I cannot add appBar - flutter

Question

I am trying to do a log in app, after finishing with the design I faced a problem where I could not add the function of going back to the old page, I searched and found about the appBar but I could not apply it.
class Body extends StatelessWidget {
const Body({
Key key,
}) : super(key: key);
#override
Widget build(BuildContext context) {
Size size = MediaQuery.of(context).size;
return Background(
child: SingleChildScrollView(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
"LOGIN",
style: TextStyle(fontWeight: FontWeight.bold),
),
SizedBox(height: size.height * 0.03),
SizedBox(height: size.height * 0.03),
RoundedInputField(
hintText: "Your Email",
onChanged: (value) {},
),
RoundedPasswordField(
onChanged: (value) {},
),
RoundedButton(
text: "LOGIN",
press: () {},
),
SizedBox(height: size.height * 0.03),
AlreadyHaveAnAccountCheck(
press: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) {
return SignUpScreen();
},
),
);
},
),
],
),
),
);
}
}

Answer 1

You must use Scaffold Widget for displaying the AppBar try below code hope its helpful to you In Scaffold widget you declare AppBar for Appbar refer ducumentation here :
class AppBarPage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Your Title'),
),
body: Container(),
);
}
}
Your Screen look like this->

Answer 2

use Scaffold.
class MyHomePage extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("MyHomePage"),
actions: [
TextButton(onPressed: (){
Navigator.of(context).pop();
}, child: Icon(Icons.arrow_back))
],
),
body:Body() ,
);
}
}
on onPressed event you can return to old page

Answer 3

appBar can be used inside Scaffold.
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('AppBar Demo'),
actions: <Widget>[
IconButton(
icon: const Icon(Icons.arrow_back),
tooltip: 'Show Snackbar',
onPressed: () {
Navigator.of(context).pop();
},
),
],
),
body: const Center(
child: Text(
'This is the home page',
style: TextStyle(fontSize: 24),
),
),
);
}