packages/flutter/lib/src/material/dialog.dart - external/github.com/flutter/flutter - Git at Google

 // Copyright 2015 The Chromium 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/foundation.dart';
 import 'package:flutter/widgets.dart';

 import 'button.dart';
 import 'button_bar.dart';
 import 'colors.dart';
 import 'ink_well.dart';
 import 'material.dart';
 import 'theme.dart';

 // Examples can assume:
 // enum Department { treasury, state }

 /// A material design dialog.
 ///
 /// This dialog widget does not have any opinion about the contents of the
 /// dialog. Rather than using this widget directly, consider using [AlertDialog]
 /// or [SimpleDialog], which implement specific kinds of material design
 /// dialogs.
 ///
 /// See also:
 ///
 ///  * [AlertDialog], for dialogs that have a message and some buttons.
 ///  * [SimpleDialog], for dialogs that offer a variety of options.
 ///  * [showDialog], which actually displays the dialog and returns its result.
 ///  * <https://material.google.com/components/dialogs.html>
 class Dialog extends StatelessWidget {
   /// Creates a dialog.
   ///
   /// Typically used in conjunction with [showDialog].
   const Dialog({
     Key key,
     this.child,
   }) : super(key: key);

   /// The widget below this widget in the tree.
   final Widget child;

   Color _getColor(BuildContext context) {
     return Theme.of(context).dialogBackgroundColor;
   }

   @override
   Widget build(BuildContext context) {
     return new Center(
       child: new Container(
         margin: const EdgeInsets.symmetric(horizontal: 40.0, vertical: 24.0),
         child: new ConstrainedBox(
           constraints: const BoxConstraints(minWidth: 280.0),
           child: new Material(
             elevation: 24.0,
             color: _getColor(context),
             type: MaterialType.card,
             child: child
           )
         )
       )
     );
   }
 }

 /// A material design alert dialog.
 ///
 /// An alert dialog informs the user about situations that require
 /// acknowledgement. An alert dialog has an optional title and an optional list
 /// of actions. The title is displayed above the content and the actions are
 /// displayed below the content.
 ///
 /// If the content is too large to fit on the screen vertically, the dialog will
 /// display the title and the actions and let the content overflow. Consider
 /// using a scrolling widget, such as [ListView], for [content] to avoid
 /// overflow.
 ///
 /// For dialogs that offer the user a choice between several options, consider
 /// using a [SimpleDialog].
 ///
 /// Typically passed as the child widget to [showDialog], which displays the
 /// dialog.
 ///
 /// ## Sample code
 ///
 /// This snippet shows a method in a [State] which, when called, displays a dialog box
 /// and returns a [Future] that completes when the dialog is dismissed.
 ///
 /// ```dart
 /// Future<Null> _neverSatisfied() async {
 ///   return showDialog<Null>(
 ///     context: context,
 ///     barrierDismissible: false, // user must tap button!
 ///     child: new AlertDialog(
 ///       title: new Text('Rewind and remember'),
 ///       content: new SingleChildScrollView(
 ///         child: new ListBody(
 ///           children: <Widget>[
 ///             new Text('You will never be satisfied.'),
 ///             new Text('You\’re like me. I’m never satisfied.'),
 ///           ],
 ///         ),
 ///       ),
 ///       actions: <Widget>[
 ///         new FlatButton(
 ///           child: new Text('Regret'),
 ///           onPressed: () {
 ///             Navigator.of(context).pop();
 ///           },
 ///         ),
 ///       ],
 ///     ),
 ///   );
 /// }
 /// ```
 ///
 /// See also:
 ///
 ///  * [SimpleDialog], which handles the scrolling of the contents but has no [actions].
 ///  * [Dialog], on which [AlertDialog] and [SimpleDialog] are based.
 ///  * [showDialog], which actually displays the dialog and returns its result.
 ///  * <https://material.google.com/components/dialogs.html#dialogs-alerts>
 class AlertDialog extends StatelessWidget {
   /// Creates an alert dialog.
   ///
   /// Typically used in conjunction with [showDialog].
   const AlertDialog({
     Key key,
     this.title,
     this.titlePadding,
     this.content,
     this.contentPadding,
     this.actions
   }) : super(key: key);

   /// The (optional) title of the dialog is displayed in a large font at the top
   /// of the dialog.
   ///
   /// Typically a [Text] widget.
   final Widget title;

   /// Padding around the title.
   ///
   /// Uses material design default if none is supplied. If there is no title, no
   /// padding will be provided.
   final EdgeInsets titlePadding;

   /// The (optional) content of the dialog is displayed in the center of the
   /// dialog in a lighter font.
   ///
   /// Typically, this is a [ListView] containing the contents of the dialog.
   /// Using a [ListView] ensures that the contents can scroll if they are too
   /// big to fit on the display.
   final Widget content;

   /// Padding around the content.
   ///
   /// Uses material design default if none is supplied.
   final EdgeInsets contentPadding;

   /// The (optional) set of actions that are displayed at the bottom of the
   /// dialog.
   ///
   /// Typically this is a list of [FlatButton] widgets.
   ///
   /// These widgets will be wrapped in a [ButtonBar].
   final List<Widget> actions;

   @override
   Widget build(BuildContext context) {
     final List<Widget> children = <Widget>[];

     if (title != null) {
       children.add(new Padding(
         padding: titlePadding ?? new EdgeInsets.fromLTRB(24.0, 24.0, 24.0, content == null ? 20.0 : 0.0),
         child: new DefaultTextStyle(
           style: Theme.of(context).textTheme.title,
           child: title,
         ),
       ));
     }

     if (content != null) {
       children.add(new Flexible(
         child: new Padding(
           padding: contentPadding ?? const EdgeInsets.fromLTRB(24.0, 20.0, 24.0, 24.0),
           child: new DefaultTextStyle(
             style: Theme.of(context).textTheme.subhead,
             child: content,
           ),
         ),
       ));
     }

     if (actions != null) {
       children.add(new ButtonTheme.bar(
         child: new ButtonBar(
           children: actions,
         ),
       ));
     }

     return new Dialog(
       child: new IntrinsicWidth(
         child: new Column(
           mainAxisSize: MainAxisSize.min,
           crossAxisAlignment: CrossAxisAlignment.stretch,
           children: children,
         ),
       ),
     );
   }
 }

 /// An option used in a [SimpleDialog].
 ///
 /// A simple dialog offers the user a choice between several options. This
 /// widget is commonly used to represent each of the options. If the user
 /// selects this option, the widget will call the [onPressed] callback, which
 /// typically uses [Navigator.pop] to close the dialog.
 ///
 /// ## Sample code
 ///
 /// ```dart
 /// new SimpleDialogOption(
 ///   onPressed: () { Navigator.pop(context, Department.treasury); },
 ///   child: const Text('Treasury department'),
 /// )
 /// ```
 ///
 /// See also:
 ///
 ///  * [SimpleDialog], for a dialog in which to use this widget.
 ///  * [showDialog], which actually displays the dialog and returns its result.
 ///  * [FlatButton], which are commonly used as actions in other kinds of
 ///    dialogs, such as [AlertDialog]s.
 ///  * <https://material.google.com/components/dialogs.html#dialogs-simple-dialogs>
 class SimpleDialogOption extends StatelessWidget {
   /// Creates an option for a [SimpleDialog].
   const SimpleDialogOption({
     Key key,
     this.onPressed,
     this.child,
   }) : super(key: key);

   /// The callback that is called when this option is selected.
   ///
   /// If this is set to null, the option cannot be selected.
   ///
   /// When used in a [SimpleDialog], this will typically call [Navigator.pop]
   /// with a value for [showDialog] to complete its future with.
   final VoidCallback onPressed;

   /// The widget below this widget in the tree.
   ///
   /// Typically a [Text] widget.
   final Widget child;

   @override
   Widget build(BuildContext context) {
     return new InkWell(
       onTap: onPressed,
       child: new Padding(
         padding: const EdgeInsets.symmetric(vertical: 8.0, horizontal: 24.0),
         child: child
       ),
     );
   }
 }

 /// A simple material design dialog.
 ///
 /// A simple dialog offers the user a choice between several options. A simple
 /// dialog has an optional title that is displayed above the choices.
 ///
 /// For dialogs that inform the user about a situation, consider using an
 /// [AlertDialog].
 ///
 /// Typically passed as the child widget to [showDialog], which displays the
 /// dialog.
 ///
 /// ## Sample code
 ///
 /// In this example, the user is asked to select between two options. These
 /// options are represented as an enum. The [showDialog] method here returns
 /// a [Future] that completes to a value of that enum. If the user cancels
 /// the dialog (e.g. by hitting the back button on Android, or tapping on the
 /// mask behind the dialog) then the future completes with the null value.
 ///
 /// The return value in this example is used as the index for a switch statement.
 /// One advantage of using an enum as the return value and then using that to
 /// drive a switch statement is that the analyzer will flag any switch statement
 /// that doesn't mention every value in the enum.
 ///
 /// ```dart
 /// Future<Null> _askedToLead() async {
 ///   switch (await showDialog<Department>(
 ///     context: context,
 ///     child: new SimpleDialog(
 ///       title: const Text('Select assignment'),
 ///       children: <Widget>[
 ///         new SimpleDialogOption(
 ///           onPressed: () { Navigator.pop(context, Department.treasury); },
 ///           child: const Text('Treasury department'),
 ///         ),
 ///         new SimpleDialogOption(
 ///           onPressed: () { Navigator.pop(context, Department.state); },
 ///           child: const Text('State department'),
 ///         ),
 ///       ],
 ///     ),
 ///   )) {
 ///     case Department.treasury:
 ///       // Let's go.
 ///       // ...
 ///     break;
 ///     case Department.state:
 ///       // ...
 ///     break;
 ///   }
 /// }
 /// ```
 ///
 /// See also:
 ///
 ///  * [SimpleDialogOption], which are options used in this type of dialog.
 ///  * [AlertDialog], for dialogs that have a row of buttons below the body.
 ///  * [Dialog], on which [SimpleDialog] and [AlertDialog] are based.
 ///  * [showDialog], which actually displays the dialog and returns its result.
 ///  * <https://material.google.com/components/dialogs.html#dialogs-simple-dialogs>
 class SimpleDialog extends StatelessWidget {
   /// Creates a simple dialog.
   ///
   /// Typically used in conjunction with [showDialog].
   const SimpleDialog({
     Key key,
     this.title,
     this.titlePadding,
     this.children,
     this.contentPadding,
   }) : super(key: key);

   /// The (optional) title of the dialog is displayed in a large font at the top
   /// of the dialog.
   ///
   /// Typically a [Text] widget.
   final Widget title;

   /// Padding around the title.
   ///
   /// Uses material design default if none is supplied. If there is no title, no
   /// padding will be provided.
   final EdgeInsets titlePadding;

   /// The (optional) content of the dialog is displayed in a
   /// [SingleChildScrollView] underneath the title.
   ///
   /// Typically a list of [SimpleDialogOption]s.
   final List<Widget> children;

   /// Padding around the content.
   ///
   /// Uses material design default if none is supplied.
   final EdgeInsets contentPadding;

   @override
   Widget build(BuildContext context) {
     final List<Widget> body = <Widget>[];

     if (title != null) {
       body.add(new Padding(
         padding: titlePadding ?? const EdgeInsets.fromLTRB(24.0, 24.0, 24.0, 0.0),
         child: new DefaultTextStyle(
           style: Theme.of(context).textTheme.title,
           child: title
         )
       ));
     }

     if (children != null) {
       body.add(new Flexible(
         child: new SingleChildScrollView(
           padding: contentPadding ?? const EdgeInsets.fromLTRB(0.0, 12.0, 0.0, 16.0),
           child: new ListBody(children: children),
         )
       ));
     }

     return new Dialog(
       child: new IntrinsicWidth(
         stepWidth: 56.0,
         child: new ConstrainedBox(
           constraints: const BoxConstraints(minWidth: 280.0),
           child: new Column(
             mainAxisSize: MainAxisSize.min,
             crossAxisAlignment: CrossAxisAlignment.stretch,
             children: body,
           )
         )
       )
     );
   }
 }

 class _DialogRoute<T> extends PopupRoute<T> {
   _DialogRoute({
     @required this.theme,
     bool barrierDismissible: true,
     @required this.child,
   }) : assert(barrierDismissible != null),
        _barrierDismissible = barrierDismissible;

   final Widget child;
   final ThemeData theme;

   @override
   Duration get transitionDuration => const Duration(milliseconds: 150);

   @override
   bool get barrierDismissible => _barrierDismissible;
   final bool _barrierDismissible;

   @override
   Color get barrierColor => Colors.black54;

   @override
   Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
     return theme != null ? new Theme(data: theme, child: child) : child;
   }

   @override
   Widget buildTransitions(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation, Widget child) {
     return new FadeTransition(
       opacity: new CurvedAnimation(
         parent: animation,
         curve: Curves.easeOut
       ),
       child: child
     );
   }
 }

 /// Displays a dialog above the current contents of the app.
 ///
 /// This function typically receives a [Dialog] widget as its child argument.
 /// Content below the dialog is dimmed with a [ModalBarrier].
 ///
 /// Returns a [Future] that resolves to the value (if any) that was passed to
 /// [Navigator.pop] when the dialog was closed.
 ///
 /// See also:
 ///  * [AlertDialog], for dialogs that have a row of buttons below a body.
 ///  * [SimpleDialog], which handles the scrolling of the contents and does
 ///    not show buttons below its body.
 ///  * [Dialog], on which [SimpleDialog] and [AlertDialog] are based.
 ///  * <https://material.google.com/components/dialogs.html>
 Future<T> showDialog<T>({
   @required BuildContext context,
   bool barrierDismissible: true,
   @required Widget child,
 }) {
   return Navigator.push(context, new _DialogRoute<T>(
     child: child,
     theme: Theme.of(context, shadowThemeOnly: true),
     barrierDismissible: barrierDismissible,
   ));
 }
	// Copyright 2015 The Chromium 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/foundation.dart';
	import 'package:flutter/widgets.dart';

	import 'button.dart';
	import 'button_bar.dart';
	import 'colors.dart';
	import 'ink_well.dart';
	import 'material.dart';
	import 'theme.dart';

	// Examples can assume:
	// enum Department { treasury, state }

	/// A material design dialog.
	///
	/// This dialog widget does not have any opinion about the contents of the
	/// dialog. Rather than using this widget directly, consider using [AlertDialog]
	/// or [SimpleDialog], which implement specific kinds of material design
	/// dialogs.
	///
	/// See also:
	///
	/// * [AlertDialog], for dialogs that have a message and some buttons.
	/// * [SimpleDialog], for dialogs that offer a variety of options.
	/// * [showDialog], which actually displays the dialog and returns its result.
	/// * <https://material.google.com/components/dialogs.html>
	class Dialog extends StatelessWidget {
	/// Creates a dialog.
	///
	/// Typically used in conjunction with [showDialog].
	const Dialog({
	Key key,
	this.child,
	}) : super(key: key);

	/// The widget below this widget in the tree.
	final Widget child;

	Color _getColor(BuildContext context) {
	return Theme.of(context).dialogBackgroundColor;
	}

	@override
	Widget build(BuildContext context) {
	return new Center(
	child: new Container(
	margin: const EdgeInsets.symmetric(horizontal: 40.0, vertical: 24.0),
	child: new ConstrainedBox(
	constraints: const BoxConstraints(minWidth: 280.0),
	child: new Material(
	elevation: 24.0,
	color: _getColor(context),
	type: MaterialType.card,
	child: child
	)
	)
	)
	);
	}
	}

	/// A material design alert dialog.
	///
	/// An alert dialog informs the user about situations that require
	/// acknowledgement. An alert dialog has an optional title and an optional list
	/// of actions. The title is displayed above the content and the actions are
	/// displayed below the content.
	///
	/// If the content is too large to fit on the screen vertically, the dialog will
	/// display the title and the actions and let the content overflow. Consider
	/// using a scrolling widget, such as [ListView], for [content] to avoid
	/// overflow.
	///
	/// For dialogs that offer the user a choice between several options, consider
	/// using a [SimpleDialog].
	///
	/// Typically passed as the child widget to [showDialog], which displays the
	/// dialog.
	///
	/// ## Sample code
	///
	/// This snippet shows a method in a [State] which, when called, displays a dialog box
	/// and returns a [Future] that completes when the dialog is dismissed.
	///
	/// ```dart
	/// Future<Null> _neverSatisfied() async {
	/// return showDialog<Null>(
	/// context: context,
	/// barrierDismissible: false, // user must tap button!
	/// child: new AlertDialog(
	/// title: new Text('Rewind and remember'),
	/// content: new SingleChildScrollView(
	/// child: new ListBody(
	/// children: <Widget>[
	/// new Text('You will never be satisfied.'),
	/// new Text('You\’re like me. I’m never satisfied.'),
	/// ],
	/// ),
	/// ),
	/// actions: <Widget>[
	/// new FlatButton(
	/// child: new Text('Regret'),
	/// onPressed: () {
	/// Navigator.of(context).pop();
	/// },
	/// ),
	/// ],
	/// ),
	/// );
	/// }
	/// ```
	///
	/// See also:
	///
	/// * [SimpleDialog], which handles the scrolling of the contents but has no [actions].
	/// * [Dialog], on which [AlertDialog] and [SimpleDialog] are based.
	/// * [showDialog], which actually displays the dialog and returns its result.
	/// * <https://material.google.com/components/dialogs.html#dialogs-alerts>
	class AlertDialog extends StatelessWidget {
	/// Creates an alert dialog.
	///
	/// Typically used in conjunction with [showDialog].
	const AlertDialog({
	Key key,
	this.title,
	this.titlePadding,
	this.content,
	this.contentPadding,
	this.actions
	}) : super(key: key);

	/// The (optional) title of the dialog is displayed in a large font at the top
	/// of the dialog.
	///
	/// Typically a [Text] widget.
	final Widget title;

	/// Padding around the title.
	///
	/// Uses material design default if none is supplied. If there is no title, no
	/// padding will be provided.
	final EdgeInsets titlePadding;

	/// The (optional) content of the dialog is displayed in the center of the
	/// dialog in a lighter font.
	///
	/// Typically, this is a [ListView] containing the contents of the dialog.
	/// Using a [ListView] ensures that the contents can scroll if they are too
	/// big to fit on the display.
	final Widget content;

	/// Padding around the content.
	///
	/// Uses material design default if none is supplied.
	final EdgeInsets contentPadding;

	/// The (optional) set of actions that are displayed at the bottom of the
	/// dialog.
	///
	/// Typically this is a list of [FlatButton] widgets.
	///
	/// These widgets will be wrapped in a [ButtonBar].
	final List<Widget> actions;

	@override
	Widget build(BuildContext context) {
	final List<Widget> children = <Widget>[];

	if (title != null) {
	children.add(new Padding(
	padding: titlePadding ?? new EdgeInsets.fromLTRB(24.0, 24.0, 24.0, content == null ? 20.0 : 0.0),
	child: new DefaultTextStyle(
	style: Theme.of(context).textTheme.title,
	child: title,
	),
	));
	}

	if (content != null) {
	children.add(new Flexible(
	child: new Padding(
	padding: contentPadding ?? const EdgeInsets.fromLTRB(24.0, 20.0, 24.0, 24.0),
	child: new DefaultTextStyle(
	style: Theme.of(context).textTheme.subhead,
	child: content,
	),
	),
	));
	}

	if (actions != null) {
	children.add(new ButtonTheme.bar(
	child: new ButtonBar(
	children: actions,
	),
	));
	}

	return new Dialog(
	child: new IntrinsicWidth(
	child: new Column(
	mainAxisSize: MainAxisSize.min,
	crossAxisAlignment: CrossAxisAlignment.stretch,
	children: children,
	),
	),
	);
	}
	}

	/// An option used in a [SimpleDialog].
	///
	/// A simple dialog offers the user a choice between several options. This
	/// widget is commonly used to represent each of the options. If the user
	/// selects this option, the widget will call the [onPressed] callback, which
	/// typically uses [Navigator.pop] to close the dialog.
	///
	/// ## Sample code
	///
	/// ```dart
	/// new SimpleDialogOption(
	/// onPressed: () { Navigator.pop(context, Department.treasury); },
	/// child: const Text('Treasury department'),
	/// )
	/// ```
	///
	/// See also:
	///
	/// * [SimpleDialog], for a dialog in which to use this widget.
	/// * [showDialog], which actually displays the dialog and returns its result.
	/// * [FlatButton], which are commonly used as actions in other kinds of
	/// dialogs, such as [AlertDialog]s.
	/// * <https://material.google.com/components/dialogs.html#dialogs-simple-dialogs>
	class SimpleDialogOption extends StatelessWidget {
	/// Creates an option for a [SimpleDialog].
	const SimpleDialogOption({
	Key key,
	this.onPressed,
	this.child,
	}) : super(key: key);

	/// The callback that is called when this option is selected.
	///
	/// If this is set to null, the option cannot be selected.
	///
	/// When used in a [SimpleDialog], this will typically call [Navigator.pop]
	/// with a value for [showDialog] to complete its future with.
	final VoidCallback onPressed;

	/// The widget below this widget in the tree.
	///
	/// Typically a [Text] widget.
	final Widget child;

	@override
	Widget build(BuildContext context) {
	return new InkWell(
	onTap: onPressed,
	child: new Padding(
	padding: const EdgeInsets.symmetric(vertical: 8.0, horizontal: 24.0),
	child: child
	),
	);
	}
	}

	/// A simple material design dialog.
	///
	/// A simple dialog offers the user a choice between several options. A simple
	/// dialog has an optional title that is displayed above the choices.
	///
	/// For dialogs that inform the user about a situation, consider using an
	/// [AlertDialog].
	///
	/// Typically passed as the child widget to [showDialog], which displays the
	/// dialog.
	///
	/// ## Sample code
	///
	/// In this example, the user is asked to select between two options. These
	/// options are represented as an enum. The [showDialog] method here returns
	/// a [Future] that completes to a value of that enum. If the user cancels
	/// the dialog (e.g. by hitting the back button on Android, or tapping on the
	/// mask behind the dialog) then the future completes with the null value.
	///
	/// The return value in this example is used as the index for a switch statement.
	/// One advantage of using an enum as the return value and then using that to
	/// drive a switch statement is that the analyzer will flag any switch statement
	/// that doesn't mention every value in the enum.
	///
	/// ```dart
	/// Future<Null> _askedToLead() async {
	/// switch (await showDialog<Department>(
	/// context: context,
	/// child: new SimpleDialog(
	/// title: const Text('Select assignment'),
	/// children: <Widget>[
	/// new SimpleDialogOption(
	/// onPressed: () { Navigator.pop(context, Department.treasury); },
	/// child: const Text('Treasury department'),
	/// ),
	/// new SimpleDialogOption(
	/// onPressed: () { Navigator.pop(context, Department.state); },
	/// child: const Text('State department'),
	/// ),
	/// ],
	/// ),
	/// )) {
	/// case Department.treasury:
	/// // Let's go.
	/// // ...
	/// break;
	/// case Department.state:
	/// // ...
	/// break;
	/// }
	/// }
	/// ```
	///
	/// See also:
	///
	/// * [SimpleDialogOption], which are options used in this type of dialog.
	/// * [AlertDialog], for dialogs that have a row of buttons below the body.
	/// * [Dialog], on which [SimpleDialog] and [AlertDialog] are based.
	/// * [showDialog], which actually displays the dialog and returns its result.
	/// * <https://material.google.com/components/dialogs.html#dialogs-simple-dialogs>
	class SimpleDialog extends StatelessWidget {
	/// Creates a simple dialog.
	///
	/// Typically used in conjunction with [showDialog].
	const SimpleDialog({
	Key key,
	this.title,
	this.titlePadding,
	this.children,
	this.contentPadding,
	}) : super(key: key);

	/// The (optional) title of the dialog is displayed in a large font at the top
	/// of the dialog.
	///
	/// Typically a [Text] widget.
	final Widget title;

	/// Padding around the title.
	///
	/// Uses material design default if none is supplied. If there is no title, no
	/// padding will be provided.
	final EdgeInsets titlePadding;

	/// The (optional) content of the dialog is displayed in a
	/// [SingleChildScrollView] underneath the title.
	///
	/// Typically a list of [SimpleDialogOption]s.
	final List<Widget> children;

	/// Padding around the content.
	///
	/// Uses material design default if none is supplied.
	final EdgeInsets contentPadding;

	@override
	Widget build(BuildContext context) {
	final List<Widget> body = <Widget>[];

	if (title != null) {
	body.add(new Padding(
	padding: titlePadding ?? const EdgeInsets.fromLTRB(24.0, 24.0, 24.0, 0.0),
	child: new DefaultTextStyle(
	style: Theme.of(context).textTheme.title,
	child: title
	)
	));
	}

	if (children != null) {
	body.add(new Flexible(
	child: new SingleChildScrollView(
	padding: contentPadding ?? const EdgeInsets.fromLTRB(0.0, 12.0, 0.0, 16.0),
	child: new ListBody(children: children),
	)
	));
	}

	return new Dialog(
	child: new IntrinsicWidth(
	stepWidth: 56.0,
	child: new ConstrainedBox(
	constraints: const BoxConstraints(minWidth: 280.0),
	child: new Column(
	mainAxisSize: MainAxisSize.min,
	crossAxisAlignment: CrossAxisAlignment.stretch,
	children: body,
	)
	)
	)
	);
	}
	}

	class _DialogRoute<T> extends PopupRoute<T> {
	_DialogRoute({
	@required this.theme,
	bool barrierDismissible: true,
	@required this.child,
	}) : assert(barrierDismissible != null),
	_barrierDismissible = barrierDismissible;

	final Widget child;
	final ThemeData theme;

	@override
	Duration get transitionDuration => const Duration(milliseconds: 150);

	@override
	bool get barrierDismissible => _barrierDismissible;
	final bool _barrierDismissible;

	@override
	Color get barrierColor => Colors.black54;

	@override
	Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
	return theme != null ? new Theme(data: theme, child: child) : child;
	}

	@override
	Widget buildTransitions(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation, Widget child) {
	return new FadeTransition(
	opacity: new CurvedAnimation(
	parent: animation,
	curve: Curves.easeOut
	),
	child: child
	);
	}
	}

	/// Displays a dialog above the current contents of the app.
	///
	/// This function typically receives a [Dialog] widget as its child argument.
	/// Content below the dialog is dimmed with a [ModalBarrier].
	///
	/// Returns a [Future] that resolves to the value (if any) that was passed to
	/// [Navigator.pop] when the dialog was closed.
	///
	/// See also:
	/// * [AlertDialog], for dialogs that have a row of buttons below a body.
	/// * [SimpleDialog], which handles the scrolling of the contents and does
	/// not show buttons below its body.
	/// * [Dialog], on which [SimpleDialog] and [AlertDialog] are based.
	/// * <https://material.google.com/components/dialogs.html>
	Future<T> showDialog<T>({
	@required BuildContext context,
	bool barrierDismissible: true,
	@required Widget child,
	}) {
	return Navigator.push(context, new _DialogRoute<T>(
	child: child,
	theme: Theme.of(context, shadowThemeOnly: true),
	barrierDismissible: barrierDismissible,
	));
	}