Why API calls fetch remote data in Flutter - Challenge Your Understanding

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why do mobile apps use API calls to get data?

Which reason best explains why mobile apps fetch data using API calls from remote servers?

A To avoid using the internet and save battery by fetching data locally

B Because local device storage is always empty and cannot save any data

C To get the latest information stored on a server that can change over time

D Because API calls automatically speed up the app without network use

💡 Hint

Think about where the newest data lives and how apps get it.

Mobile apps use API calls to connect to remote servers where the latest data is stored. This way, apps show up-to-date information instead of old or missing data.

❓ ui_behavior

intermediate

What happens in the UI when an API call is made?

When a Flutter app makes an API call to fetch remote data, what is the typical user interface behavior?

A The app shows a loading indicator until data arrives, then updates the screen

B The app immediately shows old data without waiting for the API response

C The app freezes and does not respond until the data is fully loaded

D The app closes automatically after making the API call

💡 Hint

Think about how apps keep users informed during waiting times.

Apps usually show a loading spinner or message while waiting for data, then update the UI once the data arrives to keep users informed and avoid freezing.

❓ lifecycle

advanced

When should API calls be made in a Flutter app lifecycle?

In Flutter, which lifecycle moment is best to start an API call to fetch remote data for a screen?

A Inside the main() function before runApp()

B Inside the initState() method of a StatefulWidget

C Inside the dispose() method of a StatefulWidget

D Inside the build() method of a StatelessWidget

💡 Hint

Consider when the widget is first created and ready to load data.

initState() runs once when the widget is created, making it the ideal place to start API calls. build() runs many times and dispose() is for cleanup.

❓ navigation

advanced

How does navigation affect API data fetching?

If a user navigates away from a screen before its API call finishes, what should the app do to handle the remote data fetch?

A Restart the app to reset all API calls

B Force the user to wait until the API call finishes before navigating

C Automatically navigate back to the screen after data loads

D Cancel the API call or ignore its result to avoid updating a disposed screen

💡 Hint

Think about what happens if data arrives but the screen is gone.

If the screen is no longer visible, the app should cancel or ignore the API response to prevent errors or crashes from updating a screen that does not exist.

🔧 Debug

expert

What error occurs if you update UI after widget disposal?

In Flutter, if an API call completes and tries to update the UI after the widget has been disposed, what error is most likely thrown?

A setState() called after dispose()

B NullPointerException

C IndexOutOfRangeException

D NoSuchMethodError

💡 Hint

This error warns about updating a widget that no longer exists.

Flutter throws 'setState() called after dispose()' when code tries to update a widget after it has been removed from the widget tree.