Use cases / Interactors in Android Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the main role of a Use Case (Interactor) in Android app architecture?

Choose the best description of what a Use Case (Interactor) does in an Android app.

A It handles user interface rendering and animations.

B It stores data directly in the database without any processing.

C It manages the app's business logic and coordinates data flow between repositories and UI.

D It handles network requests and responses only.

💡 Hint

Think about where the app's core rules and decisions happen.

Use Cases (Interactors) contain the business logic. They decide how data is processed and passed between data sources and the UI.

❓ ui_behavior

intermediate

How does a Use Case affect UI updates in an Android app?

Which option best describes how a Use Case interacts with the UI layer?

A It directly updates UI elements like buttons and text views.

B It provides processed data to the ViewModel or Presenter, which then updates the UI.

C It listens to UI events and handles user clicks directly.

D It manages UI animations and transitions.

💡 Hint

Consider separation of concerns between business logic and UI rendering.

Use Cases do not manipulate UI directly. They prepare data and pass it to ViewModel or Presenter, which updates the UI.

❓ lifecycle

advanced

When should a Use Case be invoked in the Android app lifecycle?

At which point in the app lifecycle is it best to call a Use Case to fetch data?

A Inside the ViewModel when the UI requests data, typically after the UI is ready.

B Inside the Application class's onCreate method.

C Inside the Activity's onCreate method before setting the content view.

D Directly inside the Repository when the app starts.

💡 Hint

Think about where UI logic and data fetching should be separated.

Use Cases are usually called by the ViewModel after the UI is ready to display data, ensuring separation of concerns and lifecycle safety.

❓ navigation

advanced

Can a Use Case handle navigation logic in an Android app?

Which statement about Use Cases and navigation is correct?

A Use Cases should only handle business logic; navigation should be handled by the UI layer or navigation controllers.

B Use Cases manage navigation by calling Android Navigation components directly.

C Use Cases replace the need for navigation components.

D Use Cases should directly trigger navigation actions to switch screens.

💡 Hint

Consider separation of concerns between business logic and UI navigation.

Use Cases focus on business rules and data. Navigation is a UI concern handled by controllers or navigation components.

🔧 Debug

expert

What is the likely cause if a Use Case returns stale data despite repository updates?

You updated data in the repository, but the Use Case still returns old data. What is the most probable reason?

A The Use Case is incorrectly modifying the repository data.

B The Use Case caches data internally and does not refresh from the repository.

C The UI layer is not calling the Use Case after data changes.

D The repository update method is asynchronous and the Use Case reads data before update completes.

💡 Hint

Think about timing and asynchronous data flow.

If repository updates are asynchronous, the Use Case might read data before the update finishes, causing stale data to be returned.