This is an API sample to showcase the following parts of the Play Core library in Kotlin:

• On-demand Play Feature Delivery
• In-app Updates
• In-app Reviews
  • For troubleshooting why the review dialog is not showing up please consult Testing in-app reviews

The sample app is a "flashlight" app that lets you light up the screen with a yellow background. You can also pick a color for the flashlight from a photo, by using the camera.

The photo color picker is an on-demand module, and will be installed only after the user clicks on the floating action button.

In-app reviews are triggered only after the user selects a color from a photo, and then turns the flashlight off.

Pay attention to the requirements for testing the in-app reviews dialog as described here. Notably, the user must have downloaded the app from Play Store, which means you need to change the sample's applicationId and upload it to Play Console, and the user must not have reviewed the app previously.

The app is designed to show how to use the respective Play Core APIs using by using the Play Core KTX artifact, which provides coroutine (suspend and Flow) versions of all Play Core APIs.

Important parts of the code to look at are:

• MainFragment - contains the main screen of the application with the flashlight on/off button, and observes states and events coming from the various ViewModels described below to handle the UI for on-demand feature installation, in-app updates and in-app reviews
• InstallViewModel - handles installation and exposes installation state of on-demand feature modules. Currently the app has one such feature module: features/picture, which is needed for extracting a color from a photo
• UpdateViewModel - exposes the availability and state of an in-app update
• ReviewViewModel - takes care of pre-warming the review request, which is needed to show the UI review quickly when requested. This ViewModel is scoped to the Activity and is shared between both Fragments in order to start pre-warming the request when a color is chosen in PaletteFragment
• PaletteFragment - this fragment is in an on-demand dynamic feature module (features/picure) and takes care of requesting the camera to take a photo and extracting the colors from it. The color is stored in the ColorViewModel which is scoped to the Activity and is shared between both Fragments

To test the on-demand feature module installation locally, you can use the following Gradle task:

./gradlew debugInstallApksForLocalTesting

This will use bundletool to build an APK set in local testing mode, and install the base app to a connected device or emulator, while also pushing all split APKs into the device's storage.

At runtime, based on the local testing meta-data set in the Manifest by bundletool, SplitInstallManager will load dynamic feature modules from local storage instead of connecting to the Play Store.

If you wish to test real behavior, including in-app updates and in-app reviews, you can use internal app sharing on the Play Store.

The task described above comes from a custom Gradle plugin that can be found in the buildSrc directory. It uses the new Android Gradle plugin Variant API to read the final location of the produced Android App Bundle file, then extracts APKs from it and installs them on the device.

While not the focus of this sample, if you're interested in learning more about custom Gradle tasks and using the Variant API, you're encouraged to look at the code or copy it to your project, however please note that this plugin is not production-ready and will not be supported.

You can also check out the Android Gradle recipes repository to see more examples of the Variant API in action.

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