SingleChildScrollView in Flutter - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What is the output of this Flutter code with SingleChildScrollView?

Consider this Flutter widget tree. What will the user see and how will it behave?

Flutter

SingleChildScrollView(
  child: Column(
    children: List.generate(30, (index) => Text('Item $index')),
  ),
)

A An error occurs because Column inside SingleChildScrollView needs a fixed height.

B Only the first few items are visible, no scrolling is possible, rest are clipped.

C The items are arranged horizontally and scroll horizontally.

D A scrollable list of 30 text items vertically, user can scroll to see all items.

💡 Hint

Think about what SingleChildScrollView does with a Column of many children.

SingleChildScrollView allows its child to be bigger than the screen and scrolls vertically by default. The Column arranges children vertically. So the user sees all 30 items by scrolling.

❓ lifecycle

intermediate

What happens if you nest multiple SingleChildScrollView widgets vertically?

Given this widget tree, what is the expected scroll behavior? SingleChildScrollView( child: SingleChildScrollView( child: Column( children: [...], ), ), )

A Only the outer SingleChildScrollView scrolls; inner one has no effect.

B Both scroll views scroll independently causing scroll conflicts.

C Flutter throws a runtime error about nested scrollables.

D The inner SingleChildScrollView scrolls, outer one does not.

💡 Hint

Think about how Flutter handles nested scroll views with the same scroll direction.

Flutter disables inner scroll views when nested vertically to avoid scroll conflicts. Only the outer scroll view scrolls.

📝 Syntax

advanced

What error does this Flutter code produce?

Examine this code snippet: SingleChildScrollView( child: Column( children: [ Container(height: 1000), Expanded(child: Text('Hello')) ], ), )

A A runtime error: Container height cannot be greater than screen height.

B A runtime error: Expanded widgets must be inside Flex widgets with bounded height.

C No error; the code runs and scrolls correctly.

D A compile-time syntax error due to missing commas.

💡 Hint

Remember how Expanded works inside Column and scroll views.

Expanded requires a bounded height from its parent. Inside SingleChildScrollView, Column has infinite height, so Expanded causes a runtime error.

❓ navigation

advanced

How to preserve scroll position when navigating back to a screen with SingleChildScrollView?

You have a screen with SingleChildScrollView showing a long list. When you navigate away and come back, the scroll resets to top. How to keep the scroll position?

A Use a ListView instead of SingleChildScrollView to automatically preserve scroll.

B Wrap SingleChildScrollView with a StatefulWidget and call setState() on return.

C Use a ScrollController and keep it alive across navigation to restore position.

D Add a Key to SingleChildScrollView to force Flutter to remember scroll position.

💡 Hint

Think about how Flutter manages scroll positions with controllers.

Using a ScrollController attached to SingleChildScrollView lets you save and restore scroll offset when navigating back.

🧠 Conceptual

expert

Why is SingleChildScrollView not recommended for very long lists?

You want to display a list of 1000 items. Why should you avoid using SingleChildScrollView with a Column for this?

A Because SingleChildScrollView builds all children at once, causing high memory use and slow performance.

B Because SingleChildScrollView does not support scrolling for more than 500 items.

C Because SingleChildScrollView automatically disables scrolling for large children.

D Because SingleChildScrollView requires a fixed height for its child, which is impossible with many items.

💡 Hint

Think about how Flutter builds widgets inside SingleChildScrollView vs ListView.

SingleChildScrollView builds all its children at once, which uses a lot of memory and slows down the app for very long lists. ListView builds items lazily.