tsacdop-podcast-app-android/lib/util/settings_sheet.dart

import 'dart:math' as math;
import 'package:flutter/material.dart';
import '../util/extension_helper.dart';

class SettingsSheet extends StatefulWidget {
  SettingsSheet({this.height, Key key}) : super(key: key);
  final double height;
  @override
  _SettingsSheetState createState() => _SettingsSheetState();
}

class _SettingsSheetState extends State<SettingsSheet>
    with TickerProviderStateMixin {
  Animation _animation;
  AnimationController _controller;
  AnimationController _slowController;
  double _initSize;
  double _startdy;
  double _move = 0;

  @override
  void initState() {
    _initSize = widget.height;
    _controller =
        AnimationController(vsync: this, duration: Duration(milliseconds: 50))
          ..addListener(() {
            if (mounted) setState(() {});
          });
    _slowController =
        AnimationController(vsync: this, duration: Duration(milliseconds: 200))
          ..addListener(() {
            if (mounted) setState(() {});
          });
    _animation =
        Tween<double>(begin: 0, end: _initSize).animate(_slowController);
    _slowController.forward();
    super.initState();
  }

  @override
  void dispose() {
    _slowController.dispose();
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.transparent,
      body: Container(
        height: context.height,
        child: Stack(alignment: Alignment.bottomCenter, children: [
          Positioned.fill(
            child: GestureDetector(
              onTap: () {
                _backToMini();
                Navigator.pop(context);
              },
              child: Container(
                color: context.scaffoldBackgroundColor.withOpacity(
                    0.8 * math.min(_animation.value / widget.height, 1.0)),
              ),
            ),
          ),
          GestureDetector(
            onVerticalDragStart: _start,
            onVerticalDragUpdate: _update,
            onVerticalDragEnd: (event) => _end(),
            child: Container(
              height: math.min(_animation.value, widget.height),
              color: Colors.white,
            ),
          )
        ]),
      ),
    );
  }

  _backToMini() {
    setState(() {
      _animation =
          Tween<double>(begin: _initSize, end: 0).animate(_slowController);
      _initSize = 0;
    });
    _slowController.forward();
  }

  _start(DragStartDetails event) {
    setState(() {
      _startdy = event.localPosition.dy;
      _animation =
          Tween<double>(begin: _initSize, end: _initSize).animate(_controller);
    });
    _controller.forward();
  }

  _update(DragUpdateDetails event) {
    setState(() {
      _move = _startdy - event.localPosition.dy;
      _animation = Tween<double>(begin: _initSize, end: _initSize + _move)
          .animate(_controller);
    });
    _controller.forward();
  }

  _end() async {
    if (_move < -50) {
      setState(() {
        _animation =
            Tween<double>(begin: _animation.value, end: 0).animate(_controller);
        _initSize = 0;
      });
      _controller.forward();
      Navigator.pop(context);
    } else {
      setState(() {
        _animation = Tween<double>(begin: _animation.value, end: widget.height)
            .animate(_controller);
        _initSize = widget.height;
      });
      _controller.forward();
    }
  }
}