spring_animated.dart

import 'package:flutter/physics.dart';
import 'package:flutter/widgets.dart';

class SpringAnimated extends StatefulWidget {
  final Widget child;
  final Offset startOffset;
  final bool shouldResetOffset;

  SpringAnimated(
      {@required this.child,
      @required this.startOffset,
      this.shouldResetOffset});

  @override
  State<StatefulWidget> createState() {
    return SpringAnimatedState();
  }
}

class SpringAnimatedState extends State<SpringAnimated>
    with SingleTickerProviderStateMixin {
  AnimationController _animationController;
  Offset _offset;
  SpringSimulation spring;

  SpringAnimatedState();

  @override
  void initState() {
    super.initState();
    _offset = widget.startOffset;
    _animationController = new AnimationController(
        vsync: this,
        lowerBound: double.negativeInfinity,
        upperBound: double.infinity,
        duration: Duration(milliseconds: 900));

    _animationController.addStatusListener(statusListener);

    Tween(
      begin: -2,
      end: 0,
    ).animate(
      CurvedAnimation(
        parent: _animationController,
        curve: Interval(0, 2),
      ),
    );

    _animationController.forward(from: -2);
  }

  void statusListener(status) {
    if (status == AnimationStatus.completed) {
      _animationController.removeStatusListener(statusListener);

      _animationController.addListener(() {
        setState(() {
          _offset = Offset(_animationController.value, 0);
        });
      });

      _animationController.animateWith(
        SpringSimulation(
          SpringDescription(mass: 1.0, stiffness: 100.0, damping: 10.0),
          _offset.dx,
          0.0,
          _animationController.velocity,
        ),
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    var x = Transform.translate(
      offset: _offset,
      child: widget.child,
    );

    if (widget.shouldResetOffset) {
      _offset = widget.startOffset;
      _animateWithTranslation();
    }

    return x;
  }

  _animateWithTranslation() {
    _animationController
        .animateTo(_offset.dx,
            duration: Duration(milliseconds: 150), curve: Curves.linear)
        .whenComplete(() {
      _animationController.animateWith(
        SpringSimulation(
          SpringDescription(mass: 1.0, stiffness: 100.0, damping: 10.0),
          _offset.dx,
          0.0,
          _animationController.velocity,
        ),
      );
    });
  }
}