What design patterns do you prefer in mobile development and why?

I prefer to use MVVM (Model-View-ViewModel) due to its advantages:

1. Separation of concerns: Clearly separates UI (View), business logic (ViewModel), and data (Model).
2. Testability: ViewModel is easy to test in isolation from the UI.
3. Lifecycle support: ViewModel survives configuration changes, maintaining state.
4. Use of LiveData/StateFlow: Simplifies reactive programming and UI updates without memory leaks.

Example structure:

• View: Activity/Fragment (XML layout, binding to ViewModel, observing LiveData/StateFlow)
• ViewModel: Contains business logic, interacts with repository, provides data for UI (LiveData/StateFlow)
• Model: Data representation (data classes, POJO)
• Repository: Intermediate layer between ViewModel and data sources (network, database)

In more complex scenarios or large projects, I may use MVI (Model-View-Intent) to improve state predictability and debugging through a unidirectional data flow.

For specific tasks, other patterns may also be applied:

• Singleton: For managing singleton objects (e.g., database manager).
• Factory Method/Abstract Factory: For creating objects.
• Observer: Built into LiveData/StateFlow.
• Builder: For creating complex objects (e.g., AlertDialog).

However, MVVM is the main and most frequently used pattern in my practice for building maintainable and scalable Android applications.