Expanded and Flexible in Flutter - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

Understanding Expanded widget behavior

Given a Row with two children: a fixed-width Container and an Expanded Container, what will be the width of the Expanded Container if the Row's total width is 300 pixels and the fixed Container is 100 pixels wide?

Flutter

Row(
  children: [
    Container(width: 100, color: Colors.red),
    Expanded(child: Container(color: Colors.blue))
  ]
)

A 200 pixels

B 100 pixels

C 300 pixels

D 0 pixels

💡 Hint

Expanded takes all remaining space after fixed widgets.

The fixed Container takes 100 pixels, so Expanded fills the rest: 300 - 100 = 200 pixels.

❓ ui_behavior

intermediate

Flexible with fit property effect

What is the difference in behavior between Flexible with fit: FlexFit.tight and Flexible with fit: FlexFit.loose inside a Row?

Flutter

Row(
  children: [
    Flexible(fit: FlexFit.tight, child: Container(color: Colors.green)),
    Flexible(fit: FlexFit.loose, child: Container(color: Colors.yellow))
  ]
)

A Both let children be any size they want without constraints.

B FlexFit.tight forces child to fill available space; FlexFit.loose lets child be smaller if it wants.

C Both force children to fill all available space equally.

D FlexFit.loose forces child to fill available space; FlexFit.tight lets child be smaller if it wants.

💡 Hint

Think about how much space the child is forced to occupy.

FlexFit.tight makes the child fill all the space allocated; FlexFit.loose allows the child to be smaller if it chooses.

❓ lifecycle

advanced

Effect of multiple Expanded widgets with flex values

In a Row with three Expanded children having flex values 1, 2, and 3 respectively, how is the available horizontal space divided among them?

Flutter

Row(
  children: [
    Expanded(flex: 1, child: Container(color: Colors.red)),
    Expanded(flex: 2, child: Container(color: Colors.green)),
    Expanded(flex: 3, child: Container(color: Colors.blue))
  ]
)

A Only the child with flex 3 gets all the space; others get none.

B All children get equal space regardless of flex values.

C The space is divided in ratio 1:2:3 among the three children.

D The first child gets all space; others get zero.

💡 Hint

Flex values act like weights for space distribution.

The total flex is 6 (1+2+3). Space is split proportionally: 1/6, 2/6, and 3/6.

🔧 Debug

advanced

Why does this layout overflow error occur?

Consider a Row with two children: a Container with fixed width 200 and an Expanded child. The Row is inside a parent with width 250. Why does a horizontal overflow error occur?

Flutter

Container(
  width: 250,
  child: Row(
    children: [
      Container(width: 200, color: Colors.red),
      Expanded(child: Container(color: Colors.blue))
    ]
  )
)

A Because the fixed Container uses 200 pixels, Expanded tries to fill remaining 50 pixels, but the child inside Expanded has no width constraints and overflows.

B Because Expanded ignores the available space and tries to be 250 pixels wide.

C Because the Row automatically expands beyond parent width causing overflow.

D Because Container with width 250 is too small to hold any children.

💡 Hint

Think about how Expanded passes constraints to its child.

Expanded gives its child max width of remaining space (50 pixels), but if the child tries to be bigger, overflow happens.

🧠 Conceptual

expert

Choosing between Expanded and Flexible

Which statement best describes when to use Expanded versus Flexible in Flutter layouts?

A Use Flexible when you want the child to ignore parent constraints; Expanded forces the child to shrink.

B Use Flexible only inside Columns; Expanded only inside Rows.

C Expanded and Flexible are interchangeable with no difference in behavior.

D Use Expanded when you want the child to fill all remaining space; use Flexible when you want the child to be able to be smaller than the available space.

💡 Hint

Think about how strictly the child fills space.

Expanded forces the child to fill remaining space; Flexible allows the child to be smaller if it wants.