Clean Architecture | App Architecture | Android Development Tutorial

Introduction

Clean Architecture is a software design philosophy that aims to create systems that are easy to maintain, test, and develop. It emphasizes the separation of concerns, making sure that each part of the system has a single responsibility and can be developed and tested in isolation.

Principles of Clean Architecture

Clean Architecture is built on several key principles:

Separation of Concerns: Different parts of the application should have distinct responsibilities.
Dependency Rule: Source code dependencies can only point inwards. Nothing in an inner circle can know anything at all about something in an outer circle.
Interface Adapters: Converting data from the format most convenient for the inner layers to the format most convenient for external agents.

Layers of Clean Architecture

Clean Architecture consists of several layers, each with its own responsibility:

Entities: These are the business objects of the application. They encapsulate the most general and high-level rules.
Use Cases: These contain the application-specific business rules. They orchestrate the flow of data to and from the entities.
Interface Adapters: This layer contains adapters and converters that transform data from the use cases and entities into a format suitable for the outer layers.
Frameworks and Drivers: This is the outermost layer, consisting of frameworks and tools such as the database, UI, and other external services.

Implementing Clean Architecture in Android

Let's see how to implement Clean Architecture in an Android project. We'll use a simple example of a note-taking app.

Entities

The entities are the core business objects. In our example, we'll have a Note entity.

public class Note {
    private String id;
    private String title;
    private String content;

    // Constructors, getters, and setters
}

Use Cases

Use cases handle the business rules of the application. For instance, we can have a use case for adding a new note.

public class AddNoteUseCase {
    private NoteRepository noteRepository;

    public AddNoteUseCase(NoteRepository noteRepository) {
        this.noteRepository = noteRepository;
    }

    public void execute(Note note) {
        noteRepository.addNote(note);
    }
}

Interface Adapters

Interface adapters convert data between the use cases and the user interface or other external interfaces. In our example, we'll have a repository interface.

public interface NoteRepository {
    void addNote(Note note);
    Note getNoteById(String id);
    List getAllNotes();
}

Frameworks and Drivers

This layer interacts with external systems. In our case, it might be the Android framework and a database. We would implement the repository interface in this layer.

public class NoteRepositoryImpl implements NoteRepository {
    private NoteDao noteDao;

    public NoteRepositoryImpl(NoteDao noteDao) {
        this.noteDao = noteDao;
    }

    @Override
    public void addNote(Note note) {
        noteDao.insert(note);
    }

    @Override
    public Note getNoteById(String id) {
        return noteDao.findById(id);
    }

    @Override
    public List getAllNotes() {
        return noteDao.getAll();
    }
}

Conclusion

Clean Architecture helps in building maintainable, testable, and scalable applications. By following its principles and layering structure, you can create Android applications that are robust and easy to evolve.

Clean Architecture in Android Development