SizedBox.expand

Learn to fill the parent with SizedBox.expand.

SizedBox.expand

SizedBox.expand produces a SizedBox that fills all the size coming from its parent. Its width and height parameters accept double.infinity. This is used to make a widget as wide or tall as its parent.

SizedBox.expand(
  child: Container(color: Colors.blue),
)

// Equivalent:
SizedBox(
  width: double.infinity,
  height: double.infinity,
  child: Container(color: Colors.blue),
)

double.infinity

double.infinity is a special value in Flutter meaning "as large as possible". SizedBox(width: double.infinity) makes the child as wide as the parent. Expanded and SizedBox.expand use this value. Inside Column and Row, the Expanded widget does a similar effect along the main axis.

Column(
  children: [
    SizedBox(
      width: double.infinity,
      child: Text('Tam genişlik'),
    ),
    SizedBox.expand(
      child: Text('Tam boyut'),
    ),
  ],
)

Exercise Print SizedBox.expand info

In main, print two lines with print: expand doldur and infinity sonsuz.

Show example solution

void main() {
  print('expand doldur');
  print('infinity sonsuz');
}

Test yourself

What does SizedBox.expand do?
- Completely fills the parent's size
- Keeps the child centered
- Hides the child
- Shrinks the child
Show answer

Completely fills the parent's size — SizedBox.expand sets width and height to double.infinity and completely fills the parent's size.

Infinite width

SizedBox(
  width: ____,
  child: Text('Tam genişlik'),
)

Show answer

SizedBox(
  width: double.infinity,
  child: Text('Tam genişlik'),
)

SizedBox.expand concepts

SizedBox.expand

Fills the parent
expand

Full size
double.infinity

Infinite size value
width + height = infinity

Equivalent to SizedBox.expand

Next lesson: The Align widget

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