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

 import 'button_theme.dart';
 import 'constants.dart';
 import 'ink_well.dart';
 import 'material.dart';
 import 'material_state.dart';
 import 'theme.dart';
 import 'theme_data.dart';

 /// Creates a button based on [Semantics], [Material], and [InkWell]
 /// widgets.
 ///
 /// This class does not use the current [Theme] or [ButtonTheme] to
 /// compute default values for unspecified parameters. It's intended to
 /// be used for custom Material buttons that optionally incorporate defaults
 /// from the themes or from app-specific sources.
 ///
 /// [RaisedButton] and [FlatButton] configure a [RawMaterialButton] based
 /// on the current [Theme] and [ButtonTheme].
 class RawMaterialButton extends StatefulWidget {
   /// Create a button based on [Semantics], [Material], and [InkWell] widgets.
   ///
   /// The [shape], [elevation], [focusElevation], [hoverElevation],
   /// [highlightElevation], [disabledElevation], [padding], [constraints],
   /// [autofocus], and [clipBehavior] arguments must not be null. Additionally,
   /// [elevation], [focusElevation], [hoverElevation], [highlightElevation], and
   /// [disabledElevation] must be non-negative.
   const RawMaterialButton({
     Key key,
     @required this.onPressed,
     this.onLongPress,
     this.onHighlightChanged,
     this.textStyle,
     this.fillColor,
     this.focusColor,
     this.hoverColor,
     this.highlightColor,
     this.splashColor,
     this.elevation = 2.0,
     this.focusElevation = 4.0,
     this.hoverElevation = 4.0,
     this.highlightElevation = 8.0,
     this.disabledElevation = 0.0,
     this.padding = EdgeInsets.zero,
     this.visualDensity = const VisualDensity(),
     this.constraints = const BoxConstraints(minWidth: 88.0, minHeight: 36.0),
     this.shape = const RoundedRectangleBorder(),
     this.animationDuration = kThemeChangeDuration,
     this.clipBehavior = Clip.none,
     this.focusNode,
     this.autofocus = false,
     MaterialTapTargetSize materialTapTargetSize,
     this.child,
     this.enableFeedback = true,
   }) : materialTapTargetSize = materialTapTargetSize ?? MaterialTapTargetSize.padded,
        assert(shape != null),
        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(padding != null),
        assert(constraints != null),
        assert(animationDuration != null),
        assert(clipBehavior != null),
        assert(autofocus != null),
        super(key: key);

   /// Called when the button is tapped or otherwise activated.
   ///
   /// If this callback and [onLongPress] are null, then the button will be disabled.
   ///
   /// See also:
   ///
   ///  * [enabled], which is true if the button is enabled.
   final VoidCallback onPressed;

   /// Called when the button is long-pressed.
   ///
   /// If this callback and [onPressed] are null, then the button will be disabled.
   ///
   /// See also:
   ///
   ///  * [enabled], which is true if the button is enabled.
   final VoidCallback onLongPress;

   /// Called by the underlying [InkWell] widget's [InkWell.onHighlightChanged]
   /// callback.
   ///
   /// If [onPressed] changes from null to non-null while a gesture is ongoing,
   /// this can fire during the build phase (in which case calling
   /// [State.setState] is not allowed).
   final ValueChanged<bool> onHighlightChanged;

   /// Defines the default text style, with [Material.textStyle], for the
   /// button's [child].
   ///
   /// If [textStyle.color] is a [MaterialStateProperty<Color>], [MaterialStateProperty.resolve]
   /// is used for the following [MaterialState]s:
   ///
   ///  * [MaterialState.pressed].
   ///  * [MaterialState.hovered].
   ///  * [MaterialState.focused].
   ///  * [MaterialState.disabled].
   final TextStyle textStyle;

   /// The color of the button's [Material].
   final Color fillColor;

   /// The color for the button's [Material] when it has the input focus.
   final Color focusColor;

   /// The color for the button's [Material] when a pointer is hovering over it.
   final Color hoverColor;

   /// The highlight color for the button's [InkWell].
   final Color highlightColor;

   /// The splash color for the button's [InkWell].
   final Color splashColor;

   /// The elevation for the button's [Material] when the button
   /// is [enabled] but not pressed.
   ///
   /// Defaults to 2.0. The value is always non-negative.
   ///
   /// See also:
   ///
   ///  * [highlightElevation], the default elevation.
   ///  * [hoverElevation], the elevation when a pointer is hovering over the
   ///    button.
   ///  * [focusElevation], the elevation when the button is focused.
   ///  * [disabledElevation], the elevation when the button is disabled.
   final double elevation;

   /// The elevation for the button's [Material] when the button
   /// is [enabled] and a pointer is hovering over it.
   ///
   /// Defaults to 4.0. The value is always non-negative.
   ///
   /// If the button is [enabled], and being pressed (in the highlighted state),
   /// then the [highlightElevation] take precedence over the [hoverElevation].
   ///
   /// See also:
   ///
   ///  * [elevation], the default elevation.
   ///  * [focusElevation], the elevation when the button is focused.
   ///  * [disabledElevation], the elevation when the button is disabled.
   ///  * [highlightElevation], the elevation when the button is pressed.
   final double hoverElevation;

   /// The elevation for the button's [Material] when the button
   /// is [enabled] and has the input focus.
   ///
   /// Defaults to 4.0. The value is always non-negative.
   ///
   /// If the button is [enabled], and being pressed (in the highlighted state),
   /// or a mouse cursor is hovering over the button, then the [hoverElevation]
   /// and [highlightElevation] take precedence over the [focusElevation].
   ///
   /// See also:
   ///
   ///  * [elevation], the default elevation.
   ///  * [hoverElevation], the elevation when a pointer is hovering over the
   ///    button.
   ///  * [disabledElevation], the elevation when the button is disabled.
   ///  * [highlightElevation], the elevation when the button is pressed.
   final double focusElevation;

   /// The elevation for the button's [Material] when the button
   /// is [enabled] and pressed.
   ///
   /// Defaults to 8.0. The value is always non-negative.
   ///
   /// See also:
   ///
   ///  * [elevation], the default elevation.
   ///  * [hoverElevation], the elevation when a pointer is hovering over the
   ///    button.
   ///  * [focusElevation], the elevation when the button is focused.
   ///  * [disabledElevation], the elevation when the button is disabled.
   final double highlightElevation;

   /// The elevation for the button's [Material] when the button
   /// is not [enabled].
   ///
   /// Defaults to 0.0. The value is always non-negative.
   ///
   /// See also:
   ///
   ///  * [elevation], the default elevation.
   ///  * [hoverElevation], the elevation when a pointer is hovering over the
   ///    button.
   ///  * [focusElevation], the elevation when the button is focused.
   ///  * [highlightElevation], the elevation when the button is pressed.
   final double disabledElevation;

   /// The internal padding for the button's [child].
   final EdgeInsetsGeometry padding;

   /// Defines how compact the button's layout will be.
   ///
   /// {@macro flutter.material.themedata.visualDensity}
   ///
   /// See also:
   ///
   ///  * [ThemeData.visualDensity], which specifies the [visualDensity] for all widgets
   ///    within a [Theme].
   final VisualDensity visualDensity;

   /// Defines the button's size.
   ///
   /// Typically used to constrain the button's minimum size.
   final BoxConstraints constraints;

   /// 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.
   ///
   /// If [shape] is a [MaterialStateProperty<ShapeBorder>], [MaterialStateProperty.resolve]
   /// is used for the following [MaterialState]s:
   ///
   /// * [MaterialState.pressed].
   /// * [MaterialState.hovered].
   /// * [MaterialState.focused].
   /// * [MaterialState.disabled].
   final ShapeBorder shape;

   /// Defines the duration of animated changes for [shape] and [elevation].
   ///
   /// The default value is [kThemeChangeDuration].
   final Duration animationDuration;

   /// Typically the button's label.
   final Widget child;

   /// Whether the button is enabled or disabled.
   ///
   /// Buttons are disabled by default. To enable a button, set its [onPressed]
   /// or [onLongPress] properties to a non-null value.
   bool get enabled => onPressed != null || onLongPress != null;

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

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

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

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

   /// Whether detected gestures should provide acoustic and/or haptic feedback.
   ///
   /// For example, on Android a tap will produce a clicking sound and a
   /// long-press will produce a short vibration, when feedback is enabled.
   ///
   /// See also:
   ///
   ///  * [Feedback] for providing platform-specific feedback to certain actions.
   final bool enableFeedback;

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

 class _RawMaterialButtonState extends State<RawMaterialButton> {
   final Set<MaterialState> _states = <MaterialState>{};

   bool get _hovered => _states.contains(MaterialState.hovered);
   bool get _focused => _states.contains(MaterialState.focused);
   bool get _pressed => _states.contains(MaterialState.pressed);
   bool get _disabled => _states.contains(MaterialState.disabled);

   void _updateState(MaterialState state, bool value) {
     value ? _states.add(state) : _states.remove(state);
   }

   void _handleHighlightChanged(bool value) {
     if (_pressed != value) {
       setState(() {
         _updateState(MaterialState.pressed, value);
         if (widget.onHighlightChanged != null) {
           widget.onHighlightChanged(value);
         }
       });
     }
   }

   void _handleHoveredChanged(bool value) {
     if (_hovered != value) {
       setState(() {
         _updateState(MaterialState.hovered, value);
       });
     }
   }

   void _handleFocusedChanged(bool value) {
     if (_focused != value) {
       setState(() {
         _updateState(MaterialState.focused, value);
       });
     }
   }

   @override
   void initState() {
     super.initState();
     _updateState(MaterialState.disabled, !widget.enabled);
   }

   @override
   void didUpdateWidget(RawMaterialButton oldWidget) {
     super.didUpdateWidget(oldWidget);
     _updateState(MaterialState.disabled, !widget.enabled);
     // If the button is disabled while a press gesture is currently ongoing,
     // InkWell makes a call to handleHighlightChanged. This causes an exception
     // because it calls setState in the middle of a build. To preempt this, we
     // manually update pressed to false when this situation occurs.
     if (_disabled && _pressed) {
       _handleHighlightChanged(false);
     }
   }

   double get _effectiveElevation {
     // These conditionals are in order of precedence, so be careful about
     // reorganizing them.
     if (_disabled) {
       return widget.disabledElevation;
     }
     if (_pressed) {
       return widget.highlightElevation;
     }
     if (_hovered) {
       return widget.hoverElevation;
     }
     if (_focused) {
       return widget.focusElevation;
     }
     return widget.elevation;
   }

   @override
   Widget build(BuildContext context) {
     final Color effectiveTextColor = MaterialStateProperty.resolveAs<Color>(widget.textStyle?.color, _states);
     final ShapeBorder effectiveShape =  MaterialStateProperty.resolveAs<ShapeBorder>(widget.shape, _states);
     final Offset densityAdjustment = widget.visualDensity.baseSizeAdjustment;
     final BoxConstraints effectiveConstraints = widget.visualDensity.effectiveConstraints(widget.constraints);
     final EdgeInsetsGeometry padding = widget.padding.add(
       EdgeInsets.only(
         left: densityAdjustment.dx,
         top: densityAdjustment.dy,
         right: densityAdjustment.dx,
         bottom: densityAdjustment.dy,
       ),
     ).clamp(EdgeInsets.zero, EdgeInsetsGeometry.infinity);

     final Widget result = ConstrainedBox(
       constraints: effectiveConstraints,
       child: Material(
         elevation: _effectiveElevation,
         textStyle: widget.textStyle?.copyWith(color: effectiveTextColor),
         shape: effectiveShape,
         color: widget.fillColor,
         type: widget.fillColor == null ? MaterialType.transparency : MaterialType.button,
         animationDuration: widget.animationDuration,
         clipBehavior: widget.clipBehavior,
         child: InkWell(
           focusNode: widget.focusNode,
           canRequestFocus: widget.enabled,
           onFocusChange: _handleFocusedChanged,
           autofocus: widget.autofocus,
           onHighlightChanged: _handleHighlightChanged,
           splashColor: widget.splashColor,
           highlightColor: widget.highlightColor,
           focusColor: widget.focusColor,
           hoverColor: widget.hoverColor,
           onHover: _handleHoveredChanged,
           onTap: widget.onPressed,
           onLongPress: widget.onLongPress,
           enableFeedback: widget.enableFeedback,
           customBorder: effectiveShape,
           child: IconTheme.merge(
             data: IconThemeData(color: effectiveTextColor),
             child: Container(
               padding: padding,
               child: Center(
                 widthFactor: 1.0,
                 heightFactor: 1.0,
                 child: widget.child,
               ),
             ),
           ),
         ),
       ),
     );
     Size minSize;
     switch (widget.materialTapTargetSize) {
       case MaterialTapTargetSize.padded:
         minSize = Size(
           kMinInteractiveDimension + densityAdjustment.dx,
           kMinInteractiveDimension + densityAdjustment.dy,
         );
         assert(minSize.width >= 0.0);
         assert(minSize.height >= 0.0);
         break;
       case MaterialTapTargetSize.shrinkWrap:
         minSize = Size.zero;
         break;
     }

     return Semantics(
       container: true,
       button: true,
       enabled: widget.enabled,
       child: _InputPadding(
         minSize: minSize,
         child: result,
       ),
     );
   }
 }

 /// A widget to pad the area around a [MaterialButton]'s inner [Material].
 ///
 /// Redirect taps that occur in the padded area around the child to the center
 /// of the child. This increases the size of the button and the button's
 /// "tap target", but not its material or its ink splashes.
 class _InputPadding extends SingleChildRenderObjectWidget {
   const _InputPadding({
     Key key,
     Widget child,
     this.minSize,
   }) : super(key: key, child: child);

   final Size minSize;

   @override
   RenderObject createRenderObject(BuildContext context) {
     return _RenderInputPadding(minSize);
   }

   @override
   void updateRenderObject(BuildContext context, covariant _RenderInputPadding renderObject) {
     renderObject.minSize = minSize;
   }
 }

 class _RenderInputPadding extends RenderShiftedBox {
   _RenderInputPadding(this._minSize, [RenderBox child]) : super(child);

   Size get minSize => _minSize;
   Size _minSize;
   set minSize(Size value) {
     if (_minSize == value)
       return;
     _minSize = value;
     markNeedsLayout();
   }

   @override
   double computeMinIntrinsicWidth(double height) {
     if (child != null)
       return math.max(child.getMinIntrinsicWidth(height), minSize.width);
     return 0.0;
   }

   @override
   double computeMinIntrinsicHeight(double width) {
     if (child != null)
       return math.max(child.getMinIntrinsicHeight(width), minSize.height);
     return 0.0;
   }

   @override
   double computeMaxIntrinsicWidth(double height) {
     if (child != null)
       return math.max(child.getMaxIntrinsicWidth(height), minSize.width);
     return 0.0;
   }

   @override
   double computeMaxIntrinsicHeight(double width) {
     if (child != null)
       return math.max(child.getMaxIntrinsicHeight(width), minSize.height);
     return 0.0;
   }

   @override
   void performLayout() {
     final BoxConstraints constraints = this.constraints;
     if (child != null) {
       child.layout(constraints, parentUsesSize: true);
       final double height = math.max(child.size.width, minSize.width);
       final double width = math.max(child.size.height, minSize.height);
       size = constraints.constrain(Size(height, width));
       final BoxParentData childParentData = child.parentData as BoxParentData;
       childParentData.offset = Alignment.center.alongOffset(size - child.size as Offset);
     } else {
       size = Size.zero;
     }
   }

   @override
   bool hitTest(BoxHitTestResult result, { Offset position }) {
     if (super.hitTest(result, position: position)) {
       return true;
     }
     final Offset center = child.size.center(Offset.zero);
     return result.addWithRawTransform(
       transform: MatrixUtils.forceToPoint(center),
       position: center,
       hitTest: (BoxHitTestResult result, Offset position) {
         assert(position == center);
         return child.hitTest(result, position: center);
       },
     );
   }
 }
	// 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/gestures.dart';
	import 'package:flutter/rendering.dart';
	import 'package:flutter/widgets.dart';

	import 'button_theme.dart';
	import 'constants.dart';
	import 'ink_well.dart';
	import 'material.dart';
	import 'material_state.dart';
	import 'theme.dart';
	import 'theme_data.dart';

	/// Creates a button based on [Semantics], [Material], and [InkWell]
	/// widgets.
	///
	/// This class does not use the current [Theme] or [ButtonTheme] to
	/// compute default values for unspecified parameters. It's intended to
	/// be used for custom Material buttons that optionally incorporate defaults
	/// from the themes or from app-specific sources.
	///
	/// [RaisedButton] and [FlatButton] configure a [RawMaterialButton] based
	/// on the current [Theme] and [ButtonTheme].
	class RawMaterialButton extends StatefulWidget {
	/// Create a button based on [Semantics], [Material], and [InkWell] widgets.
	///
	/// The [shape], [elevation], [focusElevation], [hoverElevation],
	/// [highlightElevation], [disabledElevation], [padding], [constraints],
	/// [autofocus], and [clipBehavior] arguments must not be null. Additionally,
	/// [elevation], [focusElevation], [hoverElevation], [highlightElevation], and
	/// [disabledElevation] must be non-negative.
	const RawMaterialButton({
	Key key,
	@required this.onPressed,
	this.onLongPress,
	this.onHighlightChanged,
	this.textStyle,
	this.fillColor,
	this.focusColor,
	this.hoverColor,
	this.highlightColor,
	this.splashColor,
	this.elevation = 2.0,
	this.focusElevation = 4.0,
	this.hoverElevation = 4.0,
	this.highlightElevation = 8.0,
	this.disabledElevation = 0.0,
	this.padding = EdgeInsets.zero,
	this.visualDensity = const VisualDensity(),
	this.constraints = const BoxConstraints(minWidth: 88.0, minHeight: 36.0),
	this.shape = const RoundedRectangleBorder(),
	this.animationDuration = kThemeChangeDuration,
	this.clipBehavior = Clip.none,
	this.focusNode,
	this.autofocus = false,
	MaterialTapTargetSize materialTapTargetSize,
	this.child,
	this.enableFeedback = true,
	}) : materialTapTargetSize = materialTapTargetSize ?? MaterialTapTargetSize.padded,
	assert(shape != null),
	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(padding != null),
	assert(constraints != null),
	assert(animationDuration != null),
	assert(clipBehavior != null),
	assert(autofocus != null),
	super(key: key);

	/// Called when the button is tapped or otherwise activated.
	///
	/// If this callback and [onLongPress] are null, then the button will be disabled.
	///
	/// See also:
	///
	/// * [enabled], which is true if the button is enabled.
	final VoidCallback onPressed;

	/// Called when the button is long-pressed.
	///
	/// If this callback and [onPressed] are null, then the button will be disabled.
	///
	/// See also:
	///
	/// * [enabled], which is true if the button is enabled.
	final VoidCallback onLongPress;

	/// Called by the underlying [InkWell] widget's [InkWell.onHighlightChanged]
	/// callback.
	///
	/// If [onPressed] changes from null to non-null while a gesture is ongoing,
	/// this can fire during the build phase (in which case calling
	/// [State.setState] is not allowed).
	final ValueChanged<bool> onHighlightChanged;

	/// Defines the default text style, with [Material.textStyle], for the
	/// button's [child].
	///
	/// If [textStyle.color] is a [MaterialStateProperty<Color>], [MaterialStateProperty.resolve]
	/// is used for the following [MaterialState]s:
	///
	/// * [MaterialState.pressed].
	/// * [MaterialState.hovered].
	/// * [MaterialState.focused].
	/// * [MaterialState.disabled].
	final TextStyle textStyle;

	/// The color of the button's [Material].
	final Color fillColor;

	/// The color for the button's [Material] when it has the input focus.
	final Color focusColor;

	/// The color for the button's [Material] when a pointer is hovering over it.
	final Color hoverColor;

	/// The highlight color for the button's [InkWell].
	final Color highlightColor;

	/// The splash color for the button's [InkWell].
	final Color splashColor;

	/// The elevation for the button's [Material] when the button
	/// is [enabled] but not pressed.
	///
	/// Defaults to 2.0. The value is always non-negative.
	///
	/// See also:
	///
	/// * [highlightElevation], the default elevation.
	/// * [hoverElevation], the elevation when a pointer is hovering over the
	/// button.
	/// * [focusElevation], the elevation when the button is focused.
	/// * [disabledElevation], the elevation when the button is disabled.
	final double elevation;

	/// The elevation for the button's [Material] when the button
	/// is [enabled] and a pointer is hovering over it.
	///
	/// Defaults to 4.0. The value is always non-negative.
	///
	/// If the button is [enabled], and being pressed (in the highlighted state),
	/// then the [highlightElevation] take precedence over the [hoverElevation].
	///
	/// See also:
	///
	/// * [elevation], the default elevation.
	/// * [focusElevation], the elevation when the button is focused.
	/// * [disabledElevation], the elevation when the button is disabled.
	/// * [highlightElevation], the elevation when the button is pressed.
	final double hoverElevation;

	/// The elevation for the button's [Material] when the button
	/// is [enabled] and has the input focus.
	///
	/// Defaults to 4.0. The value is always non-negative.
	///
	/// If the button is [enabled], and being pressed (in the highlighted state),
	/// or a mouse cursor is hovering over the button, then the [hoverElevation]
	/// and [highlightElevation] take precedence over the [focusElevation].
	///
	/// See also:
	///
	/// * [elevation], the default elevation.
	/// * [hoverElevation], the elevation when a pointer is hovering over the
	/// button.
	/// * [disabledElevation], the elevation when the button is disabled.
	/// * [highlightElevation], the elevation when the button is pressed.
	final double focusElevation;

	/// The elevation for the button's [Material] when the button
	/// is [enabled] and pressed.
	///
	/// Defaults to 8.0. The value is always non-negative.
	///
	/// See also:
	///
	/// * [elevation], the default elevation.
	/// * [hoverElevation], the elevation when a pointer is hovering over the
	/// button.
	/// * [focusElevation], the elevation when the button is focused.
	/// * [disabledElevation], the elevation when the button is disabled.
	final double highlightElevation;

	/// The elevation for the button's [Material] when the button
	/// is not [enabled].
	///
	/// Defaults to 0.0. The value is always non-negative.
	///
	/// See also:
	///
	/// * [elevation], the default elevation.
	/// * [hoverElevation], the elevation when a pointer is hovering over the
	/// button.
	/// * [focusElevation], the elevation when the button is focused.
	/// * [highlightElevation], the elevation when the button is pressed.
	final double disabledElevation;

	/// The internal padding for the button's [child].
	final EdgeInsetsGeometry padding;

	/// Defines how compact the button's layout will be.
	///
	/// {@macro flutter.material.themedata.visualDensity}
	///
	/// See also:
	///
	/// * [ThemeData.visualDensity], which specifies the [visualDensity] for all widgets
	/// within a [Theme].
	final VisualDensity visualDensity;

	/// Defines the button's size.
	///
	/// Typically used to constrain the button's minimum size.
	final BoxConstraints constraints;

	/// 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.
	///
	/// If [shape] is a [MaterialStateProperty<ShapeBorder>], [MaterialStateProperty.resolve]
	/// is used for the following [MaterialState]s:
	///
	/// * [MaterialState.pressed].
	/// * [MaterialState.hovered].
	/// * [MaterialState.focused].
	/// * [MaterialState.disabled].
	final ShapeBorder shape;

	/// Defines the duration of animated changes for [shape] and [elevation].
	///
	/// The default value is [kThemeChangeDuration].
	final Duration animationDuration;

	/// Typically the button's label.
	final Widget child;

	/// Whether the button is enabled or disabled.
	///
	/// Buttons are disabled by default. To enable a button, set its [onPressed]
	/// or [onLongPress] properties to a non-null value.
	bool get enabled => onPressed != null \|\| onLongPress != null;

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

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

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

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

	/// Whether detected gestures should provide acoustic and/or haptic feedback.
	///
	/// For example, on Android a tap will produce a clicking sound and a
	/// long-press will produce a short vibration, when feedback is enabled.
	///
	/// See also:
	///
	/// * [Feedback] for providing platform-specific feedback to certain actions.
	final bool enableFeedback;

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

	class _RawMaterialButtonState extends State<RawMaterialButton> {
	final Set<MaterialState> _states = <MaterialState>{};

	bool get _hovered => _states.contains(MaterialState.hovered);
	bool get _focused => _states.contains(MaterialState.focused);
	bool get _pressed => _states.contains(MaterialState.pressed);
	bool get _disabled => _states.contains(MaterialState.disabled);

	void _updateState(MaterialState state, bool value) {
	value ? _states.add(state) : _states.remove(state);
	}

	void _handleHighlightChanged(bool value) {
	if (_pressed != value) {
	setState(() {
	_updateState(MaterialState.pressed, value);
	if (widget.onHighlightChanged != null) {
	widget.onHighlightChanged(value);
	}
	});
	}
	}

	void _handleHoveredChanged(bool value) {
	if (_hovered != value) {
	setState(() {
	_updateState(MaterialState.hovered, value);
	});
	}
	}

	void _handleFocusedChanged(bool value) {
	if (_focused != value) {
	setState(() {
	_updateState(MaterialState.focused, value);
	});
	}
	}

	@override
	void initState() {
	super.initState();
	_updateState(MaterialState.disabled, !widget.enabled);
	}

	@override
	void didUpdateWidget(RawMaterialButton oldWidget) {
	super.didUpdateWidget(oldWidget);
	_updateState(MaterialState.disabled, !widget.enabled);
	// If the button is disabled while a press gesture is currently ongoing,
	// InkWell makes a call to handleHighlightChanged. This causes an exception
	// because it calls setState in the middle of a build. To preempt this, we
	// manually update pressed to false when this situation occurs.
	if (_disabled && _pressed) {
	_handleHighlightChanged(false);
	}
	}

	double get _effectiveElevation {
	// These conditionals are in order of precedence, so be careful about
	// reorganizing them.
	if (_disabled) {
	return widget.disabledElevation;
	}
	if (_pressed) {
	return widget.highlightElevation;
	}
	if (_hovered) {
	return widget.hoverElevation;
	}
	if (_focused) {
	return widget.focusElevation;
	}
	return widget.elevation;
	}

	@override
	Widget build(BuildContext context) {
	final Color effectiveTextColor = MaterialStateProperty.resolveAs<Color>(widget.textStyle?.color, _states);
	final ShapeBorder effectiveShape = MaterialStateProperty.resolveAs<ShapeBorder>(widget.shape, _states);
	final Offset densityAdjustment = widget.visualDensity.baseSizeAdjustment;
	final BoxConstraints effectiveConstraints = widget.visualDensity.effectiveConstraints(widget.constraints);
	final EdgeInsetsGeometry padding = widget.padding.add(
	EdgeInsets.only(
	left: densityAdjustment.dx,
	top: densityAdjustment.dy,
	right: densityAdjustment.dx,
	bottom: densityAdjustment.dy,
	),
	).clamp(EdgeInsets.zero, EdgeInsetsGeometry.infinity);

	final Widget result = ConstrainedBox(
	constraints: effectiveConstraints,
	child: Material(
	elevation: _effectiveElevation,
	textStyle: widget.textStyle?.copyWith(color: effectiveTextColor),
	shape: effectiveShape,
	color: widget.fillColor,
	type: widget.fillColor == null ? MaterialType.transparency : MaterialType.button,
	animationDuration: widget.animationDuration,
	clipBehavior: widget.clipBehavior,
	child: InkWell(
	focusNode: widget.focusNode,
	canRequestFocus: widget.enabled,
	onFocusChange: _handleFocusedChanged,
	autofocus: widget.autofocus,
	onHighlightChanged: _handleHighlightChanged,
	splashColor: widget.splashColor,
	highlightColor: widget.highlightColor,
	focusColor: widget.focusColor,
	hoverColor: widget.hoverColor,
	onHover: _handleHoveredChanged,
	onTap: widget.onPressed,
	onLongPress: widget.onLongPress,
	enableFeedback: widget.enableFeedback,
	customBorder: effectiveShape,
	child: IconTheme.merge(
	data: IconThemeData(color: effectiveTextColor),
	child: Container(
	padding: padding,
	child: Center(
	widthFactor: 1.0,
	heightFactor: 1.0,
	child: widget.child,
	),
	),
	),
	),
	),
	);
	Size minSize;
	switch (widget.materialTapTargetSize) {
	case MaterialTapTargetSize.padded:
	minSize = Size(
	kMinInteractiveDimension + densityAdjustment.dx,
	kMinInteractiveDimension + densityAdjustment.dy,
	);
	assert(minSize.width >= 0.0);
	assert(minSize.height >= 0.0);
	break;
	case MaterialTapTargetSize.shrinkWrap:
	minSize = Size.zero;
	break;
	}

	return Semantics(
	container: true,
	button: true,
	enabled: widget.enabled,
	child: _InputPadding(
	minSize: minSize,
	child: result,
	),
	);
	}
	}

	/// A widget to pad the area around a [MaterialButton]'s inner [Material].
	///
	/// Redirect taps that occur in the padded area around the child to the center
	/// of the child. This increases the size of the button and the button's
	/// "tap target", but not its material or its ink splashes.
	class _InputPadding extends SingleChildRenderObjectWidget {
	const _InputPadding({
	Key key,
	Widget child,
	this.minSize,
	}) : super(key: key, child: child);

	final Size minSize;

	@override
	RenderObject createRenderObject(BuildContext context) {
	return _RenderInputPadding(minSize);
	}

	@override
	void updateRenderObject(BuildContext context, covariant _RenderInputPadding renderObject) {
	renderObject.minSize = minSize;
	}
	}

	class _RenderInputPadding extends RenderShiftedBox {
	_RenderInputPadding(this._minSize, [RenderBox child]) : super(child);

	Size get minSize => _minSize;
	Size _minSize;
	set minSize(Size value) {
	if (_minSize == value)
	return;
	_minSize = value;
	markNeedsLayout();
	}

	@override
	double computeMinIntrinsicWidth(double height) {
	if (child != null)
	return math.max(child.getMinIntrinsicWidth(height), minSize.width);
	return 0.0;
	}

	@override
	double computeMinIntrinsicHeight(double width) {
	if (child != null)
	return math.max(child.getMinIntrinsicHeight(width), minSize.height);
	return 0.0;
	}

	@override
	double computeMaxIntrinsicWidth(double height) {
	if (child != null)
	return math.max(child.getMaxIntrinsicWidth(height), minSize.width);
	return 0.0;
	}

	@override
	double computeMaxIntrinsicHeight(double width) {
	if (child != null)
	return math.max(child.getMaxIntrinsicHeight(width), minSize.height);
	return 0.0;
	}

	@override
	void performLayout() {
	final BoxConstraints constraints = this.constraints;
	if (child != null) {
	child.layout(constraints, parentUsesSize: true);
	final double height = math.max(child.size.width, minSize.width);
	final double width = math.max(child.size.height, minSize.height);
	size = constraints.constrain(Size(height, width));
	final BoxParentData childParentData = child.parentData as BoxParentData;
	childParentData.offset = Alignment.center.alongOffset(size - child.size as Offset);
	} else {
	size = Size.zero;
	}
	}

	@override
	bool hitTest(BoxHitTestResult result, { Offset position }) {
	if (super.hitTest(result, position: position)) {
	return true;
	}
	final Offset center = child.size.center(Offset.zero);
	return result.addWithRawTransform(
	transform: MatrixUtils.forceToPoint(center),
	position: center,
	hitTest: (BoxHitTestResult result, Offset position) {
	assert(position == center);
	return child.hitTest(result, position: center);
	},
	);
	}
	}