flutter_paging_viewmodel_example_2

chayanforyou

Jun 19th, 2025

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class DoctorListViewModel extends StateNotifier<DoctorPagingState> {
final DefaultQueryParams _param;
DoctorListViewModel(this._param)
: super(
DoctorPagingState(
pagingState: PagingState(),
),
);
String? _searchTerm;
bool _isDisposed = false;
@override
void dispose() {
_isDisposed = true;
super.dispose();
}
/// Fetches the next page of data
Future<void> fetchNextPage() async {
final paging = state.pagingState;
if (paging.isLoading) return;
final newPaging = paging.copyWith(isLoading: true, error: null);
state = state.copyWith(pagingState: newPaging);
try {
final newKey = paging.keys?.last == null ? 0 : paging.keys!.last + 1;
final doctorResponse = await DoctorRepository.instance.getDoctors(
employeeId: _param.employeeId,
year: _param.year,
month: _param.month,
levelCode: _param.levelCode,
page: newKey,
term: _searchTerm,
selectedOnly: _param.selectedOnly,
);
final doctorData = doctorResponse.data;
final updatedPaging = paging.copyWith(
pages: [...?paging.pages, doctorData.doctors?.content ?? []],
keys: [...?paging.keys, newKey],
hasNextPage: doctorData.doctors?.hasNext,
isLoading: false,
);
state = state.copyWith(
pagingState: updatedPaging,
totalDoctors: doctorData.doctors?.totalElements ?? 0,
selectedDoctors: doctorData.selectedDoctor ?? 0,
approved: doctorData.approved ?? true,
editable: doctorData.editable ?? false,
);
// trigger the status message listener
doctorPlanApprovedNotifier.value = state.approved;
} catch (error) {
if (_isDisposed) return;
final failedPaging = paging.copyWith(
error: error,
isLoading: false,
);
state = state.copyWith(pagingState: failedPaging);
}
}
/// Updates search term and refreshes the list
void updateSearchTerm(String searchTerm) {
_searchTerm = searchTerm;
refreshList();
}
/// Refreshes the list and fetches the first page
void refreshList() {
state = state.copyWith(
pagingState: PagingState(),
totalDoctors: 0,
selectedDoctors: 0,
approved: false,
);
fetchNextPage();
}
/// Method to toggle the selection of a Doctor
void toggleSelection(DoctorData content) {
final oldPaging = state.pagingState;
int updatedSelectedCount = state.selectedDoctors;
final updatedPages = oldPaging.pages?.map((page) {
return page.map((c) {
if (c.doctor?.id == content.doctor?.id) {
final wasSelected = c.selected;
final nowSelected = !wasSelected;
if (nowSelected) {
updatedSelectedCount++;
} else {
updatedSelectedCount--;
}
return c.copyWith(selected: nowSelected);
}
return c;
}).toList();
}).toList();
state = state.copyWith(
pagingState: oldPaging.copyWith(pages: updatedPages),
selectedDoctors: updatedSelectedCount,
);
}
}
/// **Provider for ViewModel**
final doctorListViewModelProvider =
StateNotifierProvider.family.autoDispose<DoctorListViewModel, DoctorPagingState, DefaultQueryParams>((ref, param) {
return DoctorListViewModel(param);
});
// --------------------------------------------------
final doctorListState = ref.watch(doctorListViewModelProvider(_params));
final doctorListViewModel = ref.read(doctorListViewModelProvider(_params).notifier);
PagedListView<int, DoctorData>.separated(
state: doctorListState.pagingState,
fetchNextPage: doctorListViewModel.fetchNextPage,
builderDelegate: PagedChildBuilderDelegate(
itemBuilder: (context, item, index) {
return DoctorListItem(
doctorData: item,
clickable: doctorListState.editable,
onClick: () => _toggleSelection(item, doctorListViewModel),
);
},
),
separatorBuilder: (BuildContext context, int index) {
return const Divider(color: AppColors.dividerColor, height: 1);
},
),

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