examples/flutter_gallery/lib/demo/material/full_screen_dialog_demo.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:intl/intl.dart';

// This demo is based on
// https://material.io/design/components/dialogs.html#full-screen-dialog

enum DismissDialogAction {
  cancel,
  discard,
  save,
}

class DateTimeItem extends StatelessWidget {
  DateTimeItem({ Key key, DateTime dateTime, @required this.onChanged })
    : assert(onChanged != null),
      date = DateTime(dateTime.year, dateTime.month, dateTime.day),
      time = TimeOfDay(hour: dateTime.hour, minute: dateTime.minute),
      super(key: key);

  final DateTime date;
  final TimeOfDay time;
  final ValueChanged<DateTime> onChanged;

  @override
  Widget build(BuildContext context) {
    final ThemeData theme = Theme.of(context);

    return DefaultTextStyle(
      style: theme.textTheme.subtitle1,
      child: Row(
        children: <Widget>[
          Expanded(
            child: Container(
              padding: const EdgeInsets.symmetric(vertical: 8.0),
              decoration: BoxDecoration(
                border: Border(bottom: BorderSide(color: theme.dividerColor))
              ),
              child: InkWell(
                onTap: () {
                  showDatePicker(
                    context: context,
                    initialDate: date,
                    firstDate: date.subtract(const Duration(days: 30)),
                    lastDate: date.add(const Duration(days: 30)),
                  )
                  .then<void>((DateTime value) {
                    if (value != null)
                      onChanged(DateTime(value.year, value.month, value.day, time.hour, time.minute));
                  });
                },
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  children: <Widget>[
                    Text(DateFormat('EEE, MMM d yyyy').format(date)),
                    const Icon(Icons.arrow_drop_down, color: Colors.black54),
                  ],
                ),
              ),
            ),
          ),
          Container(
            margin: const EdgeInsets.only(left: 8.0),
            padding: const EdgeInsets.symmetric(vertical: 8.0),
            decoration: BoxDecoration(
              border: Border(bottom: BorderSide(color: theme.dividerColor))
            ),
            child: InkWell(
              onTap: () {
                showTimePicker(
                  context: context,
                  initialTime: time,
                )
                .then<void>((TimeOfDay value) {
                  if (value != null)
                    onChanged(DateTime(date.year, date.month, date.day, value.hour, value.minute));
                });
              },
              child: Row(
                children: <Widget>[
                  Text('${time.format(context)}'),
                  const Icon(Icons.arrow_drop_down, color: Colors.black54),
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }
}

class FullScreenDialogDemo extends StatefulWidget {
  @override
  FullScreenDialogDemoState createState() => FullScreenDialogDemoState();
}

class FullScreenDialogDemoState extends State<FullScreenDialogDemo> {
  DateTime _fromDateTime = DateTime.now();
  DateTime _toDateTime = DateTime.now();
  bool _allDayValue = false;
  bool _saveNeeded = false;
  bool _hasLocation = false;
  bool _hasName = false;
  String _eventName;

  Future<bool> _onWillPop() async {
    _saveNeeded = _hasLocation || _hasName || _saveNeeded;
    if (!_saveNeeded)
      return true;

    final ThemeData theme = Theme.of(context);
    final TextStyle dialogTextStyle = theme.textTheme.subtitle1.copyWith(color: theme.textTheme.caption.color);

    return await showDialog<bool>(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          content: Text(
            'Discard new event?',
            style: dialogTextStyle,
          ),
          actions: <Widget>[
            FlatButton(
              child: const Text('CANCEL'),
              onPressed: () {
                Navigator.of(context).pop(false); // Pops the confirmation dialog but not the page.
              },
            ),
            FlatButton(
              child: const Text('DISCARD'),
              onPressed: () {
                Navigator.of(context).pop(true); // Returning true to _onWillPop will pop again.
              },
            ),
          ],
        );
      },
    ) ?? false;
  }

  @override
  Widget build(BuildContext context) {
    final ThemeData theme = Theme.of(context);

    return Scaffold(
      appBar: AppBar(
        title: Text(_hasName ? _eventName : 'Event Name TBD'),
        actions: <Widget> [
          FlatButton(
            child: Text('SAVE', style: theme.textTheme.bodyText2.copyWith(color: Colors.white)),
            onPressed: () {
              Navigator.pop(context, DismissDialogAction.save);
            },
          ),
        ],
      ),
      body: Form(
        onWillPop: _onWillPop,
        child: Scrollbar(
          child: ListView(
            padding: const EdgeInsets.all(16.0),
            children: <Widget>[
              Container(
                padding: const EdgeInsets.symmetric(vertical: 8.0),
                alignment: Alignment.bottomLeft,
                child: TextField(
                  decoration: const InputDecoration(
                    labelText: 'Event name',
                    filled: true,
                  ),
                  style: theme.textTheme.headline5,
                  onChanged: (String value) {
                    setState(() {
                      _hasName = value.isNotEmpty;
                      if (_hasName) {
                        _eventName = value;
                      }
                    });
                  },
                ),
              ),
              Container(
                padding: const EdgeInsets.symmetric(vertical: 8.0),
                alignment: Alignment.bottomLeft,
                child: TextField(
                  decoration: const InputDecoration(
                    labelText: 'Location',
                    hintText: 'Where is the event?',
                    filled: true,
                  ),
                  onChanged: (String value) {
                    setState(() {
                      _hasLocation = value.isNotEmpty;
                    });
                  },
                ),
              ),
              Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: <Widget>[
                  Text('From', style: theme.textTheme.caption),
                  DateTimeItem(
                    dateTime: _fromDateTime,
                    onChanged: (DateTime value) {
                      setState(() {
                        _fromDateTime = value;
                        _saveNeeded = true;
                      });
                    },
                  ),
                ],
              ),
              Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: <Widget>[
                  Text('To', style: theme.textTheme.caption),
                  DateTimeItem(
                    dateTime: _toDateTime,
                    onChanged: (DateTime value) {
                      setState(() {
                        _toDateTime = value;
                        _saveNeeded = true;
                      });
                    },
                  ),
                  const Text('All-day'),
                ],
              ),
              Container(
                decoration: BoxDecoration(
                  border: Border(bottom: BorderSide(color: theme.dividerColor))
                ),
                child: Row(
                  children: <Widget> [
                    Checkbox(
                      value: _allDayValue,
                      onChanged: (bool value) {
                        setState(() {
                          _allDayValue = value;
                          _saveNeeded = true;
                        });
                      },
                    ),
                    const Text('All-day'),
                  ],
                ),
              ),
            ]
            .map<Widget>((Widget child) {
              return Container(
                padding: const EdgeInsets.symmetric(vertical: 8.0),
                height: 96.0,
                child: child,
              );
            })
            .toList(),
          ),
        ),
      ),
    );
  }
}