PositionedSlider flutter

import 'package:flutter/material.dart';

// TODO: Horizontal
enum PositionedSliderDirection { VERTICAL_UPPER, VERTICAL_LOWER }

class PositionedSlider extends StatefulWidget {
  final PositionedSliderDirection direction;
  final EdgeInsetsGeometry padding;
  final EdgeInsetsGeometry margin;
  final double left;
  final double right;
  final double top;
  final double bottom;
  final double width;
  final double heightFrom;
  final double heightTo;
  final Color color;
  final Widget child;
  final Duration duration;
  final Function onReverted;
  final Function onForwarded;
  final Function onAnimating;

  const PositionedSlider({
    Key key,
    this.direction = PositionedSliderDirection.VERTICAL_UPPER,
    this.padding,
    this.margin,
    this.left,
    this.right,
    this.top,
    this.bottom,
    this.width,
    @required this.heightFrom,
    @required this.heightTo,
    this.color,
    @required this.child,
    this.duration,
    this.onReverted,
    this.onForwarded,
    this.onAnimating,
  }) : super(key: key);

  @override
  PositionedSliderState createState() => PositionedSliderState();
}

class PositionedSliderState extends State<PositionedSlider>
    with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Animation<double> _animation;

  void forceAnimation() {
    if (_controller.isAnimating) return;
    if (_controller.isDismissed) _controller.forward();
    if (_controller.isCompleted) _controller.reverse();
  }

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

    _controller = AnimationController(
      duration: widget.duration ?? Duration(milliseconds: 500),
      vsync: this,
    )..addListener(() {
        if (_controller.isCompleted && widget.onForwarded != null)
          widget.onForwarded();

        if (_controller.isDismissed && widget.onReverted != null)
          widget.onReverted();

        if (_controller.isAnimating && widget.onAnimating != null)
          widget.onAnimating(_controller.value);
      });

    _animation = Tween<double>(begin: widget.heightFrom, end: widget.heightTo)
        .animate(_controller);
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onPanUpdate: (details) {
        if (details.delta.dy > 0) {
          if (_controller.isAnimating) return;
          if (_controller.isDismissed) {
            _controller.forward();
            return;
          }
        } else {
          if (_controller.isAnimating) return;
          if (_controller.isCompleted) {
            _controller.reverse();
            return;
          }
        }
      },
      child: Stack(
        children: <Widget>[
          Positioned(
            left: widget.left,
            top: widget.top,
            right: widget.right,
            bottom: widget.bottom,
            child: AnimatedBuilder(
              animation: _animation,
              builder: (BuildContext context, Widget child) {
                return Container(
                  padding: widget.padding,
                  margin: widget.margin,
                  width: widget.width,
                  height: _animation.value,
                  color: widget.color,
                  child: widget.child,
                );
              },
            ),
          ),
        ],
      ),
    );
  }
}





import 'package:flutter/material.dart';
import 'package:sca/app/shared/widgets/positioned_slider.dart';

class Teste extends StatefulWidget {
  @override
  _TesteState createState() => _TesteState();
}

class _TesteState extends State<Teste> {
    var sliderKey = GlobalKey<PositionedSliderState>();

    @override
    Widget build(BuildContext context) {
        Size size = MediaQuery.of(context).size;

        return PositionedSlider(
            key: sliderKey,
            direction: PositionedSliderDirection.VERTICAL_LOWER,
            duration: Duration(milliseconds: 300),
            width: size.width,
            heightFrom: 200,
            heightTo: size.height,
            color: Theme.of(context).primaryColor,
            onAnimating: (double completed) {
                print("estado da animação: ${completed.toStringAsFixed(2)}");
            },
            child: Column(
                children: <Widget>[
                    Text('Conteúdo do Container animado'),

                    RaisedButton(
                        onPressed: (){
                            sliderKey.currentState.forceAnimation();
                        },
                        child: Text('Alternar Animação do Slider'),
                    ),
                ],
            ),
        );
    }
}