My screen is not jumping to the next screen as required - flutter

Question

I am using RawMaterialButton and I need to switch screen when the button is pressed, but it is not switching?
Here is my code - first Screen:
Widget _buildListItem(String picture) {
return Row(
children: <Widget>[
Row(
children: <Widget>[
Container(
height: 100.0,
width: 130.0,
decoration: BoxDecoration(
image: DecorationImage(
image: AssetImage(picture),
fit: BoxFit.cover
),
borderRadius: BorderRadius.only(topRight: Radius.circular(10.0), bottomRight: Radius.circular(10.0))),
),
SizedBox(width: 10.0),
Container(
height: 120.0,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text('Maple Mustard Tempeh',
style: TextStyle(
fontSize: 15.0,
fontFamily: 'Montserrat',
fontWeight: FontWeight.bold
),
),
SizedBox(height: 5.0),
Text('Marinated kale, onion, tomato and roasted',
style: TextStyle(
fontSize: 11.0,
fontFamily: 'Montserrat',
fontWeight: FontWeight.bold,
color: Colors.grey
),
),
Text('garlic aioli on grilled spelt bread',
style: TextStyle(
fontSize: 11.0,
fontFamily: 'Montserrat',
fontWeight: FontWeight.bold,
color: Colors.grey
),
),
SizedBox(height: 10.0),
Row(
children: <Widget>[
Text('\u20B9 11.25',
style: TextStyle(
fontSize: 20.0,
fontFamily: 'Montserrat',
fontWeight: FontWeight.bold,
color: Colors.grey
),
),
SizedBox(width: 60.0,),
Cbutton(onPressed: ()=> item_details()),
],
),
],
),
),
],
),
],
);
}
RawMaterialButton
return new RawMaterialButton(
fillColor: Colors.green,
splashColor: Colors.greenAccent,
child: Padding(
padding: const EdgeInsets.symmetric(
horizontal: 20.0,
vertical: 8.0),
child: Row(
mainAxisSize: MainAxisSize.min,
children: const <Widget>[
Icon(
Icons.add,
color: Colors.white,),
SizedBox(width: 8.0,),
Text("Add", style: TextStyle(
color: Colors.white
),),
],
),
),
onPressed: onPressed,
shape: StadiumBorder(),
);
}
}

Answer 1

If you want to change screens, you can user Navigator.
onPressed: () {
Navigator.push( context, MaterialPageRoute(
builder: (context) => SecondScreen()
));
}