Why ViewModel survives configuration changes in Android Kotlin - Challenge Your Understanding

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why does ViewModel survive configuration changes?

In Android development, why does a ViewModel instance survive configuration changes like screen rotations?

A Because ViewModel uses static variables that persist across configuration changes.

B Because ViewModel saves its data to a local database automatically before configuration changes.

C Because ViewModel is tied to the lifecycle of the Activity or Fragment and is retained by the system during configuration changes.

D Because ViewModel is recreated every time but restores its state from savedInstanceState bundle.

💡 Hint

Think about how Android manages lifecycle and retains objects during configuration changes.

The ViewModel is designed to be tied to the lifecycle of an Activity or Fragment but is retained when configuration changes happen. This means the system keeps the same ViewModel instance alive, so data is preserved without needing to save and restore manually.

❓ ui_behavior

intermediate

What happens to UI data in ViewModel after rotation?

If you store user input in a ViewModel, what will happen to that data after the device is rotated?

A The data is cleared and replaced with default values after rotation.

B The data remains intact and accessible from the ViewModel after rotation.

C The data is saved to a file automatically and reloaded after rotation.

D The data is lost because ViewModel is destroyed and recreated on rotation.

💡 Hint

Remember what ViewModel is designed to do with data during lifecycle changes.

ViewModel survives configuration changes like rotation, so any data stored in it remains available and does not get lost.

❓ lifecycle

advanced

When is a ViewModel destroyed?

Considering Android lifecycle, when does the system destroy a ViewModel instance?

A When the associated Activity or Fragment is finishing and not just being recreated due to configuration changes.

B Immediately after every configuration change like rotation.

C When the app goes into the background for more than 5 minutes.

D When the user presses the home button.

💡 Hint

Think about the difference between finishing an Activity and just rotating the device.

The ViewModel is destroyed only when the lifecycle owner is permanently finished, such as when the Activity is closed, not during temporary configuration changes.

❓ navigation

advanced

How does ViewModel scope affect navigation between fragments?

If two fragments share a ViewModel scoped to their parent Activity, what happens to the ViewModel when navigating between these fragments?

A The same ViewModel instance is shared and survives navigation between fragments.

B Each fragment gets a new ViewModel instance when navigated to.

C The ViewModel is destroyed when leaving the first fragment and recreated for the second.

D The ViewModel data is saved to disk and reloaded for each fragment.

💡 Hint

Consider the scope of the ViewModel and how it relates to the lifecycle owner.

When ViewModel is scoped to the parent Activity, all fragments within that Activity share the same ViewModel instance, preserving data across fragment navigation.

🔧 Debug

expert

Why does this ViewModel data reset after rotation?

You have this code snippet in your Activity: val viewModel = ViewModelProvider(this).get(MyViewModel::class.java) But after rotating the device, the data in viewModel resets. What is the most likely cause?

A ViewModel does not survive rotation by design; you must manually save and restore data.

B You forgot to save the ViewModel data in onSaveInstanceState.

C You should use application context instead of Activity context to create ViewModelProvider.

D You are creating a new ViewModelProvider with 'this' referring to the Activity, but the Activity is recreated, so the ViewModel instance is new.

💡 Hint

Check what 'this' refers to and how ViewModelProvider works with lifecycle owners.

When you use 'this' inside an Activity, it refers to the current Activity instance. After rotation, the Activity is recreated, so a new ViewModelProvider is created, resulting in a new ViewModel instance. To retain data, you must use the same lifecycle owner or use ViewModelProvider tied to a persistent owner.