Missing concrete implementation of 'State.build' - flutter

Question

I am in the learning stage of flutter and facing errors. I am watching a course on Udemy. I am trying to build a Personal Expense Tracker. It's a fundamental project but, as I already told I am currently learning and am facing an error. Any help would be appreciated.
This is the code of my main.dart file:
import 'package:flutter/material.dart';
import './widgets/transaction_list.dart';
import './widgets/new_transactions.dart';
import './widgets/chart.dart';
import './models/transaction.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
final ThemeData theme = ThemeData(
primarySwatch: Colors.primaries[1],
errorColor: Colors.red,
fontFamily: 'Quicksand',
);
return MaterialApp(
title: 'Expense Planner',
theme: theme.copyWith(
colorScheme: theme.colorScheme.copyWith(secondary: Colors.amber),
),
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
#override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
final List<Transaction> _userTransactions = [];
List<Transaction> get _recentTransactions {
return _userTransactions.where((tx) {
return tx.date.isAfter(
DateTime.now().subtract(
Duration(days: 7),
),
);
}).toList();
}
void _addNewTransaction(
String txTitle, double txAmount, DateTime chosenDate) {
final newTx = Transaction(
title: txTitle,
amount: txAmount,
date: chosenDate,
id: DateTime.now().toString(),
);
setState(() {
_userTransactions.add(newTx);
});
}
void _startAddNewTransaction(BuildContext ctx) {
showModalBottomSheet(
context: ctx,
builder: (_) {
return GestureDetector(
onTap: () {},
child: NewTransaction(_addNewTransaction),
behavior: HitTestBehavior.opaque,
);
},
);
}
void _deleteTransaction(String id) {
setState(() {
_userTransactions.removeWhere((tx) => tx.id == id);
{
;
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(
'Expense Planner',
style: TextStyle(
fontFamily: 'OpenSans',
fontSize: 22,
fontWeight: FontWeight.bold,
),
),
actions: <Widget>[
IconButton(
icon: Icon(Icons.add),
onPressed: () => _startAddNewTransaction(context),
),
],
),
body: SingleChildScrollView(
child: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: <Widget>[
Chart(_recentTransactions),
TransactionList(_userTransactions, _deleteTransaction),
],
),
),
floatingActionButtonLocation:
FloatingActionButtonLocation.centerFloat,
floatingActionButton: FloatingActionButton(
child: Icon(Icons.add),
onPressed: () => _startAddNewTransaction(context),
),
);
}
});
}
}
There's some error in the _MyHomePageState class. it shows the following error
Missing concrete implementation of 'State.build'.
Try implementing the missing method, or make the class abstract.
However when I try to make the _MyHomePageState class abstract it shows the following:
Abstract classes can't be instantiated.
Try creating an instance of a concrete subtype.
Thanks & Regards,
Harshit Chitkara

Answer 1

I think 'home: MyHomePage(),' is waiting for a Widget. You have to build a Widget arround the List. After that you probably need a Scaffold inside the Widget.
#override
Widget build(BuildContext context) {
return Scaffold(
child: List<Transaction> get _recentTransactions {
return _userTransactions.where((tx) {
return tx.date.isAfter(
DateTime.now().subtract(
Duration(days: 7),
),
);
}).toList();
}
);
}
This should fix the current problem, but you can't have a return inside a return.