samples/material_3_demo/lib/main.dart

// 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 'package:flutter/scheduler.dart';

import 'color_palettes_screen.dart';
import 'component_screen.dart';
import 'elevation_screen.dart';
import 'typography_screen.dart';

void main() {
  runApp(
    const MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Material3Demo(),
    ),
  );
}

class Material3Demo extends StatefulWidget {
  const Material3Demo({super.key});

  @override
  State<Material3Demo> createState() => _Material3DemoState();
}

// NavigationRail shows if the screen width is greater or equal to
// screenWidthThreshold; otherwise, NavigationBar is used for navigation.
const double narrowScreenWidthThreshold = 450;

const double transitionLength = 500;

enum ColorSeed {
  baseColor('M3 Baseline', Color(0xff6750a4)),
  indigo('Indigo', Colors.indigo),
  blue('Blue', Colors.blue),
  teal('Teal', Colors.teal),
  green('Green', Colors.green),
  yellow('Yellow', Colors.yellow),
  orange('Orange', Colors.orange),
  deepOrange('Deep Orange', Colors.deepOrange),
  pink('Pink', Colors.pink);

  const ColorSeed(this.label, this.color);
  final String label;
  final Color color;
}

enum ScreenSelected {
  component(0),
  color(1),
  typography(2),
  elevation(3);

  const ScreenSelected(this.value);
  final int value;
}

class _Material3DemoState extends State<Material3Demo>
    with SingleTickerProviderStateMixin {
  final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
  late final AnimationController controller;
  late final CurvedAnimation railAnimation;
  bool controllerInitialized = false;
  bool showMediumSizeLayout = false;
  bool showLargeSizeLayout = false;
  bool useMaterial3 = true;
  ThemeMode themeMode = ThemeMode.system;
  bool get useLightMode {
    switch (themeMode) {
      case ThemeMode.system:
        return SchedulerBinding.instance.window.platformBrightness ==
            Brightness.light;
      case ThemeMode.light:
        return true;
      case ThemeMode.dark:
        return false;
    }
  }

  ColorSeed colorSelected = ColorSeed.baseColor;
  int screenIndex = ScreenSelected.component.value;

  @override
  initState() {
    super.initState();
    controller = AnimationController(
      duration: Duration(milliseconds: transitionLength.toInt() * 2),
      value: 0,
      vsync: this,
    );
    railAnimation = CurvedAnimation(
      parent: controller,
      curve: const Interval(0.5, 1.0),
    );
  }

  @override
  void dispose() {
    controller.dispose();
    super.dispose();
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();

    final double width = MediaQuery.of(context).size.width;
    final AnimationStatus status = controller.status;
    if (width > 1000) {
      if (width > 1500) {
        showMediumSizeLayout = false;
        showLargeSizeLayout = true;
      } else {
        showMediumSizeLayout = true;
        showLargeSizeLayout = false;
      }
      if (status != AnimationStatus.forward &&
          status != AnimationStatus.completed) {
        controller.forward();
      }
    } else {
      showMediumSizeLayout = false;
      showLargeSizeLayout = false;
      if (status != AnimationStatus.reverse &&
          status != AnimationStatus.dismissed) {
        controller.reverse();
      }
    }
    if (!controllerInitialized) {
      controllerInitialized = true;
      controller.value = width > 1000 ? 1 : 0;
    }
  }

  void handleScreenChanged(int screenSelected) {
    setState(() {
      screenIndex = screenSelected;
    });
  }

  void handleBrightnessChange(bool useLightMode) {
    setState(() {
      themeMode = useLightMode ? ThemeMode.light : ThemeMode.dark;
    });
  }

  void handleMaterialVersionChange() {
    setState(() {
      useMaterial3 = !useMaterial3;
    });
  }

  void handleColorSelect(int value) {
    setState(() {
      colorSelected = ColorSeed.values[value];
    });
  }

  Widget createScreenFor(
      ScreenSelected screenSelected, bool showNavBarExample) {
    switch (screenSelected) {
      case ScreenSelected.component:
        return Expanded(
          child: OneTwoTransition(
            animation: railAnimation,
            one: FirstComponentList(
                showNavBottomBar: showNavBarExample,
                scaffoldKey: scaffoldKey,
                showSecondList: showMediumSizeLayout || showLargeSizeLayout),
            two: SecondComponentList(
              scaffoldKey: scaffoldKey,
            ),
          ),
        );
      case ScreenSelected.color:
        return const ColorPalettesScreen();
      case ScreenSelected.typography:
        return const TypographyScreen();
      case ScreenSelected.elevation:
        return const ElevationScreen();
      default:
        return FirstComponentList(
            showNavBottomBar: showNavBarExample,
            scaffoldKey: scaffoldKey,
            showSecondList: showMediumSizeLayout || showLargeSizeLayout);
    }
  }

  PreferredSizeWidget createAppBar() {
    return AppBar(
      title: useMaterial3 ? const Text('Material 3') : const Text('Material 2'),
      actions: !showMediumSizeLayout && !showLargeSizeLayout
          ? [
              _BrightnessButton(
                handleBrightnessChange: handleBrightnessChange,
              ),
              _Material3Button(
                handleMaterialVersionChange: handleMaterialVersionChange,
              ),
              _ColorSeedButton(
                handleColorSelect: handleColorSelect,
                colorSelected: colorSelected,
              ),
            ]
          : [Container()],
    );
  }

  Widget _expandedTrailingActions() => Container(
        constraints: const BoxConstraints.tightFor(width: 250),
        padding: const EdgeInsets.symmetric(horizontal: 30),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.end,
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Row(
              children: [
                const Text('Brightness'),
                Expanded(child: Container()),
                Switch(
                    value: useLightMode,
                    onChanged: (value) {
                      handleBrightnessChange(value);
                    })
              ],
            ),
            Row(
              children: [
                useMaterial3
                    ? const Text('Material 3')
                    : const Text('Material 2'),
                Expanded(child: Container()),
                Switch(
                    value: useMaterial3,
                    onChanged: (_) {
                      handleMaterialVersionChange();
                    })
              ],
            ),
            const Divider(),
            ConstrainedBox(
              constraints: const BoxConstraints(maxHeight: 200.0),
              child: GridView.count(
                crossAxisCount: 3,
                children: List.generate(
                    ColorSeed.values.length,
                    (i) => IconButton(
                          icon: const Icon(Icons.radio_button_unchecked),
                          color: ColorSeed.values[i].color,
                          isSelected:
                              colorSelected.color == ColorSeed.values[i].color,
                          selectedIcon: const Icon(Icons.circle),
                          onPressed: () {
                            handleColorSelect(i);
                          },
                        )),
              ),
            ),
          ],
        ),
      );

  Widget _trailingActions() => Column(
        mainAxisAlignment: MainAxisAlignment.end,
        children: [
          Flexible(
            child: _BrightnessButton(
              handleBrightnessChange: handleBrightnessChange,
              showTooltipBelow: false,
            ),
          ),
          Flexible(
            child: _Material3Button(
              handleMaterialVersionChange: handleMaterialVersionChange,
              showTooltipBelow: false,
            ),
          ),
          Flexible(
            child: _ColorSeedButton(
              handleColorSelect: handleColorSelect,
              colorSelected: colorSelected,
            ),
          ),
        ],
      );

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Material 3',
      themeMode: themeMode,
      theme: ThemeData(
        colorSchemeSeed: colorSelected.color,
        useMaterial3: useMaterial3,
        brightness: Brightness.light,
      ),
      darkTheme: ThemeData(
        colorSchemeSeed: colorSelected.color,
        useMaterial3: useMaterial3,
        brightness: Brightness.dark,
      ),
      home: AnimatedBuilder(
        animation: controller,
        builder: (context, child) {
          return NavigationTransition(
            scaffoldKey: scaffoldKey,
            animationController: controller,
            railAnimation: railAnimation,
            appBar: createAppBar(),
            body: createScreenFor(
                ScreenSelected.values[screenIndex], controller.value == 1),
            navigationRail: NavigationRail(
              extended: showLargeSizeLayout,
              destinations: navRailDestinations,
              selectedIndex: screenIndex,
              onDestinationSelected: (index) {
                setState(() {
                  screenIndex = index;
                  handleScreenChanged(screenIndex);
                });
              },
              trailing: Expanded(
                child: Padding(
                  padding: const EdgeInsets.only(bottom: 20),
                  child: showLargeSizeLayout
                      ? _expandedTrailingActions()
                      : _trailingActions(),
                ),
              ),
            ),
            navigationBar: NavigationBars(
              onSelectItem: (index) {
                setState(() {
                  screenIndex = index;
                  handleScreenChanged(screenIndex);
                });
              },
              selectedIndex: screenIndex,
              isExampleBar: false,
            ),
          );
        },
      ),
    );
  }
}

class _BrightnessButton extends StatelessWidget {
  const _BrightnessButton({
    required this.handleBrightnessChange,
    this.showTooltipBelow = true,
  });

  final Function handleBrightnessChange;
  final bool showTooltipBelow;

  @override
  Widget build(BuildContext context) {
    final isBright = Theme.of(context).brightness == Brightness.light;
    return Tooltip(
      preferBelow: showTooltipBelow,
      message: 'Toggle brightness',
      child: IconButton(
        icon: isBright
            ? const Icon(Icons.dark_mode_outlined)
            : const Icon(Icons.light_mode_outlined),
        onPressed: () => handleBrightnessChange(!isBright),
      ),
    );
  }
}

class _Material3Button extends StatelessWidget {
  const _Material3Button({
    required this.handleMaterialVersionChange,
    this.showTooltipBelow = true,
  });

  final void Function() handleMaterialVersionChange;
  final bool showTooltipBelow;

  @override
  Widget build(BuildContext context) {
    final useMaterial3 = Theme.of(context).useMaterial3;
    return Tooltip(
      preferBelow: showTooltipBelow,
      message: 'Switch to Material ${useMaterial3 ? 2 : 3}',
      child: IconButton(
        icon: useMaterial3
            ? const Icon(Icons.filter_2)
            : const Icon(Icons.filter_3),
        onPressed: handleMaterialVersionChange,
      ),
    );
  }
}

class _ColorSeedButton extends StatelessWidget {
  const _ColorSeedButton({
    required this.handleColorSelect,
    required this.colorSelected,
  });

  final void Function(int) handleColorSelect;
  final ColorSeed colorSelected;

  @override
  Widget build(BuildContext context) {
    return PopupMenuButton(
      icon: Icon(
        Icons.palette_outlined,
        color: Theme.of(context).colorScheme.onSurfaceVariant,
      ),
      tooltip: 'Select a seed color',
      shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(10)),
      itemBuilder: (context) {
        return List.generate(ColorSeed.values.length, (index) {
          ColorSeed currentColor = ColorSeed.values[index];

          return PopupMenuItem(
            value: index,
            enabled: currentColor != colorSelected,
            child: Wrap(
              children: [
                Padding(
                  padding: const EdgeInsets.only(left: 10),
                  child: Icon(
                    currentColor == colorSelected
                        ? Icons.color_lens
                        : Icons.color_lens_outlined,
                    color: currentColor.color,
                  ),
                ),
                Padding(
                  padding: const EdgeInsets.only(left: 20),
                  child: Text(currentColor.label),
                ),
              ],
            ),
          );
        });
      },
      onSelected: handleColorSelect,
    );
  }
}

class NavigationTransition extends StatefulWidget {
  const NavigationTransition(
      {super.key,
      required this.scaffoldKey,
      required this.animationController,
      required this.railAnimation,
      required this.navigationRail,
      required this.navigationBar,
      required this.appBar,
      required this.body});

  final GlobalKey<ScaffoldState> scaffoldKey;
  final AnimationController animationController;
  final CurvedAnimation railAnimation;
  final Widget navigationRail;
  final Widget navigationBar;
  final PreferredSizeWidget appBar;
  final Widget body;

  @override
  State<NavigationTransition> createState() => _NavigationTransitionState();
}

class _NavigationTransitionState extends State<NavigationTransition> {
  late final AnimationController controller;
  late final CurvedAnimation railAnimation;
  late final ReverseAnimation barAnimation;
  bool controllerInitialized = false;
  bool showDivider = false;

  @override
  void initState() {
    super.initState();

    controller = widget.animationController;
    railAnimation = widget.railAnimation;

    barAnimation = ReverseAnimation(
      CurvedAnimation(
        parent: controller,
        curve: const Interval(0.0, 0.5),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    final ColorScheme colorScheme = Theme.of(context).colorScheme;

    return Scaffold(
      key: widget.scaffoldKey,
      appBar: widget.appBar,
      body: Row(
        children: <Widget>[
          RailTransition(
            animation: railAnimation,
            backgroundColor: colorScheme.surface,
            child: widget.navigationRail,
          ),
          widget.body,
        ],
      ),
      bottomNavigationBar: BarTransition(
        animation: barAnimation,
        backgroundColor: colorScheme.surface,
        child: widget.navigationBar,
      ),
      endDrawer: const NavigationDrawerSection(),
    );
  }
}

final List<NavigationRailDestination> navRailDestinations = appBarDestinations
    .map(
      (destination) => NavigationRailDestination(
        icon: Tooltip(
          message: destination.label,
          child: destination.icon,
        ),
        selectedIcon: Tooltip(
          message: destination.label,
          child: destination.selectedIcon,
        ),
        label: Text(destination.label),
      ),
    )
    .toList();

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,
          ),
        );
}

class RailTransition extends StatefulWidget {
  const RailTransition(
      {super.key,
      required this.animation,
      required this.backgroundColor,
      required this.child});

  final Animation<double> animation;
  final Widget child;
  final Color backgroundColor;

  @override
  State<RailTransition> createState() => _RailTransition();
}

class _RailTransition extends State<RailTransition> {
  late Animation<Offset> offsetAnimation;
  late Animation<double> widthAnimation;

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();

    // The animations are only rebuilt by this method when the text
    // direction changes because this widget only depends on Directionality.
    final bool ltr = Directionality.of(context) == TextDirection.ltr;

    widthAnimation = Tween<double>(
      begin: 0,
      end: 1,
    ).animate(SizeAnimation(widget.animation));

    offsetAnimation = Tween<Offset>(
      begin: ltr ? const Offset(-1, 0) : const Offset(1, 0),
      end: Offset.zero,
    ).animate(OffsetAnimation(widget.animation));
  }

  @override
  Widget build(BuildContext context) {
    return ClipRect(
      child: DecoratedBox(
        decoration: BoxDecoration(color: widget.backgroundColor),
        child: Align(
          alignment: Alignment.topLeft,
          widthFactor: widthAnimation.value,
          child: FractionalTranslation(
            translation: offsetAnimation.value,
            child: widget.child,
          ),
        ),
      ),
    );
  }
}

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,
          ),
        ),
      ),
    );
  }
}

class OneTwoTransition extends StatefulWidget {
  const OneTwoTransition({
    super.key,
    required this.animation,
    required this.one,
    required this.two,
  });

  final Animation<double> animation;
  final Widget one;
  final Widget two;

  @override
  State<OneTwoTransition> createState() => _OneTwoTransitionState();
}

class _OneTwoTransitionState extends State<OneTwoTransition> {
  late final Animation<Offset> offsetAnimation;
  late final Animation<double> widthAnimation;

  @override
  void initState() {
    super.initState();

    offsetAnimation = Tween<Offset>(
      begin: const Offset(1, 0),
      end: Offset.zero,
    ).animate(OffsetAnimation(widget.animation));

    widthAnimation = Tween<double>(
      begin: 0,
      end: 1000,
    ).animate(SizeAnimation(widget.animation));
  }

  @override
  Widget build(BuildContext context) {
    return Row(
      children: <Widget>[
        Flexible(
          flex: 1000,
          child: widget.one,
        ),
        if (widthAnimation.value.toInt() > 0) ...[
          Flexible(
            flex: widthAnimation.value.toInt(),
            child: FractionalTranslation(
              translation: offsetAnimation.value,
              child: widget.two,
            ),
          )
        ],
      ],
    );
  }
}