Google Flutter Google Flutter Performance

Question 1

Which Flutter tool provides a visual overlay showing render performance with colored bars?

Accepted Answer

Performance Overlay

Answer

The Performance Overlay displays two graphs showing GPU and CPU frame rendering times, highlighting frames that exceed 16ms.

Question 2

What is the target frame rendering time to achieve 60 FPS in Flutter?

Accepted Answer

16ms

Answer

To sustain 60 FPS, each frame must complete in under 16ms (1000ms / 60 frames).

Question 3

Which widget should you use to avoid rebuilding expensive subtrees when parent state changes?

Accepted Answer

const constructor widgets

Answer

Marking widgets as const tells the Dart compiler they are immutable, so Flutter can skip rebuilding them when the parent rebuilds.

Question 4

What does RepaintBoundary do in Flutter's rendering pipeline?

Accepted Answer

Isolates its child on a separate compositing layer to avoid repainting the whole tree

Answer

RepaintBoundary creates a new compositing layer for its child, so only that subtree is repainted when it changes, not the entire tree.

Question 5

Which Flutter DevTools tab helps identify the most expensive widgets during a performance session?

Accepted Answer

CPU Profiler / Performance tab

Answer

The CPU Profiler in Flutter DevTools shows a flame chart of method calls, identifying which widgets and functions consume the most CPU time.

Google Flutter Practice Test