Add simple playground theme export/import using JSON.

example/lib/example5_themes_playground/utils/import_export_playground_settings.dart

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+// ignore_for_file: lines_longer_than_80_chars
+import 'dart:convert';
+
+import 'package:flex_color_scheme/flex_color_scheme.dart';
+import 'package:flutter/material.dart';
+
+import '../../shared/controllers/theme_controller.dart';
+import '../../shared/model/adaptive_response.dart';
+import '../../shared/model/splash_type_enum.dart';
+import '../../shared/model/visual_density_enum.dart';
+import 'version.dart';
+
+/// Common keys used in serialisation/deserialisation
+enum JsonKeys {
+  dartType(key: 'dart_type'),
+  playgroundVersion(key: 'playground_version'),
+  typeColor(key: 'color'),
+  typeEnumAdaptiveResponse(key: 'enum_adaptive_response'),
+  typeEnumFlexAppBarStyle(key: 'enum_flex_appbar_style'),
+  typeEnumFlexFixedColorStyle(key: 'enum_flex_fixed_color_style'),
+  typeEnumFlexInputBorderType(key: 'enum_flex_input_border_type'),
+  typeEnumFlexPaletteType(key: 'enum_flex_palette_type'),
+  typeEnumFlexScaffoldBaseColor(key: 'enum_flex_scaffold_base_color'),
+  typeEnumFlexScheme(key: 'enum_flex_scheme'),
+  typeEnumFlexSchemeColor(key: 'enum_flex_scheme_color'),
+  typeEnumFlexSliderIndicatorType(key: 'enum_flex_slider_indicator_type'),
+  typeEnumFlexSurfaceMode(key: 'enum_flex_surface_mode'),
+  typeEnumFlexSystemNavBarStyle(key: 'enum_flex_system_navbar_style'),
+  typeEnumFlexTabBarStyle(key: 'enum_flex_tabbar_style'),
+  typeEnumListTileControlAffinity(key: 'enum_listtile_control_affinity'),
+  typeEnumListTileStyle(key: 'enum_listtile_style'),
+  typeEnumListTileTitleAlignment(key: 'enum_listtile_title_alignment'),
+  typeEnumMaterialTapTargetSize(key: 'enum_material_tap_target_size'),
+  typeEnumNavigationDestinationLabelBehavior(
+      key: 'enum_navigation_destination_label_behavior'),
+  typeEnumNavigationRailLabelType(key: 'enum_navigation_rail_label_type'),
+  typeEnumSchemeColor(key: 'enum_scheme_color'),
+  typeEnumShowValueIndicator(key: 'enum_show_value_indicator'),
+  typeEnumSplashType(key: 'enum_splash_type'),
+  typeEnumTabAlignment(key: 'enum_tab_alignment'),
+  typeEnumTabBarIndicatorSize(key: 'enum_tabbar_indicator_size'),
+  typeEnumThemeModeColor(key: 'enum_theme_mode'),
+  typeEnumVisualDensity(key: 'enum_visual_density'),
+
+  value(key: 'value');
+
+  final String key;
+
+  const JsonKeys({required this.key});
+}
+
+/// A function that exports the theme playground settings to JSON
+Future<String> exportPlaygroundSettings(ThemeController controller) async {
+  final Map<String, dynamic> themeData = controller.exportSavedThemeData();
+
+  // This may be useful in the future, e.g., to handle migrations when importing an older version
+  themeData[JsonKeys.playgroundVersion.key] = await getVersion();
+
+  final String data = JsonEncoder.withIndent(
+    '    ',
+    (dynamic object) {
+      /// Custom converter for types that can't be serialised
+
+      if (object is Color) {
+        return <String, String>{
+          JsonKeys.dartType.key: JsonKeys.typeColor.key,
+          JsonKeys.value.key: object.hexCode,
+        };
+      } else if (object is Enum) {
+        String? dartType;
+
+        if (object is AdaptiveResponse) {
+          dartType = JsonKeys.typeEnumAdaptiveResponse.key;
+        } else if (object is FlexAppBarStyle) {
+          dartType = JsonKeys.typeEnumFlexAppBarStyle.key;
+        } else if (object is FlexFixedColorStyle) {
+          dartType = JsonKeys.typeEnumFlexFixedColorStyle.key;
+        } else if (object is FlexInputBorderType) {
+          dartType = JsonKeys.typeEnumFlexInputBorderType.key;
+        } else if (object is FlexPaletteType) {
+          dartType = JsonKeys.typeEnumFlexPaletteType.key;
+        } else if (object is FlexScaffoldBaseColor) {
+          dartType = JsonKeys.typeEnumFlexScaffoldBaseColor.key;
+        } else if (object is FlexScheme) {
+          dartType = JsonKeys.typeEnumFlexScheme.key;
+        } else if (object is FlexSchemeColor) {
+          dartType = JsonKeys.typeEnumFlexSchemeColor.key;
+        } else if (object is FlexSliderIndicatorType) {
+          dartType = JsonKeys.typeEnumFlexSliderIndicatorType.key;
+        } else if (object is FlexSurfaceMode) {
+          dartType = JsonKeys.typeEnumFlexSurfaceMode.key;
+        } else if (object is FlexSystemNavBarStyle) {
+          dartType = JsonKeys.typeEnumFlexSystemNavBarStyle.key;
+        } else if (object is FlexTabBarStyle) {
+          dartType = JsonKeys.typeEnumFlexTabBarStyle.key;
+        } else if (object is ListTileControlAffinity) {
+          dartType = JsonKeys.typeEnumListTileControlAffinity.key;
+        } else if (object is ListTileStyle) {
+          dartType = JsonKeys.typeEnumListTileStyle.key;
+        } else if (object is ListTileTitleAlignment) {
+          dartType = JsonKeys.typeEnumListTileTitleAlignment.key;
+        } else if (object is MaterialTapTargetSize) {
+          dartType = JsonKeys.typeEnumMaterialTapTargetSize.key;
+        } else if (object is NavigationDestinationLabelBehavior) {
+          dartType = JsonKeys.typeEnumNavigationDestinationLabelBehavior.key;
+        } else if (object is NavigationRailLabelType) {
+          dartType = JsonKeys.typeEnumNavigationRailLabelType.key;
+        } else if (object is SchemeColor) {
+          dartType = JsonKeys.typeEnumSchemeColor.key;
+        } else if (object is ShowValueIndicator) {
+          dartType = JsonKeys.typeEnumShowValueIndicator.key;
+        } else if (object is SplashTypeEnum) {
+          dartType = JsonKeys.typeEnumSplashType.key;
+        } else if (object is TabAlignment) {
+          dartType = JsonKeys.typeEnumTabAlignment.key;
+        } else if (object is TabBarIndicatorSize) {
+          dartType = JsonKeys.typeEnumTabBarIndicatorSize.key;
+        } else if (object is ThemeMode) {
+          dartType = JsonKeys.typeEnumThemeModeColor.key;
+        } else if (object is VisualDensityEnum) {
+          dartType = JsonKeys.typeEnumVisualDensity.key;
+        } else {
+          debugPrint(
+              'Unhandled enum type ${object.runtimeType} with value ${object.name}');
+        }
+
+        if (dartType != null) {
+          return <String, String>{
+            JsonKeys.dartType.key: dartType,
+            JsonKeys.value.key: object.name,
+          };
+        }
+      }
+
+      return object;
+    },
+  ).convert(themeData);
+
+  return data;
+}
+
+/// A function that imports the saved theme playground settings from JSON
+Future<void> importPlaygroundSettings(
+  ThemeController controller, {
+  required String settings,
+}) {
+  final Map<String, dynamic> json =
+      jsonDecode(settings) as Map<String, dynamic>;
+
+  final Map<String, dynamic> data = <String, dynamic>{};
+
+  for (final MapEntry<String, dynamic> item in json.entries) {
+    if (_equalsIgnoreCase(item.key, JsonKeys.playgroundVersion.key)) {
+      continue;
+    }
+
+    dynamic mapped;
+
+    if (item.value is Map) {
+      final String dartType = item.value[JsonKeys.dartType.key] as String;
+      final dynamic value = item.value[JsonKeys.value.key];
+
+      if (_equalsIgnoreCase(dartType, JsonKeys.typeColor.key)) {
+        mapped = Color(int.parse("0x${value.replaceAll("#", "")}"));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumAdaptiveResponse.key)) {
+        mapped = AdaptiveResponse.values.firstWhere(
+            (AdaptiveResponse element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumFlexAppBarStyle.key)) {
+        mapped = FlexAppBarStyle.values.firstWhere((FlexAppBarStyle element) =>
+            _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumFlexFixedColorStyle.key)) {
+        mapped = FlexFixedColorStyle.values.firstWhere(
+            (FlexFixedColorStyle element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumFlexInputBorderType.key)) {
+        mapped = FlexInputBorderType.values.firstWhere(
+            (FlexInputBorderType element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumFlexPaletteType.key)) {
+        mapped = FlexPaletteType.values.firstWhere((FlexPaletteType element) =>
+            _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumFlexScaffoldBaseColor.key)) {
+        mapped = FlexScaffoldBaseColor.values.firstWhere(
+            (FlexScaffoldBaseColor element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(dartType, JsonKeys.typeEnumFlexScheme.key)) {
+        mapped = FlexScheme.values.firstWhere((FlexScheme element) =>
+            _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumFlexSliderIndicatorType.key)) {
+        mapped = FlexSliderIndicatorType.values.firstWhere(
+            (FlexSliderIndicatorType element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumFlexSurfaceMode.key)) {
+        mapped = FlexSurfaceMode.values.firstWhere((FlexSurfaceMode element) =>
+            _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumFlexSystemNavBarStyle.key)) {
+        mapped = FlexSystemNavBarStyle.values.firstWhere(
+            (FlexSystemNavBarStyle element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumFlexTabBarStyle.key)) {
+        mapped = FlexTabBarStyle.values.firstWhere((FlexTabBarStyle element) =>
+            _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumFlexSchemeColor.key)) {
+        mapped = SchemeColor.values.firstWhere((SchemeColor element) =>
+            _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumListTileControlAffinity.key)) {
+        mapped = ListTileControlAffinity.values.firstWhere(
+            (ListTileControlAffinity element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumListTileStyle.key)) {
+        mapped = ListTileStyle.values.firstWhere((ListTileStyle element) =>
+            _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumListTileTitleAlignment.key)) {
+        mapped = ListTileTitleAlignment.values.firstWhere(
+            (ListTileTitleAlignment element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumMaterialTapTargetSize.key)) {
+        mapped = MaterialTapTargetSize.values.firstWhere(
+            (MaterialTapTargetSize element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumNavigationDestinationLabelBehavior.key)) {
+        mapped = NavigationDestinationLabelBehavior.values.firstWhere(
+            (NavigationDestinationLabelBehavior element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumNavigationRailLabelType.key)) {
+        mapped = NavigationRailLabelType.values.firstWhere(
+            (NavigationRailLabelType element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumSchemeColor.key)) {
+        mapped = SchemeColor.values.firstWhere((SchemeColor element) =>
+            _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumShowValueIndicator.key)) {
+        mapped = ShowValueIndicator.values.firstWhere(
+            (ShowValueIndicator element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(dartType, JsonKeys.typeEnumSplashType.key)) {
+        mapped = SplashTypeEnum.values.firstWhere((SplashTypeEnum element) =>
+            _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumTabAlignment.key)) {
+        mapped = TabAlignment.values.firstWhere((TabAlignment element) =>
+            _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumTabBarIndicatorSize.key)) {
+        mapped = TabBarIndicatorSize.values.firstWhere(
+            (TabBarIndicatorSize element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumThemeModeColor.key)) {
+        mapped = ThemeMode.values.firstWhere((ThemeMode element) =>
+            _equalsIgnoreCase(element.name, value as String));
+      } else if (_equalsIgnoreCase(
+          dartType, JsonKeys.typeEnumVisualDensity.key)) {
+        mapped = VisualDensityEnum.values.firstWhere(
+            (VisualDensityEnum element) =>
+                _equalsIgnoreCase(element.name, value as String));
+      } else {
+        debugPrint('Unhandled type $dartType with value $value');
+      }
+    } else {
+      mapped = item.value;
+    }
+
+    if (mapped == null) {
+      debugPrint('mapped value null. Skipping.');
+    } else {
+      data[item.key] = mapped;
+    }
+  }
+
+  return controller
+      .importSavedThemeData(data)
+      .then((value) => controller.loadAll());
+}
+
+bool _equalsIgnoreCase(String? string1, String? string2) {
+  return string1?.toLowerCase() == string2?.toLowerCase();
+}