Android Development Android Performance Optimization 2

Question 1

What is the purpose of the RecyclerView.RecycledViewPool in Android?

Accepted Answer

To share recycled ViewHolders across multiple RecyclerViews

Answer

RecycledViewPool allows multiple RecyclerViews to share a pool of recycled ViewHolders, reducing view inflation overhead when displaying similar list content.

Question 2

What does 'overdraw' mean in the context of Android rendering performance?

Accepted Answer

A pixel being painted more than once per frame

Answer

Overdraw occurs when a pixel is drawn multiple times in a single frame (e.g., due to overlapping backgrounds), wasting GPU time and reducing rendering performance.

Question 3

Which Android feature allows deferring the inflation of part of a layout until it is actually needed, improving initial load time?

Accepted Answer

ViewStub

Answer

ViewStub is a lightweight, invisible View that is replaced by the inflated layout only when explicitly made visible or inflated, reducing startup inflation cost.

Question 4

What is the main benefit of using ConstraintLayout over nested LinearLayouts or RelativeLayouts?

Accepted Answer

It flattens the view hierarchy, reducing measure/layout passes

Answer

ConstraintLayout expresses complex layouts in a single flat hierarchy, avoiding nested layouts that require multiple measure/layout passes and hurt rendering performance.

Question 5

When using Room database, what should you avoid doing on the main thread to prevent ANR errors?

Accepted Answer

Running database queries synchronously

Answer

Room by default throws an exception if database queries are run on the main thread; they should be executed on a background thread (e.g., using coroutines or LiveData) to prevent blocking the UI.

Android Development Practice Test

Android Development Practice Test

Android Development Android Performance Optimization 2