Lifecycle awareness in Android Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of lifecycle awareness in Android apps?

Lifecycle awareness helps an app respond correctly to changes in its state, like when it starts, stops, or is destroyed. This keeps the app efficient and prevents crashes.

beginner

Name the main lifecycle states of an Android Activity.

The main states are: onCreate (start), onStart (visible), onResume (active), onPause (partially visible), onStop (hidden), and onDestroy (cleanup).

intermediate

What is a LifecycleObserver in Android?

A LifecycleObserver is a class that watches lifecycle events of components like Activities or Fragments and reacts to them, helping organize code and manage resources.

intermediate

Why should you avoid heavy work in onResume() and prefer lifecycle-aware components?

Heavy work in onResume() can slow the app and cause a bad user experience. Lifecycle-aware components help run tasks only when needed and stop them when not visible.

intermediate

How does ViewModel help with lifecycle awareness?

ViewModel holds UI data and survives configuration changes like screen rotations, so data is not lost and the UI stays consistent without restarting tasks.

Which lifecycle method is called when an Activity becomes visible but not yet interactive?

A onCreate()

B onStart()

C onResume()

D onPause()

onStart() is called when the Activity becomes visible to the user but is not yet in the foreground for interaction.

What interface do you implement to create a lifecycle-aware observer in Android?

A LifecycleOwner

B ViewModel

C ActivityLifecycleCallbacks

D LifecycleObserver

LifecycleObserver is the interface used to create classes that observe lifecycle events.

Which lifecycle method is best for releasing resources when an Activity is no longer visible?

A onStop()

B onPause()

C onDestroy()

D onResume()

onStop() is called when the Activity is no longer visible, making it a good place to release resources.

What happens to a ViewModel when the Activity is destroyed due to a configuration change?

A It is destroyed immediately

B It is recreated with the Activity

C It survives and retains data

D It causes a memory leak

ViewModel survives configuration changes and keeps UI data intact.

Why is lifecycle awareness important for background tasks?

A All of the above

B To prevent tasks from running when the app is stopped

C To save battery and resources

D To run tasks only when the app is visible

Lifecycle awareness helps manage background tasks efficiently, saving battery and resources by running tasks only when appropriate.

Explain the main lifecycle states of an Android Activity and what happens in each.

Think about when the Activity is created, visible, interactive, partially visible, hidden, and destroyed.

Describe how lifecycle-aware components improve app performance and user experience.

Consider how apps behave when users switch apps or rotate screens.