Building Flexible and Scalable Android Apps with MVVM: Best Practices and Tips
By - Thiyagaraj M & Godlin Josheela Rani S
🎯 Model View Controller (MVC)
The Model-View-Controller (MVC) architecture has been a popular choice for Android app development in the past. In this architecture, the view represents the user interface, the model encapsulates the data and business logic, and the controller acts as an intermediary between the view and the model.
However, MVC has certain drawbacks. One of the main challenges is that the view and the controller are tightly coupled, making it difficult to add new functionalities without modifying the existing code. This often leads to large view classes with thousands of lines of code, making code maintenance and understanding a complex task. Additionally, updating the view after performing business logic requires manual intervention, which can be error-prone.
The Model-View-Controller (MVC) architecture is a widely-used pattern that separates an application into three interconnected components: the model, the view, and the controller.
The model represents the data and business logic of the application. It encapsulates the state and behavior of the underlying data and provides methods for manipulating and accessing that data.
The view is responsible for presenting the user interface to the user. It displays the data from the model and interacts with the user for input.
The controller acts as an intermediary between the view and the model. It receives input from the user via the view and updates the model accordingly. It also handles events and triggers actions based on user interactions.
👉 Advantages of MVC architecture:
Faster app development: MVC promotes a clear separation of concerns, allowing multiple developers to collaborate and work on different components simultaneously. This can speed up the development process.
Easy incorporation of minor changes: Since the responsibilities are divided into separate components, making minor changes in the application, such as updating the UI or modifying the business logic, can be relatively straightforward.
👉 Disadvantages of MVC architecture:
Difficult for other developers to understand and make changes to the code: MVC's structure and lack of strict rules on methods can make it challenging for new developers to grasp the codebase and make modifications.
Code maintenance complexity: Without proper guidelines and practices, the codebase can become difficult to maintain over time, leading to code duplication and tangled dependencies.
Adding new functionalities to existing code can be complex, especially when the view class (Activity/Fragment) becomes large and contains a significant amount of code. This can make the codebase difficult to navigate and maintain.
Manual updating of the view after performing business logic can be error-prone, as it requires explicit calls to update the UI elements.
Code understanding and handover can be challenging for other developers, especially when there are no strict rules on methods and code organization.
🎯 Model View View-Model (MVVM)
The Model-View-ViewModel (MVVM) architecture is a modern architectural pattern that addresses the limitations of MVC by providing better separation of concerns and more efficient data flow.
In MVVM, the view represents the user interface, similar to MVC. However, the view and the model are not directly connected.
The ViewModel acts as an intermediary between the view and the model. It contains the presentation logic, handles user interactions, and exposes data to the view through data-binding mechanisms.
MVVM introduces the concept of data binding, which allows the view to bind directly to the ViewModel's properties. This enables automatic propagation of data changes from the ViewModel to the view and vice versa.
👉 Advantages of MVVM Architecture
Even more easily understandable application code: MVVM promotes a clear separation of concerns and a more intuitive structure, making the codebase easier to read, understand, and maintain.
Further decoupling of components: MVVM minimizes direct dependencies between the view and the model, which leads to improved code organization and testability.
Intuitive package structure: MVVM encourages organizing the codebase into separate modules, making it easier to navigate and locate specific functionalities.
Faster addition of new features: With its modular and extensible nature, MVVM allows development teams to add new features more quickly without disrupting existing functionalities.
👉 Disadvantages of MVVM architecture:
Slightly steep learning curve: MVVM introduces additional concepts and layers compared to simpler patterns like MVC or MVP. Understanding how the various components (view, ViewModel, and model) interact with each other may take some time, especially for developers transitioning from other patterns.
Increased number of classes: Implementing MVVM often requires the introduction of additional classes like ViewModel and data binding adapters. This can lead to a larger codebase and increased complexity, making it less suitable for small or low-complexity projects.
Designing the ViewModel upfront: Designing the ViewModel class properly from the beginning can be challenging. Striking the right balance between making it too specific or too generic requires careful consideration to ensure it meets the specific needs of the view and is reusable across different scenarios.
🎯 Notes for Architecture Migration MVC to MVVM
Planning and time allocation: Migrating from MVC to MVVM requires careful planning and time allocation. It's essential to evaluate the complexity and size of the existing codebase and allocate sufficient time for refactoring and testing.
Restructuring the codebase: The migration process involves reorganizing the codebase to adhere to the MVVM architecture. This includes creating ViewModel classes, updating data binding, and separating concerns between the view, ViewModel, and model.
Integration of Android Jetpack libraries: To leverage the full benefits of MVVM, integrating Android Jetpack libraries like Data Binding and ROOM database is recommended. This may involve modifying existing code to utilize these libraries effectively.
Refactoring and testing: During the migration, it's crucial to refactor the existing code to align with MVVM principles and ensure proper separation of concerns. Rigorous testing is essential to catch any issues introduced during the migration process and ensure the stability and reliability of the app.
Training and knowledge transfer: Developers involved in the migration process may require training or learning resources to familiarize themselves with the MVVM pattern and associated tools. Knowledge transfer among the development team is crucial to ensure a smooth transition and consistent understanding of the new architecture.
🎯 Android App MVVM Architecture
Read more Android app architecture : https://developer.android.com/jetpack/docs/guide#recommended-app-arch
🎯 Important components of MVVM in Android
Model: The Model component represents the data and business logic of the application. It encapsulates the data entities, database operations, network requests, and other backend-related functionality.
View: The View component represents the user interface and is responsible for displaying data to the user and capturing user input. It includes activities, fragments, layouts, and UI elements like buttons, text views, etc.
ViewModel: The ViewModel acts as an intermediary between the View and the Model. It contains the presentation logic and exposes data and commands that the View can bind to. It does not have a direct reference to the View, ensuring a separation of concerns.
Data Binding: Data Binding is a library provided by Android Jetpack that allows for seamless and declarative binding of data between the View and the ViewModel. It eliminates the need for manual updates and simplifies UI updates based on changes in the underlying data.
LiveData: LiveData is an observable data holder class also provided by Android Jetpack. It allows the ViewModel to expose data as LiveData objects that the View can observe. LiveData ensures that the View receives updated data whenever it changes, enabling automatic UI updates.
Observable: In some cases, the ViewModel may use the Observable pattern to notify the View of changes. Observables can be custom implementations or libraries like RxJava or Kotlin Coroutines.
Commands: The ViewModel can expose commands (e.g., button clicks) that the View can bind to. Commands encapsulate actions triggered by user interactions and provide a way to communicate from the View to the ViewModel.
Repository: The Repository serves as a single source of truth for data. It abstracts the data sources (e.g., local database, network) and provides methods for fetching and updating data. The ViewModel interacts with the Repository to access or modify the data.
Dependency Injection: Dependency Injection frameworks like Dagger or Hilt can be used to inject dependencies into the ViewModel and other components of the MVVM architecture. This promotes modularization, testability, and decoupling of dependencies.