I Found this answer

Here is the correct way to receive the data from the previous screen

From Screen B

Navigator.pop(context,"Pass your data here");

In Screen A

String results;

var receiedValue =await Navigator.push(
              context,
              MaterialPageRoute(builder: (context) => ScreenB()),
            );
            // How do I refresh the widget here to fetch updated data?
           setState(){
          results = receiedValue;
            }