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// 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:collection';
import 'dart:math' as math;
import 'package:flutter/foundation.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/widgets.dart';
import 'theme.dart';
// Minimum padding from edges of the segmented control to edges of
// encompassing widget.
const EdgeInsetsGeometry _kHorizontalItemPadding = EdgeInsets.symmetric(horizontal: 16.0);
// Minimum height of the segmented control.
const double _kMinSegmentedControlHeight = 28.0;
// The duration of the fade animation used to transition when a new widget
// is selected.
const Duration _kFadeDuration = Duration(milliseconds: 165);
/// An iOS-style segmented control.
///
/// Displays the widgets provided in the [Map] of [children] in a
/// horizontal list. Used to select between a number of mutually exclusive
/// options. When one option in the segmented control is selected, the other
/// options in the segmented control cease to be selected.
///
/// A segmented control can feature any [Widget] as one of the values in its
/// [Map] of [children]. The type T is the type of the keys used
/// to identify each widget and determine which widget is selected. As
/// required by the [Map] class, keys must be of consistent types
/// and must be comparable. The ordering of the keys will determine the order
/// of the widgets in the segmented control.
///
/// When the state of the segmented control changes, the widget calls the
/// [onValueChanged] callback. The map key associated with the newly selected
/// widget is returned in the [onValueChanged] callback. Typically, widgets
/// that use a segmented control will listen for the [onValueChanged] callback
/// and rebuild the segmented control with a new [groupValue] to update which
/// option is currently selected.
///
/// The [children] will be displayed in the order of the keys in the [Map].
/// The height of the segmented control is determined by the height of the
/// tallest widget provided as a value in the [Map] of [children].
/// The width of each child in the segmented control will be equal to the width
/// of widest child, unless the combined width of the children is wider than
/// the available horizontal space. In this case, the available horizontal space
/// is divided by the number of provided [children] to determine the width of
/// each widget. The selection area for each of the widgets in the [Map] of
/// [children] will then be expanded to fill the calculated space, so each
/// widget will appear to have the same dimensions.
///
/// A segmented control may optionally be created with custom colors. The
/// [unselectedColor], [selectedColor], [borderColor], and [pressedColor]
/// arguments can be used to override the segmented control's colors from
/// [CupertinoTheme] defaults.
///
/// See also:
///
/// * [CupertinoSegmentedControl], a segmented control widget in the style used
/// up until iOS 13.
/// * <https://developer.apple.com/design/human-interface-guidelines/ios/controls/segmented-controls/>
class CupertinoSegmentedControl<T> extends StatefulWidget {
/// Creates an iOS-style segmented control bar.
///
/// The [children] and [onValueChanged] arguments must not be null. The
/// [children] argument must be an ordered [Map] such as a [LinkedHashMap].
/// Further, the length of the [children] list must be greater than one.
///
/// Each widget value in the map of [children] must have an associated key
/// that uniquely identifies this widget. This key is what will be returned
/// in the [onValueChanged] callback when a new value from the [children] map
/// is selected.
///
/// The [groupValue] is the currently selected value for the segmented control.
/// If no [groupValue] is provided, or the [groupValue] is null, no widget will
/// appear as selected. The [groupValue] must be either null or one of the keys
/// in the [children] map.
CupertinoSegmentedControl({
Key key,
@required this.children,
@required this.onValueChanged,
this.groupValue,
this.unselectedColor,
this.selectedColor,
this.borderColor,
this.pressedColor,
this.padding,
}) : assert(children != null),
assert(children.length >= 2),
assert(onValueChanged != null),
assert(
groupValue == null || children.keys.any((T child) => child == groupValue),
'The groupValue must be either null or one of the keys in the children map.',
),
super(key: key);
/// The identifying keys and corresponding widget values in the
/// segmented control.
///
/// The map must have more than one entry.
/// This attribute must be an ordered [Map] such as a [LinkedHashMap].
final Map<T, Widget> children;
/// The identifier of the widget that is currently selected.
///
/// This must be one of the keys in the [Map] of [children].
/// If this attribute is null, no widget will be initially selected.
final T groupValue;
/// The callback that is called when a new option is tapped.
///
/// This attribute must not be null.
///
/// The segmented control passes the newly selected widget's associated key
/// to the callback but does not actually change state until the parent
/// widget rebuilds the segmented control with the new [groupValue].
///
/// The callback provided to [onValueChanged] should update the state of
/// the parent [StatefulWidget] using the [State.setState] method, so that
/// the parent gets rebuilt; for example:
///
/// {@tool snippet}
///
/// ```dart
/// class SegmentedControlExample extends StatefulWidget {
/// @override
/// State createState() => SegmentedControlExampleState();
/// }
///
/// class SegmentedControlExampleState extends State<SegmentedControlExample> {
/// final Map<int, Widget> children = const {
/// 0: Text('Child 1'),
/// 1: Text('Child 2'),
/// };
///
/// int currentValue;
///
/// @override
/// Widget build(BuildContext context) {
/// return Container(
/// child: CupertinoSegmentedControl<int>(
/// children: children,
/// onValueChanged: (int newValue) {
/// setState(() {
/// currentValue = newValue;
/// });
/// },
/// groupValue: currentValue,
/// ),
/// );
/// }
/// }
/// ```
/// {@end-tool}
final ValueChanged<T> onValueChanged;
/// The color used to fill the backgrounds of unselected widgets and as the
/// text color of the selected widget.
///
/// Defaults to [CupertinoTheme]'s `primaryContrastingColor` if null.
final Color unselectedColor;
/// The color used to fill the background of the selected widget and as the text
/// color of unselected widgets.
///
/// Defaults to [CupertinoTheme]'s `primaryColor` if null.
final Color selectedColor;
/// The color used as the border around each widget.
///
/// Defaults to [CupertinoTheme]'s `primaryColor` if null.
final Color borderColor;
/// The color used to fill the background of the widget the user is
/// temporarily interacting with through a long press or drag.
///
/// Defaults to the selectedColor at 20% opacity if null.
final Color pressedColor;
/// The CupertinoSegmentedControl will be placed inside this padding
///
/// Defaults to EdgeInsets.symmetric(horizontal: 16.0)
final EdgeInsetsGeometry padding;
@override
_SegmentedControlState<T> createState() => _SegmentedControlState<T>();
}
class _SegmentedControlState<T> extends State<CupertinoSegmentedControl<T>>
with TickerProviderStateMixin<CupertinoSegmentedControl<T>> {
T _pressedKey;
final List<AnimationController> _selectionControllers = <AnimationController>[];
final List<ColorTween> _childTweens = <ColorTween>[];
ColorTween _forwardBackgroundColorTween;
ColorTween _reverseBackgroundColorTween;
ColorTween _textColorTween;
Color _selectedColor;
Color _unselectedColor;
Color _borderColor;
Color _pressedColor;
AnimationController createAnimationController() {
return AnimationController(
duration: _kFadeDuration,
vsync: this,
)..addListener(() {
setState(() {
// State of background/text colors has changed
});
});
}
bool _updateColors() {
assert(mounted, 'This should only be called after didUpdateDependencies');
bool changed = false;
final Color selectedColor = widget.selectedColor ?? CupertinoTheme.of(context).primaryColor;
if (_selectedColor != selectedColor) {
changed = true;
_selectedColor = selectedColor;
}
final Color unselectedColor = widget.unselectedColor ?? CupertinoTheme.of(context).primaryContrastingColor;
if (_unselectedColor != unselectedColor) {
changed = true;
_unselectedColor = unselectedColor;
}
final Color borderColor = widget.borderColor ?? CupertinoTheme.of(context).primaryColor;
if (_borderColor != borderColor) {
changed = true;
_borderColor = borderColor;
}
final Color pressedColor = widget.pressedColor ?? CupertinoTheme.of(context).primaryColor.withOpacity(0.2);
if (_pressedColor != pressedColor) {
changed = true;
_pressedColor = pressedColor;
}
_forwardBackgroundColorTween = ColorTween(
begin: _pressedColor,
end: _selectedColor,
);
_reverseBackgroundColorTween = ColorTween(
begin: _unselectedColor,
end: _selectedColor,
);
_textColorTween = ColorTween(
begin: _selectedColor,
end: _unselectedColor,
);
return changed;
}
void _updateAnimationControllers() {
assert(mounted, 'This should only be called after didUpdateDependencies');
for (final AnimationController controller in _selectionControllers) {
controller.dispose();
}
_selectionControllers.clear();
_childTweens.clear();
for (final T key in widget.children.keys) {
final AnimationController animationController = createAnimationController();
if (widget.groupValue == key) {
_childTweens.add(_reverseBackgroundColorTween);
animationController.value = 1.0;
} else {
_childTweens.add(_forwardBackgroundColorTween);
}
_selectionControllers.add(animationController);
}
}
@override
void didChangeDependencies() {
super.didChangeDependencies();
if (_updateColors()) {
_updateAnimationControllers();
}
}
@override
void didUpdateWidget(CupertinoSegmentedControl<T> oldWidget) {
super.didUpdateWidget(oldWidget);
if (_updateColors() || oldWidget.children.length != widget.children.length) {
_updateAnimationControllers();
}
if (oldWidget.groupValue != widget.groupValue) {
int index = 0;
for (final T key in widget.children.keys) {
if (widget.groupValue == key) {
_childTweens[index] = _forwardBackgroundColorTween;
_selectionControllers[index].forward();
} else {
_childTweens[index] = _reverseBackgroundColorTween;
_selectionControllers[index].reverse();
}
index += 1;
}
}
}
@override
void dispose() {
for (final AnimationController animationController in _selectionControllers) {
animationController.dispose();
}
super.dispose();
}
void _onTapDown(T currentKey) {
if (_pressedKey == null && currentKey != widget.groupValue) {
setState(() {
_pressedKey = currentKey;
});
}
}
void _onTapCancel() {
setState(() {
_pressedKey = null;
});
}
void _onTap(T currentKey) {
if (currentKey != _pressedKey)
return;
if (currentKey != widget.groupValue) {
widget.onValueChanged(currentKey);
}
_pressedKey = null;
}
Color getTextColor(int index, T currentKey) {
if (_selectionControllers[index].isAnimating)
return _textColorTween.evaluate(_selectionControllers[index]);
if (widget.groupValue == currentKey)
return _unselectedColor;
return _selectedColor;
}
Color getBackgroundColor(int index, T currentKey) {
if (_selectionControllers[index].isAnimating)
return _childTweens[index].evaluate(_selectionControllers[index]);
if (widget.groupValue == currentKey)
return _selectedColor;
if (_pressedKey == currentKey)
return _pressedColor;
return _unselectedColor;
}
@override
Widget build(BuildContext context) {
final List<Widget> _gestureChildren = <Widget>[];
final List<Color> _backgroundColors = <Color>[];
int index = 0;
int selectedIndex;
int pressedIndex;
for (final T currentKey in widget.children.keys) {
selectedIndex = (widget.groupValue == currentKey) ? index : selectedIndex;
pressedIndex = (_pressedKey == currentKey) ? index : pressedIndex;
final TextStyle textStyle = DefaultTextStyle.of(context).style.copyWith(
color: getTextColor(index, currentKey),
);
final IconThemeData iconTheme = IconThemeData(
color: getTextColor(index, currentKey),
);
Widget child = Center(
child: widget.children[currentKey],
);
child = GestureDetector(
onTapDown: (TapDownDetails event) {
_onTapDown(currentKey);
},
onTapCancel: _onTapCancel,
onTap: () {
_onTap(currentKey);
},
child: IconTheme(
data: iconTheme,
child: DefaultTextStyle(
style: textStyle,
child: Semantics(
button: true,
inMutuallyExclusiveGroup: true,
selected: widget.groupValue == currentKey,
child: child,
),
),
),
);
_backgroundColors.add(getBackgroundColor(index, currentKey));
_gestureChildren.add(child);
index += 1;
}
final Widget box = _SegmentedControlRenderWidget<T>(
children: _gestureChildren,
selectedIndex: selectedIndex,
pressedIndex: pressedIndex,
backgroundColors: _backgroundColors,
borderColor: _borderColor,
);
return Padding(
padding: widget.padding ?? _kHorizontalItemPadding,
child: UnconstrainedBox(
constrainedAxis: Axis.horizontal,
child: box,
),
);
}
}
class _SegmentedControlRenderWidget<T> extends MultiChildRenderObjectWidget {
_SegmentedControlRenderWidget({
Key key,
List<Widget> children = const <Widget>[],
@required this.selectedIndex,
@required this.pressedIndex,
@required this.backgroundColors,
@required this.borderColor,
}) : super(
key: key,
children: children,
);
final int selectedIndex;
final int pressedIndex;
final List<Color> backgroundColors;
final Color borderColor;
@override
RenderObject createRenderObject(BuildContext context) {
return _RenderSegmentedControl<T>(
textDirection: Directionality.of(context),
selectedIndex: selectedIndex,
pressedIndex: pressedIndex,
backgroundColors: backgroundColors,
borderColor: borderColor,
);
}
@override
void updateRenderObject(BuildContext context, _RenderSegmentedControl<T> renderObject) {
renderObject
..textDirection = Directionality.of(context)
..selectedIndex = selectedIndex
..pressedIndex = pressedIndex
..backgroundColors = backgroundColors
..borderColor = borderColor;
}
}
class _SegmentedControlContainerBoxParentData extends ContainerBoxParentData<RenderBox> {
RRect surroundingRect;
}
typedef _NextChild = RenderBox Function(RenderBox child);
class _RenderSegmentedControl<T> extends RenderBox
with ContainerRenderObjectMixin<RenderBox, ContainerBoxParentData<RenderBox>>,
RenderBoxContainerDefaultsMixin<RenderBox, ContainerBoxParentData<RenderBox>> {
_RenderSegmentedControl({
@required int selectedIndex,
@required int pressedIndex,
@required TextDirection textDirection,
@required List<Color> backgroundColors,
@required Color borderColor,
}) : assert(textDirection != null),
_textDirection = textDirection,
_selectedIndex = selectedIndex,
_pressedIndex = pressedIndex,
_backgroundColors = backgroundColors,
_borderColor = borderColor;
int get selectedIndex => _selectedIndex;
int _selectedIndex;
set selectedIndex(int value) {
if (_selectedIndex == value) {
return;
}
_selectedIndex = value;
markNeedsPaint();
}
int get pressedIndex => _pressedIndex;
int _pressedIndex;
set pressedIndex(int value) {
if (_pressedIndex == value) {
return;
}
_pressedIndex = value;
markNeedsPaint();
}
TextDirection get textDirection => _textDirection;
TextDirection _textDirection;
set textDirection(TextDirection value) {
if (_textDirection == value) {
return;
}
_textDirection = value;
markNeedsLayout();
}
List<Color> get backgroundColors => _backgroundColors;
List<Color> _backgroundColors;
set backgroundColors(List<Color> value) {
if (_backgroundColors == value) {
return;
}
_backgroundColors = value;
markNeedsPaint();
}
Color get borderColor => _borderColor;
Color _borderColor;
set borderColor(Color value) {
if (_borderColor == value) {
return;
}
_borderColor = value;
markNeedsPaint();
}
@override
double computeMinIntrinsicWidth(double height) {
RenderBox child = firstChild;
double minWidth = 0.0;
while (child != null) {
final _SegmentedControlContainerBoxParentData childParentData = child.parentData as _SegmentedControlContainerBoxParentData;
final double childWidth = child.getMinIntrinsicWidth(height);
minWidth = math.max(minWidth, childWidth);
child = childParentData.nextSibling;
}
return minWidth * childCount;
}
@override
double computeMaxIntrinsicWidth(double height) {
RenderBox child = firstChild;
double maxWidth = 0.0;
while (child != null) {
final _SegmentedControlContainerBoxParentData childParentData = child.parentData as _SegmentedControlContainerBoxParentData;
final double childWidth = child.getMaxIntrinsicWidth(height);
maxWidth = math.max(maxWidth, childWidth);
child = childParentData.nextSibling;
}
return maxWidth * childCount;
}
@override
double computeMinIntrinsicHeight(double width) {
RenderBox child = firstChild;
double minHeight = 0.0;
while (child != null) {
final _SegmentedControlContainerBoxParentData childParentData = child.parentData as _SegmentedControlContainerBoxParentData;
final double childHeight = child.getMinIntrinsicHeight(width);
minHeight = math.max(minHeight, childHeight);
child = childParentData.nextSibling;
}
return minHeight;
}
@override
double computeMaxIntrinsicHeight(double width) {
RenderBox child = firstChild;
double maxHeight = 0.0;
while (child != null) {
final _SegmentedControlContainerBoxParentData childParentData = child.parentData as _SegmentedControlContainerBoxParentData;
final double childHeight = child.getMaxIntrinsicHeight(width);
maxHeight = math.max(maxHeight, childHeight);
child = childParentData.nextSibling;
}
return maxHeight;
}
@override
double computeDistanceToActualBaseline(TextBaseline baseline) {
return defaultComputeDistanceToHighestActualBaseline(baseline);
}
@override
void setupParentData(RenderBox child) {
if (child.parentData is! _SegmentedControlContainerBoxParentData) {
child.parentData = _SegmentedControlContainerBoxParentData();
}
}
void _layoutRects(_NextChild nextChild, RenderBox leftChild, RenderBox rightChild) {
RenderBox child = leftChild;
double start = 0.0;
while (child != null) {
final _SegmentedControlContainerBoxParentData childParentData = child.parentData as _SegmentedControlContainerBoxParentData;
final Offset childOffset = Offset(start, 0.0);
childParentData.offset = childOffset;
final Rect childRect = Rect.fromLTWH(start, 0.0, child.size.width, child.size.height);
RRect rChildRect;
if (child == leftChild) {
rChildRect = RRect.fromRectAndCorners(childRect, topLeft: const Radius.circular(3.0),
bottomLeft: const Radius.circular(3.0));
} else if (child == rightChild) {
rChildRect = RRect.fromRectAndCorners(childRect, topRight: const Radius.circular(3.0),
bottomRight: const Radius.circular(3.0));
} else {
rChildRect = RRect.fromRectAndCorners(childRect);
}
childParentData.surroundingRect = rChildRect;
start += child.size.width;
child = nextChild(child);
}
}
@override
void performLayout() {
final BoxConstraints constraints = this.constraints;
double maxHeight = _kMinSegmentedControlHeight;
double childWidth = constraints.minWidth / childCount;
for (final RenderBox child in getChildrenAsList()) {
childWidth = math.max(childWidth, child.getMaxIntrinsicWidth(double.infinity));
}
childWidth = math.min(childWidth, constraints.maxWidth / childCount);
RenderBox child = firstChild;
while (child != null) {
final double boxHeight = child.getMaxIntrinsicHeight(childWidth);
maxHeight = math.max(maxHeight, boxHeight);
child = childAfter(child);
}
constraints.constrainHeight(maxHeight);
final BoxConstraints childConstraints = BoxConstraints.tightFor(
width: childWidth,
height: maxHeight,
);
child = firstChild;
while (child != null) {
child.layout(childConstraints, parentUsesSize: true);
child = childAfter(child);
}
switch (textDirection) {
case TextDirection.rtl:
_layoutRects(
childBefore,
lastChild,
firstChild,
);
break;
case TextDirection.ltr:
_layoutRects(
childAfter,
firstChild,
lastChild,
);
break;
}
size = constraints.constrain(Size(childWidth * childCount, maxHeight));
}
@override
void paint(PaintingContext context, Offset offset) {
RenderBox child = firstChild;
int index = 0;
while (child != null) {
_paintChild(context, offset, child, index);
child = childAfter(child);
index += 1;
}
}
void _paintChild(PaintingContext context, Offset offset, RenderBox child, int childIndex) {
assert(child != null);
final _SegmentedControlContainerBoxParentData childParentData = child.parentData as _SegmentedControlContainerBoxParentData;
context.canvas.drawRRect(
childParentData.surroundingRect.shift(offset),
Paint()
..color = backgroundColors[childIndex]
..style = PaintingStyle.fill,
);
context.canvas.drawRRect(
childParentData.surroundingRect.shift(offset),
Paint()
..color = borderColor
..strokeWidth = 1.0
..style = PaintingStyle.stroke,
);
context.paintChild(child, childParentData.offset + offset);
}
@override
bool hitTestChildren(BoxHitTestResult result, { @required Offset position }) {
assert(position != null);
RenderBox child = lastChild;
while (child != null) {
final _SegmentedControlContainerBoxParentData childParentData = child.parentData as _SegmentedControlContainerBoxParentData;
if (childParentData.surroundingRect.contains(position)) {
final Offset center = (Offset.zero & child.size).center;
return result.addWithRawTransform(
transform: MatrixUtils.forceToPoint(center),
position: center,
hitTest: (BoxHitTestResult result, Offset position) {
assert(position == center);
return child.hitTest(result, position: center);
},
);
}
child = childParentData.previousSibling;
}
return false;
}
}