glide_v3.dart

import 'package:flutter/material.dart';

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

  final Animation<double> animation;
  final Widget child;

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

}

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


  @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;

    offsetAnimation = Tween<Offset>(
      begin: ltr ? const Offset(-1, 0) : const Offset(1, 0),
      end: Offset.zero,
    ).animate(
      CurvedAnimation(
        parent: widget.animation,
        curve: const Interval(
          0.25, 1.0,
          curve: Curves.easeOut,
        ),
      ),
    );

    sizeAnimation = Tween<double>(
      begin: 0,
      end: 1,
    ).animate(
      CurvedAnimation(
        parent: widget.animation,
        curve: const Interval(
          0.0, 0.75,
          curve: Curves.easeOut,
        ),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return ClipRect(
      child: Align(
        alignment: Alignment.topLeft,
        widthFactor: sizeAnimation.value,
        child: FractionalTranslation(
          translation: offsetAnimation.value,
          child: widget.child,
        ),
      ),
    );
  }
}


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

  final Animation<double> animation;
  final Widget child;

  @override
  State<BarTransition> createState() => _BarTransition();

}

class _BarTransition extends State<BarTransition> {
  late final Animation<Offset> offsetAnimation;
  late final Animation<double> sizeAnimation;


  @override
  void initState() {
    super.initState();
    offsetAnimation = Tween<Offset>(
      begin: const Offset(0, 1),
      end: Offset.zero,
    ).animate(
      CurvedAnimation(
        parent: widget.animation,
        curve: const Interval(
          0.25, 1.0,
          curve: Curves.easeOut,
        ),
      ),
    );

    sizeAnimation = Tween<double>(
      begin: 0,
      end: 1,
    ).animate(
      CurvedAnimation(
        parent: widget.animation,
        curve: const Interval(
          0.0, 0.75,
          curve: Curves.easeOut,
        ),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return ClipRect(
      child: Align(
        alignment: Alignment.topLeft,
        heightFactor: sizeAnimation.value,
        child: FractionalTranslation(
          translation: offsetAnimation.value,
          child: widget.child,
        ),
      ),
    );
  }
}


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

  final Animation<double> animation;
  final VoidCallback? onPressed;
  final Widget? child;

  @override
  State<AnimatedFloatingActionButton> createState() => _AnimatedFloatingActionButton();

}

class _AnimatedFloatingActionButton extends State<AnimatedFloatingActionButton> {
  late final Animation<ShapeBorder?> shapeAnimation;

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

    shapeAnimation = ShapeBorderTween(
      begin: const CircleBorder(),
      end: const RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(16.0))),
    ).animate(
      CurvedAnimation(
        parent: widget.animation,
        curve: Curves.easeOut,
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return ScaleTransition(
      scale: widget.animation,
      child: FloatingActionButton(
        onPressed: widget.onPressed,
        shape: shapeAnimation.value!,
        child: widget.child,
      ),
    );
  }
}

class _Destination {
  const _Destination(this.icon,  this.label);
  final IconData icon;
  final String label;
}

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

  @override
  State<Home> createState() => _HomeState();
}

class _HomeState extends State<Home> with SingleTickerProviderStateMixin {
  late final AnimationController controller;
  late final Animation<double> railAnimation;
  late final Animation<double> barAnimation;
  late final Animation<double> fabAnimation;
  int selectedIndex = 0;
  bool controllerInitialized = false;

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

    controller = AnimationController(
      duration: const Duration(milliseconds: 600),
      value: 0,
      vsync: this,
    );

    // Transition Orchestration

    railAnimation = CurvedAnimation(
      parent: controller,
      curve: const Interval(0.5, 1.0),
    );

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

    fabAnimation = CurvedAnimation(
      parent: controller,
      curve: const Interval(0.25, 0.5),
    );
  }

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

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

    final double width = MediaQuery.of(context).size.width;
    if (width < 500) {
      controller.forward();
    } else {
      controller.reverse();
    }
    if (!controllerInitialized) {
      controllerInitialized = true;
      controller.value = width < 500 ? 1 : 0;
    }
  }

  final List<_Destination> destinations = const <_Destination>[
    _Destination(Icons.home, 'Home'),
    _Destination(Icons.business, 'Business'),
    _Destination(Icons.school, 'School'),
  ];

  @override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
      animation: controller,
      builder: (BuildContext context, Widget? child) {
        return Scaffold(
          body: Row(
            children: <Widget>[
              RailTransition(
                animation: railAnimation,
                child: NavigationRail(
                  selectedIndex: selectedIndex,
                  onDestinationSelected: (int index) {
                    setState(() {
                      selectedIndex = index;
                    });
                  },
                  leading: Column(
                    children: <Widget>[
                      IconButton(
                        onPressed: () { },
                        icon: const Icon(Icons.menu),
                      ),
                      const SizedBox(height: 8),
                      FloatingActionButton(
                        onPressed: () { },
                        child: const Icon(Icons.add),
                      ),
                    ],
                  ),
                  groupAlignment: -0.35,
                  destinations: destinations.map<NavigationRailDestination>((_Destination d) {
                    return NavigationRailDestination(
                      icon: Icon(d.icon),
                      label: Text(d.label),
                    );
                  }).toList(),
                ),
              ),
              Expanded(
                child: Container(
                  color: Theme.of(context).colorScheme.surfaceVariant,
                  alignment: Alignment.center,
                ),
              ),
            ],
          ),
          floatingActionButton: AnimatedFloatingActionButton(
            animation: ReverseAnimation(fabAnimation),
            onPressed: () { },
            child: const Icon(Icons.add),
          ),
          bottomNavigationBar: BarTransition(
            animation: ReverseAnimation(barAnimation),
            child: BottomNavigationBar(
              items: destinations.map<BottomNavigationBarItem>((_Destination d) {
                return BottomNavigationBarItem(
                  icon: Icon(d.icon),
                  label: d.label,
                );
              }).toList(),
              currentIndex: selectedIndex,
              onTap: (int index) {
                setState(() {
                  selectedIndex = index;
                });
              },
            ),
          ),
        );
      }
    );
  }
}

void main() {
  runApp(
    MaterialApp(
      theme: ThemeData(useMaterial3: true),
      home: const Home(),
    ),
  );
}