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Tech Stack

For this Android application, we decided to use Kotlin as the main language.

Summary

  • Language: Kotlin
  • Architecture: Model View ViewModel (MVVM)
  • Libraries: Retrofit, RxJava, ViewModel, LiveData, DataBinding

Why use Kotlin?#

Since this was a new project we decided to experiment a new tech stack for Android. Since Kotlin was declared as a first class programming language for Android, it started becoming much more popular. You can check a comparison from Kotlin to Java programming language.

If you're new with kotlin there are many resources from where you can learn more:

  • Try Kotlin
  • Kotlin Koans - This tutorial walks you through a series of exercises to get familiar with Kotlin
  • Kotlin for Android Developers course on Udacity
  • ... There is a lot of information regarding Kotlin spread across blog posts, video tutorials, open sourced projects... You can always use Google about this and find awesome resources!

Why use a ~native approach instead of using a hybrid solution for this?#

We considered using flutter as a solution for the mobile application but since the first student working on this project had experience with Android development and did not have any experience with the flutter framework, so the team ultimately decided to build the first version of the app for Android platform. Also, the team was short on time to build the mobile application for Google Summer of Code.

Nonetheless, the community had a brief discussion about this on Systers Open Source Slack. The outcome of this was that using flutter was a good way to develop and iOS and Android version of the application at the same time and that this could be done in the future, for example on next open source programs (e.g.: Google Summer of Code).

Why use MVVM architecture?#

What is MVVM architecture?

MVVM or Model—View—ViewModel is an industry-acknowledged architecture pattern that addresses Separation of Concern by suggesting separation of the UI logic from the core business or back-end logic part of an application.

The different code layers of MVVM are:

• Model: This layer is responsible for abstration of data from different data resources, i.e., local SQLite database or a web service. Working together with ViewModel, it fetches and saves the data.

• View: The purpose of this layer is to inform the ViewModel about user's action. Therefore, it doesn't contain any business logic.

• ViewModel: It acts as an intermediate between View and the Model by providing data for the UI components like fragments or activities.

Why choose MVVM over other architectural pattern?

We chose to go with MVVM architecture for this Android application because of the following important key elements that set it apart from MVC and MVP architecture:

  • Testability

  • Modularity

  • Maintainability

  • Extensibility

MVVM overcomes the drawbacks of MVC and MVP architecture in the following ways:

  • Offers better modular structure (wherein modules are independent) as compared to what MVC provides and hence the former eases separate unit testing. Also, the code is event-driven.
  • ViewModel does not hold any kind of reference to the View.
  • Many-to-one relationship exists between View and ViewModel, which is not the case for MVP.
  • No triggering methods to update the View.
  • Enhances reusability of code and makes project files easier to maintain.