Keeping variable value after closing the application but having trouble with database - flutter

Question

I'm trying to import device Contacts and list them with checkboxes then user selects and send them to other screen and do action with them.
I have used contacts_service plugin and use following code on init
var selectedContacts = List<Contact>();
List<Contact> _contacts;
Future<void> refreshContacts() async {
var contacts = (await ContactsService.getContacts(
withThumbnails: false, iOSLocalizedLabels: true))
.toList();
setState(() {
_contacts = contacts;
});
}
And list view:
_contacts != null
? ListView.builder(
itemCount: _contacts?.length ?? 0,
itemBuilder: (BuildContext context, int index) {
Contact c = _contacts?.elementAt(index);
return CheckboxListTile(
value: selectedContacts.contains(c),
onChanged: (bool value) {
setState(() {
value
? selectedContacts.add(c)//
: selectedContacts.remove(c);//
});
},
title: Text(c.displayName ?? ""),
secondary: CircleAvatar(child: Text(c.initials())),
);
},
)
: Center(
child: CircularProgressIndicator(),
),
My problem is when app closes and reopens checkboxes are gone and selectedContacts is empty. I have spent many hours trying to get database work but i couldn't make it work mainly because 'Contact' class has phone variable as iterable and i couldn't save it to database.
I have created class on my own that has id, name, phone so it would be much easier to assign them to Database.
But then i couldn't work around value: selectedContacts.contains(c), and checkboxes wont work. I tried to create my own containst function where i take Contact c and its phone value and compare it to my list and find if phones match and send true and false still doesnt work.
My idea is var selectedContacts = here i can do database empty ? List<Contact> : import Contacts from database and after that i think i still don't know how to send that selectedContacts to another file and another main page but i can find it i assume.
I have not tried sharedpref because from what i have read it can store small size and if my User chooses many objects from 'Contact' class it will be a problem.
I am sorry if my explanation is bad .Its not that important i just want to learn, thanks in advance
UPDATE: I have tried to use Database again my code looks like this.
database.dart
import 'dart:io' as io;
import 'package:contacts_service/contacts_service.dart';
import 'package:path/path.dart';
import 'package:sqflite/sqflite.dart';
import 'package:path_provider/path_provider.dart';
class DatabaseHelper{
static final DatabaseHelper _instance = new DatabaseHelper.internal();
factory DatabaseHelper() => _instance;
static Database _db;
DatabaseHelper.internal();
static initDb() async{
io.Directory documentDirectory = await getApplicationDocumentsDirectory();
String path = join(documentDirectory.path,"contactDatabase.db");
var taskDb= await openDatabase(path,version: 1,onCreate: _onCreate);
return taskDb;
}
static void _onCreate(Database db,int version) async{
await db.execute(
"CREATE TABLE contacts(identifier TEXT PRIMARY KEY, displayName TEXT, givenName TEXT, middleName TEXT, familyName TEXT, prefix TEXT, suffix TEXT, company TEXT, jobTitle TEXT, androidAccountType TEXT, androidAccountName TEXT, emails TEXT, phones TEXT, postalAddresses TEXT, avatar TEXT, birthday TEXT, )"
);
}
static Future<void> addContact(Contact c) async{
final Database db = initDb();
await db.insert('contacts', c.toMap(),conflictAlgorithm: ConflictAlgorithm.replace,);
}
static Future<void> deleteContact(Contact c) async{
final Database db = initDb();
await db.delete('contacts', where: "id = ?", whereArgs: [c.identifier],);
}
static Future<List<Contact>> importContacts() async{
final Database db = initDb();
final List<Map<String, dynamic>> maps = await db.query('contacts');
return List.generate(maps.length, (index) => Contact.fromMap(maps[index]));
}
static Future<bool> dbEmpty() async{
final Database db = initDb();
int count = Sqflite.firstIntValue(await db.rawQuery('SELECT COUNT(*) FROM contacts'));
if (count>0){
return true;
}
else
return false;
}
}
And my contact screen looks like this.
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:contacts_service/contacts_service.dart';
import 'database.dart';
class ContactScreen extends StatefulWidget {
#override
_ContactScreenState createState() => _ContactScreenState();
}
class _ContactScreenState extends State<ContactScreen> {
void checkDb() async{
List<Contact> selectedContacts = await DatabaseHelper.dbEmpty()?DatabaseHelper.importContacts():List<Contact>();
}
List<Contact> selectedContacts;
List<Contact> _contacts;
DatabaseHelper databaseHelper = new DatabaseHelper();
#override
void initState() {
super.initState();
refreshContacts();
checkDb();
}
Future<void> refreshContacts() async {
// Load without thumbnails initially.
var contacts = (await ContactsService.getContacts(
withThumbnails: false, iOSLocalizedLabels: true))
.toList();
setState(() {
_contacts = contacts;
});
}
void addDb(Contact c){
selectedContacts.add(c);
DatabaseHelper.addContact(c);
}
void deleteDb(Contact c){
selectedContacts.remove(c);
DatabaseHelper.deleteContact(c);
}
#override
Widget build(BuildContext context) {
return SafeArea(
child: _contacts != null
? ListView.builder(
itemCount: _contacts?.length ?? 0,
itemBuilder: (BuildContext context, int index) {
Contact c = _contacts?.elementAt(index);
return CheckboxListTile(
value: selectedContacts.contains(c),
onChanged: (bool value) {
setState(() {
value
? addDb(c)//selectedContacts.add(c)
: deleteDb(c);//selectedContacts.remove(c);
});
},
title: Text(c.displayName ?? ""),
secondary: CircleAvatar(child: Text(c.initials())),
);
},
)
: Center(
child: CircularProgressIndicator(),
),
);
}
}
I couldn't make this code work.
is it okay to create my db with all text? from what i have understand contact_service getting its fromMap like its text so i also went with it.
Also contact_service codes looks like this:
String identifier, displayName, givenName, middleName, prefix, suffix, familyName, company, jobTitle;
String androidAccountTypeRaw, androidAccountName;
AndroidAccountType androidAccountType;
Iterable<Item> emails = [];
Iterable<Item> phones = [];
Iterable<PostalAddress> postalAddresses = [];
Uint8List avatar;
DateTime birthday;
String initials() {
return ((this.givenName?.isNotEmpty == true ? this.givenName[0] : "") +
(this.familyName?.isNotEmpty == true ? this.familyName[0] : ""))
.toUpperCase();
}
Contact.fromMap(Map m) {
identifier = m["identifier"];
displayName = m["displayName"];
givenName = m["givenName"];
middleName = m["middleName"];
familyName = m["familyName"];
prefix = m["prefix"];
suffix = m["suffix"];
company = m["company"];
jobTitle = m["jobTitle"];
androidAccountTypeRaw = m["androidAccountType"];
androidAccountType = accountTypeFromString(androidAccountTypeRaw);
androidAccountName = m["androidAccountName"];
emails = (m["emails"] as Iterable)?.map((m) => Item.fromMap(m));
phones = (m["phones"] as Iterable)?.map((m) => Item.fromMap(m));
postalAddresses = (m["postalAddresses"] as Iterable)
?.map((m) => PostalAddress.fromMap(m));
avatar = m["avatar"];
try {
birthday = DateTime.parse(m["birthday"]);
} catch (e) {
birthday = null;
}
}
static Map _toMap(Contact contact) {
var emails = [];
for (Item email in contact.emails ?? []) {
emails.add(Item._toMap(email));
}
var phones = [];
for (Item phone in contact.phones ?? []) {
phones.add(Item._toMap(phone));
}
var postalAddresses = [];
for (PostalAddress address in contact.postalAddresses ?? []) {
postalAddresses.add(PostalAddress._toMap(address));
}
final birthday = contact.birthday == null
? null
: "${contact.birthday.year.toString()}-${contact.birthday.month.toString().padLeft(2, '0')}-${contact.birthday.day.toString().padLeft(2, '0')}";
return {
"identifier": contact.identifier,
"displayName": contact.displayName,
"givenName": contact.givenName,
"middleName": contact.middleName,
"familyName": contact.familyName,
"prefix": contact.prefix,
"suffix": contact.suffix,
"company": contact.company,
"jobTitle": contact.jobTitle,
"androidAccountType": contact.androidAccountTypeRaw,
"androidAccountName": contact.androidAccountName,
"emails": emails,
"phones": phones,
"postalAddresses": postalAddresses,
"avatar": contact.avatar,
"birthday": birthday
};
}
Map toMap() {
return Contact._toMap(this);
}

Answer 1

In this section:
void checkDb() async{
List<Contact> selectedContacts = await DatabaseHelper.dbEmpty() ? DatabaseHelper.importContacts() : List<Contact>();
}
you cannot get contacts from database to local variable, you are created new and don't use it (because checkDb() is a method and the variable available on in methods scope). In your case, you can use FutureBuilder widget (read more here), it must me something like this:
#override
Widget build(BuildContext context) {
return FutureBuilder<List<Contact>>(
future: DatabaseHelper.importContacts(), // You can do not check contacts availability in database, just return empty list by default
builder (context, snapshot) {
// Contacts list doesn't loaded, you need to show progress loader to a user
if (!snapshot.hasData) {
return Center(
child: CircularProgressIndicator(),
);
}
return ListView.builder(); // Here your code for list
}
);
}