Android ViewModel is a crucial component in the modern Android app development ecosystem. It plays a crucial role in implementing the Model-View-ViewModel (MVVM) architectural pattern, which has become the standard for building robust, scalable, and maintainable Android applications.
In this guide, we'll take a deep dive into the Android ViewModel and explore its features, benefits, and best practices for implementation.
## What is Android ViewModel?
Android ViewModel is a part of the Android Architecture Components, which were introduced by Google to help developers build robust and maintainable Android applications. ViewModel is designed to store and manage UI-related data in a lifecycle-conscious way. It allows data to survive configuration changes such as screen rotations and helps to separate the UI controller (Activity or Fragment) from the underlying data sources.
## Benefits of using Android ViewModel
- **Lifecycle awareness**: ViewModel is lifecycle-aware, meaning it is designed to survive configuration changes and does not get destroyed when the associated UI controller is recreated.
- **Separation of concerns**: ViewModel helps separate the presentation layer from the business logic and data manipulation, making the codebase cleaner and more maintainable.
- **Testability**: It facilitates easier unit testing of the UI-related logic by decoupling it from the UI controller.
## How to use Android ViewModel
To use Android ViewModel in your app, you need to create a subclass of the ViewModel class and define the UI-related data that you want to expose to the UI controller. You then obtain an instance of the ViewModel using the ViewModelProviders class and associate it with your UI controller. Once the association is established, the ViewModel will survive configuration changes and act as a communication layer between the UI and the data sources (e.g., repositories, network calls, databases).
ViewModel can also be used in conjunction with other Android Architecture Components such as LiveData, which is an observable data holder that is lifecycle-aware. LiveData can be observed in the UI controller, and it will automatically update the UI when the underlying data changes.
## Best practices for using Android ViewModel
- **Do not store context**: Avoid storing a reference to the Context or Activity in the ViewModel, as it can lead to memory leaks. Instead, use AndroidViewModel, which is a subclass of ViewModel and provides a reference to the Application context.
- **Keep it lightweight**: ViewModel should only contain the data and business logic needed for the UI controller. Avoid complex logic or data manipulation inside the ViewModel.
- **Use MutableLiveData**: When exposing data from the ViewModel to the UI, use MutableLiveData, which is a subclass of LiveData that allows value updates. This ensures that the UI is always in sync with the underlying data.
In conclusion, Android ViewModel is a powerful component that enhances the structure and maintainability of Android apps. By leveraging ViewModel in conjunction with other Architecture Components, developers can build scalable and resilient apps that are easy to maintain and test. We hope this guide has provided you with a comprehensive understanding of Android ViewModel and how it can be integrated into your Android app development process.
