Flexible constructor

const Flexible({Key key, int flex: 1, FlexFit fit: FlexFit.loose, @required Widget child })

Creates a widget that controls how a child of a Row, Column, or Flex flexes.

Implementation 

const Flexible({
  Key key,
  this.flex = 1,
  this.fit = FlexFit.loose,
  @required Widget child,
}) : super(key: key, child: child);