Tag Archives: Kotlin

Handling Nullability in Android 11 and Beyond

Posted by David Winer, Kotlin Product Manager

Android blog banner

Last May at Google I/O, we announced that Android was going Kotlin first, and now over 60% of the top 1000 Android apps use Kotlin. One feature we love about Kotlin is that nullability is baked into its type system — when declaring a reference, you say upfront whether it can hold null values. In this post, we’ll look at how the Android 11 SDK does more to expose nullability information in its APIs and show how you can prepare your Kotlin code for it.

How does nullability in Kotlin work?

When writing code in Kotlin, you can use the question mark operator to indicate nullability: 

KOTLIN

var x: Int = 1
x = null // compilation error

var y: Int? = 1
y = null // okay

This aspect of Kotlin makes your code safer — if you later call a method or try to access a property on a non-null variable like x, you know you’re not risking a null pointer exception. We hear over and over again that this feature of Kotlin gives developers more peace of mind and leads to higher quality apps for end users.

How does nullability work with the Java programming language?

Not all of your (or Android’s) APIs are written in Kotlin. Fortunately, the Kotlin compiler recognizes annotations on Java programming languages methods that indicate whether they produce nullable or non-nullable values. For example: 

JAVA

public @Nullable String getCurrentName() {
   return currentName;
}

The @Nullable annotation ensures that when using the result of getCurrentName in a Kotlin file, you can’t dereference it without a null check. If you try, Android Studio will notify you of an error, and the Kotlin compiler will throw an error in your build. The opposite is true of @NonNull — it tells the Kotlin compiler to treat the method result as a non-null type, forbidding you from assigning that result to null later in your program.

The Kotlin compiler also recognizes two similar annotations, @RecentlyNullable and @RecentlyNonNull, which are the exact same as @Nullable and @NonNull, only they generate warnings instead of errors1.

Nullability in Android 11

Last month, we released the Android 11 Developer Preview, which allows you to test out the new Android 11 SDK. We upgraded a number of annotations in the SDK from @RecentlyNullable and @RecentlyNonNull to @Nullable and @NonNull (warnings to errors) and continued to annotate the SDK with more @RecentlyNullable and @RecentlyNonNull annotations on methods that didn’t have nullability information before.

What’s next

If you are writing in Kotlin, when upgrading from the Android 10 to the Android 11 SDK, you may notice that there are some new compiler warnings and that previous warnings may have been upgraded to errors. This is intended and a feature of the Kotlin compiler — these warnings tell you that you may be writing code that crashes your app at runtime (a risk you would miss entirely if you weren’t writing in Kotlin). As you encounter these warnings and errors, you can handle them by adding null checks to your code.

As we continue to make headway annotating the Android SDK, we’ll follow this same pattern — @RecentlyNullable and @RecentlyNonNull for one numbered release (e.g., Android 10), and then upgrade to @Nullable and @NonNull in the next release (e.g., Android 11). This practice will give you at least a full release cycle to update your Kotlin code and ensure you’re writing high-quality, robust code.

1. Due to rules regarding handling of annotations in Kotlin, there is currently a small set of cases where the compiler will throw an error for @Nullable references but not for @RecentlyNullable references.

Java is a trademark of Oracle and/or its affiliates.

Kotlin/Everywhere – it’s a wrap!

Posted by Florina Muntenescu, Developer Advocate (@FMuntenescu)

At Google I/O 2019 we announced that Android development will become increasingly Kotlin-first. Together with JetBrains, we also launched Kotlin/Everywhere - a global series of community led events focusing on the potential of using Kotlin everywhere; on Android, servers, web front-end and other platforms.

Kotlin/Everywhere events took place from May through December and we want to thank everyone for getting involved

?‍??‍?30,000+ developers participated in-person at Kotlin/Everywhere events

??200,000 views of live-streams and event recordings like Kotlin/Everywhere Bengaluru, Minsk, Chicago, Buenos Aires and more.

? 500+ events: from short evening meetups, half-day sessions, and full day events, to Kotlin/Everywhere tracks at larger events like DevFests, or even StudyJams that spanned several weeks.

?~30 speakers from Google and JetBrains gave ~70 talks at events around the world.

? 85+ countries: from United States to Chile, Kenya, Greece, Taiwan, New Zealand and so many more, with some countries hosting 1-2 events to some hosting dozens: Nigeria - 38, China - 27, India - 25 just to name a few.

? Many of the resources used or created for Kotlin/Everywhere by Google and JetBrains are available online:

General Kotlin:

Kotlin in Android:

Kotlin in Google Cloud Platform:

Multi-platform Kotlin:

We’re grateful for this engagement with Kotlin from communities around the world, as well as for all the organisers, speakers and attendees who made these events possible! To participate in more Kotlin events, check out JetBrains’ KotlinConf’19 Global initiative, happening through March 2020.

With all of the resources available, there’s never been a better time to adopt Kotlin… Everywhere!

Android’s commitment to Kotlin

Posted by David Winer, Kotlin Product Manager

Android and Kotlin banner

When we announced Kotlin as a supported language for Android, there was a tremendous amount of excitement among developers. Since then, there has been a steady increase in the number of developers using Kotlin. Today, we’re proud to say nearly 60% of the top 1,000 Android apps contain Kotlin code, with more and more Android developers introducing safer and more concise code using Kotlin.

During this year’s I/O, we announced that Android development will be Kotlin-first, and we’ve stood by that commitment. This is one of the reasons why Android is the gold partner for this year’s KotlinConf.

Seamless Kotlin on Android

In 2019, we focused on making programming in Kotlin on Android a seamless experience, with modern Kotlin-first APIs across the Android platform. Earlier this year, we launched a developer preview of Jetpack Compose, a modern UI toolkit for Android built using a Kotlin domain-specific language (DSL). We also incorporated coroutines into several of the flagship Jetpack libraries, including Room and Lifecycle. Finally, we brought Kotlin extensions (KTX) to even more major Google libraries, including Firebase and Play Core.

On the tooling side, we strengthened our commitment to Kotlin in Android Studio and the Android build pipeline. Significant updates to R8 (the code shrinker for Android) brought the ability to detect and handle Kotlin-specific bytecode patterns. Support was added for .kts Gradle build scripts in Android Studio, along with improved Kotlin support in Dagger. We worked closely with the JetBrains team to optimize support for the Kotlin plugin, and make the Kotlin editing experience in Android Studio fluid and fast.

Better Kotlin learning

This year we’ve also invested in quality Kotlin on Android learning content.

We released two free video learning courses in partnership with Udacity: Developing Android Apps in Kotlin and Advanced Android in Kotlin. This content was also released as the Codelab courses Android Kotlin Fundamentals and Advanced Android in Kotlin, for those who prefer text-based learning. The popular Kotlin Bootcamp for Programmers Udacity course was also published as a Codelabs course, helping provide a Kotlin foundation for non-Kotlin developers. Kotlin-based instructional Codelabs were also created for topics including Material Design, Kotlin coroutines, location, refactoring to Kotlin, billing in Kotlin, and Google Pay in Kotlin. It hasn’t been just about new content: we've updated Kotlin Codelab favorites to take advantage of important features such as coroutines.

Looking ahead

In 2020, Android development will continue to be Kotlin-first. We’ve been listening to your feedback, and will continue partnering with JetBrains to improve your experience with Kotlin.

This includes working with JetBrains to improve the Kotlin compiler over the next year. Our teams are making the compiler more extensible with a new backend, and making your builds faster with a significantly faster frontend. We’re also working with many of the largest annotation processors to make compilation faster for Kotlin code. You can also expect more Kotlin-first updates to Android, including more Jetpack libraries that make use of Kotlin features such as coroutines.

Thank you for letting us be part of your app development journey this year. We look forward to continuing the journey with you in 2020.

3 things to know about Kotlin from Android Dev Summit 2019

Last month’s #AndroidDevSummit was jam-packed with announcements and technical news...so much that we wouldn’t be surprised if you missed something. So all this month, we’ll be diving into key areas from throughout the summit so you don’t miss anything. First up, we’re spotlighting Kotlin, with the top things you should know:

#1: Kotlin momentum on Android

Kotlin is at the heart of modern Android development — and we’ve been excited to see how quickly it has won over developers around the world. At Android Dev Summit we announced that nearly 60% of the top 1000 Android apps on the Play Store now use Kotlin, and we’re seeing more developers adopt it every day. Kotlin has helpful features like null safety, data classes, coroutines, and complete interoperability with the Java programming language. We’re doubling down on Kotlin with more Kotlin-first APIs even beyond AndroidX — we just released KTX extensions, including coroutines support, for Play Core. There’s never been a better time to give Kotlin a try.

#2: Learn more: Getting started with Kotlin & diving into advanced Kotlin with coroutines

If you’re introducing Kotlin into an existing codebase, chances are that you’ll be calling the Java programming language from Kotlin and vice versa. At Android Dev Summit, developer advocates Murat Yener, Nicole Borrelli, and Wenbo Zhu took a look at how nullability, getters, setters, default parameters, exceptions, and more work across the two languages.

For those looking into more advanced Kotlin topics, we recommend watching Jose Alcérreca's and Yigit Boyar's talk that explains how coroutines and Flow can fit together with LiveData in your app's architecture and one on testing coroutines by Sean McQuillan and Manuel Vivo.

#3: Get certified in Kotlin

We announced the launch of our Associate Android Developer certification in Kotlin. Now you can prove your proficiency with modern Kotlin development on Android to your coworkers, your professional network, or even your future employer. As part of this launch, you can take this exam at a discount when using the code ADSCERT99 through January 25.

It’s especially great to hear from you, the Android community, at events like Android Dev Summit: what do you want to hear more about, and how can we help with something you’re working on. We asked you to submit your burning questions on Twitter and the livestream, and developer advocates Florina Muntenescu and Sean McQuillan answered your Kotlin and coroutines questions live during our #AskAndroid segment:

You can find the entire playlist of Android Dev Summit sessions and videos here. We’ll continue to spotlight other areas later this month, so keep an eye out and follow Android Developers on Twitter. Thanks so much for letting us be a part of this experience with you!

Java is a registered trademark of Oracle and/or its affiliates.

Kotlin named Breakout Project of the Year at OSCON

Posted by Wojtek Kaliciński, Developer Advocate, Android

Stephanie on Stage with Kotlin on screen

Stephanie Saad Cuthbertson announces support for Kotlin during the Developer Keynote at I/O 2017.

Today at OSCON (the O'Reilly Open Source Software Conference), Kotlin was awarded the Open Source Award for Breakout Project of the Year.

There is no doubt to us why Kotlin received this award: it’s a fast moving (but thoughtfully developed) programming language that lets you write better code, faster. It’s great to see Kotlin continue to receive the sort of recognition as Breakout Project of the Year, building on other awards like #1 fastest growing language on Github.

We’re big fans of Kotlin, and we’ve heard that you are too – feedback from you is in part why we announced support for the language over two years ago. This meant bundling the Kotlin plugin in Android Studio, along with promising to support Kotlin-built apps going forward.

But there was a long way to go for many teams at Google to provide a first class experience with Kotlin in the Android ecosystem, and to convince developers that Kotlin on Android is not just a fad, but is here to stay.

If you haven’t tried Kotlin yet, now is a great time to start! In fact, in the past two years, we’ve been adding a number of new features and upgrades to the Kotlin for Android experience, including:

  • Android Jetpack APIs now have first class support for Kotlin Coroutines, transforming the way we do async operations on Android. This includes Room, LiveData, ViewModels, WorkManager and more coming in the future.

  • Many Jetpack libraries have Kotlin extension libraries (KTX) to make using them even more fluent with Kotlin.
  • The compilation toolchain has received many improvements for Kotlin, including compiler enhancements, incremental annotation processing with KAPT, and Kotlin-specific R8 optimizations.
  • All of our documentation pages now contain Kotlin code snippets, so you can easily compare how our APIs work in both languages.
Kotlin code snippet
  • Most of our flagship samples are also written in Kotlin (including IOSched, Plaid, Sunflower and many more), along with any new samples that we make in the future.
  • We've added a language switcher to our API reference pages, so you can have a Kotlin view of the AndroidX library and the Android framework.
Kotlin view of the AndroidX library
  • We doubled down on providing guidance to developers and teams who want to switch to Kotlin on our developers.android.com/kotlin pages.
  • Our Developer Relations engineers are posting real life examples and guides on integrating Kotlin in your apps on our Medium publication, such as the great intro to Coroutines on Android series and many more.
  • If you prefer to learn Kotlin in person, you can join one of the many Kotlin/Everywhere events happening around the world. If you are an organizer in a local developer community, consider signing up to host your own event!
    This initiative is a cooperation between JetBrains and Google.
  • For those of you who don't have access to in-person training, we added a new, free course on Udacity for Developing Android apps in Kotlin. Our Kotlin Bootcamp for Programmers course is still available as well!
  • We have worked with many external partners to gather feedback and learn about their experiences with Kotlin, such as this case study with Square.
  • And lastly, we've enabled Kotlin as a supported language for Android app teams at Google. We're already seeing adoption in apps such as Google Home, Google Drive, Android System UI, Nest, with many more to follow.

The road to fully supporting Kotlin on Android was not always easy, but it was truly rewarding seeing Kotlin adoption among professional Android developers rise from a handful of early adopters to around 50% since the original announcement!

We were confident when we announced earlier this year at Google I/O 2019 that Android is going increasingly Kotlin-first, opening up the possibility for APIs built specifically around Kotlin and for Kotlin users, starting with the new, declarative UI toolkit - Jetpack Compose (still in early development).

We want to congratulate JetBrains, our partners through the Kotlin Foundation and creators of Kotlin, on receiving the OSCON Open Source Award today. It shows how disruptive and transformative Kotlin has been, and not just for the Android developer community, but beyond.

We know one thing: on Android, Kotlin is here to stay.

Truth 1.0: Fluent Assertions for Java and Android Tests

Software testing is important—and sometimes frustrating. The frustration can come from working on innately hard domains, like concurrency, but too often it comes from a thousand small cuts:
assertEquals("Message has been sent", getString(notification, EXTRA_BIG_TEXT));
assertTrue(
    getString(notification, EXTRA_TEXT)
        .contains("Kurt Kluever <[email protected]>"));
The two assertions above test almost the same thing, but they are structured differently. The difference in structure makes it hard to identify the difference in what's being tested.
A better way to structure these assertions is to use a fluent API:
assertThat(getString(notification, EXTRA_BIG_TEXT))
    .isEqualTo("Message has been sent");
assertThat(getString(notification, EXTRA_TEXT))
    .contains("Kurt Kluever <[email protected]>");
A fluent API naturally leads to other advantages:
  • IDE autocompletion can suggest assertions that fit the value under test, including rich operations like containsExactly(permission.SEND_SMS, permission.READ_SMS).
  • Failure messages can include the value under test and the expected result. Contrast this with the assertTrue call above, which lacks a failure message entirely.
Google's fluent assertion library for Java and Android is Truth. We're happy to announce that we've released Truth 1.0, which stabilizes our API after years of fine-tuning.



Truth started in 2011 as a Googler's personal open source project. Later, it was donated back to Google and cultivated by the Java Core Libraries team, the people who bring you Guava.
You might already be familiar with assertion libraries like Hamcrest and AssertJ, which provide similar features. We've designed Truth to have a simpler API and more readable failure messages. For example, here's a failure message from AssertJ:
java.lang.AssertionError:
Expecting:
  <[year: 2019
month: 7
day: 15
]>
to contain exactly in any order:
  <[year: 2019
month: 6
day: 30
]>
elements not found:
  <[year: 2019
month: 6
day: 30
]>
and elements not expected:
  <[year: 2019
month: 7
day: 15
]>
And here's the equivalent message from Truth:
value of:
    iterable.onlyElement()
expected:
    year: 2019
    month: 6
    day: 30

but was:
    year: 2019
    month: 7
    day: 15
For more details, read our comparison of the libraries, and try Truth for yourself.

Also, if you're developing for Android, try AndroidX Test. It includes Truth extensions that make assertions even easier to write and failure messages even clearer:
assertThat(notification).extras().string(EXTRA_BIG_TEXT)
    .isEqualTo("Message has been sent");
assertThat(notification).extras().string(EXTRA_TEXT)
    .contains("Kurt Kluever <[email protected]>");
Coming soon: Kotlin users of Truth can look forward to Kotlin-specific enhancements.
By Chris Povirk, Java Core Libraries

Kotlin Is Everywhere! Join the global event series

Posted by Posted by Florina Muntenescu & Wojtek Kaliciński, Developer Advocates, Android

Last week at Google I/O, we announced a big step: Android development will become increasingly Kotlin-first. It’s a language that many of you already love: over 50% of professional Android developers now use Kotlin, and it’s the fastest-growing language on GitHub. As part of this announcement, many new Jetpack APIs and features will be offered first in Kotlin. So if you’re starting a new project, you should try writing it in Kotlin; code written in Kotlin often means much less code for you–less code to type, test, and maintain.

To help you dive deeper into Kotlin, we’re happy to announce a new program we’re launching together with JetBrains: Kotlin/Everywhere, a series of community-driven events focussing on the potential of Kotlin on all platforms. We are aiming to help learn the essentials and best practices of using Kotlin everywhere, be it for Android, back-end, front-end and other platforms.

Join the Kotlin/Everywhere global event series between June and December 2019.

Who can attend the events?

Whether you are a developer, a speaker, a Kotlin User Group, a Google Developer Group member or any other community leader join us. Anyone interested in learning Kotlin and its ecosystem, sharing knowledge, and hosting a Kotlin-focused event is welcome to attend.

If you are a developer wanting to learn more about Kotlin, or a speaker excited to share your Kotlin experience with others, you can find events near you to join. Just go to the map on the website. More events will be added over time.

How to host your Kotlin/Everywhere event?

If you want to host an event in your city, you can begin by checking out the detailed organizers’ guide. It will help you to decide on the format and what kind of support you might need. All the necessary tips and tricks, materials, and branding assets are inside. Go ahead and submit your event on the official web page.

Besides the detailed organizers’ guide, we also provide you with resources such as content, codelabs, and guidance to help you maximize your success. You can also apply for support: we have speakers from Google/JetBrains and can help by providing funding for venue, food and drinks, swag, or other. We will also list your event on the official website.

Still have questions? Ask them at our hangout sessions for organizers on May 16 and 17.

Let us know if you want to take part! Apply at kotl.in/everywhere

New! Learn How to Build Android Apps with Android Jetpack and Kotlin

Posted by Dan Galpin

Developing Android Apps with Kotlin, developed by Google together with Udacity, is our newly-released, free, self-paced online course. You'll learn how to build Android apps using industry-standard tools and libraries in the Kotlin programming language.

Android development fundamentals are taught in the context of an architecture that provides the scaffolding for robust, maintainable applications. The course covers why and how to use Android Jetpack components such as Room for databases, Work Manager for background processing, the Navigation component, and more. You'll use popular community libraries to simplify common tasks such as Glide for image loading, Retrofit for networking, and Moshi for JSON parsing. The course teaches key Kotlin features such as coroutines to help you write your app code more quickly and concisely.

As you work through the course, you'll build fun and interesting apps, such as a Mars photo gallery, a trivia game, a sleep tracker and much more.

Two mobile phones with flow chart in between depicting the difference between an over view and details.
Three screens for Android Navigation Component Trivia screen on mobile

This course is intended for people who have programming experience and are comfortable with Kotlin basics. If you're new to the Kotlin language, we recommend taking the Udacity Kotlin Bootcamp course first.

The course is available free, online at Udacity; take it in your own time at your own pace.

Come learn how to build Android apps in Kotlin with us at https://www.udacity.com/course/ud9012.

Google I/O 2019: Empowering developers to build the best experiences on Android + Play

Posted by Chet Haase

It's great to be in our backyard again for Google I/O to connect with Android’s developers around the world. The 7,200 attendees at Shoreline Amphitheatre, millions of viewers on the livestream, and thousand of developers at local I/O Extended events across 80+ countries heard about our efforts to make the lives of developers easier. Today at Google I/O, we talked about two big themes; helping our developers become more productive and strengthening user privacy and security in the platform. Let's take a closer look at the major developer news at I/O so far:

Developer Productivity

This year, we focused on a simple idea - we want to save you time every today. By making everything you use even better.

Kotlin

Two years ago, we announced Kotlin was a supported language for Android. Our top developers loved it already, and since then, it’s amazing how fast it’s grown. Over 50% of professional Android developers now use Kotlin, it’s been one of the most-loved languages two years running on Stack Overflow, and one of the fastest-growing on GitHub in number of contributors.

Today we’re announcing another big step: Android development will become increasingly Kotlin-first. Many new Jetpack APIs and features will be offered first in Kotlin. If you’re starting a new project, you should write it in Kotlin; code written in Kotlin often mean much less code for you–less code to type, test, and maintain. And, in partnership with Jetbrains and the Kotlin Foundation, we’re continuing to invest in tooling, docs, trainings and events to make Kotlin even easier to learn and use. This includes Kotlin/Everywhere, a new, global series of events where you can learn more about the language, new Udacity courses, and more.

Android Jetpack

Last year, we announced Android Jetpack, Android’s API to accelerate Android development and make writing high-quality apps easy, with less code. Over 80% of our top 1000 apps are already using Jetpack, as we continue to simplify more every-day developer challenges. Today, we are releasing 6 new Jetpack libraries (in alpha), and bringing 5 libraries to beta quality. Here are 3 highlights:

  • CameraX - You’ve told us working effectively across the range of unique Android devices was tough. CameraX is a new open-source Android Jetpack library to make camera development easier and faster. It provides a consistent camera experience across devices, so you no longer have to maintain device specific configurations. You’ll find support for leading-edge hardware and software features like optical zoom, bokeh, HDR, and night mode on participating manufacturer devices. It works with almost 90% of devices (backwards compatible to L). There’s also an easy migration path from legacy Camera APIs and it works seamlessly with camera2 APIs. 70% of camera usage on Android comes from installed apps (not the device camera app) so we’re really excited to make camera development easier.

  • Architecture Components - We’ve made a number of additions and enhancements based on your feedback. You’ve told us concurrency on Android was hard. So we’re bringing you LiveData and Lifecycles w/ coroutines to support common one-shot asynchronous operations. With the ViewModel with SavedState module, you can eliminate boilerplate code and gain the benefits of using both ViewModel and SavedState with simple APIs to save and retrieve data right from your ViewModel. And in case you missed it, we announced stable releases of WorkManager (background processing) and Navigation (navigation between app screens) just a couple of months ago.
  • Jetpack Compose - Many of you have been asking us for a modern, reactive style UI toolkit for Android, which takes advantage of Kotlin and integrates seamlessly with the platform and all of your existing code. Today, we’re sharing the team’s work on Jetpack Compose. Jetpack Compose is designed to simplify UI development by combining a reactive programming model with the conciseness and ease-of-use of Kotlin. It’s compatible with the existing UI toolkit, so you can mix and match views with direct access to all of the Android and Jetpack APIs. It’s also fully declarative for defining UI components. And, it’s designed with Material, animations, and tools in mind from the start. Starting today we’re developing this in the open, and you can find all the code on AOSP.

Android Studio

Today we’re releasing Android Studio 3.5 to Beta. For months, the team has been exclusively focused on refining and polishing day-to-day development workflows, with Project Marble. Android Studio 3.5 includes better IDE memory management for large projects, lower typing latency, lint improvements, CPU usage optimizations, layout editor improvements, emulator improvements, build changes, as well as a complete rewrite of Instant Run, now called Apply Changes, that now reliably accelerates the ability to see your code changes on a device - plus over 400 high- priority bug fixes.

Machine Learning at Android scale

In Android Q, we’ve made significant improvements to Android’s Neural Networks API (NNAPI). First, we have increased the number of Operators supported from 38 to over 90. The vast majority of models can now be accelerated by NNAPI with no alterations. We’ve also introduced an introspection API for advanced users, allowing full control over which hardware components handle acceleration (e.g. DSP vs. NPU). And, we’ve worked closely with hardware vendors to deliver significant improvements in performance, both in latency and power consumption. Working with MediaTek, we were able to accelerate ML Kit’s face detection API by 9X on the Helio P90. Working with Qualcomm, we were able to accelerate Google’s Lens OCR on the Snapdragon 855’s AI Engine, increasing speed by 3X while also reducing power consumption by 3.7X.

Dynamic features and in-app updates

Last year we introduced the Android App Bundle to help you reduce app size and increase installs. Since then, we’ve seen over 80,000 app bundles in production, with average size savings of 20%. And today we have a number of announcements to help you reduce size and deliver updates to your users even faster. Today we’re glad to share that dynamic feature modules are moving from beta to stable. With dynamic feature modules, you can reduce your app size even more by choosing which parts of your app to deliver - based on conditions like device features, country. You can even deliver modules on-demand, instead of at install time. And today we’re also moving in-app updates from beta to stable. The ability to dynamically update apps is something you’ve been requesting for a long time. Let’s say you have a crucial bug in your app, and you need to push it out right away; you don’t want to wait until users discover an update in the Play Store. Now you can.

User privacy and security in Android Q

As a developer community, we all care about getting this right. It’s about building a platform that offers powerful capabilities for developers, while making sure that user safety and privacy is protected. We introduced Android Q Beta a few months ago with over 50 features and improvements around user privacy and security. These Q changes provide users more transparency and control.

As always, we are working hard to do everything we can for developers adopting the new release. We know you have your own features to build. That’s why, with these Q changes, we’ve worked very hard to minimize the impact for you, as well as to incorporate your feedback. We’ve given as long a notice period as possible, as well as complete and detailed technical information up front, to make it as easy as possible to adopt. We also want to thank the community for your ongoing feedback. It’s been a huge help to the team who are working hard to get this right. A great example are the Beta 3 storage changes, where your feedback helped us evolve the feature over the course of the Betas. Android has a longstanding commitment to minimizing all breaking changes. Our commitment is unchanged, and we’ll work hard to keep Android the open, flexible, and developer friendly platform we all love.

Be a part of Google I/O!

We’ve got a lot of great content in store for you over the next three days, including over 45 sessions across Android. We’re excited for you to join us in-person here at Shoreline, at an I/O Extended event, or online through the livestream. We’re constantly investing in our platform that connects developers to billions of users around the world. To the entire Android community, thank you for your continued support and feedback, and for being a part of Android.

Unfolding right now at #AndroidDevSummit!

Posted by Stephanie Cuthbertson, Director of Product Management

Today, at the Computer History Museum in Mountain View, CA, we kicked off the Android Dev Summit, taking a look back at the last 10 years of Android and then jumping into some important new features for Android developers. Here's a look at some of the things we shared!

Unfolding Android into new experiences

As early as Android 1.6, Android and our partners have contemplated different screen sizes and densities, enabling the platform to power a broad category of form factors and new experiences like Android TV, Android Auto, Wear OS and even Android apps on Chromebooks. Phone screens are an area where Android partners set the bar, introducing "phablets" when phone screens were small. Fast forward to today, when a phablet is... just a phone, a standard size users have come to love.

Now we see a Android device makers creating a new category: Foldables. Taking advantage of new flexible display technology, the screen can literally bend and fold.

There are two variants broadly speaking: two-screen devices and one-screen devices. When folded, foldables look like phones, fitting in your pocket or purse. When unfolded, their defining feature is what we call screen continuity. For example, start a video with the folded smaller screen - and later you can sit down and unfold the device to get a larger tablet-sized screen for a beautiful, immersive experience. As you unfold, the app seamlessly transfers to the bigger screen without missing a beat. We're optimizing Android for this new form factor. And, making changes to help developers everywhere take advantage of the possibilities this creates for amazing new experiences, new ways to engage and delight your users. Tune in to the Foldables session at Dev Summit this week to learn more. Expect to see Foldables coming from several Android manufacturers, including one Samsung previewed today and plans to offer next year.

Kotlin: updates to the fastest growing language

We made Kotlin a first class language on Android in 2017. This month we had over 118,000 new projects using Kotlin started in Android Studio - from those users who opt in to share metrics. That's a 10X increase from last year. It's become the fastest growing language in terms of growth of number of contributors on GitHub, and voted the #2 most loved language on Stack Overflow. In our surveys, the more developers use Kotlin, the higher their satisfaction.

Last week, JetBrains released the latest version of Kotlin, 1.3, which brings new language features, APIs, bug fixes, and performance improvements:

  • Inline classes allow you to create a type which doesn't allocate unless boxed. For the constrained devices that Android apps target, avoiding allocation while retaining type-safety is a big advantage.
  • Unsigned numbers are now part of the Kotlin standard library including UInt, UByte, and ULong. These new types are built using inline classes.
  • Multiplatform code previously written for Android or the JVM can now also target Javascript or native. This unlocks the possibility of reusing parts of your codebase on even more platforms.
  • Coroutines support is now stable. The language and library support combine to simplify how you interact with asynchronous operations and perform concurrent work–things that are essential to every Android app.

All of these new features of Kotlin 1.3 will be integrated into the Kotlin-specific APIs that we provide–a majority of which are through KTX extensions as part of Jetpack.

Android Jetpack: Navigation, Work Manager, and Slices

At Google I/O we announced Jetpack, the next generation of tools and Android APIs to accelerate Android application development. Jetpack builds on the foundations laid out by Support Library and Architecture. Already, 80% of top 1,000 apps and games are using one of the new Jetpack libraries in production.

This summer we moved AndroidX - Jetpack's evolution of the original Android Support Library - to public AOSP. This means you can see features and bug fixes implemented in real-time, and contribute to any of the AndroidX libraries. You can learn more about contributing here.

We've been working to get as much feedback and refinement as possible on two new Architecture Component libraries: Navigation and Work Manager, and we plan to move both to Beta this month. The Navigation Architecture Component offers a simplified way to implement Android's navigation principles in your application, using a single Activity. Plus, the new Navigation Editor in Android Studio creates and edits your navigation architecture. This eliminates navigation boilerplate, gives you atomic navigation operations, easier animated transitions and more. WorkManager makes it easy to perform background tasks in the most efficient manner, choosing the most appropriate solution based on the application state and device API level.

Navigation Editor

We're also excited to see Android Slices move to public Search experiments! At I/O this year we introduced Slices, a new way to bring users to your app. Slices are like a mini snippet of your app, where you can surface content and actions. You can book a flight, play a video, or call a ride. Slices is another example where we want to be open very early, but we want to take the time to get it right. We're moving into public EAP this month with Doist, Kayak and others. We'll run experiments surfacing Slices in Google search results. To learn more, there's also a session today at Dev Summit with more info and best practices.

Android Studio: focusing on productivity, build speed, quality and fundamentals

Android Studio is our official IDE for Android development. We asked where do you spend the most time? When we gather data from Android Studio's opted-in users we see that build time are getting faster with every release, sometimes as fast as 20%, but we also see build time getting slower and slower over time. So, how can both things be true? We've been digging in hard to understand.

It turns out build is a pretty complicated ecosystem. Developer choices makes a huge difference. Our developers are using a very broad (and growing) combination of OSes, custom plug-ins, annotation processors, languages. All of these can significantly affect times. In one case, a plugin some users like to add was silently slowing build speeds by up to 45%. Learning this, we realized we need build profiling and analysis tools so you can easily understand what's slowing your build down. We're also investing more in our own plugins to accelerate performance to make sure we continue to improve the performance of core build.

Android Studio 3.3 launches beta 3 today. In coming releases expect to see a strong focus on quality and fundamentals: reducing the number of crashes and hangs, optimizing memory usage, and fixing user-impacting bugs. We also announced today that we're making Android Studio an officially supported IDE on Chrome OS early next year; learn more here.

Android App Bundles and dynamic features

App sizes have grown dramatically, up 5x since 2012. But larger apps have downsides: lower install conversion rates, lower update rates, and higher uninstalls. This is why we built the Android App Bundle, the new publishing format that serves only the code and resources a user needs to run your app on their specific device; on average apps see 35% size savings compared to a universal APK. The app bundle also saves you time and effort with each release since you don't need to use incomplete solutions like multi-APK. Android Studio 3.2 brought full IDE support of app bundles, and there are now thousands of app bundles in production totaling billions of installs, including Google's apps like YouTube, Google Maps, Google Photos, and Google News.

The app bundle now supports uncompressed native libraries; with no additional developer work needed, the app bundle now makes apps using native libraries an average of 8% smaller to download and 16% smaller on disk on M+ devices.

Once you switch to the app bundle you can also start modularizing your app. With dynamic feature modules, you can load any app functionality on demand instead of at install time. You don't need to keep big features that are only used once, on every single device forever; dynamic features can be installed and uninstalled dynamically when your app requests them.

In-app Updates API

We've heard that you'd like more controls to ensure that users are running the latest and greatest version of your app. To address this, we're launching an In-app Updates API. We're testing the API with early access partners and will be launching it to all developers soon.

You'll have two options with this API; the first is a full-screen experience for critical updates when you expect the user to wait for the update to be applied immediately. The second option is a flexible update, which means the user can keep using the app while the update is downloaded. You can completely customize the update flow so it feels like part of your app.

Instant discovery

We're also making instant apps easier than ever to adopt. We recently made using web URLs optional, enabling you to take your existing play store deep link traffic and send users to your instant experience if it's available. Additionally, we've raised the instant app size limit to 10MB for the Try Now button on the Play Store and web banners to make it even easier to adopt.

In the Android Studio 3.3 beta, you can now build an instant-enabled app bundle. This means that you can now build and deploy both your Instant and installed experiences from a single Android Studio project, and include them in a single Android App Bundle. You only have to upload just ONE artifact for both instant and installed app.

As developers, your feedback has been critical in shaping these investment areas; you are part of how we work, from early ideas, to EAPs and canaries, Beta, and iterating after launch. We hope you join us for the next two days whether you're watching the 30+ sessions on the livestream, joining social, or with us in-person in Mountain View. From the team, a sincere thank you for all your thoughtful feedback and contributions. We hope you enjoy Android Dev Summit.