The Swift SDK for Android

https://www.swift.org/blog/nightly-swift-sdk-for-android/

by gok • 9 months ago

696 280 9 months ago

chrsstrm• 9 months ago

I'm just getting started in iOS development as a hobby, but what does this mean? Can I now build my app in Xcode with an Android target and use that binary in the Play Store? It surely can't be that easy now is it?

samtheprogram• 9 months ago

Not yet, and possibly not ever quite from Xcode. But using Swift CLI tools, yes.

The example Activty I saw is pretty rough ergonomically, but I have no doubt an ergonomic, SwiftUI-like library could be built on top of what’s currently there and/or on the roadmap.

objclxt• 9 months ago

Can I now build my app in Xcode with an Android target and use that binary in the Play Store?

No. The vision document[1] lays out the direction of travel. Currently the focus is on shared business logic and libraries, rather than full native applications (although that's certainly a goal, albeit a very long term one).

[1] https://github.com/swiftlang/swift-evolution/pull/2946/files

thenaturalist• 9 months ago

What do you mean?

This doc you linked is from August.

The blog post from today includes, in fact at the very top an XCode Swift project emulating a Pixel 9.

The docs include a detailed Getting Started for Android and they even have an Android examples repo.

Hence the SDK.

By all means, it very much is possible to build Android Swift apps in XCode.

https://www.swift.org/documentation/articles/swift-sdk-for-a...

brookst• 9 months ago

No, it’s just an Android compiler and standard libraries.

Same way there are C compilers for Windows and Linux, but that does not mean binary compatibility.

joanniso5• 9 months ago

The SDK doesn't quite work that way, your iOS-specific dependencies like SwiftUI and UIKit aren't available. For SwiftUI development, [Skip](https://skip.tools/) has a transpiler that translates your SwiftUI code into Jetpack Compose.

Without Skip, you can still share other code through JNI - similar to Kotlin Multiplatform.

Larrikin2• 9 months ago

The reverse is slowly becoming a possibility. Jet Brains just announced another improvement with Swift Export. https://kotlinlang.org/docs/native-swift-export.html

But it's not there yet

marcprux4• 9 months ago

An example of an Android app that is built using the Swift SDK for Android and is available in the Google Play Store is Skip Showcase: https://github.com/skiptools/skipapp-showcase/

(disclaimer: I work on the Skip.tools product)

colesantiago• 9 months ago

What does this mean for React Native?

Is Swift now going to be the de facto language for Mobile (and maybe Desktop) development?

akmarinov5• 9 months ago

Not a chance

React Native is popular because there’s a thousand times more React devs than native devs.

And people like to use what they know.

Also React dev experience makes anything Swift related look like stone age technology

Austin_Conlon• 9 months ago

Also React dev experience makes anything Swift related look like stone age technology

How so?

viktorcode6• 9 months ago

React Native is popular because there’s a thousand times more React devs than native devs.

Exactly this. And they come cheaper. JS dominance in development stems from business logic, not from quality of development environment or tools, or developers preference.

GZGavinZhao• 9 months ago

Flutter still exists, so as a competitor you need to beat both React Native and Flutter.

p2detar• 9 months ago

I last used RN half a decade ago, but from what I see around me - our frontend developer, who is proficient in React, actually chose to use Flutter for our iOS and Android mobile apps — and he’s quite satisfied with it.

kelvinjps10• 9 months ago

Kotlin did it first with kotlin multiplatform

hatmanstack• 9 months ago

The Simpsons did it.

wiseowise5• 9 months ago

Why would a marginal platform language become de facto language for mobile? If anything, Kotlin is much better positioned to fill the niche. It is already far, far ahead of anything Swift has to offer and is backed by a company actually making money out of the tools. What incentive does Apple have? My bet is expanding Apple services (Apple TV, Music, etc.), but is that enough for Apple to create a proper dev ecosystem? Highly unlikely.

viktorcode6• 9 months ago

It is already far, far ahead of anything Swift has to offer

Please share what Kotlin has that Swift doesn't

bingobangobungo• 9 months ago

Why cant everyone just get along and allow for KMP to work all within Android Studio instead of XCode. I'm working with this stuff everyday and that is by far my biggest headache.

jajuuka2• 9 months ago

Same reason everyone doesn't use Xamarin. Everyone has their own multiplatform framework solution.

wiseowise5• 9 months ago

JetBrains already works on Swift support within Android Studio.

TheJoeMan• 9 months ago

Does this project tie in to the SKIP transpiler? https://skip.tools/blog/bringing-swift-to-android/

I have an existing Swift / SwiftUI app that I am looking to port to Android, and have been not wanting to move to React Native.

joanniso5• 9 months ago

Yes, Skip is a major contributor to this effort!

tomovo3• 9 months ago

Are they putting work into the SDK or is there some integration going on? The way I understand it the SDK is compiled straight into Android binaries, whereas Skip transpiles? How does that work together?

wahnfrieden7• 9 months ago

You don't need to use the transpiler anymore. Skip added native Swift execution on Android recently. It has much greater compatibility than the transpiler (though they maintain both).

marcprux4• 9 months ago

Yes, Skip has been using our preview release of the Swift SDK for Android in our Fuse mode for over a year, and it has proven to be very popular! You can see our blog post about using it to build a completely native SwiftUI app for Android at https://skip.tools/blog/fully-native-android-swift-apps/

To clarify a couple of other comments about transpilation vs. compilation, Skip has two modes: Skip Lite, whereby your Swift code is transpiled into Kotlin, and Skip Fuse, whereby Swift is compiled natively for Android using the Swift SDK. Skip Fuse and Skip Lite work side-by-side, where Skip Lite is used to provide bridged integration to many popular Kotlin frameworks on Android (Lottie, Firebase, Stripe, etc.). You can read about the comparison between the two modes at https://skip.tools/docs/status/ and see a subset of our available modules at https://skip.tools/docs/modules/

We are very excited that the Swift SDK for Android is now official and we can switch over from using our own preview build of the SDK to the officially supported one.

VWWHFSfQ• 9 months ago

I think people will get excited about this and then quickly realize how painful it is to code in a foreign environment from the platform.

How miserable it would be trying to write Java or kotlin targeting iOS apps. I think this will be the same.

Just use the native tools and languages for the platform. Swift/Objc/xcode for iOS. Java/Kotlin/Android Studio for Android.

You will be so much happier.

AnthonyMouse• 9 months ago

This depends entirely on how well the thing you're using bothered to support multiple platforms.

Browsers are pretty much the gold standard here, ironically. You might have to care if it's Firefox or Chrome but it's very rare for you to have to care if it's Firefox on Windows or Mac or Linux. It's exactly why React is simultaneously horrible and everywhere.

So it can be done, it's just a question of whether that framework has done it well, ideally while also doing other things well (unlike React).

oblio3• 9 months ago

How miserable it would be trying to write Java or kotlin targeting iOS apps. I think this will be the same.

What happens in the Java/Kotlin case?

morshu90013• 9 months ago

idk about Android, but native iPhone dev is pure torture. Hence React Native.

tcoff915• 9 months ago

Android is way worse. iOS has way better APIs.

Android studio is way better than XCode though

lukko2• 9 months ago

I would love if I don't have to port my whole iOS app to Android manually. How exactly would this integration work if say business logic is handled by Swift - I'm guessing UI and SwiftUI would not be supported initially?

My app [0] uses a lot of metal shader code - I'm guessing there's no easy way to bring that across?

[0] https://apps.apple.com/app/apple-store/id1545223887

hoppp2• 9 months ago

Yeah I would also like to see SwiftUI but its apple ecosystem only.

wahnfrieden7• 9 months ago

https://skip.tools ported SwiftUI to Android.

joanniso5• 9 months ago

Metal cannot be used on Android. Your business logic can be ported - if it's separated as a library. If you don't want to separate it, Skip can handle bridging a lot of Apple libraries including SwiftUI.

lukko2• 9 months ago

Thanks - I see, so swift packages for everything.

What would be the equivalent shader / GPU language on Android? OpenGL?

fooker• 9 months ago

It'll take you thirty minutes to port the shaders with a modern LLM.

I am not joking. I have done this. Shaders are pretty simple. You'll have some weird artifacts but thats more because of platform differences than translation errors.

bigyabai• 9 months ago

Over 25% of packages in the Swift Package Index already build for Android

That's... not encouraging.

joanniso5• 9 months ago

I'm pretty happy with that number, considering this ecosystem is _brand new_. This is the lowest it'll be.

tomovo3• 9 months ago

Yes and any package dealing with UI is automatically disqualified, so 25% really is pretty good.

tclancy• 9 months ago

If you compare it to absolute zero I think you may be pleasantly surprised.

jajuuka2• 9 months ago

"You got Kotlin in my iOS."

"You got Swift in my Android."

ignoramous2• 9 months ago

Kotlin on iOS is statically compiled and interops with Swift/ObjC natively. Don't think KMP on iOS is even running a VM like Flutter has to with Dart?

https://kotlinlang.org/docs/native-overview.html

oblio3• 9 months ago

How solid is Kotlin on iOS?

randyrand2• 9 months ago

Dart runs natively. It only uses a VM in dev builds for hot reload.

In fact, you can even link native frameworks into your Dart code.

[1] https://dart.dev/overview#native-platform

[2] https://dart.dev/interop/c-interop

vips7L• 9 months ago

I don’t think anything runs in a vm on iOS since they don’t let you JIT compile code. Unless they’re doing pure interpretation, but I can’t imagine that being good for performance.

bradleyy• 9 months ago

Perfectly delivered, the Reese's commercial that keeps on giving. Although to fully match the analogy, there'd need to be some form of Kotlin+swift hybrid with a crinkly wrapper.

mosura• 9 months ago

I hope they actually stick with this. Swift embedded, for example, is a sort of proof of concept more than viable platform, and you end up battling that more than the problem you are trying to solve.

It is a shame because aesthetically Swift is easily the nicest of the modern safe languages, but there have been really odd noises in the community about project leadership that sour things.

ranie93• 9 months ago

guard let self = self else { return }

timsneath3• 9 months ago

Ha! But that's not semantically meaningful Swift code in any normal context, nor is it idiomatic. `self` is equivalent to `this` in C++, and is never normally null.

You use this construct for unwrapping nullable fields, for example something like this:

guard let httpResult else { return }

Note that you don't need to assign the value to itself in modern Swift. This line takes an optional (httpResult?) and returns early if null. If not, you can use it with strong guarantees that it's not nullable, so no need for ? or ! to unwrap it later in the scope.

akmarinov5• 9 months ago

This can now be guard let self else { return }

mojuba• 9 months ago

There's a shorter form of it:

  guard let self else { return }

which annoyingly the AI's don't know about.

saagarjha4• 9 months ago

Most use of this is misguided unfortunately :(

jitl4• 9 months ago

`guard let` is great what’s there to hate?

The big problem with swift is “expression has ambiguous type” and “expression took too long to type check”. Those don’t trade in code aesthetics but are problems I’ve never had in another language.

nicce• 9 months ago

Swift embedded, for example, is a sort of proof of concept more than viable platform, and you end up battling that more than the problem you are trying to solve.

Yet Apple has managed to create WatchOS. I don’t know what is the portion of Swift, however.

pta2002• 9 months ago

WatchOS is hardly embedded though. An Apple Watch is basically a small iPhone tied to your wrist in terms of architecture. That’s got a whole lot more in common with a full desktop computer than it does with a microcontrollers, where they often have rather weird architectures by desktop standards, and it’s quite rare to have MMUs and things like that. Also, there is no underlying OS, and no heap allocator (unless you provide one). That’s the kind of challenge that an embedded language runtime has to provide.

outadoc• 9 months ago

I'm a big lover of Kotlin Multiplatform, but I think this is pretty cool anyway. I could imagine making a native Swift library shared between the platforms for memory-sensitive work. I'm not sure about using it to write an app's entire business logic, KMP is going to be more mature for a while for this.

oblio3• 9 months ago

Do you build desktop apps, too, with Kotlin Multiplatform? How mature is it overall?

icar2• 9 months ago

I want to know this as well. My only interaction with a Kotlin Multiplatform app is Jetbrains Toolbox, and it's slow to start, has a lot of input lag and overall feels sluggish.

mr7uca3• 9 months ago

Jvm desktop is honestly the target with the best support. I always build on desktop during mobile dev first because I don't need to deal with connecting a phone or emulator. Second resizable windows by default is so helpful when building for many screen sizes. Also it has hot-reload now

danielfalbo• 9 months ago

Why can’t everything just be a progressive web app

kylecazar• 9 months ago

Because Google/Apple don't want us to circumvent their respective app stores, so they make certain features/API's a PITA (if not impossible) to use unless you are building natively.

timeon• 9 months ago

Meanwhile I considered PWAs necessary evil on iOS. I would gladly use native tools but paying developer subscription just to install private/personal apps is no-go.

throw_m239339• 9 months ago

Most people don't even know they exist (I do not count webapps in a native shell as PWA). that's the biggest issue with PWA in my experience. People aren't using them.

ripped_britches• 9 months ago

Apple and Google couldn’t take 15-30% that way

dagmx• 9 months ago

Because hardware capabilities exist outside the realm of web technologies.

ls-a• 9 months ago

Thank you. Please kill RN and Flutter already. I'm done with square UI apps that handle touches after two days

turtlebro3• 9 months ago

You can set the corner radius to whatever you like in Flutter, also the framework is quite fast, if an app doesn't respond to touches it's likely a poorly made app

ryeights3• 9 months ago

Flutter has a long-standing issue where every interaction is subject to a 1-frame delay on iOS (P2 since 2022)…

https://github.com/flutter/flutter/issues/110431

Not to mention the stuff with shader compilation lag

bitpush2• 9 months ago

I have no love for RN and Flutter, but what makes you think Swift on Android will be even remotely close to what Flutter and RN has?

If anything, Apple will launch this and quickly forget this exist.

bpavuk2• 9 months ago

although Apple has tremendous influence over Swift, Swift for Android is a grassroots effort, as said in the link. if community needs it, community will maintain it, and Apple won't get in the way. why would they?

crowbahr3• 9 months ago

It's also a false dichotomy. My money is all on KMP over any of the 3.

React isn't going anywhere but I expect 5 years from now KMP will be the tool of choice for native app startups.

lenkite• 9 months ago

Please kill RN and Flutter already.

Just No. Nobody will kill >30% of apps on the iOS store. Flutter is simply a massively superior development experience overall compared to the horrifying disaster that is SwiftUI. SwiftUI is so utterly pathetic that more than a third of all apps are now being written in Flutter.

"The compiler is unable to type-check this expression in reasonable time" -> one of the most atrocious and common errors that increases cortisol levels and reduces life expectancy amongst mobile developers.

Please kill SwiftUI already. For the sake of Humanity.

realusername3• 9 months ago

Having worked with Flutter, I also have the same opinion, I don't think you could pay me enough to use xcode and care about all these half documented apple frameworks.

The app build and upload process is painful enough as it is, I don't want more of it.

randyrand2• 9 months ago

imo, Flutter is awesome.

wahnfrieden7• 9 months ago

Related: https://skip.tools <-- SwiftUI for Android

trevor-e5• 9 months ago

Very excited to see this as an official project!

I've been toying around with multiplatform frameworks like RN and Flutter for a side project of mine but they never feel right. I'd rather use the native UI per platform and have a nice way to share business logic. KMP exists but I think for most developers wanting to build an app it's more common to build for iOS first, and then port to Android later if the app gets traction. With a little foresight of keeping shared code in a Swift Package, it seems like that's getting more and more possible which is great to see.

ivm3• 9 months ago

This is already possible with .NET and MvvmCross: a shared core library plus native UI projects for each platform. UIKit feels great in C# and it’s all been working quite well since Xamarin times, with access to the Nuget ecosystem.

trevor-e5• 9 months ago

Xamarin with .NET and MvvmCross falls into the same bucket as RN and Flutter IMO, unless something changed since the last time I looked.

frankus• 9 months ago

I think business-logic-in-JavaScript is something cross-platform folks shouldn't snooze on either, with the usual caveats of not doing anything performance-critical or where an asynchronous API would be awkward (to be clear, using JavaScriptCore or QuickJS or the like, not just running in a WebView)

But it'll run on iOS (v7.0+), Android (I think more recently) and of course web and server-side. And most importantly, it's hot-reloadable, as long as you don't run afoul of platform gatekeepers (i.e. use it for bug fixes and minor behavior changes, not like whole new features).

One of the frustrating things about mobile development is that once you ship a version, that version will almost certainly be running on at least someone's device indefinitely without being upgraded. My day job is even on step further back in that we have to get our customers to update the version of our SDK that they're integrating (which for many of them means contracting out because they don't have an in-house mobile dev team), before they ship an app update, which then needs to be installed by end-users, whose device might not even support the new deployment target…

(I've been trying to sell this to the bosses for the last 9 years or so, and never gotten the go-ahead, so there could be aspects I'm missing, but it always seemed like a huge missed opportunity).

trevor-e5• 9 months ago

OTA updates are definitely nice to have and I'm surprised there's not a way to do so with native iOS since RN and Flutter already support it. Technically it is possible with dynamic frameworks.

In practice though it's somewhat easy to workaround the lack of OTA with dynamic server configuration for clients.

bpavuk2• 9 months ago

yes. there is an aspect you are missing.

no one in their right mind wants to bundle Chromium with every app install, and every Discord user hates mobile Discord app, which is, guess what? uses Chromium!

a3w2• 9 months ago

but I think for most developers wanting to build an app it's more common to build for iOS first, and then port to Android later if the app gets traction.

Is it? There seem to be a hundred million Java developers out there, that can do an Android app, plus even release that in-house or with minimal registration fees if single dev/sideproject.

For Objective-C/Swift, there seem to be ten percent as many devs.

I always only tinkered with Android apps in my spare time, but never managed to deploy anything to iOS.

Also, outside the US, iPhones are a 10 % niche product in private hands, but companies might use a lot of iPads or provide iPhones as work phones, so perhaps companies do think of both platforms as second class citizens (behind windows/browser as two other "OS-like" primary platforms)

twof• 9 months ago

It's not really about the number of developers. If you're running a company in the US at least, most of your revenue is going to come from iOS users.

disiplus• 9 months ago

for us its pixel phones, you can choose iphone if you want but most of us want pixel. so for me its macbook + pixel. I think the iphone only is unique to US.

cosmic_cheese4• 9 months ago

It probably varies from area to area, but in the US iOS first is common.

Having developed both, it makes sense.

iOS is by far the more profitable of the two platforms and its support burden is substantially lower — far fewer versions to think about with the bulk of users running 0-2 versions behind, single form factor (only size variants), zero manufacturer skin quirks/bugs to deal with. It’s a more fertile environment for getting up and running and getting the core product shaken out.

Android can come later when you’re out of rapid iteration and have the bandwidth to deal with the idiosyncrasies of the Android world.

Jcampuzano2• 9 months ago

It's probably a US centric take you're replying to.

Having worked at multiple companies making apps in the US and the company I work at right now which is a company almost everyone knows the name of and the vast majority of our revenue comes from our native apps - practically every feature we build is iOS and web first and only if it performs well do we even consider adding to android most of the time. And it's primarily because product/execs know iOS users are more likely to pay for things.

It's sad as an android user myself, but android is very much a second class citizen in the US

pzo2• 9 months ago

react native do uses native UI per platform in contrast to flutter or compose multiplatform. React Native improved a lot - it's not the same technology that has been 5 years ago. Especially this year there were plenty of improvements also regarding speed but in react native and community plugins (new architecture rolled in, react compiler, hermes v1, nitro modules, flash list v2, legend list, react native skia, react native webgpu, expo use dom) Tooling in JS/TS ecosystem also improved a lot.

trevor-e5• 9 months ago

Yes it uses native UI by wrapping the underlying frameworks, but that still means there is a layer in between that has to be updated with fixes and new features. Every RN project I've tried in the past turned into a dependency mess since you find edge cases that are not supported by the framework.

It's definitely gotten better like you said but I just prefer to work with the native platform code even if it's a bit of extra effort.

palata7• 9 months ago

KMP exists but I think for most developers wanting to build an app it's more common to build for iOS first

This sounds US-centric to me.

The advantage of KMP is that it is pretty mature and it is used in big apps like Google workspace (Google Docs etc), so it feels like it may be in a really good position.

I used to be exited about Flutter when it started, but the speed of major releases (by the time I had rewritten my app for Flutter 2, Flutter 3 was out, or something like that) and it did not seem to get so much traction (Dart is fun, but well).

KMP builds on top of Kotlin, with big investment from JetBrains and Google. That looks extremely promising to me.

icar2• 9 months ago

At Proton they use Rust for shared logic (their claim is more than 80% of the codebase iirc), and platform specifics for the rest.

bbkane• 9 months ago

https://proton.me/blog/authenticator-rust - I think this is what you're referring to? Looks really nice

dvtkrlbs4• 9 months ago

afaik 1password also does something similar

crowbahr3• 9 months ago

The issue with that approach is that the state of the art for iOS dev is about 15 years behind the state of the art for Android dev. The amount of simple things that are incredibly painful for iOS devs to do is astounding. Some of that is because xcode is horrific, some of it is that the ecosystem is starved by disinvestment from Apple.

I've talked with colleagues in several companies and the story is always the same: the iOS repository is a patchwork of horrible patterns that shatters when you update to the latest iOS target.

At my current employer it takes 4 iOS devs longer to implement things than it takes 1.5 Android devs (0.5 because the other .5 is spent being Team Lead and architecting, planning, endless meetings etc).

When I talked with the KMP team at Google they were mentioning that their most enthusiastic user base at Google was iOS developers, begging to be saved from their tooling nightmares.

I'm sure some defensive devs will show up here but I've been at 5 different places over my decade at work and every single one of them has had endless struggles hiring iOS devs, maintaining iOS projects etc.

myHNAccount123• 9 months ago

Exact opposite experience :)

flakiness• 9 months ago

This looks like a Fluttter competitor where the UI is rendered by the Swift SDK side (vs Android-provided library).

afavour2• 9 months ago

This is really interesting. I’ve made cross platform mobile libraries before and ended up using Rust… which was fine. But there’s a huge built in advantage to using a language one half of the problem is already fluent in. Curious to see how well it combines with Swift/Webassembly.

guelo• 9 months ago

Less necessary to be fluent nowadays with LLMs.

featherless• 9 months ago

Does this result in the Swift code being compiled or transpiled?

mk89• 9 months ago

It's compiled.

From what I see in other threads, skip.tools offers the possibility to transpile SwiftUi to Compose, so you build one UI and port it to android too.

Here we're talking about sharing the code logic (written in swift) and write android UI that uses it.

orliesaurus• 9 months ago

Interesting to see excitement around this release...

BUT beyond cross‑platform hype there's a practical question... what developer tooling will look like... Are we getting first‑class debugging, package management, continuous integration for Android targets...

ALSO adoption often comes down to licensing and governance... open SDKs thrive when the steering group is transparent and responsive...

And it's worth remembering that bridging two ecosystems isn't just about code... it's about aligning design idioms, APIs and expectations... Without that you end up with uncanny valley apps...

andrekandre3• 9 months ago

  > Are we getting first‑class debugging, package management, continuous integration for Android targets...

the most important part imo.

i'd love it if you could pull/push and build/debug changes to the shared code from android studio and build it all together there, that would reduce a huge amount of friction...

flutas• 9 months ago

IMO the implementation (for me at least) is ... terrible. Why reach for this when it's, at the end of the day, just the exact same as NDK work in C++ but in Swift.

You have to use Kotlin / Other UI setup anyways (or their fully-native example, use OpenGL to draw the screen[0]), and on top of that statically assign the package path and class name in the Swift code, while making it an external func in the kotlin code[1]. You then also get to deal with the annoyances that come up with native libs.

kotlin side: /* * A native method that is implemented by the 'helloswift' native library, * which is packaged with this application. */ external fun stringFromSwift(): String

swift side: @_cdecl("Java_org_example_helloswift_MainActivity_stringFromSwift")

[0] https://github.com/swiftlang/swift-android-examples/blob/mai...

[1] https://github.com/swiftlang/swift-android-examples/tree/mai...

ktoso• 9 months ago

It's worth pointing out that the example you linked with the cdecl is not showcasing the swift-java interoperability but using "raw" JNI patterns as if you would do it with C.

This example does showcase the interoperability: https://github.com/swiftlang/swift-android-examples/tree/mai... you don't have to annotate or write any "weird" cdecls or really touch JNI details yourself when using the swift-java interop support https://github.com/swiftlang/swift-java

user3939382• 9 months ago

Whole modern stack is upside down this is a waste of talent

pzo2• 9 months ago

Happy to have it but I worry it's too little too late. I see more and more new projects choosing React Native, Flutter or Jetpack Compose Multiplatform. It's gonna take multiple years for apple or community to catch up to those. Also they should open (source) up xcode tooling for other IDE to get any better cross-platform adoption.

a3w2• 9 months ago

The example shows non-GUI code written in Swift, with Kotlin for frontend. So, still no UI in Swift?

What does it add to the linked "swift-java project" then at all, perhaps some lifetime events and a sort of batteries-included standard library?

saubeidl• 9 months ago

This looks not bad, but why would anyone use this in a world where Kotlin Multiplatform exists?

cosmic_cheese4• 9 months ago

Because some of us prefer writing Swift over writing Kotlin.

akmarinov5• 9 months ago

Pretty much everything starts iOS first, so why bother with KMP when this exists?

wiseowise5• 9 months ago

What’s stopping you from developing in KMP iOS first?

bsimpson2• 9 months ago

The most important question for every cross platform framework is what happens to the UI?

Adobe products (both the Creative Suite, and their Flex Builder environment for Flash app) had their own design system that felt foreign on every platform it shipped on. If you wanted something that felt native, you had to reimplement e.g. Apple Aqua in Flash yourself.

Flutter goes out of its way to do that work for you, aiming for a "Cupertino" theme that looks-and-feels pixel-perfect on iOS.

React Native tries to delegate to platform primitives for complex widgets, so scroll views still feel like Apple's when on Apple's platform.

Just about every top-level comment here is talking about that in one way or another; yet the blog post doesn't mention it at all.

It's possible that Apple/Swift's mindshare among developers will lead to a significant number of apps shipping the Swift version for Android even if it means using Apple's UI, simply because they can't be bothered to make something bespoke for Android. Then again, Apple takes so much pride in its design language that it might not be willing to implement anything that feels good on a platform they don't own. If they were to ship an API-compatible widget toolkit, it might e.g. use intentionally bad spring physics to remind you you aren't on an iPhone.

I wonder how big the community part of this is. Is this an open source project of non-Apple people who are trying to break Apple's platform out of its walled garden? Is a lot of it funded by Apple? Ultimately, that's going to shape a lot of how this plays out.

timsneath3• 9 months ago

It's worth noting that this doesn't add any expectations for how your UI is built. The example shown in the screenshot continues to use Jetpack Compose (Android's native UI) with Kotlin invoking Swift business logic. You can also use other UI frameworks on Android, of course, including some that are written in Swift.

One nice thing about this implementation is that it shares many of the same characteristics as Swift on other platforms: unlike some common alternatives, it's not garbage collected but uses reference counting; it uses the same underlying libraries, concurrency primitives and memory model.

Excited to see how folk use it... it's technology that will hopefully springboard some other interesting innovations.

[Disclosure: I work on developer tools and frameworks at Apple.]

wffurr2• 9 months ago

How does transpiration work without GC? I would think all the Kotlin equivalents would be GC heap allocated objects.

jitl4• 9 months ago

This seems great, we are looking for a code sharing language between platforms and the options so far are the Usual Suspects:

- TypeScript: we have a few million lines already, but it runs poorly on Android midrange devices.

- Rust: very efficient on Android / iOS but on web there’s very expensive memcopy between WASM memory and JS. Safe but hard to write and refactor casually. Would be great for server perf tho. Async has many footgun for our JS devs. Biggest long term downside: borrow checker speed limit on developer velocity for business logic.

- Kotlin: can target JS directly avoiding bridge cost. iOS devs are uneasy about it. Async story is extremely confusing. Biggest long term downside: how Byzantine the JVM ecosystem is on the server.

Until I saw this Swift wasn’t really in the running. I need to explore the web target situation. Swift is maturing but still weak in ecosystem on non-Apple platform compared to other options. Still swift is moving towards a great combo of speed + safety + usability.

Biggest long term downside: type inference pain. Swift is the only language I’ve used that will tell me “the types seem wrong / ambiguous, but the compiler has no idea what your specific mistake is” and there’s no way to fix it other than trying random code permutations. I hit that one with node-swift yesterday and gave up.

Is there anything in the works for taming the type inference or some way to force-select which overload I want?

mikeocool• 9 months ago

It's possible that Apple/Swift's mindshare among developers will lead to a significant number of apps shipping the Swift version for Android even if it means using Apple's UI

It doesn’t sound like this release includes bringing SwiftUI or UIKit to android, so unless you did a ton of work to replicate it (ala flutter) using Apple’s UI on android probably still isn’t really possible.

palata7• 9 months ago

The most important question for every cross platform framework is what happens to the UI?

I kindly disagree. The first feature I want from a cross-platform framework is that it lets me write a native UI. That's why I like KMP: I can just share a framework with an iOS app built with SwiftUI.

Sharing business logic makes a lot of sense in a ton of cases and has been done forever (C/C++/Rust/Go libraries, etc). Sharing UI in complex apps, in my experience, always ends up being a "write once - debug everywhere" nightmare.

What KMP (and I'm hoping Swift for Android) bring is the possibility to share a Kotlin (respectively Swift) library instead of sharing code with C/C++/Rust/Go. So that an Android/iOS team can keep using Android/Swift without having to introduce a third language for sharing logic.

virtue33• 9 months ago

Having worked a long time with client teams as a lead - this is always the biggest pain in the ass.

At one of my last phase startups I started shifting all our business logic stuff into our graphql server and treated it like it was part of the client teams. (we had ios/android/web as independent full apps with a very small team of devs).

Business logic is the real killer. Have one person suck it up and do it in typescript (sorry y'all) on the GQL/apollo server and all the clients can ingest it easy.

Send down viewmodels to the clients not data models. etc etc.

This helped DRAMATICALLY with complexity in the clients.

andrekandre3• 9 months ago

  > What KMP (and I'm hoping Swift for Android) bring is the possibility to share a Kotlin (respectively Swift) library instead of sharing code with C/C++/Rust/Go. So that an Android/iOS team can keep using Android/Swift without having to introduce a third language for sharing logic.

have gone down this route before, and tbh the biggest issue is dev ux (ios devs cant debug easily, model mismatches vs kotlin e.g kotlin exceptions cant be caught from swift) and in the end even kotlin multi platform isn't the same as kotlin for android, so in a sense you are still introducing a 3rd language after a fashion...

if you can fix the dev issues and have a dedicated team behind the shared logic it could work out, but still then again if you also have a website your re-implementing that logic on the front-end twice...

timcobb• 9 months ago

Sharing UI in complex apps, in my experience, always ends up being a "write once - debug everywhere" nightmare

Amen!

raspasov2• 9 months ago

React Native is pretty good at cross platform but yes, it must be tested right away on all platforms.

Retrofitting an iOS-only React Native app to Android later is possible but can be of a pain, at least initially.

isodev• 9 months ago

Indeed, "cross-platform UI" can only be as good as the average between all the platforms it supports and it usually ends up costing a lot more than using the native UI kits of each platform. Kotlin Multiplatform has been and continues to be the "happy path" for buildings apps in our studio - native UI + shared business layer. Also, in terms of API stability and mental load, Kotlin is a lot more productive than Swift... and it doesn't come with a yearly breaking cycle.

zigzag3124• 9 months ago

Sharing UI in complex apps, in my experience, always ends up being a "write once - debug everywhere" nightmare.

Was that with UI framework that wraps platform's UI framework or with one that draws controls on its own? Shared complex UI is not much of an issue with frameworks that fully implement their own controls. But quality implementation of controls from the ground up is a lot of work so there's not many good UI frameworks that do this.

JimDabell• 9 months ago

> The most important question for every cross platform framework is what happens to the UI?
I kindly disagree. The first feature I want from a cross-platform framework is that it lets me write a native UI.

I don’t understand – aren’t you agreeing?

PKop• 9 months ago

This isn't disagreeing

jcelerier• 9 months ago

Sharing UI in complex apps, in my experience, always ends up being a "write once - debug everywhere" nightmare

Compared to the tried and true method of "write many times - debug everywhere".

there is not a world in which you won't have issues on $PLATFORM because $PLATFORM themselves have their own individual bugs / issues

kristianp• 9 months ago

> The most important question for every cross platform framework is what happens to the UI? I kindly disagree.

You're still discussing the question of UI though, whether it's native or not.

kridsdale3• 9 months ago

The Browser Company did an amazing job of porting SwiftUI to Windows, where the element primitives in the language map to native Windows UI C++ classes under the hood.

Perhaps the future of Swift for Android is similar, where SwiftUI will map to Jetpack elements. That would be cool.

Remember on iOS and MacOS, SwiftUI is not "native". It's a description language that system frameworks interpret and create NSViews and UIViews and CGLayers etc out of.

aatd86• 9 months ago

Is their code available somewhere.

I need this for UIKit so that I can make my UIs in Go. I have the gist of what it would require but have yet to implement everything. (if swiftUI allowed more control over the UI tree, I would even target it but full declarative à la react with vdom diffing is no bueno for fine grained rendering control)

wahnfrieden7• 9 months ago

It exists already.

SwiftUI to Jetpack Compose: https://skip.tools

And a less mature but very interesting project with a SwiftUI-like API for UI across macOS/Linux/Windows plus some emerging support for Android and even a TUI target contributed by Miguel de Icaza: https://swiftcrossui.dev

It's a description language that system frameworks interpret and create NSViews and UIViews and CGLayers etc out of.

This is out of date. FYI parts of SwiftUI are "native" now. Notably the new Liquid Glass UI was written in "native" SwiftUI. UIKit and AppKit actually wrap SwiftUI views to render Liquid Glass now. Although SwiftUI-exclusive APIs have always existed, this was a notable step in a new direction and suggests the future of UIKit and AppKit is a unified "native" SwiftUI implementation.

They've also been ripping out UIKit/AppKit implementations of SwiftUI views... IIRC List is no longer a UITableView for instance (could be confusing with another component though).

rkapsoro• 9 months ago

They didn't port SwiftUI to windows; they wrote a Swift wrapper for WinUI. Impressive in its own right, but not SwiftUI.

saagarjha4• 9 months ago

SwiftUI in many cases generates views that were written specifically to back the description you requested. I think that’s pretty native.

marcprux4• 9 months ago

The Swift SDK for Android doesn't specify or mandate any user-interface technology, but leaves it open for other projects to build upon. For example, Skip.tools re-implements SwiftUI for Android by bridging it to Jetpack Compose, so you can use the same codebase for both your business logic as well as UI layer.

We write about it at https://skip.tools/blog/fully-native-android-swift-apps/ and an example of an app on the Play Store that demonstrates this is the Skip Showcase app: https://skip.tools/docs/samples/skipapp-showcase-fuse/

[Disclaimer: I work on the Skip product, and I am also a founding member of the Swift Android Workgroup and am the release manager for the Swift SDK for Android]

bsimpson2• 9 months ago

Appreciate the response!

Respectfully, the demos on your page look like impostors on Android. For apps that wouldn't bother supporting Android in the first place, maybe this is an improvement. But for apps that want all customers to feel considered, that's not a direction I would recommend.

Would still like to see a call out to this in the blog post above ("For UI, you can use Swift for business logic and use Android's SDK to create the interface. Or you can use a library like our partner skip.tools to write SwiftUI apps directly.")

Razengan• 9 months ago

The most important question for every cross platform framework is what happens to the UI?

For that, there needs to be a single definitive agreement on UI somewhere.

Like what does it mean to be a "list"? How does it behave with mouse, touch, keyboard?

How many different kinds of lists? (for example, a list for "favorites" behaves slightly differently than a list for "bookmarks", vs lists of "products/offers" and so on)

I bet any example you can give I or others can nitpick some flaws in that.

Hell, there are differences of opinion right off the bat: Should content move up when I scroll/swipe down or move down when I scroll up?

rustystump• 9 months ago

Very unpopular opinion but i like apps that ashew looking “native” for an original ux. Maybe it is my love for gamedev and all the crazy designs they come up with but i personally loath boring uninspired native apps esp when the native ux is terrible.

Apple wants everyone to conform because historically their ux is on point but the last update really reinforces my view.

beautron• 9 months ago

I share your unpopular opinion.

While I understand that having identical UI elements across apps aids in discoverability, I just love it so much when an app has its own bespoke interface that was clearly made with love.

Like you, it might be my love of games that has given me this preference. Would StarCraft II have a better UX if its menus used the standard Windows widgets where applicable? I think certainly not. And I think the same can be true for many non-game apps.

realusername3• 9 months ago

The debate has been settled anyways, none of the top apps (Facebook, Whatsapp, Youtube, Tiktok..) uses the native design, users simply do not care.

planb• 9 months ago

IMHO, Apps can look (and maybe even "feel") any way they want. But when it comes to integration into the system, they should be as native as possible. It'S 2025 and I can't drag and drop from/to the Gmail app on iOS - that's ridiculous (especially because I can't have real-time push notifications for IMAP in the mail app for Gmail account, which as far as I know is also a limitation by the Gmail servers, not by IMAP itself).

ChrisMarshallNY• 9 months ago

Looks like this is package compatibility, not a cross-platform UI system (although maybe that’s in the works. SwiftUI could probably port well).

al_be_back• 9 months ago

i think traditional UI should be decoupled from the language - only providing CLI and web UI (w3c web standards).

Apple's ui is very nice, but you're stuck with a whole ecosystem for life. If you want to cross-platform, as you mentioned, well, all hell breaks loose: React & co, Flutter, web assembly.

a unified, all-batteries-included system is excellent for the manufacturer/provider - they can plan, invest, manage and rollout products at a desired rate. but for developers, third-party, and consumers is very costly, intense and risky.

fun-fact from Steve Jobs bio, he was interviewing a tech hopeful for a job, the guy showed him a prototype of what would become the Dock (aqua + animations), created using an Adobe product. Abobe etc had powerful, flexible platforms - unfortunately the market was driven by eager tech geeks - so it was easy to get curried away with fancy UIs. However, that was (20 years ago) an educational issue - not a tech issue.

afro883• 9 months ago

Think of this more like Kotlin Multi Platform. Shared logic, not UI.

mkhalil• 9 months ago

Huh? Did you read the link? Did you notice the ONE screenshot clearly shows the app has a material-ui look.

I'm going to say this because I think you might not know this, but also because I think many others might not have thought about this:

Almost always, a programming language is UI agnostic. Swift SDK for Android means: You can now write Android Apps in Swift. This doesn't magically include Apple's components / SwiftUI. When you write code for a platform, specifically an SDK for an OS, all you do is expose that platform to that language.

So, as long the SDK/bindings are there, a new "Window" means whatever a the OS thinks is a Window. A Button is what is defined (or exposed/binded to) as a Button in Android.

Swift was sorta released for Windows: a new Window looks like a generic Win32 Window. The same one you would get if you used C, C++, Rust, etc..

All your examples are GREAT examples to explain how this works: - Flutter has "Cupertino" to allow people to use Flutter to make Apple apps, and not have to learn names/methods/interface of the native Apple UI. - React Native: A LOT of work was put in to make/bind Apple native objects to a React component. And the same for Android.

So again:

The Swift SDK for Android means you can write your Android apps in Swift. The same apps you might of wrote in Java or Kotlin, you can now use Swift. Meaning whatever it looked like in Java/Kotlin (using native api's), it would look like in Swift.

The SwiftUI, Apple's component library written/exposed to Swift, is something completely different.

hamburglar• 9 months ago

Almost always … a new "Window" means whatever a the OS thinks is a Window. A Button is what is defined (or exposed/binded to) as a Button in Android.

But not always, and when it’s not true, it sticks out like a sore thumb. It’s convenient for developers, but produces apps that have this uncanny valley “this isn’t quite right” quality to them. Adobe used to do this when I worked there 20 years ago (honestly don’t look at modern Adobe software if I can help it so I don’t know if they still do) with an internal component called Adobe Dialog Manager that was built expressly so developers didn’t need to worry about native widgets. The result was this “adobeness” to all the ui elments on both platforms (at this point we are talking windows vs macOS). There was no os-level button. There was an ADMButton on both platforms and it was hand-rolled behavior for rollovers and drawing styles and general interaction rules and it was this pleasantly uniform experience that sucked equally everywhere.

akmarinov5• 9 months ago

Didn’t Flutter decide not to support Liquid Glass, because it’ll be too much work?

WhereIsTheTruth• 9 months ago

Nobody cares about native UI, not even Apple, the strength of a UI toolkit is to empower creative design while retaining consistency and intuitiveness across devices

Only the UX has to feel native, the pixels are yours

WA• 9 months ago

I wrote this in another thread: I'm confident that with Liquid Glass, even more companies aren't interested anymore in the Apple UI look and rather want their own UI language, because Liquid Glass is just that bad.

hulitu• 9 months ago

The most important question for every cross platform framework is what happens to the UI?

They don't give a fsck. Compare Windows, Adobe, Apple, Google products from 10 years ago with the present ones.

dvtkrlbs4• 9 months ago

Except Flutter hit a wall with the liquid glass on IOS and Material 3 on android since they implement all the widgets from scratch implementing the new UI language will take considerable amount of effort and they are saying this is not even their roadmap RN.

zigzag3124• 9 months ago

Liquid Glass is meh anyway. Apple's Windows Vista moment.

Someone• 9 months ago

The most important question for every cross platform framework

I don’t think this is a cross platform framework. AFAICT, It’s a Swift toolchain (compiler + Swift standard library) that allows you to call Android APIs.

bool3max• 9 months ago

Flutter goes out of its way to do that work for you, aiming for a "Cupertino" theme that looks-and-feels pixel-perfect on iOS.

Key word _aiming_ lol

SergeAx• 9 months ago

I would understand people's craving for pixel perfection, smooth 120Hz scrolling, etc, if we had nothing else to want. But I believe that we are now in a totally different era when overall software quality is degrading and we lack some basic stuff here and there, even in the apps of multi-billion-valued companies. In this situation UX should be much more important than UI.

mr7uca3• 9 months ago

Sweet, now I can make a cursed android app with views written in switft that use kotlin viewmodels

palata7• 9 months ago

I have been sharing code between Android and iOS for a long time. Sharing the UI has always been a nightmare for non-trivial apps.

What makes sense to share is complex libraries, and usually I have been doing that with C/C++/Rust libraries. But it means that the team now deals with Kotlin, Swift and one (or more) of those "sharing" languages.

What I believe KMP and Swift for Android bring is that teams will be able to share libraries in Kotlin/Swift, so that they can keep writing in their preferred language without having to introduce C/C++/Rust.

I believe this approach is vastly superior to any kind of framework that tries to share the UI. Mobile devs, in my experience, want to use the native tools: Kotlin for Android and Swift for iOS.

viktorcode6• 9 months ago

Cannot agree more. The UI concepts and capabilities differ too much. Any cross platform UI solution will always be missing some hard to implement things and many recently introduced UI features. And so far I haven't seen a single non trivial app from RN / Flutter world which would feel native on iOS.

w10-1• 9 months ago

I read this announcement mainly as proving the success of the new support for SDK's. Previously, supporting another platform required invasive hodge-podge of CMake tangles at best.

Swift SDK's are a way for anyone to support any platform, as proven by the Android guys doing it on their own. There are also SDK's for Linux, wasm, and embedded (and soon, windows?). So long as you play by SDK rules, Apple won't stop you from porting Swift to a new platform, even on competitive platforms like Android.

(The inter-op story with the JVM languages is still being written; it reduces to either the C/C++ FFI or the two incomplete duals of Java's legacy JNI and newer FFI/Memory interfaces. Prototypes work fine when the semantics are the same, but beyond that, there be dragons. Cross-platform UI frameworks are similarly (and likely eternally) afflicted with bright and dark spots.)

crossroadsguy• 9 months ago

Sharing the “business logic” pretty wasn’t the problem — at least not of late. Writing UI on both was the pain, or the existing shared UI solutions. As a mobile dev I’d rather appreciate a common UI framework that doesn’t suck like react native.

tcoff915• 9 months ago

When was the last time you tried react native? It’s pretty good now that they finally completed the transition to the New Architecture. With Expo it’s pretty nice these days.

nhumrich• 9 months ago

Does this mean there is no longer any excuse to not put iMessage on the iPhone?

prirai• 9 months ago

You mean android?

danielcspaiva• 9 months ago

Rip flutter

poolnoodle• 9 months ago

Can somebody explain what goes into making a new language compatible with Android?

viktorcode6• 9 months ago

Interop with Android SDK / NDK, plus a simple way to get started with development.

tomburgs2• 9 months ago

I've worked with Flutter, React Native, and now I'm building an app in SwiftUI.

I've found a few things in the process: 1.) Neither RN nor Flutter seems to be able to create truly native applications on iOS. I've never once seen an application made in either of them and thought it was a native iOS application. 2.) Unless your application must support both platforms, android (in an economic sense) is dead weight. I was shocked to see how bafflingly little android users contributed to our revenue. I've heard this from people in other companies as well. 3.) SwiftUI (and I assume UIKit) makes it really simple to create apps according to HiG. You can feel yourself fighting the framework whenever you deviate from what Apple wants you to do. I actually think this is a good thing.

I think Apple is doing something really smart here. They're not making SwiftUI cross platform, they're making it possible for you to re-use your business logic from your SwiftUI apps in Android apps.

The way see I see it they're saying — if you want to spend the least amount of time possible building a cross platform app use Flutter or RN. If you want to create a truly native experience on both platforms, but still re-use your core business logic, Swift is your friend.

saretup• 9 months ago

android (in an economic sense) is dead weight

Well it depends on your business model. Android has much smaller user LTV in most cases (especially in apps with no ads and only IAPs/Subscriptions), but the CPI is also smaller, so the economies of scale are different. In certain situations it happens that iOS is not profitable but android is.

Farbklex• 9 months ago

What's your market? Android being financially irrelevant seems very US-centric.

tomburgs2• 9 months ago

Western & Northern Europe. It's not that it was a negligible share of Android users, it's that they didn't generate any meaningful revenue.

kurak• 9 months ago

I'd love to see a future, where I can use Swift as a bridge between Kotlin and c++ and then gradually port more and more c++ to Swift.

Does anyone know/understand what's the story for using Swift's interop with c++ on Android? Should this work right now? How?

the_arun• 9 months ago

Future - Is it possible to run swift built OS to run on Android devices 100%? Is that a threat to Android as an OS?

kurrrrrak• 9 months ago

Maybe, if someone builds this first. Same could be said about Apple running iOS (as it stands) on Android hardware. It can be done, but there are no incentives for doing this.

victor106• 9 months ago

Swift has matured significantly over the past decade — extending from cloud services to Windows applications, browser apps, and microcontrollers

Really!!! Would love to know more how that statement is true. I could not find any resources to support that claim

steve19772• 9 months ago

It is probably true in that you can actually do all of that with Swift. How much is actually used on a larger scale is another question.

cranx• 9 months ago

So this still uses the JNI for the ui? Unfortunate that is

Vipsy• 9 months ago

When it comes to UI, most of us know native wins for actual feel and simplicity. Cross-platform UI tends to create new headaches, not solutions. Still, having more options like this pushes the ecosystem forward. Let's just hope the platform docs stay sharp and open for devs who want to build confidently.

Kibranoz• 9 months ago

i am unable to try it as downloading the swift language doesn't work on fedora 42

The Swift SDK for Android

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