DART

flutter mediaquery

Container(
  width: MediaQuery.of(context).size.width,
  color: Colors.blue,
  child: Text('I cover the whole width of the screen!')
)

media query flutter

Container(
  height:MediaQuery.of(context).size.height,
  width: MediaQuery.of(context).size.width,
  color: Colors.blue,
  child: Text('I cover the whole width of the screen!')
)