returning null user back from function - sql

Question

I am working on Login page with Local db SQL in flutter.
The page isn't creating a SQL table and returning null user, thus showing the snackbar "wrong email".
I have tried to debug but can't find the solution as i am pretty new at this.
This is my sign up page:
class _RegisterState extends State<Register> {
DatabaseHelper db = new DatabaseHelper();
TextEditingController emailController = TextEditingController();
TextEditingController mobileController = TextEditingController();
Future<User> _loginUser(String email,String mobile) async{
User saveUser = User.fromMapObject({
email:"hfah#gmail.com",
mobile:"1432567890"
});
await db.saveUser(saveUser).then((val) async {
if(val == 1){
User user = await db.loginUser(email, mobile);
return user;
}
});
}
final _formKey = GlobalKey<FormState>();
final scaffoldKey = new GlobalKey<ScaffoldState>();
#override
Widget build(BuildContext context) {
final bgColor = const Color(0xFF4b0081);
return Scaffold(
resizeToAvoidBottomPadding: false,
backgroundColor: bgColor,
key: scaffoldKey,
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Image(
image: AssetImage("assets/newlogo2.png"),
width: 200,
height: 50,
),
Container(
padding: const EdgeInsets.only(top:20.0, right: 20, left: 20),
child: Form(
key: _formKey,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
TextFormField(
decoration: InputDecoration(
labelText: "Mobile No",
labelStyle: TextStyle(color: Colors.white)
),
style: TextStyle(color: Colors.white, fontSize: 20.0),
onChanged: (val) {
setState(() => mob = val);
},
controller: emailController,
),
SizedBox(height: 20.0,),
TextFormField(
validator: (val) => val.isEmpty ? 'Enter an Email' : null,
decoration: InputDecoration(
labelText: "Email ID",
labelStyle: TextStyle(color: Colors.white)
),
style: TextStyle(color: Colors.white, fontSize: 20.0),
onChanged: (val){
setState(() => email = val);
},
controller: mobileController,
),
SizedBox(height: 20.0,),
RaisedButton(
color: Colors.white,
child: Text(
'Register',
style: TextStyle(color: bgColor),
),
onPressed: () async {
User user = await _loginUser(emailController.text, mobileController.text);
if(user != null){
Navigator.of(context).push(MaterialPageRoute<Null>(
builder: (BuildContext context){
return new Home(
user:user,
);
}
));
}else{
scaffoldKey.currentState.showSnackBar(
SnackBar(content: Text("Wrong email"),)
);
}
},
splashColor: Colors.grey,
),
SizedBox(height: 12.0,),
Text(
error,
style: TextStyle(
color: Colors.red,
fontSize: 14.0
),
),
FlatButton(
color: bgColor,
child: Text(
'Back to Sign In',
style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold),
),
onPressed: () async {
setState(() {
//widget.toggleView();
},);
},
),
],
),
),
),
],
),
);
}
This is DatabaseHelper class
class DatabaseHelper{
static final DatabaseHelper _instance = new DatabaseHelper.internal();
factory DatabaseHelper() => _instance;
static Database _db;
String colemail = 'emial_id';
String tablename = 'User';
String colMobile = 'mobild_no';
Future<Database> get db async{
if(_db != null) return _db;
_db = await initDb();
return _db;
}
DatabaseHelper.internal();
initDb() async{
io.Directory documentsDirectory = await getApplicationDocumentsDirectory();
String path = join(documentsDirectory.path, "main.db");
var theDb = await openDatabase(path,version:1,onCreate: _onCreate);
return theDb;
}
void _onCreate(Database db,int version) async{
await db.execute("""
CREATE TABLE User(
user_id INTEGER PRIMARY KEY,
email_id TEXT,
mobile_no TEXT
)""");
print("Table created");
}
Future<int> saveUser(User user) async{
var dbClient = await db;
int res = await dbClient.insert(tablename, user.toMap());
return res;
}
Future<User> loginUser(String email,String mobile) async{
var dbClient = await db;
String sql = "SELECT * FROM User WHERE email_id = '$email' AND
mobile_no = '$mobile' ";
var result = await dbClient.rawQuery(sql);
if(result.length == 0) return null;
return User.fromMapObject(result.first);
}
}
And this is User class
class User{
int _user_id;
String email_id;
String mobile_no;
User(this.email_id,this.mobile_no,this._user_id);
String get emailID => email_id;
String get mobileNO => mobile_no;
int get user_id =>_user_id;
set emailID(String newMail){
this.email_id = newMail;
}
set mobileNO(String newMob){
this.mobile_no = newMob;
}
Map <String,dynamic> toMap(){
return {
'email_id': email_id,
'mobile_no': mobile_no,
'user_id':_user_id
};
}
User.fromMapObject(dynamic map){
this.email_id = map['email_id'];
this.mobile_no = map['mobile_no'];
this._user_id = map['user_id'];
}
}
Please help !!!

Answer 1

In _RegisterState class, I don't see if you instantiated DatabaseHelper db; so db is null and you are trying to invoke saveUser on null instance variable in following code
await db.saveUser(saveUser).then((val) async {
if(val == 1){
User user = await db.loginUser(email, mobile);
return user;
}
});
Replace this
Scaffold.of(context).showSnackBar(SnackBar(content: Text("Wrong email"),));
with
scaffoldKey.currentState.showSnackBar(SnackBar(content: Text("Wrong email")));

Answer 2

You just need to instantiate db:
class _RegisterState extends State<Register> {
DatabaseHelper db = new DatabaseHelper();
....
}
For the Snackbar error, replace this code:
else{
Scaffold.of(context).showSnackBar(
SnackBar(content: Text("Wrong email"),)
);
}
with:
else{
globalKey.currentState.showSnackBar(
SnackBar(content: Text("Wrong email"),)
);
}