Android Development Android Development 3

Question 1

An app crashes with a NetworkOnMainThreadException. What is the correct fix?

Accepted Answer

Move the network call to a background thread or coroutine

Answer

Android forbids network I/O on the main thread, so the call must run on a background dispatcher such as Dispatchers.IO.

Question 2

In Kotlin coroutines, which dispatcher is optimized for disk and network operations?

Accepted Answer

Dispatchers.IO

Answer

Dispatchers.IO maintains a larger thread pool tuned for blocking I/O like file and network access.

Question 3

Why does ViewModel survive configuration changes such as screen rotation?

Accepted Answer

It is retained in a ViewModelStore that outlives the Activity recreation

Answer

The ViewModelStore is kept across configuration changes, so the same ViewModel instance is handed to the recreated Activity.

Question 4

Which RecyclerView optimization avoids redrawing the entire list when only some items change?

Accepted Answer

Using DiffUtil (e.g. via ListAdapter) to dispatch minimal updates

Answer

DiffUtil computes the difference between old and new lists and dispatches only the necessary item-level updates.

Question 5

Starting with Android 6.0 (API 23), how must dangerous permissions like CAMERA be obtained?

Accepted Answer

Requested at runtime in addition to being declared in the manifest

Answer

Dangerous permissions require both a manifest declaration and an explicit runtime request that the user can deny.

Android Development Practice Test