Need Query or condition to get selected data in flutter - flutter

Question

I am stuck in creating query for the selected items and show selected data on other page. So help me to create query or condition. when I press floating action button then I want to get selected items data on other page.
Here is Main File code:
class MenuPage extends StatefulWidget {
const MenuPage({Key? key}) : super(key: key);
#override
_MenuPageState createState() => _MenuPageState();
}
class _MenuPageState extends State<MenuPage> {
DatabaseReference db = FirebaseDatabase.instance.reference();
User? curUser = FirebaseAuth.instance.currentUser;
int? len;
List<GetData>? data;
late List<bool>? avail = List.generate(
len!,
(index) => false,
);
late List<TextEditingController>? qty = List.generate(
len!,
(index) => TextEditingController(),
);
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Today's Menu"),
centerTitle: true,
backgroundColor: Colors.deepOrange,
),
body: StreamBuilder<List<GetData>>(
stream: DataStreamPublisher("Juices").getMenuStream(),
builder: (context, snapshot) {
if (snapshot.hasData) {
data = snapshot.data;
len = data!.length;
return SafeArea(
child: SingleChildScrollView(
child: Container(
margin: EdgeInsets.symmetric(vertical: 10.0),
width: double.infinity,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
SizedBox(
width: double.infinity,
child: DataTable2(
showBottomBorder: true,
headingRowHeight: 40,
showCheckboxColumn: true,
sortAscending: true,
columnSpacing: 5,
dataRowHeight: 60,
dividerThickness: 2,
bottomMargin: 20.0,
checkboxHorizontalMargin: 5,
columns: [
DataColumn2(
size: ColumnSize.L,
label: Center(
child: Text(
"Item Name",
style: TextStyle(
fontSize: 16,
fontWeight: FontWeight.w600,
),
),
),
),
DataColumn2(
size: ColumnSize.S,
label: Center(
child: Text(
"Price",
style: TextStyle(
fontSize: 16,
fontWeight: FontWeight.w600,
),
),
),
),
DataColumn2(
size: ColumnSize.L,
label: Center(
child: Text(
"Quantity",
style: TextStyle(
fontSize: 16,
fontWeight: FontWeight.w600,
),
),
),
),
],
rows: List<DataRow>.generate(
data!.length,
(index) => DataRow2(
selected: avail![index],
onSelectChanged: (bool? value) {
setState(() {
avail![index] = value!;
});
},
color: MaterialStateProperty.resolveWith<Color?>(
(Set<MaterialState> states) {
if (states.contains(MaterialState.selected)) {
return Theme.of(context)
.colorScheme
.primary
.withOpacity(0.08);
}
return null;
},
),
cells: [
DataCell(
Text(
data![index].Juice_Name,
),
),
DataCell(
Center(
child: Text(
data![index].Price,
),
),
),
DataCell(
Center(
child: IncDecButton(
Qty: qty![index],
),
),
),
],
),
),
),
),
],
),
),
),
);
} else if (snapshot.hasError) {
return Center(
child: Text(
'Add Item in Menu.',
style: TextStyle(
fontSize: 18,
),
),
);
}
return Center(
child: const CircularProgressIndicator(),
);
},
),
floatingActionButton: FloatingActionButton(
tooltip: "Proceed to Bill",
onPressed: () {
// When I pressed floating button I want only selected items data
},
child: Text("ADD"),
),
);
}
}
This is stream of GetDataPublisher
This code get data from firebase.
class DataStreamPublisher {
final String dbChild;
DatabaseReference database = FirebaseDatabase.instance.reference();
User? curUser = FirebaseAuth.instance.currentUser;
DataStreamPublisher(this.dbChild);
Stream<List<GetData>> getMenuStream() {
final dataStream = database.child(curUser!.uid).child(dbChild)
.orderByChild("Available").equalTo(true).onValue;
final streamToPublish = dataStream.map((event) {
final dataMap = Map<String, dynamic>.from(event.snapshot.value);
final dataList = dataMap.entries.map((e) {
return GetData.fromRTDB(Map<String, dynamic>.from(e.value));
}).toList();
return dataList;
});
return streamToPublish;
}
}
This is get data class
class GetData {
String Juice_Name;
String Price;
GetData({
required this.Juice_Name,
required this.Price,
});
factory GetData.fromRTDB(Map<String, dynamic> data) {
return GetData(
Juice_Name: data['Juice_Name'] ?? 'Enter Juice Name',
Price: data['Price'] ?? 'Enter Price',
);
}
}