added MeteringBloc

lib/main.dart

@@ -1,6 +1,9 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
 
+import 'models/photography_value.dart';
 import 'res/theme.dart';
+import 'screens/metering/metering_bloc.dart';
 import 'screens/metering/metering_screen.dart';
 
 void main() {
@@ -12,13 +15,16 @@ class MyApp extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return MaterialApp(
+    return BlocProvider(
+      create: (context) => MeteringBloc(Stop.third),
+      child: MaterialApp(
         title: 'Flutter Demo',
         theme: ThemeData(
           useMaterial3: true,
           colorScheme: lightColorScheme,
         ),
         home: const MeteringScreen(),
+      ),
     );
   }
 }

lib/models/exposure_pair.dart

@@ -0,0 +1,8 @@
+import 'photography_value.dart';
+
+class ExposurePair {
+  final ApertureValue aperture;
+  final ShutterSpeedValue shutterSpeed;
+
+  const ExposurePair(this.aperture, this.shutterSpeed);
+}

lib/screens/metering/components/exposure_pairs_list/exposure_pairs_list.dart

@@ -1,56 +1,12 @@
-import 'dart:math';
-
 import 'package:flutter/material.dart';
-import 'package:lightmeter/models/photography_value.dart';
+import 'package:lightmeter/models/exposure_pair.dart';
 import 'package:lightmeter/res/dimens.dart';
 import 'package:lightmeter/screens/metering/components/exposure_pairs_list/components/exposure_pair_item.dart';
 
 class ExposurePairsList extends StatelessWidget {
-  final double ev;
+  final List<ExposurePair> exposurePairs;
-  final Stop stopType;
-  final List<ApertureValue> _apertureValuesList;
-  final List<ShutterSpeedValue> _shutterSpeedValuesList;
-  late final int _apertureOffset;
-  late final int _shutterSpeedOffset;
-  late final int _itemsCount;
 
-  ExposurePairsList({
+  const ExposurePairsList(this.exposurePairs, {super.key});
-    required this.ev,
-    required this.stopType,
-    super.key,
-  })  : _apertureValuesList = apertureValues.whereStopType(stopType),
-        _shutterSpeedValuesList = shutterSpeedValues.whereStopType(stopType) {
-    late final int evSteps;
-    switch (stopType) {
-      case Stop.full:
-        evSteps = ev.floor();
-        break;
-      case Stop.half:
-        evSteps = (ev / 0.5).floor();
-        break;
-      case Stop.third:
-        evSteps = (ev / 0.3).floor();
-        break;
-    }
-
-    final evOffset = _shutterSpeedValuesList.indexOf(const ShutterSpeedValue(1, false, Stop.full)) - evSteps;
-    if (evOffset >= 0) {
-      _apertureOffset = 0;
-      _shutterSpeedOffset = evOffset;
-    } else {
-      _apertureOffset = -evOffset;
-      _shutterSpeedOffset = 0;
-    }
-
-    _itemsCount = min(
-          _apertureValuesList.length + _shutterSpeedOffset,
-          _shutterSpeedValuesList.length + _apertureOffset,
-        ) -
-        max(
-          _apertureOffset,
-          _shutterSpeedOffset,
-        );
-  }
 
   @override
   Widget build(BuildContext context) {
@@ -59,7 +15,8 @@ class ExposurePairsList extends StatelessWidget {
       children: [
         Positioned.fill(
           child: ListView.builder(
-            itemCount: _itemsCount,
+            key: ValueKey(exposurePairs.hashCode),
+            itemCount: exposurePairs.length,
             itemBuilder: (_, index) => Row(
               mainAxisAlignment: MainAxisAlignment.center,
               children: [
@@ -67,7 +24,7 @@ class ExposurePairsList extends StatelessWidget {
                   child: Align(
                     alignment: Alignment.centerLeft,
                     child: ExposurePaitListItem(
-                      _apertureValuesList[index + _apertureOffset],
+                      exposurePairs[index].aperture,
                       tickOnTheLeft: false,
                     ),
                   ),
@@ -77,7 +34,7 @@ class ExposurePairsList extends StatelessWidget {
                   child: Align(
                     alignment: Alignment.centerLeft,
                     child: ExposurePaitListItem(
-                      _shutterSpeedValuesList[index + _shutterSpeedOffset],
+                      exposurePairs[index].shutterSpeed,
                       tickOnTheLeft: true,
                     ),
                   ),

lib/screens/metering/components/topbar/topbar.dart

@@ -1,17 +1,21 @@
 import 'package:flutter/material.dart';
+import 'package:lightmeter/models/exposure_pair.dart';
 import 'package:lightmeter/res/dimens.dart';
-import 'package:lightmeter/screens/metering/components/topbar/components/reading_container.dart';
+
-import 'package:lightmeter/screens/metering/components/topbar/topbar_shape.dart';
+import 'components/reading_container.dart';
-import 'package:lightmeter/utils/text_line_height.dart';
 
 class MeteringTopBar extends StatelessWidget {
   static const _columnsCount = 3;
 
+  final ExposurePair? fastest;
+  final ExposurePair? slowest;
   final double ev;
   final int iso;
   final double nd;
 
   const MeteringTopBar({
+    required this.fastest,
+    required this.slowest,
     required this.ev,
     required this.iso,
     required this.nd,
@@ -43,14 +47,18 @@ class MeteringTopBar extends StatelessWidget {
                       SizedBox(
                         height: columnWidth / 3 * 4,
                         child: ReadingContainer(
-                          values: const [
+                          values: [
                             ReadingValue(
                               label: 'Fastest',
-                              value: 'f/5.6 - 1/2000',
+                              value: fastest != null
+                                  ? '${fastest!.aperture.toString()} - ${fastest!.shutterSpeed.toString()}'
+                                  : 'N/A',
                             ),
                             ReadingValue(
                               label: 'Slowest',
-                              value: 'f/45 - 1/30',
+                              value: fastest != null
+                                  ? '${slowest!.aperture.toString()} - ${slowest!.shutterSpeed.toString()}'
+                                  : 'N/A',
                             ),
                           ],
                         ),
@@ -63,7 +71,7 @@ class MeteringTopBar extends StatelessWidget {
                             child: ReadingContainer.singleValue(
                               value: ReadingValue(
                                 label: 'EV',
-                                value: ev.toString(),
+                                value: ev.toStringAsFixed(1),
                               ),
                             ),
                           ),

lib/screens/metering/metering_bloc.dart

@@ -0,0 +1,90 @@
+import 'dart:math';
+
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:lightmeter/models/exposure_pair.dart';
+import 'package:lightmeter/models/photography_value.dart';
+
+import 'metering_event.dart';
+import 'metering_state.dart';
+
+class MeteringBloc extends Bloc<MeteringEvent, MeteringState> {
+  final Stop stopType;
+  late final _apertureValues = apertureValues.whereStopType(stopType);
+  late final _shutterSpeedValues = shutterSpeedValues.whereStopType(stopType);
+  late final _isoValues = isoValues.whereStopType(stopType);
+  final _random = Random();
+
+  MeteringBloc(this.stopType)
+      : super(
+          const MeteringState(
+            iso: 100,
+            ev: 21.3,
+            evCompensation: 0.0,
+            nd: 0.0,
+            exposurePairs: [],
+          ),
+        ) {
+    on<MeasureEvent>(_onMeasure);
+
+    add(const MeasureEvent());
+  }
+
+  /// https://stackoverflow.com/questions/5401738/how-to-convert-between-lux-and-exposure-value
+  void _onMeasure(_, Emitter emit) {
+    double log2(double x) => log(x) / log(2);
+
+    final aperture = _apertureValues[_random.nextInt(_apertureValues.length)];
+    final shutterSpeed = _shutterSpeedValues[_random.nextInt(_shutterSpeedValues.thirdStops().length)];
+    final iso = _isoValues[_random.nextInt(_isoValues.thirdStops().length)];
+
+    final evAtSystemIso = log2(pow(aperture.value, 2).toDouble()) - log2(shutterSpeed.value);
+    final ev = evAtSystemIso - log2(iso.value / state.iso);
+    final exposurePairs = _buildExposureValues(ev);
+
+    emit(MeteringState(
+      iso: state.iso,
+      ev: ev,
+      evCompensation: state.evCompensation,
+      nd: state.nd,
+      exposurePairs: exposurePairs,
+    ));
+  }
+
+  List<ExposurePair> _buildExposureValues(double ev) {
+    late final int evSteps;
+    switch (stopType) {
+      case Stop.full:
+        evSteps = ev.floor();
+        break;
+      case Stop.half:
+        evSteps = (ev / 0.5).floor();
+        break;
+      case Stop.third:
+        evSteps = (ev / 0.3).floor();
+        break;
+    }
+    final evOffset = _shutterSpeedValues.indexOf(const ShutterSpeedValue(1, false, Stop.full)) - evSteps;
+
+    late final int apertureOffset;
+    late final int shutterSpeedOffset;
+    if (evOffset >= 0) {
+      apertureOffset = 0;
+      shutterSpeedOffset = evOffset;
+    } else {
+      apertureOffset = -evOffset;
+      shutterSpeedOffset = 0;
+    }
+
+    int itemsCount = min(_apertureValues.length + shutterSpeedOffset, _shutterSpeedValues.length + apertureOffset) -
+        max(apertureOffset, shutterSpeedOffset);
+
+    return List.generate(
+      itemsCount,
+      (index) => ExposurePair(
+        _apertureValues[index + apertureOffset],
+        _shutterSpeedValues[index + shutterSpeedOffset],
+      ),
+      growable: false,
+    );
+  }
+}

lib/screens/metering/metering_event.dart

@@ -0,0 +1,7 @@
+abstract class MeteringEvent {
+  const MeteringEvent();
+}
+
+class MeasureEvent extends MeteringEvent {
+  const MeasureEvent();
+}

lib/screens/metering/metering_screen.dart

@@ -1,37 +1,55 @@
 import 'package:flutter/material.dart';
-import 'package:lightmeter/models/photography_value.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:lightmeter/res/dimens.dart';
+import 'package:lightmeter/screens/metering/metering_event.dart';
 
 import 'components/bottom_controls/bottom_controls.dart';
 import 'components/exposure_pairs_list/exposure_pairs_list.dart';
 import 'components/topbar/topbar.dart';
+import 'metering_bloc.dart';
+import 'metering_state.dart';
 
 class MeteringScreen extends StatelessWidget {
   const MeteringScreen({super.key});
 
   @override
   Widget build(BuildContext context) {
-    const ev = 0.3;
     return Scaffold(
       backgroundColor: Theme.of(context).colorScheme.background,
-      body: Column(
+      body: BlocBuilder<MeteringBloc, MeteringState>(
+        builder: (context, state) {
+          return Column(
             children: [
-          const MeteringTopBar(
+              MeteringTopBar(
-            ev: ev,
+                fastest: state.fastest,
-            iso: 6400,
+                slowest: state.slowest,
-            nd: 0,
+                ev: state.ev,
+                iso: state.iso,
+                nd: state.nd,
               ),
               Expanded(
-            child: ExposurePairsList(
+                child: Padding(
-              ev: ev,
+                  padding: const EdgeInsets.symmetric(horizontal: Dimens.paddingM),
-              stopType: Stop.third,
+                  child: Row(
+                    children: [
+                      Expanded(
+                        flex: 2,
+                        child: ExposurePairsList(state.exposurePairs),
+                      ),
+                      const SizedBox(width: Dimens.grid16),
+                      const Spacer()
+                    ],
+                  ),
                 ),
               ),
               MeteringBottomControls(
                 onSourceChanged: () {},
-            onMeasure: () {},
+                onMeasure: () => context.read<MeteringBloc>().add(const MeasureEvent()),
                 onSettings: () {},
               ),
             ],
+          );
+        },
       ),
     );
   }

lib/screens/metering/metering_state.dart

@@ -0,0 +1,20 @@
+import 'package:lightmeter/models/exposure_pair.dart';
+
+class MeteringState {
+  final double ev;
+  final double evCompensation;
+  final int iso;
+  final double nd;
+  final List<ExposurePair> exposurePairs;
+
+  const MeteringState({
+    required this.ev,
+    required this.evCompensation,
+    required this.iso,
+    required this.nd,
+    required this.exposurePairs,
+  });
+
+  ExposurePair? get fastest => exposurePairs.isEmpty ? null : exposurePairs.first;
+  ExposurePair? get slowest => exposurePairs.isEmpty ? null : exposurePairs.last;
+}

pubspec.yaml

@@ -9,6 +9,7 @@ environment:
 dependencies:
   flutter:
     sdk: flutter
+  flutter_bloc: ^8.1.1
   material_color_utilities: ^0.2.0
 
 dev_dependencies: