[material_3_demo] Refactor application code into multiple small libra…

…ries (#2581)

material_3_demo/lib/main.dart

@@ -4,8 +4,8 @@
 
 import 'package:flutter/material.dart';
 
-import 'constants.dart';
-import 'home.dart';
+import 'src/constants.dart';
+import 'src/home.dart';
 
 void main() async {
   runApp(const App());
@@ -19,49 +19,49 @@ class App extends StatefulWidget {
 }
 
 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 _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) {
+  bool get _useLightMode => switch (_themeMode) {
     ThemeMode.system =>
       View.of(context).platformDispatcher.platformBrightness ==
           Brightness.light,
     ThemeMode.light => true,
     ThemeMode.dark => false,
   };
 
-  void handleBrightnessChange(bool useLightMode) {
+  void _handleBrightnessChange(bool useLightMode) {
     setState(() {
-      themeMode = useLightMode ? ThemeMode.light : ThemeMode.dark;
+      _themeMode = useLightMode ? ThemeMode.light : ThemeMode.dark;
     });
   }
 
-  void handleMaterialVersionChange() {
+  void _handleMaterialVersionChange() {
     setState(() {
-      useMaterial3 = !useMaterial3;
+      _useMaterial3 = !_useMaterial3;
     });
   }
 
-  void handleColorSelect(int value) {
+  void _handleColorSelect(int value) {
     setState(() {
-      colorSelectionMethod = ColorSelectionMethod.colorSeed;
-      colorSelected = ColorSeed.values[value];
+      _colorSelectionMethod = ColorSelectionMethod.colorSeed;
+      _colorSelected = ColorSeed.values[value];
     });
   }
 
-  void handleImageSelect(int 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;
+        _colorSelectionMethod = ColorSelectionMethod.image;
+        _imageSelected = ColorImageProvider.values[value];
+        _imageColorScheme = newScheme;
       });
     });
   }
@@ -71,37 +71,37 @@ class _AppState extends State<App> {
     return MaterialApp(
       debugShowCheckedModeBanner: false,
       title: 'Material 3',
-      themeMode: themeMode,
+      themeMode: _themeMode,
       theme: ThemeData(
         colorSchemeSeed:
-            colorSelectionMethod == ColorSelectionMethod.colorSeed
-                ? colorSelected.color
+            _colorSelectionMethod == ColorSelectionMethod.colorSeed
+                ? _colorSelected.color
                 : null,
         colorScheme:
-            colorSelectionMethod == ColorSelectionMethod.image
-                ? imageColorScheme
+            _colorSelectionMethod == ColorSelectionMethod.image
+                ? _imageColorScheme
                 : null,
-        useMaterial3: useMaterial3,
+        useMaterial3: _useMaterial3,
         brightness: Brightness.light,
       ),
       darkTheme: ThemeData(
         colorSchemeSeed:
-            colorSelectionMethod == ColorSelectionMethod.colorSeed
-                ? colorSelected.color
-                : imageColorScheme!.primary,
-        useMaterial3: useMaterial3,
+            _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,
+        useLightMode: _useLightMode,
+        useMaterial3: _useMaterial3,
+        colorSelected: _colorSelected,
+        imageSelected: _imageSelected,
+        handleBrightnessChange: _handleBrightnessChange,
+        handleMaterialVersionChange: _handleMaterialVersionChange,
+        handleColorSelect: _handleColorSelect,
+        handleImageSelect: _handleImageSelect,
+        colorSelectionMethod: _colorSelectionMethod,
       ),
     );
   }

material_3_demo/lib/src/animations.dart

@@ -0,0 +1,31 @@
+// 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';
+
+class SizeAnimation extends CurvedAnimation {
+  SizeAnimation(Animation<double> parent)
+    : super(
+        parent: parent,
+        curve: const Interval(0.2, 0.8, curve: Curves.easeInOutCubicEmphasized),
+        reverseCurve: Interval(
+          0,
+          0.2,
+          curve: Curves.easeInOutCubicEmphasized.flipped,
+        ),
+      );
+}
+
+class OffsetAnimation extends CurvedAnimation {
+  OffsetAnimation(Animation<double> parent)
+    : super(
+        parent: parent,
+        curve: const Interval(0.4, 1.0, curve: Curves.easeInOutCubicEmphasized),
+        reverseCurve: Interval(
+          0,
+          0.2,
+          curve: Curves.easeInOutCubicEmphasized.flipped,
+        ),
+      );
+}

material_3_demo/lib/src/bar_transition.dart

@@ -0,0 +1,59 @@
+// 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/widgets.dart';
+
+import 'animations.dart';
+
+class BarTransition extends StatefulWidget {
+  const BarTransition({
+    super.key,
+    required this.animation,
+    required this.backgroundColor,
+    required this.child,
+  });
+
+  final Animation<double> animation;
+  final Color backgroundColor;
+  final Widget child;
+
+  @override
+  State<BarTransition> createState() => _BarTransition();
+}
+
+class _BarTransition extends State<BarTransition> {
+  late final Animation<Offset> offsetAnimation;
+  late final Animation<double> heightAnimation;
+
+  @override
+  void initState() {
+    super.initState();
+
+    offsetAnimation = Tween<Offset>(
+      begin: const Offset(0, 1),
+      end: Offset.zero,
+    ).animate(OffsetAnimation(widget.animation));
+
+    heightAnimation = Tween<double>(
+      begin: 0,
+      end: 1,
+    ).animate(SizeAnimation(widget.animation));
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return ClipRect(
+      child: DecoratedBox(
+        decoration: BoxDecoration(color: widget.backgroundColor),
+        child: Align(
+          alignment: Alignment.topLeft,
+          heightFactor: heightAnimation.value,
+          child: FractionalTranslation(
+            translation: offsetAnimation.value,
+            child: widget.child,
+          ),
+        ),
+      ),
+    );
+  }
+}