packages/flutter/lib/src/material/snack_bar.dart - mirrors/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 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

 import 'button_theme.dart';
 import 'flat_button.dart';
 import 'material.dart';
 import 'scaffold.dart';
 import 'theme.dart';
 import 'theme_data.dart';

 const double _kSnackBarPadding = 24.0;
 const double _kSingleLineVerticalPadding = 14.0;
 const Color _kSnackBackground = Color(0xFF323232);

 // TODO(ianh): We should check if the given text and actions are going to fit on
 // one line or not, and if they are, use the single-line layout, and if not, use
 // the multiline layout. See link above.

 // TODO(ianh): Implement the Tablet version of snackbar if we're "on a tablet".

 const Duration _kSnackBarTransitionDuration = Duration(milliseconds: 250);
 const Duration _kSnackBarDisplayDuration = Duration(milliseconds: 4000);
 const Curve _snackBarHeightCurve = Curves.fastOutSlowIn;
 const Curve _snackBarFadeCurve = Interval(0.72, 1.0, curve: Curves.fastOutSlowIn);

 /// Specify how a [SnackBar] was closed.
 ///
 /// The [ScaffoldState.showSnackBar] function returns a
 /// [ScaffoldFeatureController]. The value of the controller's closed property
 /// is a Future that resolves to a SnackBarClosedReason. Applications that need
 /// to know how a snackbar was closed can use this value.
 ///
 /// Example:
 ///
 /// ```dart
 /// Scaffold.of(context).showSnackBar(
 ///   SnackBar( ... )
 /// ).closed.then((SnackBarClosedReason reason) {
 ///    ...
 /// });
 /// ```
 enum SnackBarClosedReason {
   /// The snack bar was closed after the user tapped a [SnackBarAction].
   action,

   /// The snack bar was closed through a [SemanticAction.dismiss].
   dismiss,

   /// The snack bar was closed by a user's swipe.
   swipe,

   /// The snack bar was closed by the [ScaffoldFeatureController] close callback
   /// or by calling [ScaffoldState.hideCurrentSnackBar] directly.
   hide,

   /// The snack bar was closed by an call to [ScaffoldState.removeCurrentSnackBar].
   remove,

   /// The snack bar was closed because its timer expired.
   timeout,
 }

 /// A button for a [SnackBar], known as an "action".
 ///
 /// Snack bar actions are always enabled. If you want to disable a snack bar
 /// action, simply don't include it in the snack bar.
 ///
 /// Snack bar actions can only be pressed once. Subsequent presses are ignored.
 ///
 /// See also:
 ///
 ///  * [SnackBar]
 ///  * <https://material.io/design/components/snackbars.html>
 class SnackBarAction extends StatefulWidget {
   /// Creates an action for a [SnackBar].
   ///
   /// The [label] and [onPressed] arguments must be non-null.
   const SnackBarAction({
     Key key,
     this.textColor,
     this.disabledTextColor,
     @required this.label,
     @required this.onPressed,
   }) : assert(label != null),
        assert(onPressed != null),
        super(key: key);

   /// The button label color. If not provided, defaults to [accentColor].
   final Color textColor;

   /// The button disabled label color. This color is shown after the
   /// [snackBarAction] is dismissed.
   final Color disabledTextColor;

   /// The button label.
   final String label;

   /// The callback to be called when the button is pressed. Must not be null.
   ///
   /// This callback will be called at most once each time this action is
   /// displayed in a [SnackBar].
   final VoidCallback onPressed;

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

 class _SnackBarActionState extends State<SnackBarAction> {
   bool _haveTriggeredAction = false;

   void _handlePressed() {
     if (_haveTriggeredAction)
       return;
     setState(() {
       _haveTriggeredAction = true;
     });
     widget.onPressed();
     Scaffold.of(context).hideCurrentSnackBar(reason: SnackBarClosedReason.action);
   }

   @override
   Widget build(BuildContext context) {
     return FlatButton(
       onPressed: _haveTriggeredAction ? null : _handlePressed,
       child: Text(widget.label),
       textColor: widget.textColor,
       disabledTextColor: widget.disabledTextColor,
     );
   }
 }

 /// A lightweight message with an optional action which briefly displays at the
 /// bottom of the screen.
 ///
 /// To display a snack bar, call `Scaffold.of(context).showSnackBar()`, passing
 /// an instance of [SnackBar] that describes the message.
 ///
 /// To control how long the [SnackBar] remains visible, specify a [duration].
 ///
 /// A SnackBar with an action will not time out when TalkBack or VoiceOver are
 /// enabled. This is controlled by [AccessibilityFeatures.accessibleNavigation].
 ///
 /// See also:
 ///
 ///  * [Scaffold.of], to obtain the current [ScaffoldState], which manages the
 ///    display and animation of snack bars.
 ///  * [ScaffoldState.showSnackBar], which displays a [SnackBar].
 ///  * [ScaffoldState.removeCurrentSnackBar], which abruptly hides the currently
 ///    displayed snack bar, if any, and allows the next to be displayed.
 ///  * [SnackBarAction], which is used to specify an [action] button to show
 ///    on the snack bar.
 ///  * <https://material.io/design/components/snackbars.html>
 class SnackBar extends StatelessWidget {
   /// Creates a snack bar.
   ///
   /// The [content] argument must be non-null.
   const SnackBar({
     Key key,
     @required this.content,
     this.backgroundColor,
     this.action,
     this.duration = _kSnackBarDisplayDuration,
     this.animation,
   }) : assert(content != null),
        assert(duration != null),
        super(key: key);

   /// The primary content of the snack bar.
   ///
   /// Typically a [Text] widget.
   final Widget content;

   /// The Snackbar's background color. By default the color is dark grey.
   final Color backgroundColor;

   /// (optional) An action that the user can take based on the snack bar.
   ///
   /// For example, the snack bar might let the user undo the operation that
   /// prompted the snackbar. Snack bars can have at most one action.
   ///
   /// The action should not be "dismiss" or "cancel".
   final SnackBarAction action;

   /// The amount of time the snack bar should be displayed.
   ///
   /// Defaults to 4.0s.
   ///
   /// See also:
   ///
   ///  * [ScaffoldState.removeCurrentSnackBar], which abruptly hides the
   ///    currently displayed snack bar, if any, and allows the next to be
   ///    displayed.
   ///  * <https://material.io/design/components/snackbars.html>
   final Duration duration;

   /// The animation driving the entrance and exit of the snack bar.
   final Animation<double> animation;

   @override
   Widget build(BuildContext context) {
     final MediaQueryData mediaQueryData = MediaQuery.of(context);
     assert(animation != null);
     final ThemeData theme = Theme.of(context);
     final ThemeData darkTheme = ThemeData(
       brightness: Brightness.dark,
       accentColor: theme.accentColor,
       accentColorBrightness: theme.accentColorBrightness,
     );
     final List<Widget> children = <Widget>[
       const SizedBox(width: _kSnackBarPadding),
       Expanded(
         child: Container(
           padding: const EdgeInsets.symmetric(vertical: _kSingleLineVerticalPadding),
           child: DefaultTextStyle(
             style: darkTheme.textTheme.subhead,
             child: content,
           ),
         ),
       ),
     ];
     if (action != null) {
       children.add(ButtonTheme.bar(
         padding: const EdgeInsets.symmetric(horizontal: _kSnackBarPadding),
         textTheme: ButtonTextTheme.accent,
         child: action,
       ));
     } else {
       children.add(const SizedBox(width: _kSnackBarPadding));
     }
     final CurvedAnimation heightAnimation = CurvedAnimation(parent: animation, curve: _snackBarHeightCurve);
     final CurvedAnimation fadeAnimation = CurvedAnimation(parent: animation, curve: _snackBarFadeCurve, reverseCurve: const Threshold(0.0));
     Widget snackbar = SafeArea(
       top: false,
       child: Row(
         children: children,
         crossAxisAlignment: CrossAxisAlignment.center,
       ),
     );
     snackbar = Semantics(
       container: true,
       liveRegion: true,
       onDismiss: () {
         Scaffold.of(context).removeCurrentSnackBar(reason: SnackBarClosedReason.dismiss);
       },
       child: Dismissible(
         key: const Key('dismissible'),
         direction: DismissDirection.down,
         resizeDuration: null,
         onDismissed: (DismissDirection direction) {
           Scaffold.of(context).removeCurrentSnackBar(reason: SnackBarClosedReason.swipe);
         },
         child: Material(
           elevation: 6.0,
           color: backgroundColor ?? _kSnackBackground,
           child: Theme(
             data: darkTheme,
             child: mediaQueryData.accessibleNavigation ? snackbar : FadeTransition(
               opacity: fadeAnimation,
               child: snackbar,
             ),
           ),
         ),
       ),
     );
     return ClipRect(
       child: mediaQueryData.accessibleNavigation ? snackbar : AnimatedBuilder(
         animation: heightAnimation,
         builder: (BuildContext context, Widget child) {
           return Align(
             alignment: AlignmentDirectional.topStart,
             heightFactor: heightAnimation.value,
             child: child,
           );
         },
         child: snackbar,
       ),
     );
   }

   // API for Scaffold.addSnackBar():

   /// Creates an animation controller useful for driving a snack bar's entrance and exit animation.
   static AnimationController createAnimationController({ @required TickerProvider vsync }) {
     return AnimationController(
       duration: _kSnackBarTransitionDuration,
       debugLabel: 'SnackBar',
       vsync: vsync,
     );
   }

   /// Creates a copy of this snack bar but with the animation replaced with the given animation.
   ///
   /// If the original snack bar lacks a key, the newly created snack bar will
   /// use the given fallback key.
   SnackBar withAnimation(Animation<double> newAnimation, { Key fallbackKey }) {
     return SnackBar(
       key: key ?? fallbackKey,
       content: content,
       backgroundColor: backgroundColor,
       action: action,
       duration: duration,
       animation: newAnimation,
     );
   }
 }
	// 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 'package:flutter/rendering.dart';
	import 'package:flutter/widgets.dart';

	import 'button_theme.dart';
	import 'flat_button.dart';
	import 'material.dart';
	import 'scaffold.dart';
	import 'theme.dart';
	import 'theme_data.dart';

	const double _kSnackBarPadding = 24.0;
	const double _kSingleLineVerticalPadding = 14.0;
	const Color _kSnackBackground = Color(0xFF323232);

	// TODO(ianh): We should check if the given text and actions are going to fit on
	// one line or not, and if they are, use the single-line layout, and if not, use
	// the multiline layout. See link above.

	// TODO(ianh): Implement the Tablet version of snackbar if we're "on a tablet".

	const Duration _kSnackBarTransitionDuration = Duration(milliseconds: 250);
	const Duration _kSnackBarDisplayDuration = Duration(milliseconds: 4000);
	const Curve _snackBarHeightCurve = Curves.fastOutSlowIn;
	const Curve _snackBarFadeCurve = Interval(0.72, 1.0, curve: Curves.fastOutSlowIn);

	/// Specify how a [SnackBar] was closed.
	///
	/// The [ScaffoldState.showSnackBar] function returns a
	/// [ScaffoldFeatureController]. The value of the controller's closed property
	/// is a Future that resolves to a SnackBarClosedReason. Applications that need
	/// to know how a snackbar was closed can use this value.
	///
	/// Example:
	///
	/// ```dart
	/// Scaffold.of(context).showSnackBar(
	/// SnackBar( ... )
	/// ).closed.then((SnackBarClosedReason reason) {
	/// ...
	/// });
	/// ```
	enum SnackBarClosedReason {
	/// The snack bar was closed after the user tapped a [SnackBarAction].
	action,

	/// The snack bar was closed through a [SemanticAction.dismiss].
	dismiss,

	/// The snack bar was closed by a user's swipe.
	swipe,

	/// The snack bar was closed by the [ScaffoldFeatureController] close callback
	/// or by calling [ScaffoldState.hideCurrentSnackBar] directly.
	hide,

	/// The snack bar was closed by an call to [ScaffoldState.removeCurrentSnackBar].
	remove,

	/// The snack bar was closed because its timer expired.
	timeout,
	}

	/// A button for a [SnackBar], known as an "action".
	///
	/// Snack bar actions are always enabled. If you want to disable a snack bar
	/// action, simply don't include it in the snack bar.
	///
	/// Snack bar actions can only be pressed once. Subsequent presses are ignored.
	///
	/// See also:
	///
	/// * [SnackBar]
	/// * <https://material.io/design/components/snackbars.html>
	class SnackBarAction extends StatefulWidget {
	/// Creates an action for a [SnackBar].
	///
	/// The [label] and [onPressed] arguments must be non-null.
	const SnackBarAction({
	Key key,
	this.textColor,
	this.disabledTextColor,
	@required this.label,
	@required this.onPressed,
	}) : assert(label != null),
	assert(onPressed != null),
	super(key: key);

	/// The button label color. If not provided, defaults to [accentColor].
	final Color textColor;

	/// The button disabled label color. This color is shown after the
	/// [snackBarAction] is dismissed.
	final Color disabledTextColor;

	/// The button label.
	final String label;

	/// The callback to be called when the button is pressed. Must not be null.
	///
	/// This callback will be called at most once each time this action is
	/// displayed in a [SnackBar].
	final VoidCallback onPressed;

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

	class _SnackBarActionState extends State<SnackBarAction> {
	bool _haveTriggeredAction = false;

	void _handlePressed() {
	if (_haveTriggeredAction)
	return;
	setState(() {
	_haveTriggeredAction = true;
	});
	widget.onPressed();
	Scaffold.of(context).hideCurrentSnackBar(reason: SnackBarClosedReason.action);
	}

	@override
	Widget build(BuildContext context) {
	return FlatButton(
	onPressed: _haveTriggeredAction ? null : _handlePressed,
	child: Text(widget.label),
	textColor: widget.textColor,
	disabledTextColor: widget.disabledTextColor,
	);
	}
	}

	/// A lightweight message with an optional action which briefly displays at the
	/// bottom of the screen.
	///
	/// To display a snack bar, call `Scaffold.of(context).showSnackBar()`, passing
	/// an instance of [SnackBar] that describes the message.
	///
	/// To control how long the [SnackBar] remains visible, specify a [duration].
	///
	/// A SnackBar with an action will not time out when TalkBack or VoiceOver are
	/// enabled. This is controlled by [AccessibilityFeatures.accessibleNavigation].
	///
	/// See also:
	///
	/// * [Scaffold.of], to obtain the current [ScaffoldState], which manages the
	/// display and animation of snack bars.
	/// * [ScaffoldState.showSnackBar], which displays a [SnackBar].
	/// * [ScaffoldState.removeCurrentSnackBar], which abruptly hides the currently
	/// displayed snack bar, if any, and allows the next to be displayed.
	/// * [SnackBarAction], which is used to specify an [action] button to show
	/// on the snack bar.
	/// * <https://material.io/design/components/snackbars.html>
	class SnackBar extends StatelessWidget {
	/// Creates a snack bar.
	///
	/// The [content] argument must be non-null.
	const SnackBar({
	Key key,
	@required this.content,
	this.backgroundColor,
	this.action,
	this.duration = _kSnackBarDisplayDuration,
	this.animation,
	}) : assert(content != null),
	assert(duration != null),
	super(key: key);

	/// The primary content of the snack bar.
	///
	/// Typically a [Text] widget.
	final Widget content;

	/// The Snackbar's background color. By default the color is dark grey.
	final Color backgroundColor;

	/// (optional) An action that the user can take based on the snack bar.
	///
	/// For example, the snack bar might let the user undo the operation that
	/// prompted the snackbar. Snack bars can have at most one action.
	///
	/// The action should not be "dismiss" or "cancel".
	final SnackBarAction action;

	/// The amount of time the snack bar should be displayed.
	///
	/// Defaults to 4.0s.
	///
	/// See also:
	///
	/// * [ScaffoldState.removeCurrentSnackBar], which abruptly hides the
	/// currently displayed snack bar, if any, and allows the next to be
	/// displayed.
	/// * <https://material.io/design/components/snackbars.html>
	final Duration duration;

	/// The animation driving the entrance and exit of the snack bar.
	final Animation<double> animation;

	@override
	Widget build(BuildContext context) {
	final MediaQueryData mediaQueryData = MediaQuery.of(context);
	assert(animation != null);
	final ThemeData theme = Theme.of(context);
	final ThemeData darkTheme = ThemeData(
	brightness: Brightness.dark,
	accentColor: theme.accentColor,
	accentColorBrightness: theme.accentColorBrightness,
	);
	final List<Widget> children = <Widget>[
	const SizedBox(width: _kSnackBarPadding),
	Expanded(
	child: Container(
	padding: const EdgeInsets.symmetric(vertical: _kSingleLineVerticalPadding),
	child: DefaultTextStyle(
	style: darkTheme.textTheme.subhead,
	child: content,
	),
	),
	),
	];
	if (action != null) {
	children.add(ButtonTheme.bar(
	padding: const EdgeInsets.symmetric(horizontal: _kSnackBarPadding),
	textTheme: ButtonTextTheme.accent,
	child: action,
	));
	} else {
	children.add(const SizedBox(width: _kSnackBarPadding));
	}
	final CurvedAnimation heightAnimation = CurvedAnimation(parent: animation, curve: _snackBarHeightCurve);
	final CurvedAnimation fadeAnimation = CurvedAnimation(parent: animation, curve: _snackBarFadeCurve, reverseCurve: const Threshold(0.0));
	Widget snackbar = SafeArea(
	top: false,
	child: Row(
	children: children,
	crossAxisAlignment: CrossAxisAlignment.center,
	),
	);
	snackbar = Semantics(
	container: true,
	liveRegion: true,
	onDismiss: () {
	Scaffold.of(context).removeCurrentSnackBar(reason: SnackBarClosedReason.dismiss);
	},
	child: Dismissible(
	key: const Key('dismissible'),
	direction: DismissDirection.down,
	resizeDuration: null,
	onDismissed: (DismissDirection direction) {
	Scaffold.of(context).removeCurrentSnackBar(reason: SnackBarClosedReason.swipe);
	},
	child: Material(
	elevation: 6.0,
	color: backgroundColor ?? _kSnackBackground,
	child: Theme(
	data: darkTheme,
	child: mediaQueryData.accessibleNavigation ? snackbar : FadeTransition(
	opacity: fadeAnimation,
	child: snackbar,
	),
	),
	),
	),
	);
	return ClipRect(
	child: mediaQueryData.accessibleNavigation ? snackbar : AnimatedBuilder(
	animation: heightAnimation,
	builder: (BuildContext context, Widget child) {
	return Align(
	alignment: AlignmentDirectional.topStart,
	heightFactor: heightAnimation.value,
	child: child,
	);
	},
	child: snackbar,
	),
	);
	}

	// API for Scaffold.addSnackBar():

	/// Creates an animation controller useful for driving a snack bar's entrance and exit animation.
	static AnimationController createAnimationController({ @required TickerProvider vsync }) {
	return AnimationController(
	duration: _kSnackBarTransitionDuration,
	debugLabel: 'SnackBar',
	vsync: vsync,
	);
	}

	/// Creates a copy of this snack bar but with the animation replaced with the given animation.
	///
	/// If the original snack bar lacks a key, the newly created snack bar will
	/// use the given fallback key.
	SnackBar withAnimation(Animation<double> newAnimation, { Key fallbackKey }) {
	return SnackBar(
	key: key ?? fallbackKey,
	content: content,
	backgroundColor: backgroundColor,
	action: action,
	duration: duration,
	animation: newAnimation,
	);
	}
	}