Architecting Your Apps

App architecture design is a crucial consideration for ensuring that your app is robust, testable and maintainable. Common architecture patterns used in android development include MVC(Model-View-Controller), MVP(Model-View-Presenter) and MVVM(Model-View-ViewModel). In this session, we will look at how to use MVVM to create production-quality android apps.

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1. Architecting Your App Beatrice Kinya, Software Engineer. Twitter: @B__Kinya, LinkedIn: Beatrice Kinya
2. Introduction ➔ A simple android app: ◆ Will have a screen(s) where the users interact with the app. ◆ Could be connecting to an api, to fetch or send data e.g. TMDB API. ◆ Could be saving data locally in the app db.
3. App Architecture: Principles ➔ Goal: Build robust , maintainable, testable production-quality apps. ➔ Separation of concerns between business logic and UI layer code. ◆ Let the UI classes, Activities or Fragments, contain logic that handles UI interactions, i.e displaying data to user, receiving user events etc.. • You can avoid many life-cycle related problems. • Adaptability to change. • Testable code.
4. Principles cont’ ➔ Drive UI from a Model, preferably a persistence model. ◆ Your app continues to work in cases of no network or users network is flaky. ◆ Models are unaffected by apps lifecycle. This way the user does not lose data in case OS destroys your app to clear up resources
5. Android Architectures ➔ Commonly used architectures patterns in Android development include: ◆ MVC: Model View Controller ◆ MVP: Model View Presenter ◆ MVVM: Model View ViewModel
6. MVC ➔ It suggests splitting the app code into 3 components: ◆ Model. This component manages application data. • It contains the business logic and rules of the application. • It handles network and database API. ◆ View. This is the UI layer. • It provides visualization of data stored in the models. • It offers an interface for users to interact with the app
7. MVC cont’ ➔ Controller. This is the logic layer. ◆ it establishes relationship between View and Model. ◆ It gets notified of the user behavior and updates Model as required.
8. MVVM ➔ Model. ◆ Represents the data layer ➔ View . ◆ Represents UI layer ➔ ViewModel.
9. ViewModel ➔ It contains data specific to a UI component, such as a fragment or an activity. ➔ It contains data handling logic to communicate with the model. ➔ It is not affected by configuration changes such as screen rotation.
10. Livedata ➔ It is an observable data holder class. ◆ It can notify other components such as activities or fragments of data changes ➔ It is lifecycle aware, meaning it respects lifecycle of other components such as activities and fragments. ◆ This way Livedata only updates app components that are in active state. A component is considered to be in active state if its life cycle is in STARTED or RESUMED state.
11. Repository ➔ ViewModel delegates updating model, i.e. saving data, fetching data, updating data to the repository module. ➔ It knows where to get the data from. ➔ It know which API calls to make when data is updated. ➔ Repositories are mediators between different data sources such as web services, caches, and persistent models
13. Resources ➔ Guide To App architecture ➔ Repository Pattern ➔ Github Project Further Reading ➔ Clean Architecture in Android
14. Questions?