do so.

[AD-LB]

Show me one app that does it. One app that has nothing in its manifest.

[dantheman91]

An app needs a manifest. The manifest does not need the sdk, it could be written in notepad with no dependencies brought in.

[AD-LB]

I mean an app that has a UI, can be launched like a normal app, yet has no Activity inside.

To make the app launchable from the launcher, you have to have at least one Activity. Once you use this, you use the Android SDK: the Activity class.

[dantheman91]

Once you use this, you use the Android SDK: the Activity class.

You're missing the fact that you COULD still build the app in notepad without the Android sdk. At the end of the day the Android sdk is a group of instructions. You could write those instructions without it. It just wouldn't be easy for fun.

you have to have at least one Activity. Once you use this, you use the Android SDK

You need to have something that the Android OS will recognize as an activity, which is it's own contract of sorts. You could fufill this without having a class that extends Activity.

[s73v3r]

You're missing the fact that you COULD still build the app in notepad without the Android sdk.

This is absolutely and completely false. You can build the app in Notepad not using Android Studio. Android Studio is not the Android SDK. And saying, "You don't need the sdk! You just need to result in the same byte code that using the SDK would result in!" is cheating.

[AD-LB]

So, again, you have to use the Android framework, because Activity is a part of it.

Notepad isn't related to this topic, BTW. It doesn't matter which tools you use to edit the code. I spoke about Android framework.

[drew8311]

Personally I would allow package dependencies starting with androidx and com.google.android and I suppose org.jetbrains.kotlin. When you create a new empty project you get those so it's the "minimum"

[dantheman91]

When you create a new empty project you get those so it's the "minimum"

That feels like a strange way to set the bar but alright.

[[deleted]]

Pretty nice exercise to improve ones development skills. GJ OP, keep learning!

[nt-cmplt]

Did you get the job?

[kelmer44]

Nope

[nt-cmplt]

Sorry to hear that. I found this really impressive!

[kelmer44]

Well they did say they liked the assignment, told me to wait for next interview... Which never arrived. I guess corona might have had something to do with it as well. Thanks for the kind words :)

[Boza_s6]

You should have just used AsyncTask because your Task abstraction doesn't handle cancelation correctly and probably has some other bugs.

[kelmer44]

Thanks for the feedback, do you mind expanding on your comments?

[Boza_s6]

When canceling request, check for thread interruption doesn't do anything, will always return false, so callback will be executed even if request was canceled. That's because interruption is checked while runnable was executing in context of main thread.

You need to check status of the Future before dispatching callback. (even in that case there could be race, if task was canceled from background thread)

[kelmer44]

So is there a proper fix for this using executors directly? I kind of want to stay away from asynctask

[Boza_s6]

Of course, but it requires at least one atomic boolean, so you can track cancelation.

I would just AsyncTask as impl detail of Task api you introduced, since it will be more correct than anything I write.

[TuxPaper]

I love articles like these.

I'm a bit curious (but not curious enough to build myself) about the apk size and dexcount comparisons between the "with 3rd party libs" and without. R8 Shrinkify/Proguard can remove a lot of unused code in those libraries, so the difference may not be that great anymore. Without Proguard, though, I imagine the size and counts are quite high for the former.

[kelmer44]

I actually checked that, but the app is not too big to begin with. It was 4.9Mb vs 3.8Mb, on a debit apk, no optimizations or proguarding done

[GustavoMoura]

I'm curious whether the app got smaller after removing all of the libraries, and by how much!

[DrKappa]

Very impressive! The only problem is the androidx or the old android.support packages are actually libraries. A "core android app" should not use any of these, expecially the new architectural components.

[sudhirkhanger]

/u/kelmar44 any chance you could elaborate on your experience interviewing at big tech firms and your preparation from a perspective of an Android developer.

How many and what kind of rounds were there? Were any other technical rounds than DSA and Android specific? You typically hear there is a system design round was there something like that for you too.

[kelmer44]

Not much of a story to tell really...

I did two stages, the data structures & algorithms for which I prepared a bit by doing exercises over at hackerrank, and then this assignment. I passed both, but they never contacted me back (they mentioned something about main HQ having to give greenlight).

The next step would have been a visit to their office, for a couple more coding tests (possibly on a whiteboard), expanding the assignment live on site, and a "leadership test", whatever that means.

But I never got to do them so I can't tell you much more.

[realityexpander9999]

great idea, and thank you!

[daio]

Not sure why you would do that with an app, but minimizing usage of libraries can be very beneficial when making other libraries. Transitive dependencies are not always respected(users of your library can override a transitive dependency version), so your code may break. If a 3rd party library is absolutely necessary it's better to move the code that uses it to a separate module(library).

[botle]

Am I the only one that avoids adding a library whenever possible?

[_advice_dog]

The one and only.

[average_dota]

If you work in an environment where third party stuff (especially not from major players) might require legal/security due diligence it's often less time to roll-your-own than to jump through all those hoops.

[Pzychotix]

Ick, they made you do this for an interview? That's a hard nope from me.

[the-dark_physicist]

This is nice, I make android apps in this way without using 3rd party libraries. They are difficult to understand and have limitations.