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Using SQLite in Flutter – Tutorial

sqlite in flutter

In this tutorial, we’ll take a look at using sqlite in flutter. SQLite is a SQL engine used in mobile devices and some computers. We can use it to persist data for our app. Persistent storage can be useful for caching network calls while fresh data is loaded and for offline apps.

SQLite in flutter can be used to persist data in Android and iOS apps. In this tutorial, we’ll be building a simple app to log data in lists such as a Grocery List. Here is a screenshot of the app.

Note: It will be useful if you’re aware of some basics of flutter. This post would be a good place to start.

 

Getting Started

Go ahead and create a new project. I’ll name mine flutter_sqlite, you can name it whatever you want.

➜  ~ flutter create flutter_sqflite

We’ll remove the default code and comments and just put in a container for now. On running the app you’ll see a blank screen.

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Listify'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Container(),
    );
  }

}

Next up, add the following dependency to your pubspec.yaml file: 

name: flutter_sqflite
description: A new Flutter project.

publish_to: 'none'

version: 1.0.0+1

environment:
  sdk: ">=2.7.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter
  sqflite:

  cupertino_icons: ^0.1.3

dev_dependencies:
  flutter_test:
    sdk: flutter

flutter:

  uses-material-design: true

 

Building the UI

We’ll create a basic text field, a button to save and a list to display our todos. First, let’s go ahead and create our input field. This will be inside of the scaffold body:

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Listify'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Container(
        alignment: Alignment.topLeft,
        padding: EdgeInsets.all(16),
        child: Column(
          children: <Widget>[
            Row(
              children: <Widget>[
                Expanded(
                  child: TextFormField(
                    decoration: InputDecoration(hintText: "Enter a task"),
                    controller: textController,
                  ),
                )
              ],
            )
          ],
        ),
      ),
    );
  }

}

Add a TextEditingController as a property of this class which will help us retrieve the data from this field.

class _MyHomePageState extends State<MyHomePage> {

  TextEditingController textController = new TextEditingController();

...

Next up, create a button to save the todo:

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Listify'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  TextEditingController textController = new TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Container(
        alignment: Alignment.topLeft,
        padding: EdgeInsets.all(16),
        child: Column(
          children: <Widget>[
            Row(
              children: <Widget>[
                Expanded(
                  child: TextFormField(
                    decoration: InputDecoration(hintText: "Enter a task"),
                    controller: textController,
                  ),
                ),
                IconButton(
                  icon: Icon(Icons.add),
                  onPressed: null,
                ),
              ],
            )
          ],
        ),
      ),
    );
  }
}

We’ll not be adding validation for the sake of simplicity, you can do that in your app. We’ll keep the focus of this article on using sqlite in flutter.

With the input field and button created, let’s add a list to display the items. But for that, we’ll need to create a model of the items. Create a file named todo.dart and add the following class:

class Todo {
  int id;
  String title;

  Todo({this.id, this.title});

  Map<String, dynamic> toMap() {
    return {'id': id, 'title': title};
  }
}

Now let’s go ahead and create our list. If you want to know how to create a ListView in Flutter, you can check out this post. We’ll be adding our list in the body of Scaffold. 

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  TextEditingController textController = new TextEditingController();
  List<Todo> taskList = new List();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Container(
        alignment: Alignment.topLeft,
        padding: EdgeInsets.all(16),
        child: Column(
          children: <Widget>[
            Row(
              children: <Widget>[
                Expanded(
                  child: TextFormField(
                    decoration: InputDecoration(hintText: "Enter a task"),
                    controller: textController,
                  ),
                ),
                IconButton(
                  icon: Icon(Icons.add),
                  onPressed: null,
                )
              ],
            ),
            SizedBox(height: 20),
            Expanded(
              child: Container(
                child: taskList.isEmpty
                    ? Container()
                    : ListView.builder(itemBuilder: (ctx, index) {
                        if (index == taskList.length) return null;
                        return ListTile(
                          title: Text(taskList[index].title),
                          leading: Text(taskList[index].id.toString()),
                        );
                      }),
              ),
            )
          ],
        ),
      ),
    );
  }

}

We’re using the ListTile which is an excellent widget providing us basic layouts of a list row.

With this done, now it’s time to go ahead and set up sqlite in flutter.

 

Creating the DatabaseHelper

Create a file named DatabaseHelper.dart, we’ll be creating DatabaseHelper as a singleton using factory constructors. Add the following code to DatabaseHelper.dart

import 'package:path/path.dart';
import 'package:sqflite/sqflite.dart';
import 'todo.dart';

class DatabaseHelper {
  static final _databaseName = "todo.db";
  static final _databaseVersion = 1;

  static final table = 'todo';

  static final columnId = 'id';
  static final columnTitle = 'title';

  DatabaseHelper._privateConstructor();
  static final DatabaseHelper instance = DatabaseHelper._privateConstructor();

  static Database _database;
  Future<Database> get database async {
    if (_database != null) return _database;
    _database = await _initDatabase();
    return _database;
  }

  _initDatabase() async {
    String path = join(await getDatabasesPath(), _databaseName);
    return await openDatabase(path,
        version: _databaseVersion, onCreate: _onCreate);
  }

  // SQL code to create the database table
  Future _onCreate(Database db, int version) async {
    await db.execute('''
          CREATE TABLE $table (
            $columnId INTEGER PRIMARY KEY AUTOINCREMENT,
            $columnTitle FLOAT NOT NULL
          )
          ''');
  }

}

The static fields are information about our database such as version, table name, db name and column names. DatabaseHelper._privateConstructor() is how we’re using factory constructors in Dart.

Next up, let’s add methods to insert, delete the table, read all data and clear all data from the table. 

Future<int> insert(Todo todo) async {
  Database db = await instance.database;
  var res = await db.insert(table, todo.toMap());
  return res;
}

Future<List<Map<String, dynamic>>> queryAllRows() async {
  Database db = await instance.database;
  var res = await db.query(table, orderBy: "$columnId DESC");
  return res;
}

Future<int> delete(int id) async {
  Database db = await instance.database;
  return await db.delete(table, where: '$columnId = ?', whereArgs: [id]);
}

Future<void> clearTable() async {
  Database db = await instance.database;
  return await db.rawQuery("DELETE FROM $table");
}

 

Note: For queryAllRows we’re using orderBy: “$columnId DESC” which will sort the rows in descending order of id. By default it’s ascending.

 

This is the base of setting up SQLite in flutter. Now we’ll see how to add and delete data using this helper class. Some of the code for helper class was referenced from this post. Here’s what the final helper class looks like: 

import 'package:path/path.dart';
import 'package:sqflite/sqflite.dart';
import 'todo.dart';

class DatabaseHelper {
  static final _databaseName = "todo.db";
  static final _databaseVersion = 1;

  static final table = 'todo';

  static final columnId = 'id';
  static final columnTitle = 'title';

  DatabaseHelper._privateConstructor();
  static final DatabaseHelper instance = DatabaseHelper._privateConstructor();

  static Database _database;
  Future<Database> get database async {
    if (_database != null) return _database;
    _database = await _initDatabase();
    return _database;
  }

  _initDatabase() async {
    String path = join(await getDatabasesPath(), _databaseName);
    return await openDatabase(path,
        version: _databaseVersion, onCreate: _onCreate);
  }

  // SQL code to create the database table
  Future _onCreate(Database db, int version) async {
    await db.execute('''
          CREATE TABLE $table (
            $columnId INTEGER PRIMARY KEY AUTOINCREMENT,
            $columnTitle FLOAT NOT NULL
          )
          ''');
  }

  Future<int> insert(Todo todo) async {
    Database db = await instance.database;
    var res = await db.insert(table, todo.toMap());
    return res;
  }

  Future<List<Map<String, dynamic>>> queryAllRows() async {
    Database db = await instance.database;
    var res = await db.query(table, orderBy: "$columnId DESC");
    return res;
  }

  Future<int> delete(int id) async {
    Database db = await instance.database;
    return await db.delete(table, where: '$columnId = ?', whereArgs: [id]);
  }

  Future<void> clearTable() async {
    Database db = await instance.database;
    return await db.rawQuery("DELETE FROM $table");
  }
}

I’ve added the clearTable method as an extra in case you want to try it out to clear the table.

 

Reading from SQLite in Flutter

We want to initialise our list with data whenever the app restarts. For this, we’ll use the queryAllRows method in initState() lifecycle callback.

Override the initState() method in _MyHomePageState class and add the following code.

@override
void initState() {
  super.initState();

  DatabaseHelper.instance.queryAllRows().then((value) {
    setState(() {
      value.forEach((element) {
        taskList.add(Todo(id: element['id'], title: element["title"]));
      });
    });
  }).catchError((error) {
    print(error);
  });
}

When the app starts, initState will get called and we’ll read the data from our database. SetState will update the UI when the data is available and our ListView will take care of the rest.

 

Inserting Data in SQLite in Flutter

To add the task entered to our database, we’ll create a method _addToDb in main.dart file. This will be invoked on ‘+’ button click:

void _addToDb() async {
  String task = textController.text;
  var id = await DatabaseHelper.instance.insert(Todo(title: task));
  setState(() {
    taskList.insert(0, Todo(id: id, title: task));
  });
}

First, we’ll get the text from the field, then add it to db and finally update our view. 

 

Note: Since we’ve marked id as AUTO INCREMENT in our Database we don’t need to set the id of our Todo Object while inserting. Insert method will provide us the id of the object inserted. We can use that to update the UI.

 

Deleting a Row

Now, the only thing left to do is to be able to delete a record in the database. Add an icon to our ListTile row using trailing argument

return ListTile(
  title: Text(taskList[index].title),
  leading: Text(taskList[index].id.toString()),
  trailing: IconButton(
    icon: Icon(Icons.delete),
    onPressed: () => _deleteTask(taskList[index].id),
  ),
);

For it’s onPressed we’ll create a method  _deleteTask which will delete the todo using the id. Finally we’ll update the UI just like before:

void _deleteTask(int id) async {
  await DatabaseHelper.instance.delete(id);
  setState(() {
    taskList.removeWhere((element) => element.id == id);
  });
}

And with that we’re done. Here’s how your final main.dart file would look like: 

import 'package:flutter/material.dart';
import 'package:flutter_sqflite/database_helper.dart';
import 'package:flutter_sqflite/todo.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Listify'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  TextEditingController textController = new TextEditingController();

  List<Todo> taskList = new List();

  @override
  void initState() {
    super.initState();

    DatabaseHelper.instance.queryAllRows().then((value) {
      setState(() {
        value.forEach((element) {
          taskList.add(Todo(id: element['id'], title: element["title"]));
        });
      });
    }).catchError((error) {
      print(error);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Container(
        alignment: Alignment.topLeft,
        padding: EdgeInsets.all(16),
        child: Column(
          children: <Widget>[
            Row(
              children: <Widget>[
                Expanded(
                  child: TextFormField(
                    decoration: InputDecoration(hintText: "Enter a task"),
                    controller: textController,
                  ),
                ),
                IconButton(
                  icon: Icon(Icons.add),
                  onPressed: _addToDb,
                )
              ],
            ),
            SizedBox(height: 20),
            Expanded(
              child: Container(
                child: taskList.isEmpty
                    ? Container()
                    : ListView.builder(itemBuilder: (ctx, index) {
                        if (index == taskList.length) return null;
                        return ListTile(
                          title: Text(taskList[index].title),
                          leading: Text(taskList[index].id.toString()),
                          trailing: IconButton(
                            icon: Icon(Icons.delete),
                            onPressed: () => _deleteTask(taskList[index].id),
                          ),
                        );
                      }),
              ),
            )
          ],
        ),
      ),
    );
  }

  void _deleteTask(int id) async {
    await DatabaseHelper.instance.delete(id);
    setState(() {
      taskList.removeWhere((element) => element.id == id);
    });
  }

  void _addToDb() async {
    String task = textController.text;
    var id = await DatabaseHelper.instance.insert(Todo(title: task));
    setState(() {
      taskList.insert(0, Todo(id: id, title: task));
    });
  }
}

One thing to note here is that the UI re-builds entirely when we add/delete an item. This can be further optimised with the use of Provider pattern in flutter, which I’ve already discussed before. Make sure to check it out.

 

Conclusion

In this tutorial, we saw how SQLite works in flutter. We added the ability to add, remove the tasks from a list and update the list simultaneously.

 

 

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