packages/flutter/lib/src/material/pickers/date_picker_dialog.dart - mirrors/flutter - Git at Google

 // 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:math' as math;

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

 import '../button_bar.dart';
 import '../button_theme.dart';
 import '../color_scheme.dart';
 import '../debug.dart';
 import '../dialog.dart';
 import '../dialog_theme.dart';
 import '../flat_button.dart';
 import '../icons.dart';
 import '../material_localizations.dart';
 import '../text_theme.dart';
 import '../theme.dart';

 import 'calendar_date_picker.dart';
 import 'date_picker_common.dart';
 import 'date_picker_header.dart';
 import 'date_utils.dart' as utils;
 import 'input_date_picker.dart';

 const Size _calendarPortraitDialogSize = Size(330.0, 518.0);
 const Size _calendarLandscapeDialogSize = Size(496.0, 346.0);
 const Size _inputPortraitDialogSize = Size(330.0, 270.0);
 const Size _inputLandscapeDialogSize = Size(496, 160.0);
 const Duration _dialogSizeAnimationDuration = Duration(milliseconds: 200);

 /// Shows a dialog containing a Material Design date picker.
 ///
 /// The returned [Future] resolves to the date selected by the user when the
 /// user confirms the dialog. If the user cancels the dialog, null is returned.
 ///
 /// When the date picker is first displayed, it will show the month of
 /// [initialDate], with [initialDate] selected.
 ///
 /// The [firstDate] is the earliest allowable date. The [lastDate] is the latest
 /// allowable date. [initialDate] must either fall between these dates,
 /// or be equal to one of them. For each of these [DateTime] parameters, only
 /// their dates are considered. Their time fields are ignored. They must all
 /// be non-null.
 ///
 /// An optional [initialEntryMode] argument can be used to display the date
 /// picker in the [DatePickerEntryMode.calendar] (a calendar month grid)
 /// or [DatePickerEntryMode.input] (a text input field) mode.
 /// It defaults to [DatePickerEntryMode.calendar] and must be non-null.
 ///
 /// An optional [selectableDayPredicate] function can be passed in to only allow
 /// certain days for selection. If provided, only the days that
 /// [selectableDayPredicate] returns true for will be selectable. For example,
 /// this can be used to only allow weekdays for selection. If provided, it must
 /// return true for [initialDate].
 ///
 /// Optional strings for the [cancelText], [confirmText], [errorFormatText],
 /// [errorInvalidText], [fieldHintText], [fieldLabelText], and [helpText] allow
 /// you to override the default text used for various parts of the dialog:
 ///
 ///   * [cancelText], label on the cancel button.
 ///   * [confirmText], label on the ok button.
 ///   * [errorFormatText], message used when the input text isn't in a proper date format.
 ///   * [errorInvalidText], message used when the input text isn't a selectable date.
 ///   * [fieldHintText], text used to prompt the user when no text has been entered in the field.
 ///   * [fieldLabelText], label for the date text input field.
 ///   * [helpText], label on the top of the dialog.
 ///
 /// An optional [locale] argument can be used to set the locale for the date
 /// picker. It defaults to the ambient locale provided by [Localizations].
 ///
 /// An optional [textDirection] argument can be used to set the text direction
 /// ([TextDirection.ltr] or [TextDirection.rtl]) for the date picker. It
 /// defaults to the ambient text direction provided by [Directionality]. If both
 /// [locale] and [textDirection] are non-null, [textDirection] overrides the
 /// direction chosen for the [locale].
 ///
 /// The [context], [useRootNavigator] and [routeSettings] arguments are passed to
 /// [showDialog], the documentation for which discusses how it is used. [context]
 /// and [useRootNavigator] must be non-null.
 ///
 /// The [builder] parameter can be used to wrap the dialog widget
 /// to add inherited widgets like [Theme].
 ///
 /// An optional [initialDatePickerMode] argument can be used to have the
 /// calendar date picker initially appear in the [DatePickerMode.year] or
 /// [DatePickerMode.day] mode. It defaults to [DatePickerMode.day], and
 /// must be non-null.
 Future<DateTime> showDatePicker({
   @required BuildContext context,
   @required DateTime initialDate,
   @required DateTime firstDate,
   @required DateTime lastDate,
   DatePickerEntryMode initialEntryMode = DatePickerEntryMode.calendar,
   SelectableDayPredicate selectableDayPredicate,
   String helpText,
   String cancelText,
   String confirmText,
   Locale locale,
   bool useRootNavigator = true,
   RouteSettings routeSettings,
   TextDirection textDirection,
   TransitionBuilder builder,
   DatePickerMode initialDatePickerMode = DatePickerMode.day,
   String errorFormatText,
   String errorInvalidText,
   String fieldHintText,
   String fieldLabelText,
 }) async {
   assert(context != null);
   assert(initialDate != null);
   assert(firstDate != null);
   assert(lastDate != null);
   initialDate = utils.dateOnly(initialDate);
   firstDate = utils.dateOnly(firstDate);
   lastDate = utils.dateOnly(lastDate);
   assert(
     !lastDate.isBefore(firstDate),
     'lastDate $lastDate must be on or after firstDate $firstDate.'
   );
   assert(
     !initialDate.isBefore(firstDate),
     'initialDate $initialDate must be on or after firstDate $firstDate.'
   );
   assert(
     !initialDate.isAfter(lastDate),
     'initialDate $initialDate must be on or before lastDate $lastDate.'
   );
   assert(
     selectableDayPredicate == null || selectableDayPredicate(initialDate),
     'Provided initialDate $initialDate must satisfy provided selectableDayPredicate.'
   );
   assert(initialEntryMode != null);
   assert(useRootNavigator != null);
   assert(initialDatePickerMode != null);
   assert(debugCheckHasMaterialLocalizations(context));

   Widget dialog = _DatePickerDialog(
     initialDate: initialDate,
     firstDate: firstDate,
     lastDate: lastDate,
     initialEntryMode: initialEntryMode,
     selectableDayPredicate: selectableDayPredicate,
     helpText: helpText,
     cancelText: cancelText,
     confirmText: confirmText,
     initialCalendarMode: initialDatePickerMode,
     errorFormatText: errorFormatText,
     errorInvalidText: errorInvalidText,
     fieldHintText: fieldHintText,
     fieldLabelText: fieldLabelText,
   );

   if (textDirection != null) {
     dialog = Directionality(
       textDirection: textDirection,
       child: dialog,
     );
   }

   if (locale != null) {
     dialog = Localizations.override(
       context: context,
       locale: locale,
       child: dialog,
     );
   }

   return showDialog<DateTime>(
     context: context,
     useRootNavigator: useRootNavigator,
     routeSettings: routeSettings,
     builder: (BuildContext context) {
       return builder == null ? dialog : builder(context, dialog);
     },
   );
 }

 class _DatePickerDialog extends StatefulWidget {
   _DatePickerDialog({
     Key key,
     @required DateTime initialDate,
     @required DateTime firstDate,
     @required DateTime lastDate,
     this.initialEntryMode = DatePickerEntryMode.calendar,
     this.selectableDayPredicate,
     this.cancelText,
     this.confirmText,
     this.helpText,
     this.initialCalendarMode = DatePickerMode.day,
     this.errorFormatText,
     this.errorInvalidText,
     this.fieldHintText,
     this.fieldLabelText,
   }) : assert(initialDate != null),
        assert(firstDate != null),
        assert(lastDate != null),
        initialDate = utils.dateOnly(initialDate),
        firstDate = utils.dateOnly(firstDate),
        lastDate = utils.dateOnly(lastDate),
        assert(initialEntryMode != null),
        assert(initialCalendarMode != null),
        super(key: key) {
     assert(
       !this.lastDate.isBefore(this.firstDate),
       'lastDate ${this.lastDate} must be on or after firstDate ${this.firstDate}.'
     );
     assert(
       !this.initialDate.isBefore(this.firstDate),
       'initialDate ${this.initialDate} must be on or after firstDate ${this.firstDate}.'
     );
     assert(
       !this.initialDate.isAfter(this.lastDate),
       'initialDate ${this.initialDate} must be on or before lastDate ${this.lastDate}.'
     );
     assert(
       selectableDayPredicate == null || selectableDayPredicate(this.initialDate),
       'Provided initialDate ${this.initialDate} must satisfy provided selectableDayPredicate'
     );
   }

   /// The initially selected [DateTime] that the picker should display.
   final DateTime initialDate;

   /// The earliest allowable [DateTime] that the user can select.
   final DateTime firstDate;

   /// The latest allowable [DateTime] that the user can select.
   final DateTime lastDate;

   final DatePickerEntryMode initialEntryMode;

   /// Function to provide full control over which [DateTime] can be selected.
   final SelectableDayPredicate selectableDayPredicate;

   /// The text that is displayed on the cancel button.
   final String cancelText;

   /// The text that is displayed on the confirm button.
   final String confirmText;

   /// The text that is displayed at the top of the header.
   ///
   /// This is used to indicate to the user what they are selecting a date for.
   final String helpText;

   /// The initial display of the calendar picker.
   final DatePickerMode initialCalendarMode;

   final String errorFormatText;

   final String errorInvalidText;

   final String fieldHintText;

   final String fieldLabelText;

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

 class _DatePickerDialogState extends State<_DatePickerDialog> {

   DatePickerEntryMode _entryMode;
   DateTime _selectedDate;
   bool _autoValidate;
   final GlobalKey _calendarPickerKey = GlobalKey();
   final GlobalKey<FormState> _formKey = GlobalKey<FormState>();

   @override
   void initState() {
     super.initState();
     _entryMode = widget.initialEntryMode;
     _selectedDate = widget.initialDate;
     _autoValidate = false;
   }

   void _handleOk() {
     if (_entryMode == DatePickerEntryMode.input) {
       final FormState form = _formKey.currentState;
       if (!form.validate()) {
         setState(() => _autoValidate = true);
         return;
       }
       form.save();
     }
     Navigator.pop(context, _selectedDate);
   }

   void _handleCancel() {
     Navigator.pop(context);
   }

   void _handelEntryModeToggle() {
     setState(() {
       switch (_entryMode) {
         case DatePickerEntryMode.calendar:
           _autoValidate = false;
           _entryMode = DatePickerEntryMode.input;
           break;
         case DatePickerEntryMode.input:
           _formKey.currentState.save();
           _entryMode = DatePickerEntryMode.calendar;
           break;
       }
     });
   }

   void _handleDateChanged(DateTime date) {
     setState(() => _selectedDate = date);
   }

   Size _dialogSize(BuildContext context) {
     final Orientation orientation = MediaQuery.of(context).orientation;
     switch (_entryMode) {
       case DatePickerEntryMode.calendar:
         switch (orientation) {
           case Orientation.portrait:
             return _calendarPortraitDialogSize;
           case Orientation.landscape:
             return _calendarLandscapeDialogSize;
         }
         break;
       case DatePickerEntryMode.input:
         switch (orientation) {
           case Orientation.portrait:
             return _inputPortraitDialogSize;
           case Orientation.landscape:
             return _inputLandscapeDialogSize;
         }
         break;
     }
     return null;
   }

   @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
     final ColorScheme colorScheme = theme.colorScheme;
     final MaterialLocalizations localizations = MaterialLocalizations.of(context);
     final Orientation orientation = MediaQuery.of(context).orientation;
     final TextTheme textTheme = theme.textTheme;
     // Constrain the textScaleFactor to the largest supported value to prevent
     // layout issues.
     final double textScaleFactor = math.min(MediaQuery.of(context).textScaleFactor, 1.3);

     final String dateText = _selectedDate != null
       ? localizations.formatMediumDate(_selectedDate)
       // TODO(darrenaustin): localize 'Date'
       : 'Date';
     final Color dateColor = colorScheme.brightness == Brightness.light
       ? colorScheme.onPrimary
       : colorScheme.onSurface;
     final TextStyle dateStyle = orientation == Orientation.landscape
       ? textTheme.headline5?.copyWith(color: dateColor)
       : textTheme.headline4?.copyWith(color: dateColor);

     final Widget actions = ButtonBar(
       buttonTextTheme: ButtonTextTheme.primary,
       layoutBehavior: ButtonBarLayoutBehavior.constrained,
       children: <Widget>[
         FlatButton(
           child: Text(widget.cancelText ?? localizations.cancelButtonLabel),
           onPressed: _handleCancel,
         ),
         FlatButton(
           child: Text(widget.confirmText ?? localizations.okButtonLabel),
           onPressed: _handleOk,
         ),
       ],
     );

     Widget picker;
     IconData entryModeIcon;
     String entryModeTooltip;
     switch (_entryMode) {
       case DatePickerEntryMode.calendar:
         picker = CalendarDatePicker(
           key: _calendarPickerKey,
           initialDate: _selectedDate,
           firstDate: widget.firstDate,
           lastDate: widget.lastDate,
           onDateChanged: _handleDateChanged,
           selectableDayPredicate: widget.selectableDayPredicate,
           initialCalendarMode: widget.initialCalendarMode,
         );
         entryModeIcon = Icons.edit;
         // TODO(darrenaustin): localize 'Switch to input'
         entryModeTooltip = 'Switch to input';
         break;

       case DatePickerEntryMode.input:
         picker = Form(
           key: _formKey,
           autovalidate: _autoValidate,
           child: InputDatePickerFormField(
             initialDate: _selectedDate,
             firstDate: widget.firstDate,
             lastDate: widget.lastDate,
             onDateSubmitted: _handleDateChanged,
             onDateSaved: _handleDateChanged,
             selectableDayPredicate: widget.selectableDayPredicate,
             errorFormatText: widget.errorFormatText,
             errorInvalidText: widget.errorInvalidText,
             fieldHintText: widget.fieldHintText,
             fieldLabelText: widget.fieldLabelText,
             autofocus: true,
           ),
         );
         entryModeIcon = Icons.calendar_today;
         // TODO(darrenaustin): localize 'Switch to calendar'
         entryModeTooltip = 'Switch to calendar';
         break;
     }

     final Widget header = DatePickerHeader(
       // TODO(darrenaustin): localize 'SELECT DATE'
       helpText: widget.helpText ?? 'SELECT DATE',
       titleText: dateText,
       titleStyle: dateStyle,
       orientation: orientation,
       isShort: orientation == Orientation.landscape,
       icon: entryModeIcon,
       iconTooltip: entryModeTooltip,
       onIconPressed: _handelEntryModeToggle,
     );

     final Size dialogSize = _dialogSize(context) * textScaleFactor;
     final DialogTheme dialogTheme = Theme.of(context).dialogTheme;
     return Dialog(
       child: AnimatedContainer(
         width: dialogSize.width,
         height: dialogSize.height,
         duration: _dialogSizeAnimationDuration,
         curve: Curves.easeIn,
         child: MediaQuery(
           data: MediaQuery.of(context).copyWith(
             textScaleFactor: textScaleFactor,
           ),
           child: Builder(builder: (BuildContext context) {
             switch (orientation) {
               case Orientation.portrait:
                 return Column(
                   mainAxisSize: MainAxisSize.min,
                   crossAxisAlignment: CrossAxisAlignment.stretch,
                   children: <Widget>[
                     header,
                     Expanded(child: picker),
                     actions,
                   ],
                 );
               case Orientation.landscape:
                 return Row(
                   mainAxisSize: MainAxisSize.min,
                   crossAxisAlignment: CrossAxisAlignment.stretch,
                   children: <Widget>[
                     header,
                     Flexible(
                       child: Column(
                         mainAxisSize: MainAxisSize.min,
                         crossAxisAlignment: CrossAxisAlignment.stretch,
                         children: <Widget>[
                           Expanded(child: picker),
                           actions,
                         ],
                       ),
                     ),
                   ],
                 );
             }
             return null;
           }),
         ),
       ),
       insetPadding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 24.0),
       // The default dialog shape is radius 2 rounded rect, but the spec has
       // been updated to 4, so we will use that here for the Date Picker, but
       // only if there isn't one provided in the theme.
       shape: dialogTheme.shape ?? const RoundedRectangleBorder(
         borderRadius: BorderRadius.all(Radius.circular(4.0))
       ),
       clipBehavior: Clip.antiAlias,
     );
   }
 }
	// 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:math' as math;

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

	import '../button_bar.dart';
	import '../button_theme.dart';
	import '../color_scheme.dart';
	import '../debug.dart';
	import '../dialog.dart';
	import '../dialog_theme.dart';
	import '../flat_button.dart';
	import '../icons.dart';
	import '../material_localizations.dart';
	import '../text_theme.dart';
	import '../theme.dart';

	import 'calendar_date_picker.dart';
	import 'date_picker_common.dart';
	import 'date_picker_header.dart';
	import 'date_utils.dart' as utils;
	import 'input_date_picker.dart';

	const Size _calendarPortraitDialogSize = Size(330.0, 518.0);
	const Size _calendarLandscapeDialogSize = Size(496.0, 346.0);
	const Size _inputPortraitDialogSize = Size(330.0, 270.0);
	const Size _inputLandscapeDialogSize = Size(496, 160.0);
	const Duration _dialogSizeAnimationDuration = Duration(milliseconds: 200);

	/// Shows a dialog containing a Material Design date picker.
	///
	/// The returned [Future] resolves to the date selected by the user when the
	/// user confirms the dialog. If the user cancels the dialog, null is returned.
	///
	/// When the date picker is first displayed, it will show the month of
	/// [initialDate], with [initialDate] selected.
	///
	/// The [firstDate] is the earliest allowable date. The [lastDate] is the latest
	/// allowable date. [initialDate] must either fall between these dates,
	/// or be equal to one of them. For each of these [DateTime] parameters, only
	/// their dates are considered. Their time fields are ignored. They must all
	/// be non-null.
	///
	/// An optional [initialEntryMode] argument can be used to display the date
	/// picker in the [DatePickerEntryMode.calendar] (a calendar month grid)
	/// or [DatePickerEntryMode.input] (a text input field) mode.
	/// It defaults to [DatePickerEntryMode.calendar] and must be non-null.
	///
	/// An optional [selectableDayPredicate] function can be passed in to only allow
	/// certain days for selection. If provided, only the days that
	/// [selectableDayPredicate] returns true for will be selectable. For example,
	/// this can be used to only allow weekdays for selection. If provided, it must
	/// return true for [initialDate].
	///
	/// Optional strings for the [cancelText], [confirmText], [errorFormatText],
	/// [errorInvalidText], [fieldHintText], [fieldLabelText], and [helpText] allow
	/// you to override the default text used for various parts of the dialog:
	///
	/// * [cancelText], label on the cancel button.
	/// * [confirmText], label on the ok button.
	/// * [errorFormatText], message used when the input text isn't in a proper date format.
	/// * [errorInvalidText], message used when the input text isn't a selectable date.
	/// * [fieldHintText], text used to prompt the user when no text has been entered in the field.
	/// * [fieldLabelText], label for the date text input field.
	/// * [helpText], label on the top of the dialog.
	///
	/// An optional [locale] argument can be used to set the locale for the date
	/// picker. It defaults to the ambient locale provided by [Localizations].
	///
	/// An optional [textDirection] argument can be used to set the text direction
	/// ([TextDirection.ltr] or [TextDirection.rtl]) for the date picker. It
	/// defaults to the ambient text direction provided by [Directionality]. If both
	/// [locale] and [textDirection] are non-null, [textDirection] overrides the
	/// direction chosen for the [locale].
	///
	/// The [context], [useRootNavigator] and [routeSettings] arguments are passed to
	/// [showDialog], the documentation for which discusses how it is used. [context]
	/// and [useRootNavigator] must be non-null.
	///
	/// The [builder] parameter can be used to wrap the dialog widget
	/// to add inherited widgets like [Theme].
	///
	/// An optional [initialDatePickerMode] argument can be used to have the
	/// calendar date picker initially appear in the [DatePickerMode.year] or
	/// [DatePickerMode.day] mode. It defaults to [DatePickerMode.day], and
	/// must be non-null.
	Future<DateTime> showDatePicker({
	@required BuildContext context,
	@required DateTime initialDate,
	@required DateTime firstDate,
	@required DateTime lastDate,
	DatePickerEntryMode initialEntryMode = DatePickerEntryMode.calendar,
	SelectableDayPredicate selectableDayPredicate,
	String helpText,
	String cancelText,
	String confirmText,
	Locale locale,
	bool useRootNavigator = true,
	RouteSettings routeSettings,
	TextDirection textDirection,
	TransitionBuilder builder,
	DatePickerMode initialDatePickerMode = DatePickerMode.day,
	String errorFormatText,
	String errorInvalidText,
	String fieldHintText,
	String fieldLabelText,
	}) async {
	assert(context != null);
	assert(initialDate != null);
	assert(firstDate != null);
	assert(lastDate != null);
	initialDate = utils.dateOnly(initialDate);
	firstDate = utils.dateOnly(firstDate);
	lastDate = utils.dateOnly(lastDate);
	assert(
	!lastDate.isBefore(firstDate),
	'lastDate $lastDate must be on or after firstDate $firstDate.'
	);
	assert(
	!initialDate.isBefore(firstDate),
	'initialDate $initialDate must be on or after firstDate $firstDate.'
	);
	assert(
	!initialDate.isAfter(lastDate),
	'initialDate $initialDate must be on or before lastDate $lastDate.'
	);
	assert(
	selectableDayPredicate == null \|\| selectableDayPredicate(initialDate),
	'Provided initialDate $initialDate must satisfy provided selectableDayPredicate.'
	);
	assert(initialEntryMode != null);
	assert(useRootNavigator != null);
	assert(initialDatePickerMode != null);
	assert(debugCheckHasMaterialLocalizations(context));

	Widget dialog = _DatePickerDialog(
	initialDate: initialDate,
	firstDate: firstDate,
	lastDate: lastDate,
	initialEntryMode: initialEntryMode,
	selectableDayPredicate: selectableDayPredicate,
	helpText: helpText,
	cancelText: cancelText,
	confirmText: confirmText,
	initialCalendarMode: initialDatePickerMode,
	errorFormatText: errorFormatText,
	errorInvalidText: errorInvalidText,
	fieldHintText: fieldHintText,
	fieldLabelText: fieldLabelText,
	);

	if (textDirection != null) {
	dialog = Directionality(
	textDirection: textDirection,
	child: dialog,
	);
	}

	if (locale != null) {
	dialog = Localizations.override(
	context: context,
	locale: locale,
	child: dialog,
	);
	}

	return showDialog<DateTime>(
	context: context,
	useRootNavigator: useRootNavigator,
	routeSettings: routeSettings,
	builder: (BuildContext context) {
	return builder == null ? dialog : builder(context, dialog);
	},
	);
	}

	class _DatePickerDialog extends StatefulWidget {
	_DatePickerDialog({
	Key key,
	@required DateTime initialDate,
	@required DateTime firstDate,
	@required DateTime lastDate,
	this.initialEntryMode = DatePickerEntryMode.calendar,
	this.selectableDayPredicate,
	this.cancelText,
	this.confirmText,
	this.helpText,
	this.initialCalendarMode = DatePickerMode.day,
	this.errorFormatText,
	this.errorInvalidText,
	this.fieldHintText,
	this.fieldLabelText,
	}) : assert(initialDate != null),
	assert(firstDate != null),
	assert(lastDate != null),
	initialDate = utils.dateOnly(initialDate),
	firstDate = utils.dateOnly(firstDate),
	lastDate = utils.dateOnly(lastDate),
	assert(initialEntryMode != null),
	assert(initialCalendarMode != null),
	super(key: key) {
	assert(
	!this.lastDate.isBefore(this.firstDate),
	'lastDate ${this.lastDate} must be on or after firstDate ${this.firstDate}.'
	);
	assert(
	!this.initialDate.isBefore(this.firstDate),
	'initialDate ${this.initialDate} must be on or after firstDate ${this.firstDate}.'
	);
	assert(
	!this.initialDate.isAfter(this.lastDate),
	'initialDate ${this.initialDate} must be on or before lastDate ${this.lastDate}.'
	);
	assert(
	selectableDayPredicate == null \|\| selectableDayPredicate(this.initialDate),
	'Provided initialDate ${this.initialDate} must satisfy provided selectableDayPredicate'
	);
	}

	/// The initially selected [DateTime] that the picker should display.
	final DateTime initialDate;

	/// The earliest allowable [DateTime] that the user can select.
	final DateTime firstDate;

	/// The latest allowable [DateTime] that the user can select.
	final DateTime lastDate;

	final DatePickerEntryMode initialEntryMode;

	/// Function to provide full control over which [DateTime] can be selected.
	final SelectableDayPredicate selectableDayPredicate;

	/// The text that is displayed on the cancel button.
	final String cancelText;

	/// The text that is displayed on the confirm button.
	final String confirmText;

	/// The text that is displayed at the top of the header.
	///
	/// This is used to indicate to the user what they are selecting a date for.
	final String helpText;

	/// The initial display of the calendar picker.
	final DatePickerMode initialCalendarMode;

	final String errorFormatText;

	final String errorInvalidText;

	final String fieldHintText;

	final String fieldLabelText;

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

	class _DatePickerDialogState extends State<_DatePickerDialog> {

	DatePickerEntryMode _entryMode;
	DateTime _selectedDate;
	bool _autoValidate;
	final GlobalKey _calendarPickerKey = GlobalKey();
	final GlobalKey<FormState> _formKey = GlobalKey<FormState>();

	@override
	void initState() {
	super.initState();
	_entryMode = widget.initialEntryMode;
	_selectedDate = widget.initialDate;
	_autoValidate = false;
	}

	void _handleOk() {
	if (_entryMode == DatePickerEntryMode.input) {
	final FormState form = _formKey.currentState;
	if (!form.validate()) {
	setState(() => _autoValidate = true);
	return;
	}
	form.save();
	}
	Navigator.pop(context, _selectedDate);
	}

	void _handleCancel() {
	Navigator.pop(context);
	}

	void _handelEntryModeToggle() {
	setState(() {
	switch (_entryMode) {
	case DatePickerEntryMode.calendar:
	_autoValidate = false;
	_entryMode = DatePickerEntryMode.input;
	break;
	case DatePickerEntryMode.input:
	_formKey.currentState.save();
	_entryMode = DatePickerEntryMode.calendar;
	break;
	}
	});
	}

	void _handleDateChanged(DateTime date) {
	setState(() => _selectedDate = date);
	}

	Size _dialogSize(BuildContext context) {
	final Orientation orientation = MediaQuery.of(context).orientation;
	switch (_entryMode) {
	case DatePickerEntryMode.calendar:
	switch (orientation) {
	case Orientation.portrait:
	return _calendarPortraitDialogSize;
	case Orientation.landscape:
	return _calendarLandscapeDialogSize;
	}
	break;
	case DatePickerEntryMode.input:
	switch (orientation) {
	case Orientation.portrait:
	return _inputPortraitDialogSize;
	case Orientation.landscape:
	return _inputLandscapeDialogSize;
	}
	break;
	}
	return null;
	}

	@override
	Widget build(BuildContext context) {
	final ThemeData theme = Theme.of(context);
	final ColorScheme colorScheme = theme.colorScheme;
	final MaterialLocalizations localizations = MaterialLocalizations.of(context);
	final Orientation orientation = MediaQuery.of(context).orientation;
	final TextTheme textTheme = theme.textTheme;
	// Constrain the textScaleFactor to the largest supported value to prevent
	// layout issues.
	final double textScaleFactor = math.min(MediaQuery.of(context).textScaleFactor, 1.3);

	final String dateText = _selectedDate != null
	? localizations.formatMediumDate(_selectedDate)
	// TODO(darrenaustin): localize 'Date'
	: 'Date';
	final Color dateColor = colorScheme.brightness == Brightness.light
	? colorScheme.onPrimary
	: colorScheme.onSurface;
	final TextStyle dateStyle = orientation == Orientation.landscape
	? textTheme.headline5?.copyWith(color: dateColor)
	: textTheme.headline4?.copyWith(color: dateColor);

	final Widget actions = ButtonBar(
	buttonTextTheme: ButtonTextTheme.primary,
	layoutBehavior: ButtonBarLayoutBehavior.constrained,
	children: <Widget>[
	FlatButton(
	child: Text(widget.cancelText ?? localizations.cancelButtonLabel),
	onPressed: _handleCancel,
	),
	FlatButton(
	child: Text(widget.confirmText ?? localizations.okButtonLabel),
	onPressed: _handleOk,
	),
	],
	);

	Widget picker;
	IconData entryModeIcon;
	String entryModeTooltip;
	switch (_entryMode) {
	case DatePickerEntryMode.calendar:
	picker = CalendarDatePicker(
	key: _calendarPickerKey,
	initialDate: _selectedDate,
	firstDate: widget.firstDate,
	lastDate: widget.lastDate,
	onDateChanged: _handleDateChanged,
	selectableDayPredicate: widget.selectableDayPredicate,
	initialCalendarMode: widget.initialCalendarMode,
	);
	entryModeIcon = Icons.edit;
	// TODO(darrenaustin): localize 'Switch to input'
	entryModeTooltip = 'Switch to input';
	break;

	case DatePickerEntryMode.input:
	picker = Form(
	key: _formKey,
	autovalidate: _autoValidate,
	child: InputDatePickerFormField(
	initialDate: _selectedDate,
	firstDate: widget.firstDate,
	lastDate: widget.lastDate,
	onDateSubmitted: _handleDateChanged,
	onDateSaved: _handleDateChanged,
	selectableDayPredicate: widget.selectableDayPredicate,
	errorFormatText: widget.errorFormatText,
	errorInvalidText: widget.errorInvalidText,
	fieldHintText: widget.fieldHintText,
	fieldLabelText: widget.fieldLabelText,
	autofocus: true,
	),
	);
	entryModeIcon = Icons.calendar_today;
	// TODO(darrenaustin): localize 'Switch to calendar'
	entryModeTooltip = 'Switch to calendar';
	break;
	}

	final Widget header = DatePickerHeader(
	// TODO(darrenaustin): localize 'SELECT DATE'
	helpText: widget.helpText ?? 'SELECT DATE',
	titleText: dateText,
	titleStyle: dateStyle,
	orientation: orientation,
	isShort: orientation == Orientation.landscape,
	icon: entryModeIcon,
	iconTooltip: entryModeTooltip,
	onIconPressed: _handelEntryModeToggle,
	);

	final Size dialogSize = _dialogSize(context) * textScaleFactor;
	final DialogTheme dialogTheme = Theme.of(context).dialogTheme;
	return Dialog(
	child: AnimatedContainer(
	width: dialogSize.width,
	height: dialogSize.height,
	duration: _dialogSizeAnimationDuration,
	curve: Curves.easeIn,
	child: MediaQuery(
	data: MediaQuery.of(context).copyWith(
	textScaleFactor: textScaleFactor,
	),
	child: Builder(builder: (BuildContext context) {
	switch (orientation) {
	case Orientation.portrait:
	return Column(
	mainAxisSize: MainAxisSize.min,
	crossAxisAlignment: CrossAxisAlignment.stretch,
	children: <Widget>[
	header,
	Expanded(child: picker),
	actions,
	],
	);
	case Orientation.landscape:
	return Row(
	mainAxisSize: MainAxisSize.min,
	crossAxisAlignment: CrossAxisAlignment.stretch,
	children: <Widget>[
	header,
	Flexible(
	child: Column(
	mainAxisSize: MainAxisSize.min,
	crossAxisAlignment: CrossAxisAlignment.stretch,
	children: <Widget>[
	Expanded(child: picker),
	actions,
	],
	),
	),
	],
	);
	}
	return null;
	}),
	),
	),
	insetPadding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 24.0),
	// The default dialog shape is radius 2 rounded rect, but the spec has
	// been updated to 4, so we will use that here for the Date Picker, but
	// only if there isn't one provided in the theme.
	shape: dialogTheme.shape ?? const RoundedRectangleBorder(
	borderRadius: BorderRadius.all(Radius.circular(4.0))
	),
	clipBehavior: Clip.antiAlias,
	);
	}
	}