FlatButton taking up whole screen in flutter web - flutter

Question

I am building a webapp with flutter where I want to add google sign in. The button itself works fine, but whatever I try, it just takes up my whole screen. I tried putting the button in the class in a container and putting it in a sizedbox on the page I actually want to use it on, and limiting the size of the button itself. This is my first time with flutter web, so I'd really like to know why this is happening.
Here is my code for the button:
class GoogleButton extends StatefulWidget {
#override
_GoogleButtonState createState() => _GoogleButtonState();
final DatabaseRepo databaseRepo;
final InitRepo initRepo;
GoogleButton(this.databaseRepo, this.initRepo);
}
class _GoogleButtonState extends State<GoogleButton> {
bool _isProcessing = false;
#override
Widget build(BuildContext context) {
return SizedBox(
height: MediaQuery.of(context).size.height / 10,
child: FlatButton(
height: MediaQuery.of(context).size.height / 10,
onPressed: () async {
setState(() {
_isProcessing = true;
});
await signInWithGoogle().then((result) {
print(result);
Navigator.of(context).pop();
Navigator.of(context).push(
MaterialPageRoute(
fullscreenDialog: true,
builder: (context) =>
MainPage(widget.databaseRepo, widget.initRepo),
),
);
}).catchError((error) {
print('Registration Error: $error');
});
setState(() {
_isProcessing = false;
});
},
child: Padding(
padding: const EdgeInsets.fromLTRB(0, 10, 0, 10),
child: _isProcessing
? CircularProgressIndicator(
valueColor: new AlwaysStoppedAnimation<Color>(
Colors.blueGrey,
),
)
: Row(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(left: 20),
child: Text(
'Bejelentkezés',
style: TextStyle(
fontSize: 20,
color: Colors.blueGrey,
),
))
]))),
);
}
}
Just to be on the safe side, here is the code for the page itself:
import 'package:flutter/material.dart';
import 'package:foci_dev/repo/database_repo.dart';
import 'package:foci_dev/repo/init_repo.dart';
import 'package:foci_dev/ui/google_button.dart';
class SignInPage extends StatelessWidget {
final DatabaseRepo databaseRepo;
final InitRepo initRepo;
SignInPage(this.databaseRepo, this.initRepo);
#override
Widget build(BuildContext context) {
return Container(
color: Colors.grey[800],
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Container(
height: MediaQuery.of(context).size.height / 5,
width: MediaQuery.of(context).size.height / 5,
child: Column(
children: [
Image(image: AssetImage('lib/assets/icon.png')),
Container(
height: MediaQuery.of(context).size.height / 10,
child: ButtonTheme(
height: 20,
child:
GoogleButton(this.databaseRepo, this.initRepo))),
],
)),
],
),
);
}
}
Thank you very much for your help, I really don't know what to do.