How to change items of a gridview in flutter - flutter

Question

I am new to flutter and i current have an app that has a grid view that gets its list from an api. Some of the grid view items have child nodes in them, so what i want to achieve is to set a click function that checks if there is a child node and if that is true; i would want to re-populate the same grid view but with only members of the child node. is this possible in flutter?
import 'package:bringam/network/Models/ProductGroupModel.dart';
import 'package:bringam/network/sharedpreferences/SharedPreferences.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:http/http.dart' as http;
import 'dart:convert';
class Product_Category extends StatefulWidget {
#override
_Product_CategoryState createState() => _Product_CategoryState();
}
class _Product_CategoryState extends State<Product_Category> {
Future<List<ProductGroupModel>> _getChildrenCategories(String tag) async {
List<ProductGroupModel> categories = [];
SharedPref sharedPref = SharedPref();
var cacheCategories =
json.decode(await sharedPref.read('PRODUCT_CATEGORY'));
// FILTERING THE LIST STARTS
var filteredJson =
cacheCategories.where((i) => i["ParentGroupId"] == tag).toList();
// FILTERING THE LIST ENDS
for (var u in filteredJson) {
ProductGroupModel productCat = ProductGroupModel(
u["Description"],
u["IconURL"],
u["ProductGroup"],
u["ParentGroupId"],
u["HasChildNode"],
u["Order"]);
categories.add(productCat);
}
print(categories);
return categories;
}
Future<List<ProductGroupModel>> _getCategories() async {
List<ProductGroupModel> categories = [];
SharedPref sharedPref = SharedPref();
var cacheCategories =
json.decode(await sharedPref.read('PRODUCT_CATEGORY'));
if (cacheCategories.isEmpty) {
var data = await http.get(
'PRIVATE API ENDPOINT PLEASE');
var jsonData = json.decode(data.body);
// FILTERING THE LIST STARTS
var filteredJson =
jsonData.where((i) => i["ParentGroupId"] == '0').toList();
// FILTERING THE LIST ENDS
for (var u in filteredJson) {
ProductGroupModel productCat = ProductGroupModel(
u["Description"],
u["IconURL"],
u["ProductGroup"],
u["ParentGroupId"],
u["HasChildNode"],
u["Order"]);
categories.add(productCat);
}
} else {
// FILTERING THE LIST STARTS
var filteredJson =
cacheCategories.where((i) => i["ParentGroupId"] == '0').toList();
// FILTERING THE LIST ENDS
for (var u in filteredJson) {
ProductGroupModel productCat = ProductGroupModel(
u["Description"],
u["IconURL"],
u["ProductGroup"],
u["ParentGroupId"],
u["HasChildNode"],
u["Order"]);
categories.add(productCat);
}
return categories;
}
}
#override
Widget build(BuildContext context) {
return FutureBuilder(
future: _getCategories(),
builder: (BuildContext context,
AsyncSnapshot<List<ProductGroupModel>> snapshot) {
if (snapshot.data == null) {
return Center(
child: CircularProgressIndicator(),
);
} else {
return GridView.builder(
itemCount: snapshot.data.length,
gridDelegate:
SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount:
2),
itemBuilder: (BuildContext context, int index) {
return Card(
elevation: 0,
color: Colors.transparent,
child: Hero(
tag: snapshot.data[index].ProductGroup,
child: Material(
color: Colors.transparent,
child: InkWell(
onTap: () {
bool hasChild = snapshot.data[index].HasChildNode;
if (hasChild == true) {
setState(() {
_getChildrenCategories(
snapshot.data[index].ProductGroup);
});
} else {
Scaffold.of(context).showSnackBar(SnackBar(
content: new Text("Nothing found!"),
duration: const Duration(milliseconds: 500)));
}
},
child: GridTile(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
CircleAvatar(
backgroundImage:
NetworkImage(snapshot.data[index].IconURL),
radius: 75.0,
),
Text(
snapshot.data[index].Description,
style: TextStyle(
fontWeight: FontWeight.bold,
fontSize: 20.0,
color: Colors.white,
),
),
],
),
),
),
),
),
);
});
}
},
);
}
}
//THE MODEL CLASS
class ProductGroupModel {
final String Description;
final String IconURL;
final String ProductGroup;
final String ParentGroupId;
final bool HasChildNode;
final int Order;
ProductGroupModel(
this.Description,
this.IconURL,
this.ProductGroup,
this.ParentGroupId,
this.HasChildNode,
this.Order,
);
}