Save json data in favorite list in flutter - json

Question

I'm trying to add my data to a Favorited list but I have no idea how to do that I just saved it in Favorited list but when restart the app nothing saved any idea how to save in shared preferences or some thing like it
code for loading json as follows
List mydata = List();
final _savedata = Set<Map>();
Future<void> getjsondata() async {
final String response = await rootBundle.loadString('assets/data.json');
final data = await json.decode(response);
setState(() {
mydata = data["InfoPlate"];
});
}
and this one for add data to favorited list
void _pushSaved() {
Navigator.of(context).push(
new MaterialPageRoute<void>(
builder: (BuildContext context) {
final Iterable<ListTile> tiles = _savedata.map(
(Myinfo) {
return new ListTile(
title: Text(Myinfo['type']),
);
},
);
final List<Widget> divided = ListTile.divideTiles(
context: context,
tiles: tiles,
).toList();
return new Scaffold(
appBar: new AppBar(
title: const Text('Favorited info Plate '),
),
body: new ListView(children: divided),
);
},
),
);
}
and this is the rest of code for the adding button in card
Widget _buildDataList() {
return ListView.builder(
itemCount: mydata.length,
padding: const EdgeInsets.all(8.0),
itemBuilder: (context, int index) {
return _buildRowInfo(mydata[index]);
});
}
Widget _buildRowInfo(Map myinfo) {
final bool favourited = _savedata.contains(myinfo);
void _favorscreen() {
setState(() {
if (favourited) {
_savedata.remove(myinfo);
} else {
_savedata.add(myinfo);
}
});
}
return Directionality(
textDirection: TextDirection.rtl,
child: Card(
child: ListTile(
visualDensity: VisualDensity.comfortable,
title: Text(myinfo['type']),
trailing: new IconButton(
icon: Icon(favourited ? Icons.favorite : Icons.favorite_border),
color: favourited ? Colors.red : null,
onPressed: _favorscreen,
),
),
),
);
}
}

Answer 1

It is possible to store data locally using shared_preferences.
All you need is an instance of SharedPreferences.
class ExampleWidget extends StatefulWidget {
#override
_ExampleWidgetState createState() => _ExampleWidgetState();
}
class _ExampleWidgetState extends State<ExampleWidget> {
SharedPreferences sharedPreferences;
#override
void initState() {
super.initState();
Future.delayed(Duration.zero, () async {
sharedPreferences = await SharedPreferences.getInstance();
});
}
Then, to read or write data, sharedPreferences is a key-value database and exposes setters and getters. It does not allow to store Set, so you will need to encode and decode data payload depending on the operation you perform.
Future<bool> _writeData(Set<Map> setOfMaps) {
return sharedPreferences.setString(
'your_key',
jsonEncode(setOfMaps.toList()),
);
}
Set<Map> _readData() {
final encodedData = sharedPreferences.getString('your_key');
return jsonDecode(encodedData).toSet();
}