Simple Flutter sqflite login->write to db->navigate->retrieve from db flow - sqlite

Question

What is the correct way to handle this, I have done a lot of searching and most samples which use future builders use them to draw lists so maybe I should be avoiding them all together here.
I want to submit a login form, perform the network request and draw a progress bar while the login is happening, and if successful navigate to a home page. If unsuccessful it should just kill the progress bar and redraw the home page. That part seems to be working, unsure if I am using the Navigator correctly.
The login call returns a user and access token object. The Homepage needs to retrieve the access token which was written to the db by the successful login response. From what I can tell the navigation is happening too quickly and the retrieval of the access token appears to happen before the navigation to the home page.
class LoginPage extends StatefulWidget {
LoginPage({Key key, this.title}) : super(key: key);
final String title;
#override
_LoginPageState createState() => _LoginPageState();
}
class _LoginPageState extends State<LoginPage> {
bool _isValidForm = true;
Future<LoginResponse> _user;
void _submitLogin() {
setState(() {
if (_isValidForm) {
_user = login().then((_) => Navigator.push(context, MaterialPageRoute(builder: (context) => HomePage())));
}
});
}
Widget _buildLoginForm(AsyncSnapshot<LoginResponse> snapshot) {
if (snapshot.connectionState != ConnectionState.none && !snapshot.hasData) {
return new Center(child: new CircularProgressIndicator());
} else {
return SafeArea(
child: Center(
child: new ListView(
children: <Widget>[
//..more views
Padding(
padding: EdgeInsets.fromLTRB(16.0, 0.0, 16.0, 16.0),
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
//..email and password fields
FlatButton(
child: new Text(
'SIGN IN',
),
onPressed: _submitLogin),
]),
)
],
),
),
);
}
}
#override
Widget build(BuildContext context) {
return new FutureBuilder(
future: _user,
builder: (context, AsyncSnapshot<LoginResponse> snapshot) {
return new Scaffold(
backgroundColor: kMyGreen,
body: _buildLoginForm(snapshot),
);
},
);
}
Future<LoginResponse> login() async {
final response = await http.post(...);
if (response.statusCode == 200) {
var loginResponse = LoginResponse.fromJson(json.decode(response.body));
//Write the user details to local db
DBProvider.db.newUser(loginResponse.user);
//Write the tokens to local db
DBProvider.db.newToken(loginResponse.tokens);
return loginResponse;
} else {
throw Exception('Failed to login');
}
}
}
Database methods:
newUser(User newUser) async {
final db = await database;
//get the biggest id in the table
var table = await db.rawQuery("SELECT MAX(id)+1 as id FROM User");
int id = table.first["id"];
//insert to the table using the new id
var raw = await db.rawInsert(
"INSERT Into User (id,first_name,last_name)"
" VALUES (?,?,?)",
[id, newUser.firstName, newUser.lastName]);
return raw;
}
newToken(Tokens newTokens) async {
final db = await database;
//await db.rawDelete("DELETE FROM Token");
//get the biggest id in the table
var table = await db.rawQuery("SELECT MAX(id)+1 as id FROM Token");
int id = table.first["id"];
//insert to the table using the new id
var raw = await db.rawInsert(
"INSERT Into Token (id,access_token,refresh_token)"
" VALUES (?,?,?)",
[id, newTokens.accessToken, newTokens.refreshToken]);
return raw;
}
Future<Tokens> getToken() async {
final db = await database;
var res = await db.query("Token", limit: 1);
return res.isNotEmpty ? Tokens.fromJson(res.first) : null;
}
Home page
class HomePage extends StatefulWidget {
HomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage>{
#override
void initState() {
super.initState();
getHomePageStuff();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Home Page"),
),
body: Center(
child: RaisedButton(
onPressed: () {},
child: Text('Go back!'),
),
),
);
}
}
Future<HomePageStuffResponse> getHomePageStuff() async {
Tokens token = await DBProvider.db.getToken();
//Accessing the token here throws an NPE
var accessToken = token.accessToken;
debugPrint("token = " + accessToken);
final response = await http.get(..);
if (response.statusCode == 200) {
debugPrint("FETCH SUCCESS");
return stuff;
} else {
throw Exception('Failed to fetch home page stuff');
}
}

Answer 1

You can simply wrap Scaffold's body in FutureBuilder like this
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Home Page"),
),
body: FutureBuilder<HomePageStuffResponse>(
future: getHomePageStuff(),
builder: (context, snap) {
if(snap.hasError) {
return ErrorWidget('Error occurred while fetching data');
}
if(snap.hasData) {
return Center(
child: RaisedButton(
onPressed: () {},
child: Text('Go back!'),
),
);
}
}
),
);
}
}
Future<HomePageStuffResponse> getHomePageStuff() async {
Tokens token = await DBProvider.db.getToken();
//Accessing the token here throws an NPE
var accessToken = token.accessToken;
debugPrint("token = " + accessToken);
final response = await http.get(..);
if (response.statusCode == 200) {
debugPrint("FETCH SUCCESS");
return stuff;
} else {
throw Exception('Failed to fetch home page stuff');
}
}

Answer 2

Okay I was pretty close. Navigation is fine the way it is, the issue was the writing to the db was not being awaited on so that would happen simultaneously to the navigation (the newUser and newToken calls). As I would navigate to the home screen and try and read the access token the call would fail because it did not exist yet.
This was made a little harder to figure out because the debugger is a little strange in Android Studio for flutter so I just had to log everything to the console to see the issue.
If you read my question thank you for your time :)