Now in Android App - Kotlin Multiplatform Edition

Welcome to the Kotlin Multiplatform edition of Now in Android, a community-driven initiative to bring the best of Android development content to developers across platforms. This repository is a branch of the original Now in Android project, reimagined and re-engineered using Kotlin Multiplatform technology to make the project truly cross-platform.

Learn how this app was designed and built in the design case study, architecture learning journey and modularization learning journey.

This is the repository for the Now in Android app.

Now in Android is a multiplatform app built with Kotlin and Compose Multiplatform. It follows Android and Kotlin Multiplatform development best practices and is intended to be a useful reference for developers. As a running app, it's intended to help developers keep up-to-date with the world of Android development by providing regular news updates.

The app is currently in development. The Android release application uses the com.google.samples.apps.nowinandroid package that is available on the Play Store.

Project Status

This project is a work in progress 🚧. Please note that the CI may not function normally at this time.

Changes to Convention Plugins

Numerous changes have been made on top of the original Now in Android app. We've replaced several third-party libraries with ones that support Kotlin Multiplatform. Here are some conventions I've documented:

• KmpLibraryConventionPlugin: Convention for Kotlin Multiplatform Libraries
• KotlinInjectConventionPlugin: Convention for using kotlin-inject as a replacement for Hilt
• SqlDelightConventionPlugin: Convention for using SQLDelight for storing local data, replacing Android Room.

Changes to Modules

To transform the main app into a Compose Multiplatform app capable of running on multiple platforms, all modules need to be converted to Kotlin Multiplatform libraries. The project structure of these modules should be adjusted to align with Kotlin Multiplatform source sets.

As Firebase Analytics does not yet support Kotlin Multiplatform, the implementation in :core:analytics has been removed, leaving an empty implementation in its place.

Status for modules

Module	Progress	Desktop supported	Android supported	iOS supported	Web supported
app	In progress	✅	✅	✅	✅
app-nia-catalog	Done	✅	✅	✅	✅
:core:analytics	Done	✅	✅️	✅	✅
:core:common	Done	✅	✅	✅	✅
:core:data	Done	✅	✅️	✅	✅
:core:data-test	Done	✅	✅️	✅	✅
:core:database	Done	✅	✅️	✅	✅
:core:datastore	Done	✅	✅️	✅	✅
:core:datastore-proto	Done	✅	✅️	✅	✅
:core:datastore-test	Removed	❌	❌	❌	❌
:core:designsystem	Done	✅	✅	✅	✅
:core:domain	Done	✅	✅️	✅	✅
:core:model	Done	✅	✅️	✅	✅
:core:network	Done	✅	✅️	✅	✅
:core:notification	Done	✅	✅️	✅	✅
:core:screenshot-testing	Done	✅	✅️	✅	❌
:core:testing	Done	✅	✅️	✅	✅
:core:ui	Done	✅	✅️	✅	✅
:feature:bookmarks	Done	✅	✅️	✅	✅
:feature:foryou	Done	✅	✅️	✅	✅
:feature:interests	Done	✅	✅️	✅	✅
:feature:search	Done	✅	✅️	✅	✅
:feature:settings	Done	✅	✅️	✅	✅
:feature:topic	Done	✅	✅️	✅	✅
lint	Done	N/A	✅	N/A	N/A
:sync:sync-test	Done	✅	✅	✅	✅
:sync:work	Done	✅	✅️	✅	✅
ui-test-manifest	Removed	❌	❌	❌	❌

✅: Functioning properly
❔: Not yet tested, but expected to work
✔️: Successfully compiled
❌: Not functioning, requires further attention
🚧: Work in progress

Running the Project

This project supports running on Android, iOS, Desktop (JVM), macOS, and Web (WASM). Both the app and app-nia-catalog modules support all platforms.

Running on Android

1. Create an Android Virtual Device (AVD).
2. Select app-android from the list of run configurations.
3. Choose your AVD and click "Run".

To run the design system catalog on Android, select app-nia-catalog-android.

Running on Desktop

To run the desktop application, follow these steps:

1. Navigate to Run | Edit Configurations.
2. Click the plus button and select "Gradle" from the dropdown menu.
3. In the "Tasks and arguments" field, paste the following command:

   desktopRun -DmainClass=MainKt --quiet
   

4. Choose the Gradle project: nowinandroid:app.
5. Click "OK" to save the configuration.

Running on Web (WASM)

To run the application in a web browser using WebAssembly:

./gradlew :app:wasmJsBrowserDevelopmentRun

For the design system catalog:

./gradlew :app-nia-catalog:wasmJsBrowserDevelopmentRun

Running on iOS

For instructions on running the application on iOS, please refer to this guide.

Features

Now in Android displays content from the Now in Android series. Users can browse for links to recent videos, articles and other content. Users can also follow topics they are interested in, and be notified when new content is published which matches interests they are following.

Screenshots

Development Environment

Now in Android uses the Gradle build system and can be imported directly into Android Studio (make sure you are using the latest stable version available here).

Change the run configuration to app-android.

The Android app host can be built and run with the debug and release build variants.

Once you're up and running, you can refer to the learning journeys below to get a better understanding of which libraries and tools are being used, the reasoning behind the approaches to UI, testing, architecture and more, and how all of these different pieces of the project fit together to create a complete app.

Architecture

The Now in Android app follows the official architecture guidance and is described in detail in the architecture learning journey.

Modularization

The Now in Android app has been fully modularized and you can find the detailed guidance and description of the modularization strategy used in modularization learning journey.

Build

The Android app host contains the usual debug and release build variants. There are no product flavors. The shared app module owns the Compose Multiplatform app code, while app-android packages that shared app as an Android application.

The benchmarks module is used to test startup performance and generate a baseline profile (see below for more information).

app-nia-catalog is a shared standalone app that displays the list of components that are stylized for Now in Android. app-nia-catalog-android packages that catalog for Android.

For normal Android development use the debug variant of app-android. For UI performance testing use the release app package through the benchmarks module.

Testing

To facilitate testing of components, Now in Android uses dependency injection with Koin.

Most data layer components are defined as interfaces. Then, concrete implementations (with various dependencies) are bound to provide those interfaces to other components in the app. In tests, Now in Android notably does not use any mocking libraries. Instead, production implementations can be replaced with test doubles through the app's dependency injection graph or via manual constructor injection for ViewModel tests.

These test doubles implement the same interface as the production implementations and generally provide a simplified (but still realistic) implementation with additional testing hooks. This results in less brittle tests that may exercise more production code, instead of just verifying specific calls against mocks.

Examples:

• In instrumentation tests, a temporary folder is used to store the user's preferences, which is wiped after each test. This allows using the real DataStore and exercising all related code, instead of mocking the flow of data updates.

• There are Test implementations of each repository, which implement the normal, full repository interface and also provide test-only hooks. ViewModel tests use these Test repositories, and thus can use the test-only hooks to manipulate the state of the Test repository and verify the resulting behavior, instead of checking that specific repository methods were called.

To run the tests execute the following gradle tasks:

• testDebugUnitTest runs Android unit tests for the debug variant.
• testAndroidHostTest runs Android host-side KMP tests, including Android Roborazzi tests, on CI.
• connectedDebugAndroidTest runs instrumented tests against the debug variant.

Note

Screenshot baselines are generated on CI. Prefer spotlessCheck, testDebugUnitTest, :lint:test, and the targeted platform compile tasks locally before opening a PR.

Screenshot tests

A screenshot test takes a screenshot of a screen or a UI component within the app, and compares it with a previously recorded screenshot which is known to be rendered correctly.

For example, Now in Android has screenshot tests to verify that navigation and feature screens are displayed correctly on different screen sizes.

Now In Android uses Roborazzi to run screenshot tests of certain screens and UI components. When working with screenshot tests the following gradle tasks are useful:

• verifyRoborazziAndroidHostTest runs Android host screenshot tests, verifying screenshots against the known correct screenshots.
• recordRoborazziAndroidHostTest records new Android host "known correct" screenshots. Use this command when you have made changes to the UI and manually verified that they are rendered correctly.
• compareRoborazziAndroidHostTest creates comparison images between failed tests and known correct images.

Note

Note on failing screenshot tests
The known correct screenshots stored in this repository are recorded on CI using Linux. Other platforms may (and probably will) generate slightly different images, making the screenshot tests fail. When working on a non-Linux platform, a workaround to this is to run recordRoborazziAndroidHostTest on the main branch before starting work. After making changes, verifyRoborazziAndroidHostTest will identify only legitimate changes.

For more information about screenshot testing check out this talk.

UI

The app was designed using Material 3 guidelines. Learn more about the design process and obtain the design files in the Now in Android Material 3 Case Study (design assets also available as a PDF).

The Screens and UI elements are built entirely using Jetpack Compose.

The app has two themes:

• Dynamic color - uses colors based on the user's current color theme (if supported)
• Default theme - uses predefined colors when dynamic color is not supported

Each theme also supports dark mode.

The app uses adaptive layouts to support different screen sizes.

Find out more about the UI architecture here.

Performance

Benchmarks

Find all tests written using Macrobenchmark in the benchmarks module. This module also contains the test to generate the Baseline profile.

Baseline profiles

The baseline profile for this app is located at app/src/main/baseline-prof.txt. It contains rules that enable AOT compilation of the critical user path taken during app launch. For more information on baseline profiles, read this document.

Note

The baseline profile needs to be re-generated for release builds that touch code which changes app startup.

To generate the baseline profile, run the baseline profile task from the benchmarks module on an AOSP Android Emulator. Then copy the resulting baseline profile from the emulator to app/src/main/baseline-prof.txt.

Compose compiler metrics

Run the following command to get and analyze compose compiler metrics:

./gradlew :app-android:assembleRelease -PenableComposeCompilerMetrics=true -PenableComposeCompilerReports=true

The reports files will be added to build/compose-reports. The metrics files will also be added to build/compose-metrics.

For more information on Compose compiler metrics, see this blog post.

License

Now in Android is distributed under the terms of the Apache License (Version 2.0). See the license for more information.