GIF Source: Bitlue_DemoVideo

Bitlue is an app where you can check the Bitcoin's current market price value (Bitcoin + value = Bitlue) and its records.

The price values were requested from Blockchain API.

In the last 3 days, I developed this nice app using the following tech stack:

• Kotlin
• MVVM architecture
• Jetpack Architecture Components: ViewModel, Navigation...
• Hilt - Dependency injection
• Coroutines + Flow
• Material Design Components
• Retrofit
• MPAndroidChart

In this section I will explain the MVVM architecture followed and all its different parts:

First of all, the UI is strongly supported by a solid design system supported by the Material Design. Thanks to that, create a consistent design and a dark theme in parallel were able to achieve.

This project follows the Single-Activity pattern, where MainActivity.kt its the base Activity. From it we can differentiate 2 Fragments:

• BitcoinValueFragment.kt: you can check the current price value of the Bitcoin and a chart of its records.

• FilterSettingsDialogFragment.kt: filters the chart values between 2 filters: time range(enum class FilterTimeRange) and rolling average(enum class FilterRollingAverage).

Both Fragments are consuming the same ViewModel: MainViewModel.kt. The FilterSettingsDialogFragment was highly dependent on the BitcoinValueFragment and vice-versa, so I thought it make sense to share the same ViewModel.

Apart from the use of LiveData to display some reactive data, the other part of the communication between the Fragments and the ViewModel is made by the unidirectional event-state data flow pattern. This pattern allows to separate the UI events (of Fragments) from the UI states (requested by the MainViewModel). It highly achieves to decouple the UI logic and the business logic and it organizes them in a better way.

The chart in the BitcoinValueFragment is powered by MPAndroidChart. In addition, a custom view called BitcoinValueChart was created to wrap all needed setup code for the final chart.

It was built a BitcoinRepository.kt which consumes from BlockchainRemoteDataSource.kt that provides with all Bitcoin information from BlockchainAPI.kt using Retrofit.

A separate interface DataSource was created because it was planned to create a LocalDataSource to be able to save some values locally in a Room database. Unfortunately this was not possible to accomplish in the given time.

In order to keep the UI model (domain model) separate from any DTO model, I created 2 different types of models:

• BitcoinRecordInfo & BitcoinValue as domain models. BitcoinRecordInfo to display some general info in the BitcoinValueFragment, and BitcoinValue to display values in the chart.
• BlockchainResponseDTO & BitcoinValueDTO as the remote source models. Used to retrieve data from the BlockchainAPI.

Both of them make use of their own mappers which are used in the Repository layer to map the DTOs to the domain model when retrieving the Bitcoin info.

Find attach to the project folder a Debug APK. In addition, a few screenshots and a demo video can be found also in the project folder:

• Bitlue_DemoVideo.mp4
• Bitlue_LightTheme_HomeScreen.png
• Bitlue_LightTheme_FilterSettings.png
• Bitlue_DarkTheme_HomeScreen.png
• Bitlue_DarkTheme_FilterSettings.png

I hope you could enjoy my work and could appreciate the effort in it.

Don't hesitate to ask any question if you have.