Spacer class

Spacer creates an adjustable, empty spacer that can be used to tune the spacing between widgets in a Flex container, like Row or Column.

The Spacer widget will take up any available space, so setting the Flex.mainAxisAlignment on a flex container that contains a Spacer to MainAxisAlignment.spaceAround, MainAxisAlignment.spaceBetween, or MainAxisAlignment.spaceEvenly will not have any visible effect: the Spacer has taken up all of the additional space, therefore there is none left to redistribute.

const Row(
  children: <Widget>[
    Text('Begin'),
    Spacer(), // Defaults to a flex of one.
    Text('Middle'),
    // Gives twice the space between Middle and End than Begin and Middle.
    Spacer(flex: 2),
    Text('End'),
  ],
)

See also:

• Row and Column, which are the most common containers to use a Spacer in.
• SizedBox, to create a box with a specific size and an optional child.