Expanded textfield strach a lot - flutter

Question

and at the signup screen I got some problems when I run my app on the device. This happens with the screen : photo with textfields. What I should change to my code to everything to be in place? The app is made with flutter , should I add a height and width to containers? Or should I erase the Expanded and try something else
class SignupPage extends StatefulWidget {
#override
_SignupPageState createState() => _SignupPageState();
}
class _SignupPageState extends State<SignupPage> {
final _formKey = GlobalKey<FormState>();
String email = '';
String password = '';
String error = '';
String _selectedRole = 'Select a User Role';
String get selectedRole => _selectedRole;
int selectedValue;
String selectedString;
// void setSelectedRole(String role) {
// _selectedRole = role;
// }
bool loading = false;
final Authentication authentication = Authentication();
int selectedIndex1 = 0;
final elements1 = [
"Customer",
"Business",
];
List<Widget> _buildItems1() {
return elements1
.map((val) => MySelectionItem(
title: val,
))
.toList();
}
#override
Widget build(BuildContext context) {
return Scaffold(
// resizeToAvoidBottomInset: false,
// resizeToAvoidBottomPadding: false,
body: Container(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
child: Column(
children: <Widget>[
Container(
margin: EdgeInsets.only(top: 30.0),
child: Row(
children: <Widget>[
IconButton(
icon: Icon(Icons.arrow_back_ios, color: Colors.blue),
onPressed: () {
Navigator.pushReplacement(
context,
MaterialPageRoute(
builder: (context) => LoginScreen()));
},
)
],
),
),
Padding(
padding: const EdgeInsets.only(top: 20.0),
child: RichText(
text: TextSpan(
text: 'Tariffo',
style: TextStyle(
color: Colors.blue,
fontFamily: 'SignPainter',
fontSize: 60),
),
),
),
Expanded(
child: Container(
child: Form(
key: _formKey,
child: Column(
children: <Widget>[
Padding(
padding: const EdgeInsets.only(
left: 40.0, right: 40.0, top: 30.0),
child: TextFormField(
validator: (val) => val.isEmpty ? 'enter name' : null,
onChanged: (val) {
setState(() => name = val);
},
style: TextStyle(color: Colors.black),
decoration: InputDecoration(
hintText: 'Enter Name',
hintStyle: TextStyle(
fontFamily: 'Antra',
fontSize: 12.0,
color: Colors.black)),
),
),
Expanded(
child: Padding(
padding: const EdgeInsets.only(
left: 40.0, right: 40.0, top: 40.0),
child: TextFormField(
validator: (val) =>
val.isEmpty ? 'Enter Email' : null,
onChanged: (val) {
setState(() => email = val);
},
style: TextStyle(color: Colors.black),
decoration: InputDecoration(
hintText: 'Enter email',
hintStyle: TextStyle(
fontFamily: 'Antra',
fontSize: 12.0,
color: Colors.black)),
),
),
),
Expanded(
child: Padding(
padding: const EdgeInsets.only(
left: 40.0, right: 40.0, top: 10.0),
child: TextFormField(
validator: (val) => val.length < 8
? 'enter password > 8 digits'
: null,
onChanged: (val) {
setState(() => password = val);
},
style: TextStyle(color: Colors.black),
decoration: InputDecoration(
hintText: 'Enter Password',
hintStyle: TextStyle(
fontFamily: 'Antra',
fontSize: 12.0,
color: Colors.black)),
obscureText: true,
),
),
),
Expanded(
child: Padding(
padding: const EdgeInsets.symmetric(vertical:10.0),
child: DirectSelect(
itemExtent: 50.0,
selectedIndex: selectedIndex1,
backgroundColor: Colors.white30,
child: MySelectionItem(
isForList: false,
title: elements1[selectedIndex1],
),
onSelectedItemChanged: (index) {
setState(() {
selectedIndex1 = index;
});
},
items: _buildItems1()),
),
),
Expanded(
child: Padding(
padding: const EdgeInsets.symmetric(vertical:40.0),
child: MaterialButton(
color: Colors.blue,
height: 30,
minWidth: 300,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10)),
onPressed: () async {
if (_formKey.currentState.validate()) {
setState(() => loading = true);
dynamic result = await authentication
.createUserWithEmailAndPassword(email, password,
name, elements1[selectedIndex1]);
if (elements1[selectedIndex1] == 'Business') {
Navigator.push(
context,
new MaterialPageRoute(
builder: (_) => BusinessPage()));
} else {
Navigator.push(
context,
new MaterialPageRoute(
builder: (_) => Homepage()));
}
if (result == null) {
setState(() => error =
'Sorry,These credentials will not work out');
loading = false;
}
}
},
child: Text(
'Sign up',
style: TextStyle(
fontFamily: 'Antra', color: Colors.white),
),
),
),
),
],
),
),
),
),
_createAccountLabel(),
],
),
),
);
}
Widget _createAccountLabel() {
return InkWell(
onTap: () {
Navigator.push(
context, MaterialPageRoute(builder: (context) => LoginPage()));
},
child: Container(
margin: EdgeInsets.symmetric(vertical: 20),
padding: EdgeInsets.all(15),
alignment: Alignment.bottomCenter,
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'Do you have an account ?',
style: TextStyle(fontSize: 13, fontWeight: FontWeight.w600),
),
SizedBox(
width: 10,
),
Text(
'Login',
style: TextStyle(
color: Colors.blue,
fontSize: 13,
fontWeight: FontWeight.w600),
),
],
),
),
);
}
}