Refractor

Same code of widget in different widget can be shorten by making new widget by refractor 

example

Container(
  margin: EdgeInsets.all(15),
  decoration: BoxDecoration(
    color: Color(0xFF1d1f33),
    borderRadius: BorderRadius.circular(12),

this above code is used multiple times in different widget so we use refractor

then by refractor we can name new widget replacing this above code

example  --  ReusableCard(),

by Refracting, this code made by android studio

A Key is an identifier for Widgets, Elements and SemanticsNodes.

class ReusableCard extends StatelessWidget {
  const ReusableCard({
    Key key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      margin: EdgeInsets.all(15),
      decoration: BoxDecoration(
        color: Color(0xFF1d1f33),
        borderRadius: BorderRadius.circular(12),
      ),
    );
  }
}