How to implement pagination in Flutter Search Delegate? - flutter

Question

I am trying to implement pagination in my app when a user searches for something.
I have been able to fetch and display my data(limited to like 12 results) but I have been unable to get more results due to Search Delegate not being a stateful class.
Is there a way I can use setState effectively to load more data by adding to my already fetched listView?
Code
import 'dart:math';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:official_coolkicks/models/shoe.dart';
import 'package:official_coolkicks/providers/search-provider.dart';
import 'package:official_coolkicks/providers/shoe-provider.dart';
import 'package:official_coolkicks/themes/adjust_settings_icons.dart';
import 'package:official_coolkicks/views/widgets/category/shoeCard.dart';
import 'package:official_coolkicks/views/widgets/filtering/filter_chip.dart';
import 'package:provider/provider.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
import 'package:shared_preferences/shared_preferences.dart';
class CategorySearch extends SearchDelegate<Shoe> {
#override
ThemeData appBarTheme(BuildContext context) {
assert(context != null);
final ThemeData theme = Theme.of(context);
assert(theme != null);
return theme;
}
ScrollController _sc = new ScrollController();
List<Shoe> shoes;
int page = 1;
bool isLoading = false;
#override
String get searchFieldLabel => 'Search in Men\'s Shoes';
var random = new Random();
Future _saveList() async {
SharedPreferences.getInstance().then((prefs) {
prefs.setStringList("searchHistory", searchHistory);
});
}
Widget content;
#override
List<Widget> buildActions(BuildContext context) {
return [
IconButton(
icon: Icon(Icons.clear),
onPressed: () {
query = "";
},
)
];
}
#override
Widget buildLeading(BuildContext context) {
return IconButton(
icon: AnimatedIcon(
icon: AnimatedIcons.menu_arrow,
progress: transitionAnimation,
),
onPressed: () {
close(context, null);
});
}
#override
Widget buildResults(BuildContext context) {
final double height = MediaQuery.of(context).size.height;
return StatefulBuilder(
builder: (BuildContext context, StateSetter setState) {
void loadMore() {
setState(() {
page++;
isLoading = true;
print('ISLOADING IS EQUALS TO $isLoading');
});
}
setState(() {
if (page > 1) {
page++;
print('PAGE IS NOW $page');
}
});
return FutureBuilder(
future: _search(page),
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
if (snapshot.hasError) {
print(snapshot.error);
return Center(
child: Text('Check your Internet connection and try again'),
);
} else if (snapshot.data.length == 0) {
return Center(
child: Text('No search results found'),
);
}
return Container(
height: height,
child: Stack(
children: [
Column(
children: <Widget>[
Expanded(
child: NotificationListener<ScrollNotification>(
child: GridView.count(
padding: EdgeInsets.all(15),
controller:
new ScrollController(keepScrollOffset: false),
shrinkWrap: true,
childAspectRatio:
MediaQuery.of(context).size.width /
(MediaQuery.of(context).size.height / 1.3),
scrollDirection: Axis.vertical,
crossAxisCount: 2,
crossAxisSpacing: 15,
mainAxisSpacing: 15,
children: List.generate(
snapshot.data.length,
(index) {
return ShoeCard(
index: random.nextInt(1000000),
shoe: snapshot.data[index]);
},
),
),
onNotification: (ScrollNotification scrollInfo) {
if (scrollInfo.metrics.pixels ==
scrollInfo.metrics.maxScrollExtent) {
// loadMore();
}
return false;
},
)),
],
),
Align(
alignment: FractionalOffset.bottomCenter,
child: Container(
height: isLoading ? 50 : 0,
child: Center(
child: CircularProgressIndicator(),
))),
Align(
alignment: FractionalOffset.bottomRight,
child: Padding(
padding: const EdgeInsets.all(8.0),
child: FloatingActionButton(
child: Icon(AdjustSettings.adjust),
backgroundColor: Colors.deepPurple,
onPressed: () {
Navigator.push(
context,
CupertinoPageRoute(
builder: (context) => FilterChipDisplay()));
},
),
),
),
],
));
} else {
return Center(
child: CircularProgressIndicator(),
);
}
},
);
});
}
#override
Widget buildSuggestions(BuildContext context) {
// List<Product> shoeList = products;
return Container();
}
Future<List<Shoe>> _search(int page) async {
String baseurl = "https://coolke.herokuapp.com";
String formatter(String url) {
return baseurl + url;
}
String url = formatter('/coolke/getCategorySearch/Men/$query?$page');
final result = await http.get(url);
final nlist = json.decode(result.body);
final list = nlist['shoes'] as List;
return list.map((e) => Shoe.fromJson(e)).toList();
}
}