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204 lines
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<a href="https://play.google.com/store/apps/details?id=com.google.samples.apps.nowinandroid"><img src="https://play.google.com/intl/en_us/badges/static/images/badges/en_badge_web_generic.png" height="70"></a>
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Now in Android App
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==================
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**Learn how this app was designed and built in the [design case study](https://goo.gle/nia-figma), [architecture learning journey](docs/ArchitectureLearningJourney.md) and [modularization learning journey](docs/ModularizationLearningJourney.md).**
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This is the repository for the [Now in Android](https://developer.android.com/series/now-in-android)
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app. It is a **work in progress** 🚧.
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**Now in Android** is a fully functional Android app built entirely with Kotlin and Jetpack Compose. It
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follows Android design and development best practices and is intended to be a useful reference
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for developers. As a running app, it's intended to help developers keep up-to-date with the world
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of Android development by providing regular news updates.
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The app is currently in development. The `prodRelease` variant is [available on the Play Store](https://play.google.com/store/apps/details?id=com.google.samples.apps.nowinandroid).
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# Features
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**Now in Android** displays content from the
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[Now in Android](https://developer.android.com/series/now-in-android) series. Users can browse for
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links to recent videos, articles and other content. Users can also follow topics they are interested
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in, and be notified when new content is published which matches interests they are following.
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## Screenshots
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# Development Environment
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**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](https://developer.android.com/studio)).
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Change the run configuration to `app`.
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The `demoDebug` and `demoRelease` build variants can be built and run (the `prod` variants use a backend server which is not currently publicly available).
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Once you're up and running, you can refer to the learning journeys below to get a better
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understanding of which libraries and tools are being used, the reasoning behind the approaches to
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UI, testing, architecture and more, and how all of these different pieces of the project fit
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together to create a complete app.
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# Architecture
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The **Now in Android** app follows the
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[official architecture guidance](https://developer.android.com/topic/architecture)
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and is described in detail in the
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[architecture learning journey](docs/ArchitectureLearningJourney.md).
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# Modularization
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The **Now in Android** app has been fully modularized and you can find the detailed guidance and
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description of the modularization strategy used in
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[modularization learning journey](docs/ModularizationLearningJourney.md).
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# Build
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The app contains the usual `debug` and `release` build variants.
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In addition, the `benchmark` variant of `app` is used to test startup performance and generate a
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baseline profile (see below for more information).
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`app-nia-catalog` is a standalone app that displays the list of components that are stylized for
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**Now in Android**.
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The app also uses
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[product flavors](https://developer.android.com/studio/build/build-variants#product-flavors) to
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control where content for the app should be loaded from.
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The `demo` flavor uses static local data to allow immediate building and exploring of the UI.
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The `prod` flavor makes real network calls to a backend server, providing up-to-date content. At
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this time, there is not a public backend available.
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For normal development use the `demoDebug` variant. For UI performance testing use the
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`demoRelease` variant.
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# Testing
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To facilitate testing of components, **Now in Android** uses dependency injection with
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[Hilt](https://developer.android.com/training/dependency-injection/hilt-android).
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Most data layer components are defined as interfaces.
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Then, concrete implementations (with various dependencies) are bound to provide those interfaces to
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other components in the app.
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In tests, **Now in Android** notably does _not_ use any mocking libraries.
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Instead, the production implementations can be replaced with test doubles using Hilt's testing APIs
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(or via manual constructor injection for `ViewModel` tests).
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These test doubles implement the same interface as the production implementations and generally
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provide a simplified (but still realistic) implementation with additional testing hooks.
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This results in less brittle tests that may exercise more production code, instead of just verifying
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specific calls against mocks.
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Examples:
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- In instrumentation tests, a temporary folder is used to store the user's preferences, which is
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wiped after each test.
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This allows using the real `DataStore` and exercising all related code, instead of mocking the
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flow of data updates.
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- There are `Test` implementations of each repository, which implement the normal, full repository
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interface and also provide test-only hooks.
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`ViewModel` tests use these `Test` repositories, and thus can use the test-only hooks to
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manipulate the state of the `Test` repository and verify the resulting behavior, instead of
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checking that specific repository methods were called.
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To run the tests execute the following gradle tasks:
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- `testDemoDebug` run all local tests against the `demoDebug` variant.
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- `connectedDemoDebugAndroidTest` run all instrumented tests against the `demoDebug` variant.
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**Note:** You should not run `./gradlew test` or `./gradlew connectedAndroidTest` as this will execute
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tests against _all_ build variants which is both unecessary and will result in failures as only the
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`demoDebug` variant is supported. No other variants have any tests (although this might change in future).
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## Screenshot tests
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A screenshot test takes a screenshot of a screen or a UI component within the app, and compares it
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with a previously recorded screenshot which is known to be rendered correctly.
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For example, Now in Android has [screenshot tests](https://github.com/android/nowinandroid/blob/main/app/src/testDemoDebug/kotlin/com/google/samples/apps/nowinandroid/ui/NiaAppScreenSizesScreenshotTests.kt)
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to verify that the navigation is displayed correctly on different screen sizes
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([known correct screenshots](https://github.com/android/nowinandroid/tree/main/app/src/testDemoDebug/screenshots)).
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Now In Android uses [Roborazzi](https://github.com/takahirom/roborazzi) to run screenshot tests
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of certain screens and UI components. When working with screenshot tests the following gradle tasks are useful:
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- `verifyRoborazziDemoDebug` run all screenshot tests, verifying the screenshots against the known
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correct screenshots.
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- `recordRoborazziDemoDebug` record new "known correct" screenshots. Use this command when you have
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made changes to the UI and manually verified that they are rendered correctly. Screenshots will be
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stored in `modulename/src/test/screenshots`.
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- `compareRoborazziDemoDebug` create comparison images between failed tests and the known correct
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images. These can also be found in `modulename/src/test/screenshots`.
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**Note:** The known correct screenshots stored in this repository are recorded on CI using Linux. Other
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platforms may (and probably will) generate slightly different images, making the screenshot tests fail.
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When working on a non-Linux platform, a workaround to this is to run `recordRoborazziDemoDebug` on the
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`main` branch before starting work. After making changes, `verifyRoborazziDemoDebug` will identify only
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legitimate changes.
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For more information about screenshot testing
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[check out this talk](https://www.droidcon.com/2023/11/15/easy-screenshot-testing-with-compose/).
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# UI
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The app was designed using [Material 3 guidelines](https://m3.material.io/). Learn more about the design process and
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obtain the design files in the [Now in Android Material 3 Case Study](https://goo.gle/nia-figma) (design assets [also available as a PDF](docs/Now-In-Android-Design-File.pdf)).
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The Screens and UI elements are built entirely using [Jetpack Compose](https://developer.android.com/jetpack/compose).
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The app has two themes:
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- Dynamic color - uses colors based on the [user's current color theme](https://material.io/blog/announcing-material-you) (if supported)
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- Default theme - uses predefined colors when dynamic color is not supported
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Each theme also supports dark mode.
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The app uses adaptive layouts to
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[support different screen sizes](https://developer.android.com/guide/topics/large-screens/support-different-screen-sizes).
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Find out more about the [UI architecture here](docs/ArchitectureLearningJourney.md#ui-layer).
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# Performance
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## Benchmarks
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Find all tests written using [`Macrobenchmark`](https://developer.android.com/topic/performance/benchmarking/macrobenchmark-overview)
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in the `benchmarks` module. This module also contains the test to generate the Baseline profile.
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## Baseline profiles
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The baseline profile for this app is located at [`app/src/main/baseline-prof.txt`](app/src/main/baseline-prof.txt).
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It contains rules that enable AOT compilation of the critical user path taken during app launch.
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For more information on baseline profiles, read [this document](https://developer.android.com/studio/profile/baselineprofiles).
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> [!NOTE]
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> The baseline profile needs to be re-generated for release builds that touch code which changes app startup.
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To generate the baseline profile, select the `benchmark` build variant and run the
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`BaselineProfileGenerator` benchmark test on an AOSP Android Emulator.
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Then copy the resulting baseline profile from the emulator to [`app/src/main/baseline-prof.txt`](app/src/main/baseline-prof.txt).
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## Compose compiler metrics
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Run the following command to get and analyse compose compiler metrics:
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```bash
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./gradlew assembleRelease -PenableComposeCompilerMetrics=true -PenableComposeCompilerReports=true
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```
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The reports files will be added to [build/compose-reports](build/compose-reports). The metrics files will also be
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added to [build/compose-metrics](build/compose-metrics).
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For more information on Compose compiler metrics, see [this blog post](https://medium.com/androiddevelopers/jetpack-compose-stability-explained-79c10db270c8).
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# License
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**Now in Android** is distributed under the terms of the Apache License (Version 2.0). See the
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[license](LICENSE) for more information.
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