There are many ways of doing it, I am listing few here.
Using backgroundColor
Scaffold(
backgroundColor: Colors.black,
body: Center(...),
)
Using Container
in SizedBox.expand
Scaffold(
body: SizedBox.expand(
child: Container(
color: Colors.black,
child: Center(...)
),
),
)
Using Theme
Theme(
data: Theme.of(context).copyWith(scaffoldBackgroundColor: Colors.black),
child: Scaffold(
body: Center(...),
),
)