A robotic rover is to be landed by NASA on a plateau on Mars. This plateau, which is curiously rectangular, must be navigated by the rovers so that their on-board cameras can get a complete view of the surrounding terrain to send back to Earth.
This is a sample project implementing logic to download available instruction sets, create custom ones and processing them to show the user the result of the applied instructions on the Mars Rover. The app is developed in Kotlin with full Jetpack Compose ui and MVVM architecture.
To follow clean code principles and avoid dependencies being used where they shouldn't, the app has been divided in 4 distinct modules:
- App: Includes only the main manifest of the app, the MainActivity class and logic to set up dependency injection.
- Ui: The ui module is an Android library module that includes all the logic related to the visual side of the app. This includes the App entrypoint into the compose world, the app screens, navigation logic, viewModels and several related utilities.
- Domain: This pure Kotlin module has all the core business logic to request data to the main repository and process it to a format that the app can show to the user.
- Data: This pure Kotlin module contains the data source of the app and has logic related to handling network connections.
This different modules have dependencies on each other when needed, but always trying to avoid oversharing information. The dependency graph between them can be seen here:
The main features found in the app are:
- Instruction selector: Shows a list of available instructions for the user to choose. Also has access to the custom instructions builder.
- Instruction builder: From the instruction selector, you can access the instructions builder screen. Here you can create your own instructions by configuring all params.
- Instruction viewer: From the instruction selector or the instruction builder you can navigate to the instruction viewer. This screen will process your instructions and show you the result of the movements or an error if the instructions con not be recovered or processed.
| Library | Description |
|---|---|
| Retrofit | Abstracts away HTTP connections and working with REST APIs. |
| Kotlinx serialization | This plugin automatically creates serializers and deserializers for the json format. |
| Arrow | Adds functional programming helpers to manage business logic. |
| Koin | Lightweight dependency injection framework easy to setup and work with. |
| Jetpack Compose | The new official UI framework for Android. |
| Material 3 | The new material components specification, with new guidelines for colors, shapes and fonts. |
| Navigation compose | The official way of handling navigation in full Compose apps. |
| Compose Lint checks | A group of lint checks that help creating composable functions without mistakes. |
Important
Android Studio Stable (Hedgehog 2023.1.1) doesn't include yet support for rendering Compose layout previews when you target API 34. Because of this issue, most of the previews will fail to render in this Android Studio version until Google releases the next IDE versions.
As small as this app is, it showcases a number of best practices considered the standard for Android development currently. Some of these practices are:
- Full Kotlin development: The app is written 100% in Kotlin, resulting in code more concise and expressive.
- MVVM architecture: This architecture is recommended by Google as it offers a clean separation of concerns between your ui and business logic.
- Kotlin's coroutines for async programming: Coroutines simplify handling async or concurrent operations and make the code more readable and testable.
- Follows Material Design guidelines: Using standard design principles makes easier for the user to understand how to navigate your app and makes sure it is accessible for most people.
- Dependency injection: Dependency injection frameworks help separate concerns, reuse instances of components and makes it easy to replace components for testing.
- Testing: Test help catch code issues early and improve its maintainability and reusability. In this app, 95% of the business logic is unit tested and 60% of the ui logic is covered by ui tests.