packages/flutter/lib/src/material/floating_action_button.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/painting.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

 import 'button.dart';
 import 'colors.dart';
 import 'floating_action_button_theme.dart';
 import 'scaffold.dart';
 import 'theme.dart';
 import 'theme_data.dart';
 import 'tooltip.dart';

 const BoxConstraints _kSizeConstraints = BoxConstraints.tightFor(
   width: 56.0,
   height: 56.0,
 );

 const BoxConstraints _kMiniSizeConstraints = BoxConstraints.tightFor(
   width: 40.0,
   height: 40.0,
 );

 const BoxConstraints _kExtendedSizeConstraints = BoxConstraints(
   minHeight: 48.0,
   maxHeight: 48.0,
 );

 class _DefaultHeroTag {
   const _DefaultHeroTag();
   @override
   String toString() => '<default FloatingActionButton tag>';
 }

 /// A material design floating action button.
 ///
 /// A floating action button is a circular icon button that hovers over content
 /// to promote a primary action in the application. Floating action buttons are
 /// most commonly used in the [Scaffold.floatingActionButton] field.
 ///
 /// {@youtube 560 315 https://www.youtube.com/watch?v=2uaoEDOgk_I}
 ///
 /// Use at most a single floating action button per screen. Floating action
 /// buttons should be used for positive actions such as "create", "share", or
 /// "navigate". (If more than one floating action button is used within a
 /// [Route], then make sure that each button has a unique [heroTag], otherwise
 /// an exception will be thrown.)
 ///
 /// If the [onPressed] callback is null, then the button will be disabled and
 /// will not react to touch. It is highly discouraged to disable a floating
 /// action button as there is no indication to the user that the button is
 /// disabled. Consider changing the [backgroundColor] if disabling the floating
 /// action button.
 ///
 /// {@tool dartpad --template=stateless_widget_material}
 /// This example shows how to display a [FloatingActionButton] in a
 /// [Scaffold], with a pink [backgroundColor] and a thumbs up [Icon].
 ///
 /// ![](https://flutter.github.io/assets-for-api-docs/assets/material/floating_action_button.png)
 ///
 /// ```dart
 /// Widget build(BuildContext context) {
 ///   return Scaffold(
 ///     appBar: AppBar(
 ///       title: const Text('Floating Action Button'),
 ///     ),
 ///     body: Center(
 ///       child: const Text('Press the button below!')
 ///     ),
 ///     floatingActionButton: FloatingActionButton(
 ///       onPressed: () {
 ///         // Add your onPressed code here!
 ///       },
 ///       child: Icon(Icons.navigation),
 ///       backgroundColor: Colors.green,
 ///     ),
 ///   );
 /// }
 /// ```
 /// {@end-tool}
 ///
 /// {@tool dartpad --template=stateless_widget_material}
 /// This example shows how to make an extended [FloatingActionButton] in a
 /// [Scaffold], with a  pink [backgroundColor], a thumbs up [Icon] and a
 /// [Text] label that reads "Approve".
 ///
 /// ![](https://flutter.github.io/assets-for-api-docs/assets/material/floating_action_button_label.png)
 ///
 /// ```dart
 /// Widget build(BuildContext context) {
 ///   return Scaffold(
 ///     appBar: AppBar(
 ///       title: const Text('Floating Action Button Label'),
 ///     ),
 ///     body: Center(
 ///       child: const Text('Press the button with a label below!'),
 ///     ),
 ///     floatingActionButton: FloatingActionButton.extended(
 ///       onPressed: () {
 ///         // Add your onPressed code here!
 ///       },
 ///       label: Text('Approve'),
 ///       icon: Icon(Icons.thumb_up),
 ///       backgroundColor: Colors.pink,
 ///     ),
 ///   );
 /// }
 /// ```
 /// {@end-tool}
 ///
 /// See also:
 ///
 ///  * [Scaffold], in which floating action buttons typically live.
 ///  * [RaisedButton], another kind of button that appears to float above the
 ///    content.
 ///  * <https://material.io/design/components/buttons-floating-action-button.html>
 class FloatingActionButton extends StatelessWidget {
   /// Creates a circular floating action button.
   ///
   /// The [mini] and [clipBehavior] arguments must not be null. Additionally,
   /// [elevation], [highlightElevation], and [disabledElevation] (if specified)
   /// must be non-negative.
   const FloatingActionButton({
     Key key,
     this.child,
     this.tooltip,
     this.foregroundColor,
     this.backgroundColor,
     this.focusColor,
     this.hoverColor,
     this.splashColor,
     this.heroTag = const _DefaultHeroTag(),
     this.elevation,
     this.focusElevation,
     this.hoverElevation,
     this.highlightElevation,
     this.disabledElevation,
     @required this.onPressed,
     this.mini = false,
     this.shape,
     this.clipBehavior = Clip.none,
     this.focusNode,
     this.autofocus = false,
     this.materialTapTargetSize,
     this.isExtended = false,
   }) : assert(elevation == null || elevation >= 0.0),
        assert(focusElevation == null || focusElevation >= 0.0),
        assert(hoverElevation == null || hoverElevation >= 0.0),
        assert(highlightElevation == null || highlightElevation >= 0.0),
        assert(disabledElevation == null || disabledElevation >= 0.0),
        assert(mini != null),
        assert(clipBehavior != null),
        assert(isExtended != null),
        assert(autofocus != null),
        _sizeConstraints = mini ? _kMiniSizeConstraints : _kSizeConstraints,
        super(key: key);

   /// Creates a wider [StadiumBorder]-shaped floating action button with
   /// an optional [icon] and a [label].
   ///
   /// The [label], [autofocus], and [clipBehavior] arguments must not be null.
   /// Additionally, [elevation], [highlightElevation], and [disabledElevation]
   /// (if specified) must be non-negative.
   FloatingActionButton.extended({
     Key key,
     this.tooltip,
     this.foregroundColor,
     this.backgroundColor,
     this.focusColor,
     this.hoverColor,
     this.heroTag = const _DefaultHeroTag(),
     this.elevation,
     this.focusElevation,
     this.hoverElevation,
     this.splashColor,
     this.highlightElevation,
     this.disabledElevation,
     @required this.onPressed,
     this.shape,
     this.isExtended = true,
     this.materialTapTargetSize,
     this.clipBehavior = Clip.none,
     this.focusNode,
     this.autofocus = false,
     Widget icon,
     @required Widget label,
   }) : assert(elevation == null || elevation >= 0.0),
        assert(focusElevation == null || focusElevation >= 0.0),
        assert(hoverElevation == null || hoverElevation >= 0.0),
        assert(highlightElevation == null || highlightElevation >= 0.0),
        assert(disabledElevation == null || disabledElevation >= 0.0),
        assert(isExtended != null),
        assert(clipBehavior != null),
        assert(autofocus != null),
        _sizeConstraints = _kExtendedSizeConstraints,
        mini = false,
        child = _ChildOverflowBox(
          child: Row(
            mainAxisSize: MainAxisSize.min,
            children: icon == null
              ? <Widget>[
                  const SizedBox(width: 20.0),
                  label,
                  const SizedBox(width: 20.0),
                ]
              : <Widget>[
                  const SizedBox(width: 16.0),
                  icon,
                  const SizedBox(width: 8.0),
                  label,
                  const SizedBox(width: 20.0),
                ],
          ),
        ),
        super(key: key);

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

   /// Text that describes the action that will occur when the button is pressed.
   ///
   /// This text is displayed when the user long-presses on the button and is
   /// used for accessibility.
   final String tooltip;

   /// The default foreground color for icons and text within the button.
   ///
   /// If this property is null, then the [Theme]'s
   /// [ThemeData.floatingActionButtonTheme.foregroundColor] is used. If that
   /// property is also null, then the [Theme]'s
   /// [ThemeData.colorScheme.onSecondary] color is used.
   ///
   /// Although the color of theme's `accentIconTheme` currently provides a
   /// default that supercedes the `onSecondary` color, this dependency
   /// has been deprecated:  https://flutter.dev/go/remove-fab-accent-theme-dependency.
   /// It will be removed in the future.
   final Color foregroundColor;

   /// The button's background color.
   ///
   /// If this property is null, then the [Theme]'s
   /// [ThemeData.floatingActionButtonTheme.backgroundColor] is used. If that
   /// property is also null, then the [Theme]'s
   /// [ThemeData.colorScheme.secondary] color is used.
   final Color backgroundColor;

   /// The color to use for filling the button when the button has input focus.
   ///
   /// Defaults to [ThemeData.focusColor] for the current theme.
   final Color focusColor;

   /// The color to use for filling the button when the button has a pointer
   /// hovering over it.
   ///
   /// Defaults to [ThemeData.hoverColor] for the current theme.
   final Color hoverColor;

   /// The splash color for this [FloatingActionButton]'s [InkWell].
   ///
   /// If null, [FloatingActionButtonThemeData.splashColor] is used, if that is
   /// null, [ThemeData.splashColor] is used.
   final Color splashColor;

   /// The tag to apply to the button's [Hero] widget.
   ///
   /// Defaults to a tag that matches other floating action buttons.
   ///
   /// Set this to null explicitly if you don't want the floating action button to
   /// have a hero tag.
   ///
   /// If this is not explicitly set, then there can only be one
   /// [FloatingActionButton] per route (that is, per screen), since otherwise
   /// there would be a tag conflict (multiple heroes on one route can't have the
   /// same tag). The material design specification recommends only using one
   /// floating action button per screen.
   final Object heroTag;

   /// The callback that is called when the button is tapped or otherwise activated.
   ///
   /// If this is set to null, the button will be disabled.
   final VoidCallback onPressed;

   /// The z-coordinate at which to place this button relative to its parent.
   ///
   /// This controls the size of the shadow below the floating action button.
   ///
   /// Defaults to 6, the appropriate elevation for floating action buttons. The
   /// value is always non-negative.
   ///
   /// See also:
   ///
   ///  * [highlightElevation], the elevation when the button is pressed.
   ///  * [disabledElevation], the elevation when the button is disabled.
   final double elevation;

   /// The z-coordinate at which to place this button relative to its parent when
   /// the button has the input focus.
   ///
   /// This controls the size of the shadow below the floating action button.
   ///
   /// Defaults to 8, the appropriate elevation for floating action buttons
   /// while they have focus. The value is always non-negative.
   ///
   /// See also:
   ///
   ///  * [elevation], the default elevation.
   ///  * [highlightElevation], the elevation when the button is pressed.
   ///  * [disabledElevation], the elevation when the button is disabled.
   final double focusElevation;

   /// The z-coordinate at which to place this button relative to its parent when
   /// the button is enabled and has a pointer hovering over it.
   ///
   /// This controls the size of the shadow below the floating action button.
   ///
   /// Defaults to 8, the appropriate elevation for floating action buttons while
   /// they have a pointer hovering over them. The value is always non-negative.
   ///
   /// See also:
   ///
   ///  * [elevation], the default elevation.
   ///  * [highlightElevation], the elevation when the button is pressed.
   ///  * [disabledElevation], the elevation when the button is disabled.
   final double hoverElevation;

   /// The z-coordinate at which to place this button relative to its parent when
   /// the user is touching the button.
   ///
   /// This controls the size of the shadow below the floating action button.
   ///
   /// Defaults to 12, the appropriate elevation for floating action buttons
   /// while they are being touched. The value is always non-negative.
   ///
   /// See also:
   ///
   ///  * [elevation], the default elevation.
   final double highlightElevation;

   /// The z-coordinate at which to place this button when the button is disabled
   /// ([onPressed] is null).
   ///
   /// This controls the size of the shadow below the floating action button.
   ///
   /// Defaults to the same value as [elevation]. Setting this to zero makes the
   /// floating action button work similar to a [RaisedButton] but the titular
   /// "floating" effect is lost. The value is always non-negative.
   ///
   /// See also:
   ///
   ///  * [elevation], the default elevation.
   ///  * [highlightElevation], the elevation when the button is pressed.
   final double disabledElevation;

   /// Controls the size of this button.
   ///
   /// By default, floating action buttons are non-mini and have a height and
   /// width of 56.0 logical pixels. Mini floating action buttons have a height
   /// and width of 40.0 logical pixels with a layout width and height of 48.0
   /// logical pixels. (The extra 4 pixels of padding on each side are added as a
   /// result of the floating action button having [MaterialTapTargetSize.padded]
   /// set on the underlying [RawMaterialButton.materialTapTargetSize].)
   final bool mini;

   /// The shape of the button's [Material].
   ///
   /// The button's highlight and splash are clipped to this shape. If the
   /// button has an elevation, then its drop shadow is defined by this
   /// shape as well.
   final ShapeBorder shape;

   /// {@macro flutter.widgets.Clip}
   ///
   /// Defaults to [Clip.none], and must not be null.
   final Clip clipBehavior;

   /// True if this is an "extended" floating action button.
   ///
   /// Typically [extended] buttons have a [StadiumBorder] [shape]
   /// and have been created with the [FloatingActionButton.extended]
   /// constructor.
   ///
   /// The [Scaffold] animates the appearance of ordinary floating
   /// action buttons with scale and rotation transitions. Extended
   /// floating action buttons are scaled and faded in.
   final bool isExtended;

   /// {@macro flutter.widgets.Focus.focusNode}
   final FocusNode focusNode;

   /// {@macro flutter.widgets.Focus.autofocus}
   final bool autofocus;

   /// Configures the minimum size of the tap target.
   ///
   /// Defaults to [ThemeData.materialTapTargetSize].
   ///
   /// See also:
   ///
   ///  * [MaterialTapTargetSize], for a description of how this affects tap targets.
   final MaterialTapTargetSize materialTapTargetSize;

   final BoxConstraints _sizeConstraints;

   static const double _defaultElevation = 6;
   // TODO(gspencer): verify focus and hover elevation values are correct
   // according to spec.
   static const double _defaultFocusElevation = 8;
   static const double _defaultHoverElevation = 10;
   static const double _defaultHighlightElevation = 12;
   static const ShapeBorder _defaultShape = CircleBorder();
   static const ShapeBorder _defaultExtendedShape = StadiumBorder();

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

     // Applications should no longer use accentIconTheme's color to configure
     // the foreground color of floating action buttons. For more information, see
     // https://flutter.dev/go/remove-fab-accent-theme-dependency.
     if (this.foregroundColor == null && floatingActionButtonTheme.foregroundColor == null) {
       final bool accentIsDark = theme.accentColorBrightness == Brightness.dark;
       final Color defaultAccentIconThemeColor = accentIsDark ? Colors.white : Colors.black;
       if (theme.accentIconTheme.color != defaultAccentIconThemeColor) {
         debugPrint(
           'Warning: '
           'The support for configuring the foreground color of '
           'FloatingActionButtons using ThemeData.accentIconTheme '
           'has been deprecated. Please use ThemeData.floatingActionButtonTheme '
           'instead. See '
           'https://flutter.dev/go/remove-fab-accent-theme-dependency. '
           'This feature was deprecated after v1.13.2.'
         );
       }
     }

     final Color foregroundColor = this.foregroundColor
       ?? floatingActionButtonTheme.foregroundColor
       ?? theme.colorScheme.onSecondary;
     final Color backgroundColor = this.backgroundColor
       ?? floatingActionButtonTheme.backgroundColor
       ?? theme.colorScheme.secondary;
     final Color focusColor = this.focusColor
       ?? floatingActionButtonTheme.focusColor
       ?? theme.focusColor;
     final Color hoverColor = this.hoverColor
       ?? floatingActionButtonTheme.hoverColor
       ?? theme.hoverColor;
     final Color splashColor = this.splashColor
       ?? floatingActionButtonTheme.splashColor
       ?? theme.splashColor;
     final double elevation = this.elevation
       ?? floatingActionButtonTheme.elevation
       ?? _defaultElevation;
     final double focusElevation = this.focusElevation
       ?? floatingActionButtonTheme.focusElevation
       ?? _defaultFocusElevation;
     final double hoverElevation = this.hoverElevation
       ?? floatingActionButtonTheme.hoverElevation
       ?? _defaultHoverElevation;
     final double disabledElevation = this.disabledElevation
       ?? floatingActionButtonTheme.disabledElevation
       ?? elevation;
     final double highlightElevation = this.highlightElevation
       ?? floatingActionButtonTheme.highlightElevation
       ?? _defaultHighlightElevation;
     final MaterialTapTargetSize materialTapTargetSize = this.materialTapTargetSize
       ?? theme.materialTapTargetSize;
     final TextStyle textStyle = theme.textTheme.button.copyWith(
       color: foregroundColor,
       letterSpacing: 1.2,
     );
     final ShapeBorder shape = this.shape
       ?? floatingActionButtonTheme.shape
       ?? (isExtended ? _defaultExtendedShape : _defaultShape);

     Widget result = RawMaterialButton(
       onPressed: onPressed,
       elevation: elevation,
       focusElevation: focusElevation,
       hoverElevation: hoverElevation,
       highlightElevation: highlightElevation,
       disabledElevation: disabledElevation,
       constraints: _sizeConstraints,
       materialTapTargetSize: materialTapTargetSize,
       fillColor: backgroundColor,
       focusColor: focusColor,
       hoverColor: hoverColor,
       splashColor: splashColor,
       textStyle: textStyle,
       shape: shape,
       clipBehavior: clipBehavior,
       focusNode: focusNode,
       autofocus: autofocus,
       child: child,
     );

     if (tooltip != null) {
       result = Tooltip(
         message: tooltip,
         child: result,
       );
     }

     if (heroTag != null) {
       result = Hero(
         tag: heroTag,
         child: result,
       );
     }

     return MergeSemantics(child: result);
   }

   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     properties.add(ObjectFlagProperty<VoidCallback>('onPressed', onPressed, ifNull: 'disabled'));
     properties.add(StringProperty('tooltip', tooltip, defaultValue: null));
     properties.add(ColorProperty('foregroundColor', foregroundColor, defaultValue: null));
     properties.add(ColorProperty('backgroundColor', backgroundColor, defaultValue: null));
     properties.add(ColorProperty('focusColor', focusColor, defaultValue: null));
     properties.add(ColorProperty('hoverColor', hoverColor, defaultValue: null));
     properties.add(ColorProperty('splashColor', splashColor, defaultValue: null));
     properties.add(ObjectFlagProperty<Object>('heroTag', heroTag, ifPresent: 'hero'));
     properties.add(DoubleProperty('elevation', elevation, defaultValue: null));
     properties.add(DoubleProperty('focusElevation', focusElevation, defaultValue: null));
     properties.add(DoubleProperty('hoverElevation', hoverElevation, defaultValue: null));
     properties.add(DoubleProperty('highlightElevation', highlightElevation, defaultValue: null));
     properties.add(DoubleProperty('disabledElevation', disabledElevation, defaultValue: null));
     properties.add(DiagnosticsProperty<ShapeBorder>('shape', shape, defaultValue: null));
     properties.add(DiagnosticsProperty<FocusNode>('focusNode', focusNode, defaultValue: null));
     properties.add(FlagProperty('isExtended', value: isExtended, ifTrue: 'extended'));
     properties.add(DiagnosticsProperty<MaterialTapTargetSize>('materialTapTargetSize', materialTapTargetSize, defaultValue: null));
   }
 }

 // This widget's size matches its child's size unless its constraints
 // force it to be larger or smaller. The child is centered.
 //
 // Used to encapsulate extended FABs whose size is fixed, using Row
 // and MainAxisSize.min, to be as wide as their label and icon.
 class _ChildOverflowBox extends SingleChildRenderObjectWidget {
   const _ChildOverflowBox({
     Key key,
     Widget child,
   }) : super(key: key, child: child);

   @override
   _RenderChildOverflowBox createRenderObject(BuildContext context) {
     return _RenderChildOverflowBox(
       textDirection: Directionality.of(context),
     );
   }

   @override
   void updateRenderObject(BuildContext context, _RenderChildOverflowBox renderObject) {
     renderObject.textDirection = Directionality.of(context);
   }
 }

 class _RenderChildOverflowBox extends RenderAligningShiftedBox {
   _RenderChildOverflowBox({
     RenderBox child,
     TextDirection textDirection,
   }) : super(child: child, alignment: Alignment.center, textDirection: textDirection);

   @override
   double computeMinIntrinsicWidth(double height) => 0.0;

   @override
   double computeMinIntrinsicHeight(double width) => 0.0;

   @override
   void performLayout() {
     final BoxConstraints constraints = this.constraints;
     if (child != null) {
       child.layout(const BoxConstraints(), parentUsesSize: true);
       size = Size(
         math.max(constraints.minWidth, math.min(constraints.maxWidth, child.size.width)),
         math.max(constraints.minHeight, math.min(constraints.maxHeight, child.size.height)),
       );
       alignChild();
     } else {
       size = constraints.biggest;
     }
   }
 }
	// 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/painting.dart';
	import 'package:flutter/rendering.dart';
	import 'package:flutter/widgets.dart';

	import 'button.dart';
	import 'colors.dart';
	import 'floating_action_button_theme.dart';
	import 'scaffold.dart';
	import 'theme.dart';
	import 'theme_data.dart';
	import 'tooltip.dart';

	const BoxConstraints _kSizeConstraints = BoxConstraints.tightFor(
	width: 56.0,
	height: 56.0,
	);

	const BoxConstraints _kMiniSizeConstraints = BoxConstraints.tightFor(
	width: 40.0,
	height: 40.0,
	);

	const BoxConstraints _kExtendedSizeConstraints = BoxConstraints(
	minHeight: 48.0,
	maxHeight: 48.0,
	);

	class _DefaultHeroTag {
	const _DefaultHeroTag();
	@override
	String toString() => '<default FloatingActionButton tag>';
	}

	/// A material design floating action button.
	///
	/// A floating action button is a circular icon button that hovers over content
	/// to promote a primary action in the application. Floating action buttons are
	/// most commonly used in the [Scaffold.floatingActionButton] field.
	///
	/// {@youtube 560 315 https://www.youtube.com/watch?v=2uaoEDOgk_I}
	///
	/// Use at most a single floating action button per screen. Floating action
	/// buttons should be used for positive actions such as "create", "share", or
	/// "navigate". (If more than one floating action button is used within a
	/// [Route], then make sure that each button has a unique [heroTag], otherwise
	/// an exception will be thrown.)
	///
	/// If the [onPressed] callback is null, then the button will be disabled and
	/// will not react to touch. It is highly discouraged to disable a floating
	/// action button as there is no indication to the user that the button is
	/// disabled. Consider changing the [backgroundColor] if disabling the floating
	/// action button.
	///
	/// {@tool dartpad --template=stateless_widget_material}
	/// This example shows how to display a [FloatingActionButton] in a
	/// [Scaffold], with a pink [backgroundColor] and a thumbs up [Icon].
	///
	/// ![](https://flutter.github.io/assets-for-api-docs/assets/material/floating_action_button.png)
	///
	/// ```dart
	/// Widget build(BuildContext context) {
	/// return Scaffold(
	/// appBar: AppBar(
	/// title: const Text('Floating Action Button'),
	/// ),
	/// body: Center(
	/// child: const Text('Press the button below!')
	/// ),
	/// floatingActionButton: FloatingActionButton(
	/// onPressed: () {
	/// // Add your onPressed code here!
	/// },
	/// child: Icon(Icons.navigation),
	/// backgroundColor: Colors.green,
	/// ),
	/// );
	/// }
	/// ```
	/// {@end-tool}
	///
	/// {@tool dartpad --template=stateless_widget_material}
	/// This example shows how to make an extended [FloatingActionButton] in a
	/// [Scaffold], with a pink [backgroundColor], a thumbs up [Icon] and a
	/// [Text] label that reads "Approve".
	///
	/// ![](https://flutter.github.io/assets-for-api-docs/assets/material/floating_action_button_label.png)
	///
	/// ```dart
	/// Widget build(BuildContext context) {
	/// return Scaffold(
	/// appBar: AppBar(
	/// title: const Text('Floating Action Button Label'),
	/// ),
	/// body: Center(
	/// child: const Text('Press the button with a label below!'),
	/// ),
	/// floatingActionButton: FloatingActionButton.extended(
	/// onPressed: () {
	/// // Add your onPressed code here!
	/// },
	/// label: Text('Approve'),
	/// icon: Icon(Icons.thumb_up),
	/// backgroundColor: Colors.pink,
	/// ),
	/// );
	/// }
	/// ```
	/// {@end-tool}
	///
	/// See also:
	///
	/// * [Scaffold], in which floating action buttons typically live.
	/// * [RaisedButton], another kind of button that appears to float above the
	/// content.
	/// * <https://material.io/design/components/buttons-floating-action-button.html>
	class FloatingActionButton extends StatelessWidget {
	/// Creates a circular floating action button.
	///
	/// The [mini] and [clipBehavior] arguments must not be null. Additionally,
	/// [elevation], [highlightElevation], and [disabledElevation] (if specified)
	/// must be non-negative.
	const FloatingActionButton({
	Key key,
	this.child,
	this.tooltip,
	this.foregroundColor,
	this.backgroundColor,
	this.focusColor,
	this.hoverColor,
	this.splashColor,
	this.heroTag = const _DefaultHeroTag(),
	this.elevation,
	this.focusElevation,
	this.hoverElevation,
	this.highlightElevation,
	this.disabledElevation,
	@required this.onPressed,
	this.mini = false,
	this.shape,
	this.clipBehavior = Clip.none,
	this.focusNode,
	this.autofocus = false,
	this.materialTapTargetSize,
	this.isExtended = false,
	}) : assert(elevation == null \|\| elevation >= 0.0),
	assert(focusElevation == null \|\| focusElevation >= 0.0),
	assert(hoverElevation == null \|\| hoverElevation >= 0.0),
	assert(highlightElevation == null \|\| highlightElevation >= 0.0),
	assert(disabledElevation == null \|\| disabledElevation >= 0.0),
	assert(mini != null),
	assert(clipBehavior != null),
	assert(isExtended != null),
	assert(autofocus != null),
	_sizeConstraints = mini ? _kMiniSizeConstraints : _kSizeConstraints,
	super(key: key);

	/// Creates a wider [StadiumBorder]-shaped floating action button with
	/// an optional [icon] and a [label].
	///
	/// The [label], [autofocus], and [clipBehavior] arguments must not be null.
	/// Additionally, [elevation], [highlightElevation], and [disabledElevation]
	/// (if specified) must be non-negative.
	FloatingActionButton.extended({
	Key key,
	this.tooltip,
	this.foregroundColor,
	this.backgroundColor,
	this.focusColor,
	this.hoverColor,
	this.heroTag = const _DefaultHeroTag(),
	this.elevation,
	this.focusElevation,
	this.hoverElevation,
	this.splashColor,
	this.highlightElevation,
	this.disabledElevation,
	@required this.onPressed,
	this.shape,
	this.isExtended = true,
	this.materialTapTargetSize,
	this.clipBehavior = Clip.none,
	this.focusNode,
	this.autofocus = false,
	Widget icon,
	@required Widget label,
	}) : assert(elevation == null \|\| elevation >= 0.0),
	assert(focusElevation == null \|\| focusElevation >= 0.0),
	assert(hoverElevation == null \|\| hoverElevation >= 0.0),
	assert(highlightElevation == null \|\| highlightElevation >= 0.0),
	assert(disabledElevation == null \|\| disabledElevation >= 0.0),
	assert(isExtended != null),
	assert(clipBehavior != null),
	assert(autofocus != null),
	_sizeConstraints = _kExtendedSizeConstraints,
	mini = false,
	child = _ChildOverflowBox(
	child: Row(
	mainAxisSize: MainAxisSize.min,
	children: icon == null
	? <Widget>[
	const SizedBox(width: 20.0),
	label,
	const SizedBox(width: 20.0),
	]
	: <Widget>[
	const SizedBox(width: 16.0),
	icon,
	const SizedBox(width: 8.0),
	label,
	const SizedBox(width: 20.0),
	],
	),
	),
	super(key: key);

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

	/// Text that describes the action that will occur when the button is pressed.
	///
	/// This text is displayed when the user long-presses on the button and is
	/// used for accessibility.
	final String tooltip;

	/// The default foreground color for icons and text within the button.
	///
	/// If this property is null, then the [Theme]'s
	/// [ThemeData.floatingActionButtonTheme.foregroundColor] is used. If that
	/// property is also null, then the [Theme]'s
	/// [ThemeData.colorScheme.onSecondary] color is used.
	///
	/// Although the color of theme's `accentIconTheme` currently provides a
	/// default that supercedes the `onSecondary` color, this dependency
	/// has been deprecated: https://flutter.dev/go/remove-fab-accent-theme-dependency.
	/// It will be removed in the future.
	final Color foregroundColor;

	/// The button's background color.
	///
	/// If this property is null, then the [Theme]'s
	/// [ThemeData.floatingActionButtonTheme.backgroundColor] is used. If that
	/// property is also null, then the [Theme]'s
	/// [ThemeData.colorScheme.secondary] color is used.
	final Color backgroundColor;

	/// The color to use for filling the button when the button has input focus.
	///
	/// Defaults to [ThemeData.focusColor] for the current theme.
	final Color focusColor;

	/// The color to use for filling the button when the button has a pointer
	/// hovering over it.
	///
	/// Defaults to [ThemeData.hoverColor] for the current theme.
	final Color hoverColor;

	/// The splash color for this [FloatingActionButton]'s [InkWell].
	///
	/// If null, [FloatingActionButtonThemeData.splashColor] is used, if that is
	/// null, [ThemeData.splashColor] is used.
	final Color splashColor;

	/// The tag to apply to the button's [Hero] widget.
	///
	/// Defaults to a tag that matches other floating action buttons.
	///
	/// Set this to null explicitly if you don't want the floating action button to
	/// have a hero tag.
	///
	/// If this is not explicitly set, then there can only be one
	/// [FloatingActionButton] per route (that is, per screen), since otherwise
	/// there would be a tag conflict (multiple heroes on one route can't have the
	/// same tag). The material design specification recommends only using one
	/// floating action button per screen.
	final Object heroTag;

	/// The callback that is called when the button is tapped or otherwise activated.
	///
	/// If this is set to null, the button will be disabled.
	final VoidCallback onPressed;

	/// The z-coordinate at which to place this button relative to its parent.
	///
	/// This controls the size of the shadow below the floating action button.
	///
	/// Defaults to 6, the appropriate elevation for floating action buttons. The
	/// value is always non-negative.
	///
	/// See also:
	///
	/// * [highlightElevation], the elevation when the button is pressed.
	/// * [disabledElevation], the elevation when the button is disabled.
	final double elevation;

	/// The z-coordinate at which to place this button relative to its parent when
	/// the button has the input focus.
	///
	/// This controls the size of the shadow below the floating action button.
	///
	/// Defaults to 8, the appropriate elevation for floating action buttons
	/// while they have focus. The value is always non-negative.
	///
	/// See also:
	///
	/// * [elevation], the default elevation.
	/// * [highlightElevation], the elevation when the button is pressed.
	/// * [disabledElevation], the elevation when the button is disabled.
	final double focusElevation;

	/// The z-coordinate at which to place this button relative to its parent when
	/// the button is enabled and has a pointer hovering over it.
	///
	/// This controls the size of the shadow below the floating action button.
	///
	/// Defaults to 8, the appropriate elevation for floating action buttons while
	/// they have a pointer hovering over them. The value is always non-negative.
	///
	/// See also:
	///
	/// * [elevation], the default elevation.
	/// * [highlightElevation], the elevation when the button is pressed.
	/// * [disabledElevation], the elevation when the button is disabled.
	final double hoverElevation;

	/// The z-coordinate at which to place this button relative to its parent when
	/// the user is touching the button.
	///
	/// This controls the size of the shadow below the floating action button.
	///
	/// Defaults to 12, the appropriate elevation for floating action buttons
	/// while they are being touched. The value is always non-negative.
	///
	/// See also:
	///
	/// * [elevation], the default elevation.
	final double highlightElevation;

	/// The z-coordinate at which to place this button when the button is disabled
	/// ([onPressed] is null).
	///
	/// This controls the size of the shadow below the floating action button.
	///
	/// Defaults to the same value as [elevation]. Setting this to zero makes the
	/// floating action button work similar to a [RaisedButton] but the titular
	/// "floating" effect is lost. The value is always non-negative.
	///
	/// See also:
	///
	/// * [elevation], the default elevation.
	/// * [highlightElevation], the elevation when the button is pressed.
	final double disabledElevation;

	/// Controls the size of this button.
	///
	/// By default, floating action buttons are non-mini and have a height and
	/// width of 56.0 logical pixels. Mini floating action buttons have a height
	/// and width of 40.0 logical pixels with a layout width and height of 48.0
	/// logical pixels. (The extra 4 pixels of padding on each side are added as a
	/// result of the floating action button having [MaterialTapTargetSize.padded]
	/// set on the underlying [RawMaterialButton.materialTapTargetSize].)
	final bool mini;

	/// The shape of the button's [Material].
	///
	/// The button's highlight and splash are clipped to this shape. If the
	/// button has an elevation, then its drop shadow is defined by this
	/// shape as well.
	final ShapeBorder shape;

	/// {@macro flutter.widgets.Clip}
	///
	/// Defaults to [Clip.none], and must not be null.
	final Clip clipBehavior;

	/// True if this is an "extended" floating action button.
	///
	/// Typically [extended] buttons have a [StadiumBorder] [shape]
	/// and have been created with the [FloatingActionButton.extended]
	/// constructor.
	///
	/// The [Scaffold] animates the appearance of ordinary floating
	/// action buttons with scale and rotation transitions. Extended
	/// floating action buttons are scaled and faded in.
	final bool isExtended;

	/// {@macro flutter.widgets.Focus.focusNode}
	final FocusNode focusNode;

	/// {@macro flutter.widgets.Focus.autofocus}
	final bool autofocus;

	/// Configures the minimum size of the tap target.
	///
	/// Defaults to [ThemeData.materialTapTargetSize].
	///
	/// See also:
	///
	/// * [MaterialTapTargetSize], for a description of how this affects tap targets.
	final MaterialTapTargetSize materialTapTargetSize;

	final BoxConstraints _sizeConstraints;

	static const double _defaultElevation = 6;
	// TODO(gspencer): verify focus and hover elevation values are correct
	// according to spec.
	static const double _defaultFocusElevation = 8;
	static const double _defaultHoverElevation = 10;
	static const double _defaultHighlightElevation = 12;
	static const ShapeBorder _defaultShape = CircleBorder();
	static const ShapeBorder _defaultExtendedShape = StadiumBorder();

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

	// Applications should no longer use accentIconTheme's color to configure
	// the foreground color of floating action buttons. For more information, see
	// https://flutter.dev/go/remove-fab-accent-theme-dependency.
	if (this.foregroundColor == null && floatingActionButtonTheme.foregroundColor == null) {
	final bool accentIsDark = theme.accentColorBrightness == Brightness.dark;
	final Color defaultAccentIconThemeColor = accentIsDark ? Colors.white : Colors.black;
	if (theme.accentIconTheme.color != defaultAccentIconThemeColor) {
	debugPrint(
	'Warning: '
	'The support for configuring the foreground color of '
	'FloatingActionButtons using ThemeData.accentIconTheme '
	'has been deprecated. Please use ThemeData.floatingActionButtonTheme '
	'instead. See '
	'https://flutter.dev/go/remove-fab-accent-theme-dependency. '
	'This feature was deprecated after v1.13.2.'
	);
	}
	}

	final Color foregroundColor = this.foregroundColor
	?? floatingActionButtonTheme.foregroundColor
	?? theme.colorScheme.onSecondary;
	final Color backgroundColor = this.backgroundColor
	?? floatingActionButtonTheme.backgroundColor
	?? theme.colorScheme.secondary;
	final Color focusColor = this.focusColor
	?? floatingActionButtonTheme.focusColor
	?? theme.focusColor;
	final Color hoverColor = this.hoverColor
	?? floatingActionButtonTheme.hoverColor
	?? theme.hoverColor;
	final Color splashColor = this.splashColor
	?? floatingActionButtonTheme.splashColor
	?? theme.splashColor;
	final double elevation = this.elevation
	?? floatingActionButtonTheme.elevation
	?? _defaultElevation;
	final double focusElevation = this.focusElevation
	?? floatingActionButtonTheme.focusElevation
	?? _defaultFocusElevation;
	final double hoverElevation = this.hoverElevation
	?? floatingActionButtonTheme.hoverElevation
	?? _defaultHoverElevation;
	final double disabledElevation = this.disabledElevation
	?? floatingActionButtonTheme.disabledElevation
	?? elevation;
	final double highlightElevation = this.highlightElevation
	?? floatingActionButtonTheme.highlightElevation
	?? _defaultHighlightElevation;
	final MaterialTapTargetSize materialTapTargetSize = this.materialTapTargetSize
	?? theme.materialTapTargetSize;
	final TextStyle textStyle = theme.textTheme.button.copyWith(
	color: foregroundColor,
	letterSpacing: 1.2,
	);
	final ShapeBorder shape = this.shape
	?? floatingActionButtonTheme.shape
	?? (isExtended ? _defaultExtendedShape : _defaultShape);

	Widget result = RawMaterialButton(
	onPressed: onPressed,
	elevation: elevation,
	focusElevation: focusElevation,
	hoverElevation: hoverElevation,
	highlightElevation: highlightElevation,
	disabledElevation: disabledElevation,
	constraints: _sizeConstraints,
	materialTapTargetSize: materialTapTargetSize,
	fillColor: backgroundColor,
	focusColor: focusColor,
	hoverColor: hoverColor,
	splashColor: splashColor,
	textStyle: textStyle,
	shape: shape,
	clipBehavior: clipBehavior,
	focusNode: focusNode,
	autofocus: autofocus,
	child: child,
	);

	if (tooltip != null) {
	result = Tooltip(
	message: tooltip,
	child: result,
	);
	}

	if (heroTag != null) {
	result = Hero(
	tag: heroTag,
	child: result,
	);
	}

	return MergeSemantics(child: result);
	}

	@override
	void debugFillProperties(DiagnosticPropertiesBuilder properties) {
	super.debugFillProperties(properties);
	properties.add(ObjectFlagProperty<VoidCallback>('onPressed', onPressed, ifNull: 'disabled'));
	properties.add(StringProperty('tooltip', tooltip, defaultValue: null));
	properties.add(ColorProperty('foregroundColor', foregroundColor, defaultValue: null));
	properties.add(ColorProperty('backgroundColor', backgroundColor, defaultValue: null));
	properties.add(ColorProperty('focusColor', focusColor, defaultValue: null));
	properties.add(ColorProperty('hoverColor', hoverColor, defaultValue: null));
	properties.add(ColorProperty('splashColor', splashColor, defaultValue: null));
	properties.add(ObjectFlagProperty<Object>('heroTag', heroTag, ifPresent: 'hero'));
	properties.add(DoubleProperty('elevation', elevation, defaultValue: null));
	properties.add(DoubleProperty('focusElevation', focusElevation, defaultValue: null));
	properties.add(DoubleProperty('hoverElevation', hoverElevation, defaultValue: null));
	properties.add(DoubleProperty('highlightElevation', highlightElevation, defaultValue: null));
	properties.add(DoubleProperty('disabledElevation', disabledElevation, defaultValue: null));
	properties.add(DiagnosticsProperty<ShapeBorder>('shape', shape, defaultValue: null));
	properties.add(DiagnosticsProperty<FocusNode>('focusNode', focusNode, defaultValue: null));
	properties.add(FlagProperty('isExtended', value: isExtended, ifTrue: 'extended'));
	properties.add(DiagnosticsProperty<MaterialTapTargetSize>('materialTapTargetSize', materialTapTargetSize, defaultValue: null));
	}
	}

	// This widget's size matches its child's size unless its constraints
	// force it to be larger or smaller. The child is centered.
	//
	// Used to encapsulate extended FABs whose size is fixed, using Row
	// and MainAxisSize.min, to be as wide as their label and icon.
	class _ChildOverflowBox extends SingleChildRenderObjectWidget {
	const _ChildOverflowBox({
	Key key,
	Widget child,
	}) : super(key: key, child: child);

	@override
	_RenderChildOverflowBox createRenderObject(BuildContext context) {
	return _RenderChildOverflowBox(
	textDirection: Directionality.of(context),
	);
	}

	@override
	void updateRenderObject(BuildContext context, _RenderChildOverflowBox renderObject) {
	renderObject.textDirection = Directionality.of(context);
	}
	}

	class _RenderChildOverflowBox extends RenderAligningShiftedBox {
	_RenderChildOverflowBox({
	RenderBox child,
	TextDirection textDirection,
	}) : super(child: child, alignment: Alignment.center, textDirection: textDirection);

	@override
	double computeMinIntrinsicWidth(double height) => 0.0;

	@override
	double computeMinIntrinsicHeight(double width) => 0.0;

	@override
	void performLayout() {
	final BoxConstraints constraints = this.constraints;
	if (child != null) {
	child.layout(const BoxConstraints(), parentUsesSize: true);
	size = Size(
	math.max(constraints.minWidth, math.min(constraints.maxWidth, child.size.width)),
	math.max(constraints.minHeight, math.min(constraints.maxHeight, child.size.height)),
	);
	alignChild();
	} else {
	size = constraints.biggest;
	}
	}
	}