Flutter, stuck on log in - flutter

Question

I'm trying to redirect to a new screen after logging in
I am writing an app and need help with changing which screen is being seen, when the google sign in button is pressed it authenticates the profile, but I have no idea how to make it go to the home page after it logs in, so it just redirects back to the log-in page and the log-in process repeats. Any way for me to fix this?
import 'package:flutter/material.dart';
import 'auth.dart';
import 'flutter_auth_buttons.dart';
class LoginScreen2 extends StatelessWidget {
final Color backgroundColor1;
final Color backgroundColor2;
final Color highlightColor;
final Color foregroundColor;
final AssetImage logo;
LoginScreen2({Key k, this.backgroundColor1, this.backgroundColor2, this.highlightColor, this.foregroundColor, this.logo});
#override
Widget build(BuildContext context) {
return Column(
children: <Widget>[
Container(
decoration: new BoxDecoration(
gradient: new LinearGradient(
begin: Alignment.centerLeft,
end: new Alignment(1.0, 0.0),
// 10% of the width, so there are ten blinds.
colors: [this.backgroundColor1, this.backgroundColor2],
// whitish to gray
tileMode: TileMode
.repeated, // repeats the gradient over the canvas
),
),
height: MediaQuery
.of(context)
.size
.height,
child: Column(
children: <Widget>[
Container(
padding: const EdgeInsets.only(top: 150.0, bottom: 50.0),
child: Center(
child: new Column(
children: <Widget>[
Container(
height: 128.0,
width: 128.0,
child: new CircleAvatar(
backgroundColor: Colors.transparent,
foregroundColor: this.foregroundColor,
radius: 100.0,
child: new Text(
"",
style: TextStyle(
fontSize: 40.0,
fontWeight: FontWeight.w100,
),
),
),
),
new Padding(
padding: const EdgeInsets.all(16.0),
)
],
),
),
),
new Container(
width: MediaQuery
.of(context)
.size
.width,
margin: const EdgeInsets.only(left: 40.0, right: 40.0),
alignment: Alignment.center,
decoration: BoxDecoration(
),
padding: const EdgeInsets.only(left: 0.0, right: 10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.spaceBetween,
),
),
new Container(
width: MediaQuery
.of(context)
.size
.width,
margin: const EdgeInsets.only(
left: 40.0, right: 40.0, top: 10.0),
alignment: Alignment.center,
decoration: BoxDecoration(
),
padding: const EdgeInsets.only(left: 0.0, right: 10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.spaceBetween,
),
),
new Container(
width: MediaQuery
.of(context)
.size
.width,
margin: const EdgeInsets.only(
left: 40.0, right: 40.0, top: 30.0),
alignment: Alignment.center,
child: new Row(
),
),
new Container(
width: MediaQuery
.of(context)
.size
.width,
margin: const EdgeInsets.only(
left: 100.0, right: 40.0, top: 10.0),
alignment: Alignment.center,
child: new Row(
children: <Widget>[
GoogleSignInButton(onPressed: () =>authService.googleSignIn (
)) ,
new Expanded(
child: new FlatButton(
padding: const EdgeInsets.symmetric(
vertical: 20.0, horizontal: 20.0),
color: Colors.transparent,
onPressed: () => {},
child: Text(
"",
style: TextStyle(
color: this.foregroundColor.withOpacity(0.5)),
),
),
),
],
),
),
new Expanded(child: Divider(),),
new Container(
width: MediaQuery
.of(context)
.size
.width,
margin: const EdgeInsets.only(
left: 40.0, right: 40.0, top: 10.0, bottom: 20.0),
alignment: Alignment.center,
child: new Row(
children: <Widget>[
new Expanded(
child: new FlatButton(
padding: const EdgeInsets.symmetric(
vertical: 20.0, horizontal: 20.0),
color: Colors.transparent,
onPressed: () => {},
child: Text(
"Don't have an account? Create One",
style: TextStyle(
color: this.foregroundColor.withOpacity(0.5)),
),
),
),
],
),
),
],
),
)
]);
}}
class SubPage extends StatelessWidget{
#override
Widget build(BuildContext context){
return new Scaffold(
appBar: new AppBar(
title: new Text('Tile'),
),
body: new GridView.count(
crossAxisCount: 2,
children: new List<Widget>.generate(1000, (index) {
return new GridTile(
child: new Card(
color: Colors.blue.shade200,
child: new Center(
child: new Text('tile $index'),
)
),
);
}),
),
);
}
}

Answer 1

I shall assume that the google sign in button is calling an async job that authenticates the user info and returns a promise that informs if its a successful login or not.
In this case, you can navigate to the home page once the response is received.
GoogleSignInButton(
onPressed: () => authService.googleSignIn ().then((response){
if(response is okay){
Navigator.push(context, MaterialPageRoute(builder: (context) => HomePage()));
}
})
)

Answer 2

I think you don't know how to redirect from one screen to another in Flutter.
This will help you out: https://flutter.dev/docs/development/ui/navigation
In your case you need to use Navigator.pushReplacement when your Google Sign In is completed.
Navigator.pushReplacement(
context, MaterialPageRoute(builder: (BuildContext context) => MyHomePage()));
And Google Sign In may return the Future using which you can perform below operation.
Here then is a callback to be called when Google sign in future complete.
authService.googleSignIn.then((someValue){
Navigator.pushReplacement(
context, MaterialPageRoute(builder: (BuildContext context) => MyHomePage()));
});