The getter 'name' was called on null - flutter

Question

I'm trying to make an app that has basically the same mechanics as a simple todo-app. My problem is, when I try to open the screen where I can create a new project/todo(new_project_screen), there should be loaded some TextFields, but they don't. Instead, this error occurs. I tried several solutions from stackoverflow, but nothing worked and I have no idea why it's not working.(sorry for my bad english, I'm not a native xD)
Here is my code:
main.dart:
import 'package:flutter/material.dart';
import 'package:leisy/surface/main_screen.dart';
void main() {
WidgetsFlutterBinding.ensureInitialized();
runApp(App());
}
class App extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Leisy',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MainScreen(),
);
}
}
main_screen.dart:
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:sqflite/sqflite.dart';
import 'package:leisy/db/database_helper.dart';
import 'package:leisy/model/project.dart';
import 'package:leisy/surface/settings_screen.dart';
import 'package:leisy/surface/new_project_screen.dart';
class MainScreen extends StatefulWidget {
#override
_MainScreenState createState() => _MainScreenState();
}
class _MainScreenState extends State<MainScreen> {
DatabaseHelper databaseHelper = DatabaseHelper();
List<Project> projectList = [];
int count = 0;
#override
Widget build(BuildContext context) {
if (projectList == null) {
projectList = <Project>[];
updateListView();
}
debugPrint("Building entire main screen scaffold");
return Scaffold(
appBar: AppBar(
title: Text("Leisy"),
),
drawer: Drawer(
child: ListView(
padding: EdgeInsets.zero,
children: <Widget>[
DrawerHeader(
child: Center(
child: Text(
"Menü",
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.white,
fontSize: 25,
),
),
),
decoration: BoxDecoration(color: Colors.blue),
),
ListTile(
leading: Icon(Icons.home),
title: Text('Home'),
onTap: () => {Navigator.of(context).pop()},
),
ListTile(
leading: Icon(Icons.add),
title: Text('Neues Projekt'),
onTap: () => {
Navigator.of(context).push(new MaterialPageRoute(
builder: (context) => new NewProjectScreen()))
},
),
ListTile(
leading: Icon(Icons.settings),
title: Text('Einstellungen'),
onTap: () => {
Navigator.of(context).push(
MaterialPageRoute(builder: (context) => SettingsScreen()))
},
)
],
),
),
body: getProjectListView(),
floatingActionButton: FloatingActionButton(
child: Icon(Icons.add),
onPressed: navigateToNewProject,
),
);
}
ListView getProjectListView() {
TextStyle titleStyle = Theme.of(context).textTheme.subtitle1;
return ListView.builder(
itemCount: count,
itemBuilder: (BuildContext context, int position) {
return Card(
color: Colors.white,
elevation: 2.0,
child: ListTile(
leading: CircleAvatar(
backgroundColor: Colors.blue,
),
title: Text(
this.projectList[position].name,
style: titleStyle,
),
subtitle: Text(this.projectList[position].date),
onTap: () {
debugPrint('ListTile Tapped');
//navigateToDetail() einfügen
},
),
);
});
}
void _showSnackBar(BuildContext context, String message) {
final snackBar = SnackBar(
content: Text(message),
);
ScaffoldMessenger.of(context).showSnackBar(snackBar);
}
void navigateToNewProject() async {
bool result = await Navigator.push(context, MaterialPageRoute(builder: (context) => NewProjectScreen()));
if (result == true) {
updateListView();
}
}
void updateListView() {
final Future<Database> dbFuture = databaseHelper.initDB();
dbFuture.then((database) {
Future<List<Project>> projectListFuture = databaseHelper.getProjectList();
projectListFuture.then((projectList) {
setState(() {
this.projectList = projectList;
this.count = projectList.length;
});
});
});
}
}
new_project_screen.dart:
import 'package:flutter/material.dart';
import 'package:leisy/db/database_helper.dart';
import 'package:leisy/model/project.dart';
import 'package:leisy/surface/main_screen.dart';
import 'package:leisy/surface/settings_screen.dart';
class NewProjectScreen extends StatefulWidget {
#override
_NewProjectScreenState createState() => _NewProjectScreenState();
}
class _NewProjectScreenState extends State<NewProjectScreen> {
Project project;
DatabaseHelper helper = DatabaseHelper();
TextEditingController nameController = TextEditingController();
TextEditingController dateController = TextEditingController();
TextEditingController locationController = TextEditingController();
#override
Widget build(BuildContext context) {
nameController.text = project.name;
dateController.text = project.date;
locationController.text = project.location;
return Scaffold(
appBar: AppBar(
title: Text("Neues Projekt"),
leading: IconButton(
icon: Icon(Icons.arrow_back),
onPressed: () {
Navigator.pop(context);
},
),
),
drawer: Drawer(
child: ListView(
padding: EdgeInsets.zero,
children: <Widget>[
DrawerHeader(
child: Center(
child: Text(
"Menü",
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.white,
fontSize: 25,
),
),
),
decoration: BoxDecoration(color: Colors.blue),
),
ListTile(
leading: Icon(Icons.home),
title: Text('Home'),
onTap: () => {
Navigator.of(context).push(
MaterialPageRoute(builder: (context) => MainScreen()))
},
),
ListTile(
leading: Icon(Icons.add),
title: Text('Neues Projekt'),
onTap: () => {Navigator.of(context).pop()},
),
ListTile(
leading: Icon(Icons.settings),
title: Text('Einstellungen'),
onTap: () => {
Navigator.of(context).push(
MaterialPageRoute(builder: (context) => SettingsScreen()))
},
)
],
),
),
body: Padding(
padding: EdgeInsets.all(8.0),
child: ListView(
children: <Widget>[
TextField(
controller: nameController,
decoration: InputDecoration(labelText: 'Name'),
style: TextStyle(fontSize: 20),
onChanged: (value) {
setState(() {
updateName();
});
},
),
TextField(
decoration: InputDecoration(labelText: 'Datum'),
style: TextStyle(fontSize: 20),
onChanged: (value) {
setState(() {
updateDate();
});
},
),
TextField(
decoration: InputDecoration(labelText: 'Ort'),
style: TextStyle(fontSize: 20),
onChanged: (value) {
setState(() {
updateLocation();
});
},
),
Row(
children: <Widget>[
Expanded(
child: ElevatedButton(
style: ButtonStyle(
backgroundColor: MaterialStateProperty.all(
Theme.of(context).primaryColorDark),
),
child: Text('Speichern'),
onPressed: () {
setState(() {
_save();
});
},
)),
Expanded(
child: ElevatedButton(
style: ButtonStyle(
backgroundColor: MaterialStateProperty.all(
Theme.of(context).primaryColorDark),
),
child: Text('Abbrechen'),
onPressed: () {
setState(() {
_cancel();
});
},
)),
],
)
],
)
)
);
}
void _save() async {
Navigator.pop(context, true);
await helper.insertProject(project);
}
void _showSnackBar(String message) {
SnackBar snackBar = SnackBar(content: Text(message));
ScaffoldMessenger.of(context).showSnackBar(snackBar);
}
void _cancel() async {
Navigator.pop(context, true);
_showSnackBar('Vorgang abgebrochen');
}
void updateName() {
project.name = nameController.text;
}
void updateDate() {
project.date = dateController.text;
}
void updateLocation() {
project.location = locationController.text;
}
}
project.dart:
class Project {
int _id;
String _name;
String _date;
String _location;
String _personaldb;
Project(this._name, this._date, this._location, this._personaldb);
Project.withId(
this._id, this._name, this._date, this._location, this._personaldb);
int get id => _id;
String get name => _name;
String get date => _date;
String get location => _location;
String get personalDB => _personaldb;
set name(String newName) {
if (newName.length <= 63) {
this._name = newName;
}
}
set date(String newDate) {
this._date = newDate;
}
set location(String newLocation) {
this._location = newLocation;
}
set personalDB(String newPersonalDB) {
this._personaldb = newPersonalDB;
}
Map<String, dynamic> toMap() {
var map = Map<String, dynamic>();
if (id != null) {
map['id'] = _id;
}
map['name'] = _name;
map['date'] = _date;
map['location'] = _location;
map['personalDB'] = _personaldb;
return map;
}
Project.fromMapObject(Map<String, dynamic> map) {
this._id = map['id'];
this._name = map['name'];
this._date = map['date'];
this._location = map['location'];
this._personaldb = map['personalDB'];
}
}
database_helper.dart:
import 'dart:async';
import 'dart:io';
import 'package:path_provider/path_provider.dart';
import 'package:sqflite/sqflite.dart';
import 'package:leisy/model/project.dart';
class DatabaseHelper {
static DatabaseHelper _databaseHelper;
static Database _database;
String projectTable = 'project_table';
String colId = 'id';
String colName = 'name';
String colDate = 'date';
String colLocation = 'location';
String colPersonalDB = 'personalDB';
DatabaseHelper._createInstance();
factory DatabaseHelper() {
if (_databaseHelper == null) {
_databaseHelper = DatabaseHelper._createInstance();
}
return _databaseHelper;
}
Future<Database> get database async {
if (_database == null) {
_database = await initDB();
}
return _database;
}
Future<Database> initDB() async {
Directory directory = await getApplicationDocumentsDirectory();
String path = directory.path + 'projects.db';
var projectsDB = await openDatabase(path, version: 1, onCreate: _createDB);
return projectsDB;
}
void _createDB(Database db, int newVersion) async {
await db.execute('CREATE TABLE $projectTable('
'$colId INTEGER PRIMARY KEY AUTOINCREMENT,'
'$colName TEXT,'
'$colDate TEXT,'
'$colLocation TEXT,'
'$colPersonalDB TEXT)');
}
Future<List<Map<String, dynamic>>> getProjectMapList() async {
Database db = await this.database;
var result = await db.query(projectTable);
return result;
}
Future<int> insertProject(Project project) async {
Database db = await this.database;
var result = await db.insert(projectTable, project.toMap());
return result;
}
Future<int> updateProject(Project project) async {
var db = await this.database;
var result = await db.update(projectTable, project.toMap(), where: '$colId = ?', whereArgs: [project.id]);
return result;
}
Future<int> deleteProject(int id) async {
var db = await this.database;
int result = await db.delete(projectTable, where: '$colId = $id');
return result;
}
Future<int> getCount() async {
Database db = await this.database;
List<Map<String, dynamic>> x = await db.rawQuery('SELECT COUNT (*) from $projectTable');
int result = Sqflite.firstIntValue(x);
return result;
}
Future<List<Project>> getProjectList() async {
var projectMapList = await getProjectMapList();
int count = projectMapList.length;
List<Project> projectList = <Project>[];
for (int i = 0; i < count; i++) {
projectList.add(Project.fromMapObject(projectMapList[i]));
}
return projectList;
}
}
Error:
======== Exception caught by widgets library =======================================================
The following NoSuchMethodError was thrown building NewProjectScreen(dirty, state: _NewProjectScreenState#670bc):
The getter 'name' was called on null.
Receiver: null
Tried calling: name
The relevant error-causing widget was:
NewProjectScreen file:///C:/Users/gabri/AndroidStudioProjects/leisy/lib/surface/main_screen.dart:116:89
When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:54:5)
#1 _NewProjectScreenState.build (package:leisy/surface/new_project_screen.dart:24:35)
#2 StatefulElement.build (package:flutter/src/widgets/framework.dart:4612:27)
#3 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4495:15)
#4 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4667:11)
...
====================================================================================================
If anybody can help me, I would really appreciate it. And if anything in my code is inconvenient or badly implemented, please be kind with me I'm a beginner at this.

Answer 1

The file new_project_screen.dart has the problem
To be exact, the problem can be found in lines 24:35
And seems like that project variable is null project.name;
That is because you are creating Project project but isn't instancied yet. Is just a null variable
See the image below, will help you to understand a bit:
https://dartpad.dev/1ebc897cd3f547cc0b79e52290a63653
So to fix it, you need to create the instance previously