Merge pull request #71 from nimblehq/feature/17-scroll-to-load-more-s…

…urveys

[#17] [Integrate] As a logged-in user, I can scroll to load more surveys

lib/screens/home/home_pages_widget.dart

@@ -7,23 +7,51 @@ import '../../gen/assets.gen.dart';
 
 const _imageOpacity = 0.6;
 
-class HomePagesWidget extends StatelessWidget {
+class HomePagesWidget extends StatefulWidget {
   final List<SurveyModel> surveys;
   final ValueNotifier<int> currentPage;
-  final PageController _pageController = PageController();
   final VoidCallback onNextButtonPressed;
+  final bool isRefreshing;
+  final VoidCallback onLoadMore;
 
-  HomePagesWidget({
+  const HomePagesWidget({
     Key? key,
     required this.surveys,
     required this.currentPage,
     required this.onNextButtonPressed,
+    required this.onLoadMore,
+    required this.isRefreshing,
   }) : super(key: key);
 
+  @override
+  State<HomePagesWidget> createState() => _HomePagesWidgetState();
+}
+
+class _HomePagesWidgetState extends State<HomePagesWidget> {
+  final PageController _pageController = PageController(initialPage: 0);
+
+  @override
+  void dispose() {
+    _pageController.dispose();
+    super.dispose();
+  }
+
+  void _handlePageChanged(int index) {
+    widget.currentPage.value = index;
+
+    if (index == widget.surveys.length - 1) {
+      widget.onLoadMore();
+    }
+  }
+
   @override
   Widget build(BuildContext context) {
+    if (widget.isRefreshing && widget.surveys.isNotEmpty) {
+      _pageController.jumpToPage(0);
+    }
+
     return PageView.builder(
-      itemCount: surveys.length,
+      itemCount: widget.surveys.length,
       controller: _pageController,
       itemBuilder: (_, int index) {
         return Container(
@@ -34,7 +62,7 @@ class HomePagesWidget extends StatelessWidget {
                 opacity: _imageOpacity,
                 child: FadeInImage.assetNetwork(
                   placeholder: Assets.images.placeholder.path,
-                  image: surveys[index].coverImageUrl,
+                  image: widget.surveys[index].coverImageUrl,
                   fit: BoxFit.cover,
                   width: double.infinity,
                   height: double.infinity,
@@ -51,8 +79,8 @@ class HomePagesWidget extends StatelessWidget {
                         right: 0,
                       ),
                       child: HomeFooterWidget(
-                        survey: surveys[index],
-                        onNextButtonPressed: onNextButtonPressed,
+                        survey: widget.surveys[index],
+                        onNextButtonPressed: widget.onNextButtonPressed,
                       ),
                     ),
                   ),
@@ -62,9 +90,7 @@ class HomePagesWidget extends StatelessWidget {
           ),
         );
       },
-      onPageChanged: (int index) {
-        currentPage.value = index;
-      },
+      onPageChanged: _handlePageChanged,
     );
   }
 }

lib/screens/home/home_screen.dart

@@ -33,8 +33,14 @@ class _HomeScreenState extends ConsumerState<HomeScreen> {
     _initData();
   }
 
-  Future<void> _initData() async {
-    ref.read(homeViewModelProvider.notifier).loadSurveys(isRefreshing: false);
+  void _initData() {
+    _loadSurveys();
+  }
+
+  Future<void> _loadSurveys({bool isRefreshing = false}) async {
+    ref
+        .read(homeViewModelProvider.notifier)
+        .loadSurveys(isRefreshing: isRefreshing);
   }
 
   @override
@@ -43,11 +49,15 @@ class _HomeScreenState extends ConsumerState<HomeScreen> {
           loading: () => _buildHomeScreen(isLoading: true),
           error: () => _buildHomeScreen(),
           loadCachedSurveysSuccess: () => _buildHomeScreen(),
-          loadSurveysSuccess: () => _buildHomeScreen(),
+          loadSurveysSuccess: (isRefreshing) =>
+              _buildHomeScreen(isRefreshing: isRefreshing),
         );
   }
 
-  Widget _buildHomeScreen({bool isLoading = false}) {
+  Widget _buildHomeScreen({
+    bool isLoading = false,
+    bool isRefreshing = false,
+  }) {
     final surveys = ref.watch(_surveysStreamProvider).value ?? [];
     final errorMessage = ref.watch(_errorStreamProvider).value ?? "";
 
@@ -92,6 +102,8 @@ class _HomeScreenState extends ConsumerState<HomeScreen> {
                           extra: survey,
                         );
                       },
+                      onLoadMore: _loadSurveys,
+                      isRefreshing: isRefreshing,
                     ),
                     const HomeHeaderWidget(),
                     Align(

lib/screens/home/home_state.dart

@@ -9,7 +9,8 @@ class HomeState with _$HomeState {
   const factory HomeState.loadCachedSurveysSuccess() =
       _LoadCachedSurveysSuccess;
 
-  const factory HomeState.loadSurveysSuccess() = _LoadSurveysSuccess;
+  const factory HomeState.loadSurveysSuccess(bool isRefreshing) =
+      _LoadSurveysSuccess;
 
   const factory HomeState.error() = _error;
 }

lib/screens/home/home_view_model.dart

@@ -7,9 +7,9 @@ import 'package:survey_flutter/usecases/base/base_use_case.dart';
 import 'package:survey_flutter/usecases/get_cached_surveys_use_case.dart';
 import 'package:survey_flutter/usecases/get_surveys_use_case.dart';
 
-// TODO: Integrate load more
-const _pageNumber = 1;
+int _pageNumber = 1;
 const _pageSize = 10;
+List<SurveyModel> _loadedSurveys = [];
 
 final homeViewModelProvider =
     StateNotifierProvider.autoDispose<HomeViewModel, HomeState>((ref) {
@@ -39,25 +39,43 @@ class HomeViewModel extends StateNotifier<HomeState> {
   final _error = StreamController<String>();
   Stream<String> get error => _error.stream;
 
+  void _handleError(Failed result) {
+    if (result.isNotFoundError()) {
+      _surveys.add(_loadedSurveys);
+      state = const HomeState.loadSurveysSuccess(false);
+    } else {
+      _error.add(result.getErrorMessage());
+      state = const HomeState.error();
+    }
+  }
+
   Future<void> loadSurveys({required bool isRefreshing}) async {
     if (!isRefreshing) {
       _loadSurveysFromCache();
     }
-    _loadSurveysFromRemote();
+    _loadSurveysFromRemote(isRefreshing: isRefreshing);
   }
 
-  void _loadSurveysFromRemote() async {
+  void _loadSurveysFromRemote({required bool isRefreshing}) async {
+    if (isRefreshing) {
+      _loadedSurveys.clear();
+      _pageNumber = 1;
+    }
     final result = await _getSurveysUseCase.call(SurveysParams(
       pageNumber: _pageNumber,
       pageSize: _pageSize,
     ));
+
     if (result is Success<List<SurveyModel>>) {
       final newSurveys = result.value;
-      _surveys.add(newSurveys);
-      state = const HomeState.loadSurveysSuccess();
+      if (newSurveys.isNotEmpty) {
+        _loadedSurveys.addAll(newSurveys);
+        _surveys.add(_loadedSurveys);
+        state = HomeState.loadSurveysSuccess(isRefreshing);
+        _pageNumber++;
+      }
     } else if (result is Failed) {
-      _error.add((result as Failed).getErrorMessage());
-      state = const HomeState.error();
+      _handleError(result as Failed);
     }
   }
 

lib/usecases/base/use_case_result.dart

@@ -23,4 +23,8 @@ class Failed<T> extends Result<T> {
 
   String getErrorMessage() =>
       NetworkExceptions.getErrorMessage(exception.actualException);
+
+  bool isNotFoundError() =>
+      this.exception.actualException ==
+      const NetworkExceptions.notFound("Not found");
 }

test/screens/home/home_view_model_test.dart

@@ -56,7 +56,7 @@ void main() {
             stateStream,
             emitsInOrder([
               const HomeState.loadCachedSurveysSuccess(),
-              const HomeState.loadSurveysSuccess()
+              const HomeState.loadSurveysSuccess(false),
             ]));
       },
     );