Source: What’s New with Android Jetpack from Android Developer
Last year, we launched Android Jetpack, a collection of software components designed to accelerate Android development and make writing high-quality apps easier. Jetpack was built with you in mind — to take the hardest, most common developer problems on Android and make your lives easier.
Jetpack has seen incredible adoption and momentum. Today, 80% of the top 1,000 apps in the Play store are using Jetpack. We’ve also heard feedback from so many of you across our early access developer programs and user studies, as well as Reddit, Stack Overflow, and Slack, that has helped shape these APIs. Very humbly, thank you.
Today, we are excited to share with you 11 Jetpack libraries that can be used in development now and an early-development, open-source project called Jetpack Compose to simplify UI development.
We’ve heard from many of you that developing camera apps or integrating camera functionality within your existing apps is hard. With the new CameraX library, we want to enable you to create great camera-driven experiences in your application without worrying about the underlying device behavior. This API is backwards compatible to Android 5.0 (API 21) or higher, ensuring that the same code works on most devices in the market. While it leverages the capabilities of camera2, it uses a simpler, use case-based approach that is lifecycle-aware eliminating significant amount of boilerplate code vs camera2. Finally, it enables you to access the same functionality as the native camera app on supported devices. These optional Extensions enable features like Portrait, Night, HDR, and Beauty.
LiveData and Lifecycles w/ coroutines
We heard you loud and clear and agree that LiveData must support your common one-shot asynchronous operations. With Lifecycle & LiveData KTX, you can do so with Kotlin coroutines that are lifecycle-aware. Kotlin coroutines have been well received by the developer community for how they simplify the way concurrency is handled within Android apps. We want to simplify it even further and enabling you to use them safely by offering coroutine scopes tied to lifecycles, coroutine dispatchers that are lifecycle-aware, and support for simple asynchronous chains with the new liveData builder.
The Benchmark library provides you a quick way to benchmark your app code, whether it is written in Kotlin, the Java programming language or native code. We use this library to continuously benchmark Jetpack libraries we release to ensure we do not introduce any latency into your code. You can now do the same right within your development environment in Android Studio, easily measuring database queries, view inflation, or a RecyclerView scroll. The library takes care of what is needed to provide reliable and consistent results like handling warm-up periods, removing outliers, and locking CPU clocks.
To maximize security of an application’s data at-rest, the new Security library implements security best practices for you. It provides strong security that balances encryption with performance for consumer apps like banking and chat. It also provides a maximum level of security for apps that require a hardware-backed keystore with user presence and simplifies many operations including key generation and validation.
ViewModel with SavedState
ViewModel provided you an easy way to save your UI data in the event of a configuration change. It did not save your app state in the event of process death, and many of you have been relying on SavedInstanceState alongside ViewModel. 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.
ViewPager2, the next generation of ViewPager, is now based on RecyclerView and supports vertical scrolling and RTL (Right-to-Left) layouts. It also provides a much easier way to listen for page data changes with
ConstraintLayout 2.0 brings up new optimizations, and new way of customizing layouts, with the addition of helper classes. As part of ConstraintLayout 2.0, MotionLayout provides an easy way to manage motion and widget animation in your applications. You can easily describe transitions between layouts and animation of properties. MotionLayout is fully declarative in XML, allowing you to describe even complex transitions without requiring any code.
Users are accustomed to biometric credentials on their phones, but if your app requires a biometric login, it is important to make sure that users are provided a consistent and safe way to enter their credentials. The Biometrics library provides a simple system prompt giving the user a trustworthy experience.
With the Jetpack Enterprise library, your managed enterprise apps can send feedback back to Enterprise Mobility Management providers in the form of keyed app states, while taking advantage of backwards compatibility with managed configurations.
Android for Cars
With the Android for Cars libraries, you can provide your users a driver-optimized version of your app that will be automatically installed onto the vehicle’s infotainment system in vehicles equipped with the Android Automotive OS. It also allows your apps to work with the Android Auto app, providing the driver-optimized version anytime on their device.
Today, we open-sourced an early preview of Jetpack Compose, a new unbundled toolkit designed to simplify UI development by combining a reactive programming model with the conciseness and ease-of-use of Kotlin. We have always done our best work when we did it with you – our developer community. That’s why we decided to develop Jetpack Compose in the open, starting today.
In that vein, we took a step back and chatted with many of you. We heard strong feedback from developers that they like the modern, reactive APIs that Flutter, React Native, Litho, and Vue.js represent. We also heard that developers love Kotlin, with over 53% of professional Android developers using it and with 20% higher language satisfaction ratings than the Java programming language. Kotlin has become the fastest-growing language in terms of number of contributors on GitHub.
So, we decided to invest in the reactive approach to declarative programming and create an easier way to build UIs with Kotlin.
We are building Compose with a few core principles:
A Compose application is made up of composable functions that transform application data into a UI hierarchy. A function is all you need to create a new UI component. To create a composable function just add the @Composable annotation to the function name. Under the hood, Compose uses a custom Kotlin compiler plug-in so when the underlying data changes, the composable functions can be re-invoked to generate an updated UI hierarchy. The simple example below prints a string to the screen.
We know that adopting any new framework is a big change for existing projects and codebases, which is why we’ve designed Compose like all of Jetpack — with individual components that you can adopt at your own pace and are compatible with existing views.
If you want to learn more about Jetpack Compose or download its source to try it for yourself, check out http://d.android.com/jetpackcompose
We’d love to hear from you as we iterate on this exciting future together. Send us feedback by posting comments below, and please file any bugs you run into on AOSP or directly through the feedback buttons in the Android Studio Jetpack Compose build in AOSP. Since this is an early preview, we do not recommend trying this on any production projects.