Fix back button when going back after swiping

lib/main.dart

@@ -1,6 +1,7 @@
 import 'package:calorimeter/food_entry/food_entry_bloc.dart';
-import 'package:calorimeter/perdate/perdate_pageview.dart';
+import 'package:calorimeter/perdate/perdate_pageview_controller.dart';
 import 'package:calorimeter/storage/storage.dart';
+import 'package:calorimeter/utils/date_time_helper.dart';
 import 'package:calorimeter/utils/settings_bloc.dart';
 import 'package:calorimeter/utils/theme_bloc.dart';
 import 'package:flutter/material.dart';
@@ -18,14 +19,8 @@ void main() async {
 
   var storage = await FoodStorage.create();
   await storage.buildFoodLookupDatabase();
-  timeNow = DateTime.now().copyWith(
-      hour: 0,
-      isUtc: true,
-      minute: 0,
-      second: 0,
-      millisecond: 0,
-      microsecond: 0);
 
+  timeNow = DateTimeHelper.now();
   entriesForToday = await storage.getEntriesForDate(timeNow);
 
   var kcalLimit = await storage.readLimit();
@@ -87,14 +82,8 @@ class MainApp extends StatelessWidget {
                   GoRoute(
                     path: '/',
                     builder: (context, state) {
-                      return PerDatePageview(
+                      return PerDatePageViewController(
-                        initalDate: DateTime.now().copyWith(
+                        initialDate: DateTimeHelper.now(),
-                          hour: 0,
-                          minute: 0,
-                          second: 0,
-                          millisecond: 0,
-                          microsecond: 0,
-                        ),
                       );
                     },
                   ),

lib/perdate/perdate_pageview.dart

@@ -1,76 +1,50 @@
+import 'dart:developer';
+
+import 'package:calorimeter/perdate/perdate_pageview_controller.dart';
 import 'package:calorimeter/perdate/perdate_widget.dart';
 import 'package:flutter/material.dart';
+import 'package:provider/provider.dart';
 
-class PerDatePageview extends StatefulWidget {
+class PerDatePageView extends StatelessWidget {
   // this is the date for which the PerDate widget will be shown on screen
   // left of it will be yesterday's PerDate widget
   // right of it will be tomorrow's PerDate widget
-  final DateTime initalDate;
+  final DateTime initialDate;
-  const PerDatePageview({required this.initalDate, super.key});
+  final PageController pageController;
 
-  @override
+  const PerDatePageView({
-  State<PerDatePageview> createState() => _PerDatePageviewState();
+    required this.initialDate,
-}
+    required this.pageController,
-
+    super.key,
-class _PerDatePageviewState extends State<PerDatePageview> {
+  });
-  late PageController pageController;
-  late DateTime displayedDate;
-  late List<int> visitedIndexes = [];
-  final int initialOffset = 36500000;
-
-  //TODO: that is just ugly
-  bool backButtonWasPressed = false;
-
-  @override
-  void initState() {
-    super.initState();
-    pageController = PageController(initialPage: initialOffset);
-    displayedDate = widget.initalDate;
-    visitedIndexes.add(initialOffset);
-  }
 
   @override
   Widget build(BuildContext context) {
-    return BackButtonListener(
+    log("PerDatePageView's build()");
-      onBackButtonPressed: () async {
+    return PageView.builder(
-        if (visitedIndexes.length == 1) {
+        reverse: true,
-          return false;
+        controller: pageController,
-        }
+        onPageChanged: (value) {
+          log("onPageChanged() with value $value");
 
-        visitedIndexes.removeLast();
+          var diff = value - pageController.initialPage;
+          var newDate = initialDate.subtract(Duration(days: diff));
+          log("newDate = $newDate");
 
-        backButtonWasPressed = true;
+          context
-        pageController.jumpToPage(visitedIndexes.last);
+              .read<PageViewStateProvider>()
+              .addVisitedindexIfNotVisitedByBackButton(value);
+          context.read<PageViewStateProvider>().setDisplayedDate(newDate);
+        },
+        itemBuilder: (context, index) {
+          log("itemBuilder() called with index $index");
+          var dateToBuildWidgetFor = initialDate
+              .subtract(Duration(days: index - pageController.initialPage));
 
-        return true;
+          return PerDateWidget(
-      },
+            key: ValueKey(dateToBuildWidgetFor.toString()),
-      child: PageView.builder(
+            date: dateToBuildWidgetFor,
-          reverse: true,
+          );
-          controller: pageController,
+        });
-          onPageChanged: (value) {
-            if (backButtonWasPressed) {
-              backButtonWasPressed = false;
-              return;
-            }
-
-            visitedIndexes.add(value);
-          },
-          itemBuilder: (context, index) {
-            var dateToBuildWidgetFor =
-                displayedDate.subtract(Duration(days: index - initialOffset));
-
-            return PerDateWidget(
-                key: ValueKey(dateToBuildWidgetFor.toString()),
-                date: dateToBuildWidgetFor.copyWith(isUtc: true),
-                onDateSelected: (dateSelected) {
-                  if (dateSelected == null) return;
-
-                  var diff = dateSelected.difference(dateToBuildWidgetFor);
-                  var newIndex = index - diff.inDays;
-
-                  pageController.jumpToPage(newIndex);
-                });
-          }),
-    );
   }
 }

lib/perdate/perdate_pageview_controller.dart

@@ -0,0 +1,147 @@
+import 'dart:developer';
+
+import 'package:barcode_scan2/barcode_scan2.dart';
+import 'package:calorimeter/food_entry/food_entry_bloc.dart';
+import 'package:calorimeter/perdate/perdate_pageview.dart';
+import 'package:calorimeter/utils/app_drawer.dart';
+import 'package:calorimeter/utils/calendar_floating_button.dart';
+import 'package:calorimeter/utils/date_time_helper.dart';
+import 'package:calorimeter/utils/rectangular_notch_shape.dart';
+import 'package:calorimeter/utils/scan_food_floating_button.dart';
+import 'package:calorimeter/utils/sum_widget.dart';
+import 'package:calorimeter/utils/theme_switcher_button.dart';
+import 'package:flutter/material.dart';
+import 'package:intl/intl.dart';
+import 'package:provider/provider.dart';
+
+class PerDatePageViewController extends StatelessWidget {
+  // this is the date for which the PerDate widget will be shown on screen
+  // left of it will be yesterday's PerDate widget
+  // right of it will be tomorrow's PerDate widget
+  final DateTime initialDate;
+  final PageController pageController;
+  static final int initialOffset = 36500000;
+
+  const PerDatePageViewController._(
+      {required this.initialDate, required this.pageController});
+
+  factory PerDatePageViewController({required initialDate}) {
+    return PerDatePageViewController._(
+        initialDate: initialDate,
+        pageController: PageController(initialPage: initialOffset));
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return ChangeNotifierProvider(
+      create: (context) => PageViewStateProvider(
+        initialDate: initialDate,
+        initialOffset: initialOffset,
+      ),
+      child: Builder(builder: (context) {
+        return BackButtonListener(
+          onBackButtonPressed: () async {
+            context.read<PageViewStateProvider>().backButtonWasPressed = true;
+            var visitedIndexes =
+                context.read<PageViewStateProvider>().visitedIndexes;
+            if (visitedIndexes.length == 1) {
+              return false;
+            }
+
+            visitedIndexes.removeLast();
+            pageController.jumpToPage(visitedIndexes.last);
+
+            return true;
+          },
+          child: Scaffold(
+            appBar: AppBar(
+              title: Builder(builder: (context) {
+                return Text(DateFormat.yMMMMd('de').format(
+                    context.watch<PageViewStateProvider>().displayedDate));
+              }),
+              actions: const [ThemeSwitcherButton()],
+            ),
+            bottomNavigationBar: BottomAppBar(
+              shape: const RectangularNotchShape(),
+              color: Theme.of(context).colorScheme.secondary,
+              child: Builder(builder: (context) {
+                return SumWidget(
+                    date: context.watch<PageViewStateProvider>().displayedDate);
+              }),
+            ),
+            drawer: const AppDrawer(),
+            floatingActionButton: OverflowBar(children: [
+              ScanFoodFAB(
+                onPressed: () {
+                  var result = BarcodeScanner.scan();
+                  context.read<FoodEntryBloc>().add(
+                        BarcodeScanned(
+                          scanResultFuture: result,
+                          forDate: context
+                              .read<PageViewStateProvider>()
+                              .displayedDate,
+                        ),
+                      );
+                },
+              ),
+              const SizedBox(width: 8),
+              CalendarFAB(
+                startFromDate: DateTimeHelper.now(),
+                onDateSelected: (dateSelected) {
+                  if (dateSelected == null) return;
+
+                  var dateDiff = dateSelected.difference(initialDate).inDays;
+
+                  log("dateDiff = $dateDiff");
+                  pageController.jumpToPage(initialOffset - dateDiff);
+                },
+              ),
+            ]),
+            floatingActionButtonLocation:
+                FloatingActionButtonLocation.endDocked,
+            body: PerDatePageView(
+              pageController: pageController,
+              initialDate: initialDate,
+            ),
+          ),
+        );
+      }),
+    );
+  }
+}
+
+class PageViewStateProvider with ChangeNotifier {
+  DateTime _displayedDate;
+  final List<int> _visitedIndexes;
+  bool _backButtonWasPressed = false;
+
+  PageViewStateProvider({required DateTime initialDate, int initialOffset = 0})
+      : _displayedDate = initialDate,
+        _visitedIndexes = [] {
+    _visitedIndexes.add(initialOffset);
+  }
+
+  set backButtonWasPressed(val) => _backButtonWasPressed = val;
+  get backButtonWasPressed => _backButtonWasPressed;
+
+  get displayedDate => _displayedDate;
+  void setDisplayedDate(date) {
+    _displayedDate = date;
+    notifyListeners();
+  }
+
+  get visitedIndexes => _visitedIndexes;
+
+  void addVisitedIndex(int index) {
+    _visitedIndexes.add(index);
+  }
+
+  void addVisitedindexIfNotVisitedByBackButton(int index) {
+    if (_backButtonWasPressed) {
+      _backButtonWasPressed = false;
+      return;
+    }
+
+    addVisitedIndex(index);
+  }
+}

lib/perdate/perdate_widget.dart

@@ -1,22 +1,11 @@
-import 'package:barcode_scan2/barcode_scan2.dart';
-import 'package:calorimeter/utils/scan_food_floating_button.dart';
-import 'package:calorimeter/utils/app_drawer.dart';
 import 'package:calorimeter/food_entry/food_entry_bloc.dart';
 import 'package:calorimeter/perdate/entry_list.dart';
-import 'package:calorimeter/storage/storage.dart';
-import 'package:calorimeter/utils/calendar_floating_button.dart';
-import 'package:calorimeter/utils/rectangular_notch_shape.dart';
-import 'package:calorimeter/utils/sum_widget.dart';
-import 'package:calorimeter/utils/theme_switcher_button.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
-import 'package:intl/intl.dart';
 
 class PerDateWidget extends StatefulWidget {
   final DateTime date;
-  final Function(DateTime?) onDateSelected;
+  const PerDateWidget({super.key, required this.date});
-  const PerDateWidget(
-      {super.key, required this.date, required this.onDateSelected});
 
   @override
   State<PerDateWidget> createState() => _PerDateWidgetState();
@@ -24,9 +13,6 @@ class PerDateWidget extends StatefulWidget {
 
 class _PerDateWidgetState extends State<PerDateWidget>
     with AutomaticKeepAliveClientMixin<PerDateWidget> {
-  late FoodStorage storage;
-  List<FoodEntryState> entries = [];
-
   @override
   void initState() {
     context
@@ -35,11 +21,6 @@ class _PerDateWidgetState extends State<PerDateWidget>
     super.initState();
   }
 
-  @override
-  void dispose() {
-    super.dispose();
-  }
-
   @override
   Widget build(BuildContext context) {
     super.build(context);
@@ -50,43 +31,10 @@ class _PerDateWidgetState extends State<PerDateWidget>
           showNewSnackbarWith(context, pageState.errorString!);
         }
       },
-      builder: (context, globalState) {
+      builder: (context, pageState) {
-        return Scaffold(
+        return FoodEntryList(
-            appBar: AppBar(
+            entries: pageState.foodEntries[widget.date] ?? [],
-              title: Text(DateFormat.yMMMMd('de').format(widget.date)),
+            date: widget.date);
-              actions: const [ThemeSwitcherButton()],
-            ),
-            body: FoodEntryList(
-                entries: globalState.foodEntries[widget.date] ?? [],
-                date: widget.date),
-            bottomNavigationBar: BottomAppBar(
-                shape: const RectangularNotchShape(),
-                color: Theme.of(context).colorScheme.secondary,
-                child: SumWidget(
-                    foodEntries: globalState.foodEntries[widget.date] ?? [])),
-            drawer: const AppDrawer(),
-            floatingActionButton: OverflowBar(children: [
-              ScanFoodFloatingButton(
-                onPressed: () {
-                  var result = BarcodeScanner.scan();
-                  context.read<FoodEntryBloc>().add(
-                        BarcodeScanned(
-                          scanResultFuture: result,
-                          forDate: widget.date,
-                        ),
-                      );
-                },
-              ),
-              const SizedBox(width: 8),
-              CalendarFloatingButton(
-                startFromDate: widget.date,
-                onDateSelected: (dateSelected) {
-                  widget.onDateSelected(dateSelected);
-                },
-              ),
-            ]),
-            floatingActionButtonLocation:
-                FloatingActionButtonLocation.endDocked);
       },
     );
   }

lib/storage/storage.dart

@@ -1,6 +1,7 @@
 import 'dart:io';
 
 import 'package:calorimeter/food_entry/food_entry_bloc.dart';
+import 'package:calorimeter/utils/date_time_helper.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:universal_platform/universal_platform.dart';
 
@@ -157,7 +158,7 @@ class FoodStorage {
     // get a list of dates of the last 365 days
     var dates = List<DateTime>.generate(365, (idx) {
       var durationToPast = Duration(days: idx);
-      return DateTime.now().subtract(durationToPast);
+      return DateTimeHelper.now().subtract(durationToPast);
     });
 
     for (var date in dates.reversed) {

lib/utils/calendar_floating_button.dart

@@ -1,10 +1,11 @@
+import 'package:calorimeter/utils/date_time_helper.dart';
 import 'package:flutter/material.dart';
 
-class CalendarFloatingButton extends StatelessWidget {
+class CalendarFAB extends StatelessWidget {
   final DateTime startFromDate;
   final Function(DateTime?) onDateSelected;
 
-  const CalendarFloatingButton(
+  const CalendarFAB(
       {super.key, required this.startFromDate, required this.onDateSelected});
 
   @override
@@ -15,17 +16,18 @@ class CalendarFloatingButton extends StatelessWidget {
           locale: const Locale('de'),
           context: context,
           initialDate: startFromDate,
-          currentDate: DateTime.now(),
+          currentDate: DateTimeHelper.now(),
-          firstDate: DateTime.now().subtract(const Duration(days: 365 * 10)),
+          firstDate:
-          lastDate: DateTime.now().add(const Duration(days: 365 * 10)),
+              DateTimeHelper.now().subtract(const Duration(days: 365 * 10)),
+          lastDate: DateTimeHelper.now().add(const Duration(days: 365 * 10)),
         );
 
         if (!context.mounted) return;
 
-        onDateSelected(datePicked);
+        onDateSelected(datePicked?.copyWith(isUtc: true));
       },
       heroTag: "calendarFAB",
-      child: const Icon(Icons.today),
+      child: const Icon(Icons.date_range),
     );
   }
 }

lib/utils/date_time_helper.dart

@@ -0,0 +1,12 @@
+class DateTimeHelper {
+  static DateTime now() {
+    return DateTime.now().copyWith(
+      isUtc: true,
+      hour: 0,
+      minute: 0,
+      second: 0,
+      millisecond: 0,
+      microsecond: 0,
+    );
+  }
+}

lib/utils/scan_food_floating_button.dart

@@ -1,8 +1,8 @@
 import 'package:flutter/material.dart';
 
-class ScanFoodFloatingButton extends StatelessWidget {
+class ScanFoodFAB extends StatelessWidget {
   final Function() onPressed;
-  const ScanFoodFloatingButton({super.key, required this.onPressed});
+  const ScanFoodFAB({super.key, required this.onPressed});
 
   @override
   Widget build(BuildContext context) {

lib/utils/sum_widget.dart

@@ -4,53 +4,57 @@ import 'package:calorimeter/food_entry/food_entry_bloc.dart';
 import 'package:calorimeter/utils/settings_bloc.dart';
 
 class SumWidget extends StatelessWidget {
-  final List<FoodEntryState> foodEntries;
+  final DateTime date;
-  const SumWidget({required this.foodEntries, super.key});
+
+  const SumWidget({super.key, required this.date});
 
   @override
   Widget build(BuildContext context) {
-    return BlocBuilder<SettingsDataBloc, SettingsState>(
+    return BlocBuilder<FoodEntryBloc, GlobalEntryState>(
-      builder: (context, state) {
+        builder: (context, entryState) {
-        var sum = 0.0;
+      return BlocBuilder<SettingsDataBloc, SettingsState>(
-        for (var entry in foodEntries) {
+        builder: (context, settingsState) {
-          sum += entry.kcalPer100 / 100 * entry.mass;
+          var sum = 0.0;
-        }
+          for (var entry in entryState.foodEntries[date] ?? []) {
-        var diff = state.kcalLimit - sum;
+            sum += entry.kcalPer100 / 100 * entry.mass;
-        var diffLimit = state.kcalLimit ~/ 4;
+          }
+          var diff = settingsState.kcalLimit - sum;
+          var diffLimit = settingsState.kcalLimit ~/ 4;
 
-        var textColor = Theme.of(context).colorScheme.onSecondary;
+          var textColor = Theme.of(context).colorScheme.onSecondary;
-        var newTextColor = textColor;
+          var newTextColor = textColor;
-        var brightness = Theme.of(context).brightness;
+          var brightness = Theme.of(context).brightness;
 
-        switch (brightness) {
+          switch (brightness) {
-          case Brightness.dark:
+            case Brightness.dark:
-            if (diff < 0) {
+              if (diff < 0) {
-              newTextColor = Colors.red[900]!;
+                newTextColor = Colors.red[900]!;
-            } else if (diff < diffLimit) {
+              } else if (diff < diffLimit) {
-              newTextColor = Colors.orange[900]!;
+                newTextColor = Colors.orange[900]!;
-            }
+              }
-            break;
+              break;
 
-          case Brightness.light:
+            case Brightness.light:
-            if (diff < 0) {
+              if (diff < 0) {
-              newTextColor = Colors.redAccent;
+                newTextColor = Colors.redAccent;
-            } else if (diff < diffLimit) {
+              } else if (diff < diffLimit) {
-              newTextColor = Colors.orangeAccent;
+                newTextColor = Colors.orangeAccent;
-            }
+              }
-            break;
+              break;
-        }
+          }
 
-        return Align(
+          return Align(
-          alignment: Alignment.centerLeft,
+            alignment: Alignment.centerLeft,
-          child: Text(
+            child: Text(
-            'kcal heute: ${sum.ceil().toString()}/${state.kcalLimit.ceil()}',
+              'kcal heute: ${sum.ceil().toString()}/${settingsState.kcalLimit.ceil()}',
-            style: Theme.of(context)
+              style: Theme.of(context)
-                .textTheme
+                  .textTheme
-                .bodyLarge!
+                  .bodyLarge!
-                .copyWith(color: newTextColor),
+                  .copyWith(color: newTextColor),
-          ),
+            ),
-        );
+          );
-      },
+        },
-    );
+      );
+    });
   }
 }