Flutter List View Data Duplication when I do setState and pagination with StreamBuilder - flutter

Question

I am implementation the list data from API to show in list view. There I am using Streambuiler and pull to refresh library for scrolling changes. I set the new data from API to local list inside StreamBuilder. Every time when I made setState for state changes. The StreamBuilder rebuild and setting data again. Then my list was duplicated, I do not know yet what's wrong with my code. I am developing the App with flutter recently. Please check my code what is wrong in there. 🙏🙏🙏
class OrderListScreen extends StatefulWidget {
#override
_OrderListScreenState createState() => _OrderListScreenState();
}
class _OrderListScreenState extends State<OrderListScreen> {
String showingFromDate, showingToDate;
OrderBloc _orderBloc;
OrderListOb _orderListOb = OrderListOb();
int paginationPage = 0;
DateTime fromDate, toDate;
List<Orders> _orderList = [];
var _refreshController = RefreshController();
#override
void initState() {
super.initState();
_orderBloc = OrderBloc();
initDate();
fetchAPI();
}
#override
void dispose() {
super.dispose();
_orderBloc.dispose();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: defaultAppBar("Order List Screen", showBackArrow: false),
body: Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
children: [
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
textView("From Date", isBold: true),
textView("To Date", isBold: true),
],
),
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
ActionChip(
padding: EdgeInsets.all(4.0),
avatar: Icon(
Icons.calendar_today_sharp,
color: Colors.white,
size: 18,
),
backgroundColor: PRIMARY_COLOR,
label: textView(showingFromDate, textColor: Colors.white),
onPressed: () {
_selectDate(context, isFromDate: true);
},
),
ActionChip(
padding: EdgeInsets.all(4.0),
avatar: Icon(
Icons.calendar_today_sharp,
color: Colors.white,
size: 18,
),
backgroundColor: PRIMARY_COLOR,
label: textView(showingToDate, textColor: Colors.white),
onPressed: () {
_selectDate(context, isFromDate: false);
},
),
],
),
StreamBuilder(
stream: _orderBloc.orderListStream(),
initialData:
BaseResponse(data: null, message: MsgState.loading),
builder: (BuildContext context, AsyncSnapshot snapshot) {
BaseResponse ob = snapshot.data;
if (ob.message == MsgState.loading) {
return Center(
child: Container(
child: CircularProgressIndicator(),
),
);
} else if (ob.message == MsgState.data ) {
_orderListOb = OrderListOb();
_orderListOb = ob.data;
_orderList.addAll(_orderListOb.result.orders);
return buildListView();
} else {
return handleErrorWidget(ob.data);
}
},
),
],
),
));
}
Widget buildListView() {
return Container(
height: 450,
child: SmartRefresher(
enablePullUp: _orderListOb.result.orders.length > 9,
enablePullDown: true,
onRefresh: () {
print("Pull To Refresh");
},
onLoading: () {
paginationPage = _orderListOb.result.pagination.nextId;
fetchAPI(); //Do pagination
},
controller: _refreshController,
child: ListView.builder(
shrinkWrap: true,
physics: ClampingScrollPhysics(),
itemCount: _orderList.length,
itemBuilder: (BuildContext context, int index) {
return InkWell(
onTap: () {
context.navigateName("order_detail", data: {
'isAcceptOrder': true,
'order_id': _orderList[index].id
});
},
child: orderItemWidget(_orderList[index],
isAcceptedOrder: false));
}),
),
);
}
void fetchAPI() {
_orderBloc.getOrderList(
serviceId: ServiceTypes.AIRCON_SERVICE.value,
fromDate: DateUtil.requestDateFormat(fromDate.toString()),
toDate: DateUtil.requestDateFormat(toDate.toString()),
page: paginationPage);
}
void initDate() {
showingFromDate = DateUtil.covertDate(DateUtil.getCurrentDate().toString());
showingToDate = DateUtil.covertDate(DateUtil.getCurrentDate().toString());
fromDate = DateUtil.getCurrentDate();
toDate = DateUtil.getCurrentDate();
}
void resetData() {
print("Clear");
paginationPage = 0;
_orderList.clear();
}
_selectDate(BuildContext context, {bool isFromDate = true}) async {
final DateTime picked = await showDatePicker(
context: context,
initialDate: isFromDate ? fromDate : toDate, // Refer step 1
firstDate: DateTime(2000),
lastDate: DateTime(2025),
);
if (picked != null)
setState(() {
if (isFromDate) {
showingFromDate = DateUtil.covertDate(picked.toString());
fromDate = picked;
} else {
showingToDate = DateUtil.covertDate(picked.toString());
toDate = picked;
}
resetData();
fetchAPI();
});
}
}

Answer 1

The problem is that you're doing _orderList.addAll(_orderListOb.result.orders); . Instead, you should clean the list before or just _orderList=_orderListOb.result.orders;

Answer 2

Check for existence the value before adding to list, if list doesnt contain the value then add like this:
if(!_orderList.contains(_orderListOb.result.orders))
_orderList.addAll(_orderListOb.result.orders);
I hope it will work!