Hot reload and hot restart in Flutter - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What happens to the app state after a hot reload?

You have a Flutter app running with a counter value of 5. You change the UI code to display the counter in red and perform a hot reload. What will be the counter value displayed after the hot reload?

A The counter value resets to 0 because the app restarts.

B The counter value remains 5 and the UI updates to show the counter in red.

C The app crashes because hot reload cannot update UI colors.

D The counter value becomes null because the state is lost.

💡 Hint

Hot reload updates the UI without losing the current state.

Hot reload injects updated source code files into the running Dart Virtual Machine (VM). It preserves the app state and updates the UI immediately.

❓ lifecycle

intermediate

What is the main difference between hot reload and hot restart?

Which statement correctly describes the difference between hot reload and hot restart in Flutter?

A Hot reload preserves app state; hot restart resets app state and rebuilds the app.

B Hot reload resets app state; hot restart preserves app state.

C Both hot reload and hot restart reset app state but hot restart is faster.

D Hot reload rebuilds the entire app; hot restart only updates changed widgets.

💡 Hint

Think about what happens to the app's variables and UI after each action.

Hot reload updates code and UI without losing state. Hot restart fully restarts the app, resetting all state and rebuilding from main().

🔧 Debug

advanced

Why might a hot reload not reflect changes in some Flutter code?

You changed the initialization code inside the main() function but after hot reload, the changes do not appear in the running app. Why?

A Hot reload only works if you save the file twice.

B Hot reload only updates UI widgets, not any Dart code.

C Hot reload does not rerun main(), so changes in main() are not applied.

D Hot reload requires a full app restart to update any code.

💡 Hint

Consider which parts of the app lifecycle hot reload affects.

Hot reload injects updated source code but does not rerun main(). Changes in main() or global variables require hot restart.

❓ navigation

advanced

What happens to navigation stack after a hot restart?

Your Flutter app has navigated through several screens. You perform a hot restart. What will be the navigation stack state after the restart?

A The navigation stack resets and the app returns to the initial screen.

B The navigation stack is preserved and you stay on the current screen.

C The app crashes because navigation state cannot be restored.

D The navigation stack duplicates the current screen multiple times.

💡 Hint

Think about what hot restart does to the app state and memory.

Hot restart resets the app state including navigation stack, so the app starts fresh at the initial screen.

🧠 Conceptual

expert

Why is hot reload faster than hot restart in Flutter?

Choose the best explanation for why hot reload is faster than hot restart.

A Hot reload recompiles the entire app but skips UI rebuilding.

B Hot reload runs a background process that preloads all assets.

C Hot reload clears the app cache before applying changes, making it faster.

D Hot reload only updates changed source code in the Dart VM without restarting the app, preserving state.

💡 Hint

Consider what parts of the app lifecycle each process affects.

Hot reload injects updated source code into the running Dart VM and rebuilds UI without restarting the app or losing state, making it faster than hot restart.