How to get data from model class with using SQFlite in Flutter? - flutter

Question

Here I use SqFlite functionality with model class for data store. But problem is that, when I click on button, addData method was called null.
This is my model class.
import 'dart:convert';
DatabaseModel fromJson({String str}) {
final jsonData = json.decode(str);
return DatabaseModel.fromMap(jsonData);
}
String toJson(DatabaseModel databaseModel) {
final dyn = databaseModel.toMap();
return json.encode(dyn);
}
class DatabaseModel {
String id;
String imageUrl;
String title;
String description;
String newsLink;
String createDate;
String category;
String footerTitle;
DatabaseModel(
{this.id,
this.imageUrl,
this.title,
this.description,
this.newsLink,
this.createDate,
this.category,
this.footerTitle});
factory DatabaseModel.fromMap(Map<String, dynamic> json) => DatabaseModel(
id: json['id'],
imageUrl: json['imageUrl'],
title: json['title'],
description: json['description'],
newsLink: json['newsLink'],
createDate: json['createDate'],
category: json['category'],
footerTitle: json['footerTitle']);
Map<String, dynamic> toMap() => {
'id': id,
'imageUrl': imageUrl,
'title': title,
'description': description,
'newsLink': newsLink,
'createDate': createDate,
'category': category,
'footerTitle': footerTitle
};
}
Now, I display my database class which I use for Add, Delete, and Get data. In this class I use Model class because I want to display my data in Bookmark class.
import 'dart:io';
import 'package:news_app/src/model/bookmark_db_provider.dart';
import 'package:path/path.dart';
import 'package:path_provider/path_provider.dart';
import 'package:sqflite/sqflite.dart';
class DatabaseProvider {
// DatabaseProvider._();
// static final DatabaseProvider db = DatabaseProvider._();
Database _database;
Future<Database> get database async {
if (_database != null) return _database;
_database = await getDatabaseInstance();
return _database;
}
Future<Database> getDatabaseInstance() async {
Directory directory = await getApplicationDocumentsDirectory();
String path = join(directory.path, 'bookmark.db');
return await openDatabase(path, version: 1,
onCreate: (Database db, int version) async {
await db.execute('create table Bookmark ('
'id integer primary key autoincrement,'
'imageUrl text,'
'title text,'
'description text,'
'newsLink text,'
'createDate text,'
'category text,'
'footerTitle text'
')');
});
}
addToDatabase(DatabaseModel databaseModel) async {
final db = await database;
var raw = await db.insert('Bookmark', databaseModel.toMap(),
conflictAlgorithm: ConflictAlgorithm.replace);
return raw;
}
updateDatabase(DatabaseModel databaseModel) async {
final db = await database;
var response = await db.update('Bookmark', databaseModel.toMap(),
where: 'id = ?', whereArgs: [databaseModel.id]);
return response;
}
Future<DatabaseModel> getDatabaseModelWithId(int id) async {
final db = await database;
var response = await db.query('Bookmark', where: 'id = ?', whereArgs: [id]);
return response.isNotEmpty ? DatabaseModel.fromMap(response.first) : null;
}
Future<List<DatabaseModel>> getAllData() async {
final db = await database;
var response = await db.query('Bookmark');
List<DatabaseModel> list =
response.map((c) => DatabaseModel.fromMap(c)).toList();
return list;
}
deleteDatabase(int id) async {
final db = await database;
return db.delete('Bookmark', where: 'id = ?', whereArgs: [id]);
}
deleteAllDatabase() async {
final db = await database;
db.delete('Bookmark');
}
}
Here I display my BookMark class. This class I use for display data for user.
import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
import 'package:news_app/src/model/bookmark_db_provider.dart';
import 'package:news_app/src/screens/home.dart';
import 'package:news_app/src/utils/database.dart';
class BookMark extends StatefulWidget {
#override
_BookMarkState createState() => _BookMarkState();
}
class _BookMarkState extends State<BookMark> {
DatabaseProvider databaseProvider;
#override
void initState() {
super.initState();
databaseProvider = DatabaseProvider();
}
#override
void dispose() {
super.dispose();
}
#override
Widget build(BuildContext context) {
return WillPopScope(
onWillPop: () => Navigator.push(
context, MaterialPageRoute(builder: (context) => HomePage())),
child: Scaffold(
backgroundColor: Theme.of(context).primaryColor,
appBar: AppBar(
backgroundColor: Theme.of(context).appBarTheme.color,
elevation: 0,
centerTitle: true,
title: Text(
'BookMark News',
style: TextStyle(fontSize: 23, fontWeight: FontWeight.bold),
),
),
body: Container(
padding: EdgeInsets.all(8.0),
child: FutureBuilder<List<DatabaseModel>>(
future: databaseProvider.getAllData(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.hasData) {
return ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (BuildContext context, int index) {
var common = snapshot.data[index];
return Card(
elevation: 5.0,
child: ListTile(
leading: SizedBox(
height: 85,
width: 79,
child: Container(
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(5.0),
image: DecorationImage(
image:
NetworkImage(common['imageUrl']),
fit: BoxFit.cover)),
),
),
title: Text(common['title']),
isThreeLine: true,
subtitle: Text(common['footerTitle']),
trailing: Column(
children: <Widget>[
Text(common['createDate']),
Text(common['category'])
],
),
),
);
});
} else {}
return Center(
child: CircularProgressIndicator(),
);
},
)
)),
);
}
}
I all of data in Home Page and in this Page when I pressed on button it display Method was called null. This type I handle onclick.
onPressed: () async {
print('added data');
dbHelper.addToDatabase(DatabaseModel(
imageUrl: allNewsDetail[index]['image_url'],
category: allNewsDetail[index]['category'],
footerTitle: allNewsDetail[index]['footer_title'],
createDate: allNewsDetail[index]['created_date'],
newsLink: allNewsDetail[index]['news_link'],
description: allNewsDetail[index]['description'],
title: allNewsDetail[index]['title']));
Navigator.push(context,MaterialPageRoute(builder: (context) =>BookMark()));
}
When click on button it displays this error.
The method 'getAllData' was called on null.
Receiver: null
Tried calling: getAllData()
Please check This code I give me solution for it.

Answer 1

You are not passing in the databaseProvider into this class and that is why you are getting null!