Kotlin Coroutines and Flow Use Cases on Android: A Playground You Can Clone

What the Kotlin Coroutines and Flow repository actually contains

This is a playground project, and the README says so directly: "You can quickly look up and play around with the different Coroutine and Flow Android implementations." Concretely, the repository ships an Android app with seventeen coroutine use cases and four Flow use cases, plus a separate playground package whose examples run directly on the JVM, without an emulator. The list is not abstract. It covers a single network request, two sequential requests, several requests concurrently, a variable amount of requests, a request with timeout, retrying requests, and timeout plus retry combined. Further down it covers Room, debugging coroutines, offloading an expensive calculation to a background thread, cooperative cancellation, spreading a calculation across several coroutines, exception handling, continuing execution after the user leaves the screen, WorkManager, and a performance analysis of dispatchers, coroutine count and yielding.

The intended reader is an Android developer who already writes Kotlin and wants to see the shape of each pattern. It is not a dependency you add to a production module, and the README never presents it as one. Every use case has its own Activity and Jetpack ViewModel, and the ViewModels hold most of the coroutine-related code. Activities observe LiveData or StateFlow from the ViewModel and render the received UiState. That separation is the point: you can open one ViewModel file and see the coroutine logic without scrolling past UI code.

How the mock API and ViewModel wiring work

The project uses retrofit and okhttp together with a MockNetworkInterceptor. According to the README, this lets you define how the API should behave, and everything is configurable: HTTP status codes, response data and delays. Each use case defines a certain behaviour of the mock API, so the retry use case can be made to fail a fixed number of times and the timeout use case can be made slow on purpose. That is the mechanism that makes the samples runnable without a backend and without flaky external calls.

The API exposes two endpoints. One returns the names of the most recent Android versions, and the other returns the features of a certain Android version. That pairing is what makes the sequential-request use case meaningful: fetch the version list, then fetch the features of the latest version. The same two endpoints also make the concurrent use case meaningful, because the second request depends on the first only in the sequential variant.

The data flow is uniform across use cases. A ViewModel starts a coroutine, calls the API through retrofit, maps the response into a UiState, and exposes that state as LiveData or StateFlow. The Activity subscribes and renders. Because the network layer is intercepted rather than real, the interesting variable is the coroutine configuration, not the HTTP client. Unit tests exist for most use cases, which is the strongest signal here: the coroutine behaviour is asserted, not just demonstrated.

Cloning the repository and running your first use case

There is no published artifact and no install command in the README. The way in is to clone the repository and open it in Android Studio, then run the app module. The README does not document a minimum Android Studio or Gradle version, so check the Gradle wrapper and the build files in the repository before assuming your local toolchain matches.

Start by cloning and entering the project:

git clone https://github.com/LukasLechnerDev/Kotlin-Coroutines-and-Flow-UseCases-on-Android.git
cd Kotlin-Coroutines-and-Flow-UseCases-on-Android

The repository root contains the usual Android layout: app/, playground/, build.gradle, settings.gradle, gradle/, gradlew, gradlew.bat, gradle.properties, documentation/ and LICENSE. The app module holds the use cases; the playground module holds JVM-only examples.

If you want to read code before running anything, the use case packages sit under app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases. For example, the first coroutine use case is the file the README links for performing a single network request:

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase1/PerformSingleNetworkRequestViewModel.kt

Open that file first. It is the smallest complete example of the ViewModel pattern the project repeats: a coroutine, a retrofit call, a UiState, and an exposed state for the Activity. The README also notes that use case 2 ships two alternative implementations, one using old-school callbacks, which is the fastest way to see what the coroutine version replaced. To run the JVM-only examples instead of the app, use the playground package; the README states those examples run directly on the JVM, so no emulator is involved.

Where this repository stops being the right tool

The samples are deliberately small, and the mock interceptor hides the failure modes that dominate real apps. A configurable status code and a configurable delay are not the same as a flaky connection, a cancelled request mid-flight, or a token refresh racing a retry. The retry and timeout use cases show the operator shape; they do not show you how to budget retries against a user-visible loading state.

There is also no versioning story. The repository has no releases, so there is nothing to pin and nothing to upgrade. If you copy a ViewModel into a production module, you own it from that moment, and future changes to the repository will not reach you. The README points to a paid online course built on these use cases, and to a set of related videos and blog posts, for the conceptual explanation. The repository itself is the code, not the curriculum.

Finally, the use case list is broad but not exhaustive. There is no Compose sample in the README's project setup description, which describes Activities listening to LiveData or StateFlow. If your app is Compose-first, you will be translating the rendering half of every example yourself. That translation is usually mechanical, but it is work the repository does not do for you.

Comparing it with the Kotlin documentation and codelabs

The official Kotlin and Android documentation explains coroutine and Flow concepts with minimal, self-contained snippets. The difference in approach is that those snippets have no app around them: no ViewModel, no Activity, no fake network layer, no test. This repository inverts that. Every concept is embedded in a running Android app, and the surrounding wiring is part of the example.

That inversion cuts both ways. It is slower to skim, because you read a ViewModel and a state class before you reach the three lines that matter. It is faster to trust, because the same three lines are exercised by a unit test and by a screen you can tap. If you want to understand what a Flow intermediate operator does in isolation, the documentation is the better first stop. If you want to see how that operator behaves when the upstream is a retrofit call inside a ViewModel that survives a configuration change, this repository answers that question in one file.

Licence, maintenance and upgrade cost

The project is licensed under Apache-2.0, and the LICENSE file sits at the repository root. Apache-2.0 permits commercial use and modification and includes an explicit patent grant, but it also requires that you preserve the licence and attribution notices in the files you reuse. Copying a ViewModel file into a closed-source app is a licensing question, not just a code question, so read the LICENSE text and your own organisation's policy rather than treating the identifier as a formality. This is not legal advice.

The repository is not archived, and the last push was on 2026-03-02. That is roughly six months before today, so treat it as a reference that is occasionally touched rather than a project with a release cadence. The absence of releases reinforces this: there is no changelog to read, no migration guide, and no version to upgrade to. Your upgrade cost is whatever it costs to re-read the files you copied and re-apply the changes you made on top. For a playground that is the correct trade-off. For a dependency it would not be.

Editorial conclusion

Adopt this repository if you learn by reading runnable code and want a side-by-side reference for sequential versus concurrent requests, retry with timeout, cooperative cancellation, or exposing a Flow from a ViewModel. Skip it if you need a published artifact to depend on: it is an app, not a library, and the README points to a paid course for the full walkthrough. Before trusting any single use case, open its package under app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases, check whether that use case has a corresponding unit test, and read the MockNetworkInterceptor configuration to see which delay and status code the sample was built around.

Frequently asked questions

Official sources

1. Issues
2. License: Apache-2.0
3. LukasLechnerDev/Kotlin-Coroutines-and-Flow-UseCases-on-Android on GitHub
4. README