snapshot of https://github.com/flutter/samples.git (main, 2026-09-16; blobs > 131072B omitted)

material_3_demo/lib/main.dart

@@ -0,0 +1,107 @@
+// Copyright 2021 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+
+import 'src/constants.dart';
+import 'src/home.dart';
+
+void main() async {
+  runApp(const App());
+}
+
+class App extends StatefulWidget {
+  const App({super.key});
+
+  @override
+  State<App> createState() => _AppState();
+}
+
+class _AppState extends State<App> {
+  bool _useMaterial3 = true;
+  ThemeMode _themeMode = ThemeMode.system;
+  ColorSeed _colorSelected = ColorSeed.baseColor;
+  ColorImageProvider _imageSelected = ColorImageProvider.leaves;
+  ColorScheme? _imageColorScheme = const ColorScheme.light();
+  ColorSelectionMethod _colorSelectionMethod = ColorSelectionMethod.colorSeed;
+
+  bool get _useLightMode => switch (_themeMode) {
+    ThemeMode.system =>
+      View.of(context).platformDispatcher.platformBrightness ==
+          Brightness.light,
+    ThemeMode.light => true,
+    ThemeMode.dark => false,
+  };
+
+  void _handleBrightnessChange(bool useLightMode) {
+    setState(() {
+      _themeMode = useLightMode ? ThemeMode.light : ThemeMode.dark;
+    });
+  }
+
+  void _handleMaterialVersionChange() {
+    setState(() {
+      _useMaterial3 = !_useMaterial3;
+    });
+  }
+
+  void _handleColorSelect(int value) {
+    setState(() {
+      _colorSelectionMethod = ColorSelectionMethod.colorSeed;
+      _colorSelected = ColorSeed.values[value];
+    });
+  }
+
+  void _handleImageSelect(int value) {
+    final String url = ColorImageProvider.values[value].url;
+    ColorScheme.fromImageProvider(provider: NetworkImage(url)).then((
+      newScheme,
+    ) {
+      setState(() {
+        _colorSelectionMethod = ColorSelectionMethod.image;
+        _imageSelected = ColorImageProvider.values[value];
+        _imageColorScheme = newScheme;
+      });
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      debugShowCheckedModeBanner: false,
+      title: 'Material 3',
+      themeMode: _themeMode,
+      theme: ThemeData(
+        colorSchemeSeed:
+            _colorSelectionMethod == ColorSelectionMethod.colorSeed
+            ? _colorSelected.color
+            : null,
+        colorScheme: _colorSelectionMethod == ColorSelectionMethod.image
+            ? _imageColorScheme
+            : null,
+        useMaterial3: _useMaterial3,
+        brightness: Brightness.light,
+      ),
+      darkTheme: ThemeData(
+        colorSchemeSeed:
+            _colorSelectionMethod == ColorSelectionMethod.colorSeed
+            ? _colorSelected.color
+            : _imageColorScheme!.primary,
+        useMaterial3: _useMaterial3,
+        brightness: Brightness.dark,
+      ),
+      home: Home(
+        useLightMode: _useLightMode,
+        useMaterial3: _useMaterial3,
+        colorSelected: _colorSelected,
+        imageSelected: _imageSelected,
+        handleBrightnessChange: _handleBrightnessChange,
+        handleMaterialVersionChange: _handleMaterialVersionChange,
+        handleColorSelect: _handleColorSelect,
+        handleImageSelect: _handleImageSelect,
+        colorSelectionMethod: _colorSelectionMethod,
+      ),
+    );
+  }
+}